JP2019032211A - Nuclear medicine diagnosis device - Google Patents

Abstract

An object of the present invention is to provide a nuclear medicine diagnostic apparatus capable of accurately performing absorption correction, scattering correction, and body motion correction. A coincidence circuit generates a sinogram from radiation generated from a radiopharmaceutical in a subject. On the other hand, the 3D scanner 12 optically captures a breast (which is a target of nuclear medicine diagnosis) to obtain a three-dimensional image of the breast. An absorption coefficient value is assumed inside the outline of the three-dimensional image acquired by the 3D scanner 12. An absorption coefficient sinogram representing the distribution of the assumed absorption coefficient values is created. The sinogram is corrected for absorption using the absorption coefficient sinogram. By using an absorption coefficient sinogram representing the distribution of assumed absorption coefficient values inside the contour of a three-dimensional image photographed by the 3D scanner 12, the radiopharmaceutical is not distributed over the entire imaging region. Also, the absorption correction can be performed accurately. [Selection] Figure 1

Description

  The present invention relates to a nuclear medicine diagnosis apparatus, and more particularly to a technique that mainly targets a local region such as a breast or a head.

  Conventionally, for example, a PET (Positron Emission Tomography) apparatus is used as a breast dedicated nuclear medicine diagnostic apparatus whose imaging region is a breast. Mammogram (mammography) using PET is performed using a mammogram PET apparatus as shown in FIG. FIG. 21 is a schematic side view of a conventional mammo PET apparatus. As shown in FIG. 21, the top plate 101 on which the subject M is placed, the gantry 102 having the opening 102 a, and the ring surrounding the breast of the subject M are arranged and embedded in the gantry 102. The detected detector 103 and a console 104 for accumulating data are provided.

  The breast of the subject M to which the radiopharmaceutical has been administered in advance is inserted into the opening 102 a of the gantry 102, and 511 KeV pair annihilation photons emitted from the breast of the subject M are detected by the detector 103 in the gantry 102. Then, the time when the photon is detected is measured, and when the difference in detection time between the two detection elements in the detector 103 is within a certain time (TW: Time Window), it is counted as a pair of annihilation photons. (Simultaneous counting), and the pair disappearance occurrence point is specified as a straight line of the detected pair.

  The data detected in this way is called “emission data”, and this data is stored in the console 104. Image reconstruction is performed from the emission data to obtain a PET image. By administering a radiopharmaceutical that easily accumulates in a specific lesion to the breast of the subject M, if the lesion exists in the breast of the subject M, the lesion appears as a high pixel value on the PET image and is identified. can do. Then, the acquired PET image is displayed on a monitor (not shown), and after confirming the success or failure of imaging, the image is transferred from the console 104 to the server for use in diagnosis or the like.

  In order to quantitatively measure the radioactivity concentration in the subject in the PET image as well as the breast, various data correction processes are required. Typical correction processes include sensitivity correction, attenuation correction, scattering correction, random correction, attenuation correction, dead time correction, and absorption correction. Further, in examination (imaging) using PET, a long time is required even if the object to be imaged is a local part such as a breast or a head. Therefore, body movement always occurs. Therefore, it is necessary to perform body motion correction.

  Among these corrections, absorption correction, scattering correction, and body motion correction require a map that represents a quantitative parameter distribution within the imaging region. Conventionally, in order to create a map as described above, transmission data obtained by irradiating an external source of positron emitting nuclides is required. Alternatively, CT data obtained from an X-ray CT (Computed Tomography) apparatus or MRI data obtained from a magnetic resonance imaging apparatus may be used instead of transmission data.

  In the case of using these data, there is a problem that the accuracy is lowered unless photographing is performed with the same posture (posture) as photographing with PET. Further, there is a problem that the exposure dose increases in transmission data and CT data. On the other hand, MRI data has a problem that it takes a long time for MRI examination.

  Thus, in recent years, there are reconstruction algorithms that do not require such data (for example, see Non-Patent Documents 1 and 2). In Non-Patent Documents 1 and 2, the distribution shape of the absorption coefficient sinogram can be estimated from measurement data of PET that measures the time difference of detection of annihilation radiation (also referred to as “time-of-flight difference”) (TOF: Time Of Flight) information. . Then, the PET image and the absorption coefficient sinogram can be estimated simultaneously. The reconstruction algorithms in Non-Patent Documents 1 and 2 are also called “simultaneous reconstruction algorithms” because PET images and absorption coefficient maps (for example, absorption coefficient sinograms) are estimated simultaneously. In the case of the simultaneous reconstruction algorithm, these corrections such as absorption correction can be performed using only the TOF information and the emission data.

  In order to set the breast, there is a mammographic PET apparatus in which an optical imaging means such as a CCD (Charge-Coupled Device) is mounted on the gantry 102 (see FIG. 21) (see, for example, Patent Document 1).

JP 2009-300319 A

A. Rezaei, M. Defrise and J. Nuyts, “ML-reconstruction for TOF-PET with simultaneous estimation of the Attenuation Factors”, IEEE Trans. Med. Imag., 33 (7), 1563-1572, 2014

V. Y. Panin, H. Bal, M. Defrise, C. Hayden and M. E. Casey, “Transmission-less Brain TOF PET Imaging using MLACF”, 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, Seoul, Republic of Korea, 2013.

However, when correction is performed using only TOF information and emission data as in the simultaneous reconstruction algorithm, there are the following problems.
That is, depending on the type of medicine, it is not always distributed over the entire imaging region. For example, when FDG (fluorodeoxyglucose) is used, it is distributed throughout the body, but when FLT (fluorothymidine) or FET (fluoroethyltyrosine) is used, it is not distributed throughout the imaging region. As a result, since accurate contour information is not known, these corrections cannot be performed accurately.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a nuclear medicine diagnostic apparatus capable of accurately performing absorption correction, scattering correction, and body motion correction.

In order to achieve such an object, the present invention has the following configuration.
That is, a nuclear medicine diagnostic apparatus according to the present invention includes a detector that detects radiation generated from a radiopharmaceutical in a subject, test data generation means that generates test data from the radiation detected by the detector, Optical imaging means for optically photographing the subject to obtain a three-dimensional image of the subject, and absorption coefficient values are assumed inside the contour of the three-dimensional image obtained by the optical photographing means, respectively. An absorption coefficient map creating means for creating an absorption coefficient map representing the distribution of the absorption coefficient value; an absorption correcting means for absorbing and correcting the inspection data using the absorption coefficient map created by the absorption coefficient map creating means; Is provided.

  [Operation / Effect] According to the nuclear medicine diagnostic apparatus of the present invention, the detector detects the radiation generated from the radiopharmaceutical in the subject, and the inspection data generating means uses the inspection data from the radiation detected by the detector. Is generated. On the other hand, the optical imaging means optically images a subject (which is a target of nuclear medicine diagnosis) to obtain a three-dimensional image of the subject. An absorption coefficient value is assumed inside the contour of the three-dimensional image acquired by the optical photographing means. The absorption coefficient map creating means creates an absorption coefficient map representing the assumed distribution of absorption coefficient values. Using the absorption coefficient map, the absorption correction unit absorbs and corrects the inspection data. The contour of the three-dimensional image acquired by the optical imaging means does not depend on the distribution of the radiopharmaceutical. Therefore, the radiopharmaceutical can be obtained by using the absorption coefficient map representing the distribution of the assumed absorption coefficient values inside the contour of the three-dimensional image photographed by the optical photographing means without using the CT image or the MRI image. Even when it is not distributed over the entire imaging region, absorption correction can be performed accurately.

  Further, a nuclear medicine diagnostic apparatus according to the present invention includes a detector that detects radiation generated from a radiopharmaceutical in a subject, test data generation means that generates test data from the radiation detected by the detector, The optical imaging means for optically photographing the subject to obtain a three-dimensional image of the subject, and the model data simulating the inside of the outline of the three-dimensional image obtained by the optical photographing means, the total number of events of the radiation Probability, which is the ratio of the number of detected radiation by scattered radiation to simulation, is obtained by simulation, and the scatter projection data creating means for creating scattered projection data representing the distribution of scattered radiation from the probability is created by the scatter projection data creating means. Scatter correction means for performing scatter correction on the inspection data using the scatter projection data thus obtained.

  [Operation / Effect] According to the nuclear medicine diagnostic apparatus of the present invention, the detector detects the radiation generated from the radiopharmaceutical in the subject, and the inspection data generating means uses the inspection data from the radiation detected by the detector. Is generated. On the other hand, the optical imaging means optically images a subject (which is a target of nuclear medicine diagnosis) to obtain a three-dimensional image of the subject. In model data imitating the inside of the contour of the three-dimensional image acquired by the optical imaging means, a probability that is the ratio of the number of detected radiations by scattered rays to the total number of radiation events is obtained by simulation (for example, Monte Carlo simulation). . Scattered projection data creating means creates scattered projection data representing the distribution of scattered radiation from the probability. Using the scatter projection data, the scatter correction means scatter-corrects the inspection data. As described in the absorption correction, the contour of the three-dimensional image acquired by the optical imaging means does not depend on the distribution of the radiopharmaceutical. Therefore, it was obtained by simulation in model data imitating the inside of the outline of a three-dimensional image photographed by an optical photographing means without using a CT image or an MRI image (detection of radiation by scattered radiation with respect to the total number of radiation events). By using scatter projection data representing the distribution of scattered radiation from the probability (which is a ratio of numbers), scatter correction can be accurately performed even when the radiopharmaceutical is not distributed over the entire imaging region.

  Further, a nuclear medicine diagnostic apparatus according to the present invention includes a detector that detects radiation generated from a radiopharmaceutical in a subject, test data generation means that generates test data from the radiation detected by the detector, An optical imaging unit that optically captures a subject to acquire a three-dimensional image of the subject, and a contour of the three-dimensional image acquired by the optical imaging unit is used to calculate a temporal change amount associated with body movement. And a body motion correcting unit that corrects the body movement of the examination data using the amount of change obtained by the change amount calculating unit.

  [Operation / Effect] According to the nuclear medicine diagnostic apparatus of the present invention, the detector detects the radiation generated from the radiopharmaceutical in the subject, and the inspection data generating means uses the inspection data from the radiation detected by the detector. Is generated. On the other hand, the optical imaging means optically images a subject (which is a target of nuclear medicine diagnosis) to obtain a three-dimensional image of the subject. Using the contour of the three-dimensional image acquired by the optical photographing means, the change amount calculating means calculates a temporal change amount associated with body movement. Then, using the amount of change obtained by the amount-of-change calculating unit, the body movement correcting unit corrects the body movement of the examination data. As described in the absorption correction and the scattering correction, the contour of the three-dimensional image acquired by the optical imaging unit does not depend on the distribution of the radiopharmaceutical. Furthermore, the distribution of the radiopharmaceutical varies with time, but the contour of the three-dimensional image acquired by the optical imaging means does not vary with time except for body movement. In other words, if there is a change in the contour of the three-dimensional image, the amount of change due to the change is considered to be due to body movement. Therefore, by using the contour of the three-dimensional image photographed by the optical photographing means without using the CT image or the MRI image, the temporal change amount associated with the body movement is calculated, and the change amount is used to obtain the radioactivity. Even when the medicine is not distributed over the entire imaging region, body motion correction can be performed accurately.

  An example of the imaging region of the subject is the breast. When the imaging region is a breast, absorption correction, scattering correction, and body motion correction are performed assuming that the inside of the contour is water. In particular, in the case of absorption correction, assuming that the inside of the contour is water, the water absorption coefficient value is uniformly determined, and a map representing the distribution of the water absorption coefficient value is created as an absorption coefficient map. The absorption coefficient value of water is known, and it is possible to easily perform the absorption correction by determining uniformly the absorption coefficient value of water assuming that the inside of the contour is water. In the case of scattering correction, the probability is obtained by simulation in model data assuming that the inside of the contour is water, and scattering projection data is created from the probability.

  The imaging region is not particularly limited. It is preferably a local site, for example, the head. When the imaging region is the head, absorption correction and scattering correction are performed by combining the face surface layer model, skeleton model, dentition model, and the like of the subject obtained in advance with the contour. Body motion correction may be applied to the head.

  In particular, in the case of absorption correction, absorption correction is performed by determining a combination of the absorption coefficient value of air, the absorption coefficient value of brain tissue, and the absorption coefficient value of bone. In the case of brain tissue, since it is regarded as an area that can be approximated by water, the absorption coefficient value of water is used. Specifically, in the case of absorption correction, the position of the face surface layer corresponding to the face surface layer of the contour and the inside of the contour are obtained from model data including the face surface model, skeleton model, and dentition model of the subject obtained in advance. The skeleton position corresponding to the skeleton and the dentition position corresponding to the dentition in the contour are determined. Then, bone resorption values are assigned to the skeleton position and the dentition position, water or air absorption coefficient values are assigned to positions other than the skeleton position / dentition position and the face surface layer position, and assigned to each position. A map representing the distribution of the bone absorption coefficient value and the water or air absorption coefficient value is created as an absorption coefficient map. As described above, the absorption coefficient value of water (absorption coefficient value of brain tissue) is known, and the absorption coefficient value of bone and the absorption coefficient value of air are also known. By using model data composed of a skeleton model and a dentition model and assigning a bone absorption coefficient value and a water or air absorption coefficient value to each position, the absorption correction can be easily performed.

  In the case of scatter correction, from the model data consisting of the subject's face surface model, skeleton model, and dentition model, the face surface layer position corresponding to the contour face surface layer, and the skeleton inside the contour The model data imitating the contour is reconstructed by determining the skeleton position and the dentition position corresponding to the dentition in the outline. A probability is obtained from the reconstructed model data by simulation, and scattering projection data is created from the probability.

  In addition, the above-described examples of the nuclear medicine diagnosis apparatus according to the present invention (the former example) are generated by a reconstruction unit that reconstructs examination data and generates a reconstructed image, and the reconstruction unit. The reconstructed image and the three-dimensional image acquired by the optical photographing means are arranged to be arranged on the same monitor and displayed on a parallel display control means.

  In addition, another example (the latter example) of the above-described nuclear medicine diagnosis apparatus according to the present invention includes a reconstructing unit that reconstructs examination data to generate a reconstructed image, and a reconstructing unit that generates the reconstructed image. And a superimposed display control unit that superimposes and displays the reconstructed image and the three-dimensional image acquired by the optical imaging unit. The former example and the latter example may be combined.

  When the imaging site is a breast, the subject is placed on a horizontal surface in a prone position, and includes a top plate having an opening through which the breast is guided downward, and the opening of the top plate has left and right breasts. Are both configured to be insertable, and a structure in which a detector is provided below the opening of the top plate is preferable. When photographing a breast, the subject is placed on the horizontal surface of the top plate in a prone position, and either the left or right breast is guided downward through the opening of the top plate. The opening is configured with a size that allows both the left and right breasts to be inserted. With one of the left and right breasts guided downward through the opening, the one breast is imaged by a detector provided at the bottom of the opening. When imaging of the one breast is completed, the other breast is imaged by a detector provided at the lower part of the opening while the other breast is guided downward through the opening. In this way, the opening can be individually photographed through both the left and right breasts.

According to the nuclear medicine diagnostic apparatus of the present invention, the detector detects the radiation generated from the radiopharmaceutical in the subject, and the inspection data generating means generates the inspection data from the radiation detected by the detector. On the other hand, the optical imaging means optically images a subject (which is a target of nuclear medicine diagnosis) to obtain a three-dimensional image of the subject.
In the case of absorption correction, an absorption coefficient value is assumed inside the contour of the three-dimensional image acquired by the optical photographing means. The absorption coefficient map creating means creates an absorption coefficient map representing the assumed distribution of absorption coefficient values. Using the absorption coefficient map, the absorption correction unit absorbs and corrects the inspection data. By using an absorption coefficient map representing the distribution of assumed absorption coefficient values inside the contour of a three-dimensional image photographed by an optical photographing means without using a CT image or an MRI image, the radiopharmaceutical can be captured by the imaging region. Even if it is not distributed throughout, absorption correction can be performed accurately.
In the case of scattering correction, in the model data simulating the inside of the outline of the three-dimensional image acquired by the optical imaging means, the probability that is the ratio of the number of radiation detected by scattered radiation to the total number of radiation events is simulated. Ask. Scattered projection data creating means creates scattered projection data representing the distribution of scattered radiation from the probability. Using the scatter projection data, the scatter correction means scatter-corrects the inspection data. It was obtained by simulation in model data imitating the inside of the outline of a three-dimensional image photographed by an optical photographing means without using a CT image or an MRI image (the number of radiation detected by scattered radiation relative to the total number of radiation events). By using scatter projection data representing the distribution of scattered radiation from the probability (which is a ratio), scatter correction can be accurately performed even when the radiopharmaceutical is not distributed over the entire imaging region.
In the case of body motion correction, the change amount calculating means calculates the temporal change amount associated with the body motion using the contour of the three-dimensional image acquired by the optical photographing means. Then, using the amount of change obtained by the amount-of-change calculating unit, the body movement correcting unit corrects the body movement of the examination data. Using a contour of a three-dimensional image photographed by an optical photographing means without using a CT image or an MRI image, a temporal change amount according to body movement is calculated, and the radiopharmaceutical is obtained by using the change amount. Even if it is not distributed over the entire imaging region, body motion correction can be performed accurately.

(A) is a schematic side view of the mammo PET apparatus according to Examples 1 to 3, (b) is a schematic plan view of the gantry for breast examination of (a), and (c) is an enlarged view of the 3D scanner of (a). is there. 1 is a block diagram of a mammo PET apparatus according to Embodiment 1. FIG. 6 is a flowchart of a series of image processing including absorption correction according to the first exemplary embodiment. This is a mode of parallel display of a breast three-dimensional image obtained by optical imaging and a PET image. This is a superimposing display mode of a three-dimensional image of a breast obtained by optical imaging and a PET image. 6 is a block diagram of a mammo PET apparatus according to Embodiment 2. FIG. 10 is a flowchart of a series of image processing including scattering correction according to the second embodiment. It is a schematic diagram of a scattered radiation model used in an Effective Source Scatter Estimation (ESSE) method for obtaining a scattered radiation component by applying Monte Carlo simulation. It is a flowchart of preparation of the scattering sinogram in ESSE method. FIG. 6 is a block diagram of a mammo PET apparatus according to a third embodiment. 12 is a flowchart of a series of image processing including body motion correction according to the third exemplary embodiment. (A) is a schematic diagram of each breast image before and after body movement related to parallel movement, and (b) is a schematic diagram of each breast image before and after body movement related to rotational movement. (A) is a schematic side view of a head PET device according to Examples 4 and 5 when a rail is provided, and (b) is a schematic side view of a head PET device according to Examples 4 and 5 when a rail is not provided. FIG. FIG. 10 is a block diagram of a head PET device according to a fourth embodiment. (A) is a flowchart of a series of image processing including the absorption correction of Example 4, (b) is a flowchart regarding creation of an absorption coefficient sinogram. It is a schematic diagram with which it uses for description regarding the deformation | transformation of each model data. FIG. 10 is a block diagram of a head PET device according to a fifth embodiment. (A) is a flowchart of a series of image processing including scattering correction of Example 5, and (b) is a flowchart regarding creation of a scattering sinogram. It is a schematic side view of the mammo PET apparatus which concerns on modification implementation of Examples 1-3. It is a schematic diagram with which it uses for description of LOR (Line Of Response) crossing the exterior of an outline. It is a schematic side view of the conventional whole body PET apparatus.

Embodiment 1 of the present invention will be described below with reference to the drawings.
1A is a schematic side view of the mammo PET apparatus according to the first to third embodiments, and FIG. 1B is a schematic plan view of the breast examination gantry in FIG. FIG. 2C is an enlarged view of the 3D scanner in FIG. 1A, and FIG. 2 is a block diagram of the mammo PET apparatus according to the first embodiment. In the present embodiment 1, a PET apparatus will be described as an example of a nuclear medicine diagnosis apparatus, including later-described embodiments 2 to 5, and in addition to the later-described embodiments 2 and 3, an imaging region will be described. A mammographic PET apparatus will be described as an example of a breast-only nuclear medicine diagnostic apparatus having a breast. Moreover, FIG. 1 is a structure common to Examples 1-3.

  As shown to Fig.1 (a), the mammo PET apparatus 1 is provided with the top plate 2 which mounts the test object M on a horizontal surface in a prone position. In Example 1, including Examples 2 and 3 to be described later, the top plate 2 has an opening 2a through which the breast is guided downward. Both openings 2a of the top plate 2 are configured to be insertable. Below the top plate 2 is provided with a breast examination gantry 4 equipped with a detector 3 for detecting radiation (photons) generated from a radiopharmaceutical in the subject M, and with a base 5 for supporting the top plate 2. ing. In addition, the mammo PET apparatus 1 includes a coincidence counting circuit 6 (see FIG. 2), an image processing unit 7 (see FIG. 2), a controller 8 (see FIG. 2), and a memory unit 9 (see FIG. 2). An input unit 10 (see FIG. 2), a monitor 11 (see also FIG. 2), and a 3D scanner 12 (see also FIG. 2) are provided. Further, in the first embodiment, the mammo PET apparatus 1 includes an absorption coefficient map creating unit 15 (see FIG. 2). The coincidence circuit 6 corresponds to the inspection data generation unit in the present invention, the image processing unit 7 in the first embodiment corresponds to the absorption correction unit and the reconstruction unit in the present invention, and the controller 8 corresponds to the parallel in the present invention. The 3D scanner 12 corresponds to the display control unit and the superimposed display control unit. The 3D scanner 12 corresponds to the optical photographing unit in the present invention. The absorption coefficient map creation unit 15 corresponds to the absorption coefficient map creation unit in the present invention.

  As shown in FIGS. 1 (a) and 1 (b), a breast examination gantry 4 includes a ring-shaped housing 4a that houses a plurality of detectors 3 arranged to surround the breast, An elevating drive mechanism 4b that drives the housing 4a to move up and down in the vertical direction is provided. In FIG. 1B, for the sake of simplicity, only eight detectors 3 are shown, but it should be noted that in reality, more detectors 3 are provided.

  The breast examination gantry 4 is moved together with the detector 3 and the housing 4a only on the rail R (see FIG. 1A) installed on the floor surface. As the breast examination gantry 4 moves only on the rail R in this way, the top board 2 and the breast examination gantry 4 have geometric limitations. In other words, for example, when the breast examination gantry is freely moved by a caster, the degree of freedom in alignment between the subject and the apparatus is high, and collision prevention depends on the operator. Therefore, for example, the rail R is designed to be positioned directly below the opening 2a, and the top plate 2 and the breast examination gantry 4 are geometrically limited by the movement of the breast examination gantry 4 only on the rail R. Thus, it is possible to appropriately align the subject M and the apparatus.

  Specifically, first, the breast examination gantry 4 is located away from the opening 2a, and after the operator visually confirms that the breast of the subject M has been inserted into the opening 2a, the detector 3 The breast examination gantry 4 is moved so that the center of the housing 4a housing the container and the center of the opening 2a coincide. After the center of the housing 4a coincides with the center of the opening 2a, the elevating drive mechanism 4b is driven so as to move the housing 4a upward, so that the detector 3 approaches the breast (upward). Can be moved. The movement of the breast examination gantry 4 is movement in one direction (horizontal movement on the rail R, up-and-down movement of the housing 4a), and the movement distance is determined. Therefore, as shown in FIG. 1A, it can be easily operated from the operation panel 10a of the input unit 10 (see FIG. 2) or the like at a position away from the subject M. Further, by installing a non-contact collision prevention sensor (for example, a distance sensor) or the like in the breast examination gantry 4, it is possible to automatically set the alignment.

  The 3D scanner 12 of the first embodiment is an optical photographing unit (optical camera) for absorption correction described later, but an optical camera may be provided separately from the 3D scanner 12. By displaying the optical image obtained by the optical camera on the monitor 11, it is possible to confirm the insertion of the breast and the setting from an angle that is difficult to visually confirm in the vicinity of the apparatus.

  Further, when the breast examination gantry moves while the breast is inserted into the opening 2a at the end of the examination (imaging), a collision between the breast examination gantry and the breast may occur. Therefore, for example, a sensor or a contact sensor for detecting that a load is applied to the top plate 2 is installed on the top plate 2, or an optical image obtained by the optical camera is subjected to image processing, so that the subject M opens the opening 2a. It is preferable to control so that the breast examination gantry 4 is moved only after confirming that the breast is removed from the breast. That is, it is preferable to control so that the breast examination gantry 4 cannot be moved only after confirming that the subject M has removed the breast from the opening 2a.

  A subject M to which a radiopharmaceutical has been administered in advance is placed on the top 2 in the prone position, and the breast of the subject M in the prone position is inserted into the opening 2a. In order to photograph the inserted breast, the breast examination gantry 4 is moved after the operator visually confirms that the breast of the subject M has been inserted into the opening 2a. After the center of the housing 4a that houses the detector 3 coincides with the center of the opening 2a, the elevating drive mechanism 4b is driven so as to move the housing 4a upward, thereby bringing the detector 3 close to the breast. Move in the direction (upward). The photon from the breast inserted into the opening 2a is counted by the detector 3 and sent to the coincidence counting circuit 6 (see FIG. 2) only when coincidence is counted. Thereby, the breast inserted into the opening 2a is photographed.

  When imaging of the breast inserted into the opening 2a is completed, the breast is removed from the opening 2a. In order to photograph the other breast, the other breast is inserted into the opening 2a. Then, the same picture is taken. Unless there are special circumstances, the left and right breasts are each photographed.

  Next, as shown in FIG. 2, the coincidence count data simultaneously counted by the coincidence counting circuit 6 is collected (generated) as inspection data consisting of a sinogram. The generated inspection data is sent to the image processing unit 7 and the controller 8, and the image processing unit 7 reconstructs while accumulating the inspection data, thereby acquiring a PET image which is a reconstructed image. In the first embodiment, by using the absorption coefficient map (for example, absorption coefficient sinogram) created by the absorption coefficient map creating unit 15, the inspection data (sinogram) is reconstructed and corrected for absorption. In the first embodiment, absorption correction is performed by incorporating an absorption coefficient sinogram into an image reconstruction calculation formula (for example, a successive approximation formula) to obtain a PET image from which the influence of absorption is eliminated. Since the calculation formula for image reconstruction incorporating the absorption coefficient sinogram is a known technique, its description is omitted. The image processing unit 7 is configured by a GPU (Graphics Processing Unit) or the like.

  The controller 8 is configured by a central processing unit (CPU) or a programmable device (for example, an FPGA (Field Programmable Gate Array)) in which a hardware circuit (for example, a logic circuit) used therein can be changed according to program data. Yes. In the first embodiment, the controller 8 has a parallel display control function and a superimposed display control function. These functions will be described in detail later.

  The memory unit 9 is composed of a storage medium represented by ROM (Read-only Memory), RAM (Random-Access Memory), and the like. In the present embodiment 1, including later-described embodiments 2 to 5, the inspection data collected (generated) by the coincidence counting circuit 6, the PET image reconstructed by the image processing unit 7, and the 3D scanner 12 were acquired. The three-dimensional image is written and stored in the memory unit 9 and read from the memory unit 9 as necessary. In the first embodiment, the absorption coefficient sinogram created by the absorption coefficient map creating unit 15 is also written and stored in the memory unit 9 and read from the RAM as necessary.

  The input unit 10 sends data and commands input by the operator to the controller 8. The input unit 10 includes a pointing device represented by a mouse, a keyboard, a joystick, a trackball, a touch panel, and the like.

  The monitor 11 is configured to display the modes of FIGS. 4 and 5 described later on the screen. The monitor 11 may be configured with a touch panel, and the monitor 11 may be configured to have the function of the input unit 10.

  The 3D scanner 12 optically photographs the breast of the subject M and acquires a three-dimensional image of the breast. The 3D scanner 12 is provided in the breast examination gantry 4 (see FIG. 1). As shown in FIG. 1C, the 3D scanner 12 includes a light source 12a that emits infrared light, and two cameras 12b that perform optical imaging by detecting light emitted from the breast. Specific functions of the 3D scanner 12 will be described in detail later.

  The absorption coefficient map creation unit 15 assumes an absorption coefficient value inside the contour of the three-dimensional image acquired by the 3D scanner 12, and creates an absorption coefficient sinogram representing the distribution of the assumed absorption coefficient value. . The absorption coefficient map creating unit 15 is configured by a CPU or programmable device similar to the controller 8 or a GPU similar to the image processing unit 7. A specific function of the absorption coefficient map creating unit 15 will be described later in detail.

  Next, a series of image processing including absorption correction according to the first embodiment will be described with reference to FIGS. FIG. 3 is a flowchart of a series of image processing including absorption correction according to the first embodiment, and FIG. 4 is a mode of parallel display of a three-dimensional image of a breast obtained by optical imaging and a PET image. Reference numeral 5 denotes a superimposing display mode of a breast three-dimensional image obtained by optical imaging and a PET image. Note that the breast of the subject M (see FIG. 1A) to which the radiopharmaceutical has been administered in advance has already been inserted into the opening 2a (see FIG. 1A), and the detector 3 (see FIG. 1). ) Will be described as being close to the breast and ready for breast imaging.

(Step S1) Optical photography
The breast is irradiated with infrared light from a light source 12a (see FIG. 1C) of the 3D scanner 12 (see FIGS. 1 and 2). Each camera 12b (see FIG. 1C) takes an optical image by detecting light emitted from the breast. Then, a three-dimensional image of the breast is obtained using triangulation. A three-dimensional image of the breast acquired by the 3D scanner 12 is sent to the absorption coefficient map creating unit 15 (see FIG. 2) via the controller 8 (see FIG. 2). Further, a three-dimensional image of the breast is also sent to the memory unit 9 (see FIG. 2) via the controller 8.

(Step S2) Creation of Absorption Coefficient Sinomogram The absorption coefficient map creation unit 15 assumes an absorption coefficient value inside the contour of the three-dimensional image acquired by the 3D scanner 12, and each assumed distribution of the absorption coefficient value is assumed. To create an absorption coefficient sinogram. It is preferable to binarize a three-dimensional image of the breast acquired by the 3D scanner 12 by threshold processing. By binarizing the three-dimensional image of the breast, the contour in the breast and the inside of the contour are set to “1”, and the outside of the contour in the breast is set to “0”.

  In Example 1, including Examples 2 and 3 described later, the imaging region is the breast. Therefore, assuming that the inside of the contour is water, it is uniformly determined by the water absorption coefficient value, and a sinogram representing the distribution of the water absorption coefficient value is created as an absorption coefficient sinogram. The water absorption coefficient value is known, and the water absorption coefficient value of 0.0096 / mm is used. The absorption coefficient sinogram created by the absorption coefficient map creation unit 15 is sent to the memory unit 9 via the controller 8. Then, the absorption coefficient sinogram is written and stored in the memory unit 9.

(Step S3) Generation of Examination Data Subsequently, the detector 3 detects radiation (photons) generated from the radiopharmaceutical in the breast of the subject M, and the coincidence circuit 6 (see FIG. 2) simultaneously counts the radiation. The coincidence data is collected (generated) as inspection data consisting of a sinogram. The generated inspection data is sent to the image processing unit 7 (see FIG. 2) and the controller 8.

(Step S4) Absorption Correction / Reconstruction The image processing unit 7 acquires a PET image that is a reconstructed image by reconstructing while accumulating examination data. At that time, the absorption coefficient sinogram is read from the memory unit 9 and sent to the image processing unit 7 via the controller 8, and the absorption coefficient sinogram is incorporated into the successive approximation formula to perform absorption correction. In addition, absorption correction is performed by obtaining the transmittance of the radiation (photon) from the absorption coefficient image, and converting the inspection data into the data in which the influence of the absorption of the radiation (photon) is eliminated by dividing the transmittance. Also good. That is, absorption correction may be performed before reconstruction. The PET image after the absorption correction is sent to the memory unit 9 via the controller 8. Then, the PET image after the absorption correction is written and stored in the memory unit 9.

(Step S5) Display on Monitor A three-dimensional image of the breast obtained by optical imaging and a PET image after absorption correction are read out from the memory unit 9, and the monitor 11 (FIGS. 1, 2, and 4) is connected via the controller 8. And (see FIG. 5). In FIG. 4, the controller 8 performs display control (parallel display control) by arranging the three-dimensional image P ₁ and the PET image P _{2 of} the breast obtained by optical imaging on the same monitor 11. In FIG. 5, the controller 8 performs display control (superimposition display control) by superimposing the breast three-dimensional image P ₁ and the PET image P ₂ obtained by optical imaging. In FIGS. 4 and 5, the breast is displayed in the Antero-Posterior (that is, the front) direction in which the breast is viewed from the front to the back of the subject M, but the view direction may be switched. For example, the head-to-tail direction (CC: Cranio-Caudal) (also called “Top View”), the view direction seen from the inside to the outside of the breast, You may switch to MLO: Medio-Lateral Oblique). However, when the imaging region is the breast and optical imaging is performed from the direction as shown in FIG. 1A, the view direction in the posterior-anterior direction (ie, the back) cannot be switched. Please keep in mind.

  According to the mammo PET apparatus 1 according to the first embodiment, the detector 3 detects the radiation generated from the radiopharmaceutical in the subject M, and the coincidence counting circuit 6 calculates the inspection data from the radiation detected by the detector 3. (In each embodiment, a sinogram) is generated. On the other hand, the optical imaging means (3D scanner 12 in each embodiment) optically images a subject M (a breast in this embodiment 1) (a subject of nuclear medicine diagnosis) to obtain a three-dimensional image of the breast. An absorption coefficient value is assumed inside the contour of the three-dimensional image acquired by the optical photographing means (3D scanner 12). The absorption coefficient map creating unit 15 creates an absorption coefficient map (absorption coefficient sinogram in the first embodiment) representing the assumed distribution of the absorption coefficient values. Using the absorption coefficient map (absorption coefficient sinogram), the absorption correction means (image processing unit 7 in the first embodiment) absorbs and corrects the inspection data (sinogram). The contour of the three-dimensional image acquired by the optical imaging means (3D scanner 12) does not depend on the distribution of the radiopharmaceutical. Accordingly, an absorption coefficient map (absorption coefficient) representing the distribution of assumed absorption coefficient values inside the contour of a three-dimensional image photographed by the optical photographing means (3D scanner 12) without using a CT image or an MRI image. By using the sinogram), even when the radiopharmaceutical is not distributed throughout the imaging region (breast), the absorption correction can be performed accurately.

  In the first embodiment, the imaging region is the breast. When the imaging region is a breast, absorption correction is performed assuming that the inside of the contour is water. Assuming the inside of the contour is water, the water absorption coefficient value is uniformly determined, and a map representing the distribution of the water absorption coefficient value is created as an absorption coefficient map (absorption coefficient sinogram). The absorption coefficient value of water is known, and it is possible to easily perform the absorption correction by determining uniformly the absorption coefficient value of water assuming that the inside of the contour is water.

As shown in FIG. 4, the reconstructed image (PET image P _{2 in} FIG. 4) generated by the reconstructing means (image processing unit 7) and the three-dimensional image (3D scanner 12) acquired by the optical photographing means (3D scanner 12). In FIG. 4, the three-dimensional image P ₁ ) is displayed side by side on the same monitor 11 (parallel display). As shown in FIG. 5, the reconstructed image (PET image P _{2 in} FIG. 5) generated by the reconstructing means (image processing unit 7) and the three-dimensional image (3D scanner 12) acquired by the optical imaging means (3D scanner 12). In FIG. 5, the three-dimensional image P ₁ ) is superimposed and displayed (superimposed display). Moreover, you may combine the aspect of FIG. 4, and the aspect of FIG.

  When the imaging region is a breast as in the first embodiment, the subject M is placed on a horizontal surface in a prone position, and the top plate 2 having an opening 2a through which the breast is guided downward is provided. The opening 2a of the plate 2 is preferably sized so that both the left and right breasts can be inserted, and the detector 3 is preferably provided below the opening 2a of the top plate 2. When photographing a breast, the subject M is placed on the horizontal surface of the top board 2 in a prone position, and either the left or right breast is guided downward through the opening 2a of the top board 2. The opening 2a has a size that allows both the left and right breasts to be inserted. With one of the left and right breasts guided downward through the opening 2a, the one breast is imaged by the detector 3 provided at the lower part of the opening 2a. When imaging of the one breast is completed, the other breast is imaged by the detector 3 provided at the lower part of the opening 2a with the other breast guided downward through the opening 2a. In this manner, the opening 2a can be individually photographed through both the left and right breasts.

Next, Embodiment 2 of the present invention will be described with reference to the drawings.
FIG. 6 is a block diagram of the mammo PET apparatus according to the second embodiment. Constituent elements common to the above-described first embodiment are denoted by the same reference numerals, description thereof is omitted, and illustration is omitted.

  In the above-described first embodiment, the absorption correction is performed using the optically photographed three-dimensional image. On the other hand, in the second embodiment, scattering correction is performed using a three-dimensional image optically photographed.

  A mammo PET apparatus 1 (see FIG. 1) includes a top plate 2 (see FIG. 1), a detector 3 (see FIG. 1), and a breast examination gantry 4 (see FIG. 1), which are the same as those in the first embodiment. ) And a base 5 (see FIG. 1). As shown in FIG. 6, the mammo PET apparatus 1 includes a coincidence circuit 6, an image processing unit 7, a controller 8, a memory unit 9, an input unit 10, a monitor 11, and a 3D scanner 12 similar to those in the first embodiment. I have. Further, in the second embodiment, the mammo PET apparatus 1 includes a scatter projection data creation unit 25. The coincidence circuit 6 corresponds to the inspection data generation unit in the present invention, the image processing unit 7 in the second embodiment corresponds to the scattering correction unit and the reconstruction unit in the present invention, and the controller 8 corresponds to the parallel in the present invention. The 3D scanner 12 corresponds to an optical imaging unit in the present invention, and the scattered projection data creation unit 25 corresponds to the scattered projection data creation unit in the present invention.

  In the second embodiment, using the scatter projection data (for example, scatter sinogram) created by the scatter projection data creation unit 25, the inspection data (sinogram) is reconstructed and scatter correction is performed. In the second embodiment, scattering correction is performed by acquiring a PET image in which the influence of scattered radiation is eliminated by incorporating a scattering sinogram into a calculation formula (for example, a successive approximation formula) for image reconstruction. Since a calculation formula for image reconstruction incorporating a scatter sinogram is a known technique, a description thereof will be omitted.

  The scatter projection data creation unit 25 obtains, by simulation, a probability that is the ratio of the number of detected radiations by scattered rays to the total number of radiation events in the model data imitating the outline of the three-dimensional image acquired by the 3D scanner 12. A scattering sinogram representing the distribution of scattered radiation is created from the probability. The scattered projection data creation unit 25 is configured by a CPU or programmable device similar to the controller 8 or a GPU similar to the image processing unit 7. The specific function of the scattered projection data creation unit 25 will be described later in detail.

  Next, a series of image processing including scattering correction according to the second embodiment will be described with reference to FIGS. FIG. 7 is a flowchart of a series of image processing including scattering correction of the second embodiment, and FIG. 8 is a scattering used in an effective source scatter estimation (ESSE) method for obtaining a scattered radiation component by applying a Monte Carlo simulation. FIG. 9 is a schematic diagram of a line model, and FIG. 9 is a flowchart for creating a scattering sinogram in the ESSE method. As in the first embodiment described above, it will be assumed that the preparation for breast imaging has already been completed.

(Step S11) Optical Photography Step S11 in FIG. 7 is the same as step S1 in the first embodiment described above, and a description thereof will be omitted. In the second embodiment, a three-dimensional image of the breast acquired by the 3D scanner 12 (see FIGS. 1 and 6) is converted into a scatter projection data creation unit 25 (see FIG. 6) via the controller 8 (see FIG. 6). (See). Further, the three-dimensional image of the breast is also sent to the memory unit 9 (see FIG. 6) via the controller 8.

(Step S <b> 12) Scattering sinogram creation The scatter projection data creation unit 25, in the model data imitating the outline of the three-dimensional image acquired by the 3D scanner 12, determines the number of detected radiations by scattered radiation with respect to the total number of radiation events. A probability as a ratio is obtained by simulation, and a scattering sinogram representing the distribution of scattered radiation is created from the probability. Similar to the first embodiment described above, binarization processing is performed on the three-dimensional image of the breast acquired by the 3D scanner 12 by threshold processing, so that the contour in the breast and the inside of the contour are “1”, and the contour outside the breast is outside. Is preferably "0".

  In Example 2, including Example 1 and Example 3 described later, the imaging region is the breast. Therefore, a probability is obtained by simulation in model data assuming that the inside of the contour is water, and a scattering sinogram is created from the probability. For example, a scattered radiation model (see FIG. 8) used in an effective source scatter estimation (hereinafter abbreviated as “ESSE”) method for obtaining a scattered radiation component by applying Monte Carlo simulation is obtained with a breast acquired by the 3D scanner 12. The inside of the contour in the three-dimensional image is replaced with model data assuming water.

  Then, in step S14, which will be described later, scatter correction / reconstruction is performed by an Astonish method, which is an image reconstruction method in which scatter correction is incorporated into the Three-Dimensional Ordered Subsets Expectation Maximization (3D-OSEM) method. Refer to References 1 and 2 for specific methods of the ESSE method (Reference 1: “Introduction of the Philips emission CT device“ BRIGHTVIEW X ””, [online], Hitachi, Internet <URL : http://www.innervision.co.jp/ad/suite/hitachi/technical_notes/151265>) Also, for a specific method for estimating the scattering components in projection data using the ESSE method, see References. 2 (Reference 2: Shigeji Higuchi, “New 3D Image Reconstruction Method in the Age of SPECT / CT (Astonish)”, [online], Internet <URL: http://www.hitachi.co .jp / products / healthcare / products-support / contents / medix / pdf / vol48 / P25-30.pdf>).

  The model data assuming that the inside of the contour in the three-dimensional image of the breast acquired by the 3D scanner 12 is water is a scattered radiation model (water absorber) used in the ESSE method as shown in FIG. . Reference numeral A in FIG. 8 is a source that generates photons and causes scattered radiation, and reference numeral B in FIG. 8 indicates that scattered radiation generated from a point A source is finally detected by the detector 3 (also in FIG. 1). Point) 8 is a source of point A, and τ (X ′) in FIG. 8 is the distance from point B to the outline (body surface) of the breast. The reference sign As (X ′) is a scattered radiation source that is detected by the detector 3 as the scattered radiation generated at point B is attenuated by the distance τ (X ′) to the body surface.

  In the model of FIG. 8, the following probabilities P1 to P4 are respectively defined. P1 is a probability that the scattered radiation generated from the point A is directed to the point B, P2 is a probability that the scattered radiation generated from the point B is directed to the detector 3, and P3 is a probability that the scattered radiation is not attenuated by the detector 3. P4 is the probability that this scattered radiation will be attenuated but detected by the detector 3. In the ESSE method, the model shown in FIG. 8 is used, and the scattered radiation generated at point B is attenuated by the distance τ (X ′) to the body surface, and is detected and measured by the detector 3 as As (X ′). The scattering component in the projection data (that is, the scattered projection data) is estimated from this.

More specifically, first, a scattered radiation source kernel (Scatter Source Kernel) k (see FIG. 9) is calculated from the model in consideration of the probabilities P1 to P4 using Monte Carlo simulation. Moreover, finally the attenuation coefficients of the scattered rays generated (mu _S) decrease from the water weak coefficient (mu ₀₎ and subtracted relative scattered radiation attenuation coefficient kernel (Relative Scatter Source Attenuation Coefficient Kernel) Δμ S (= μ S -μ ₀ ) (see FIG. 9) is also calculated by simulation. Next, three kernels k, k × Δμ _S , k × (Δμ _S ) ² are created from these kernels k, Δμ _S.

Next, as shown in FIG. 9, these three kernels k, k × Δμ _S , k × (Δμ _S ) ² are convolved (convolved) with the radiation distribution of the source at the point A, and 3 Create two images. Thereto, respectively coefficients 1, -τ, 1 / 2τ multiplied by ^two, to one image by summation. This image is an image corresponding to the parentheses in the following formula (1). Here, as described above, τ is the distance from point B to the contour (body surface) of the breast.

The image density multiplied by the electron density distribution (ρ _S ) is the effective scattered radiation source A _S (shown as “Effective Scatter Source” in FIG. 9) (see the above equation (1)). ). By the A _S forward projecting (Forward Projection), scattered radiation components included in the projection data in the collection angle is estimated. In the case of forward projection, the scattered radiation component is calculated in consideration of blur due to Collimator Distance Response (CDR) (indicated as “FP with CDR blur” in FIG. 9). This makes it possible to estimate the scattering component in the projection data (shown as “Scatter Estimation” in FIG. 9).

  The scattering component in the projection data estimated in this way is created as a scattering sinogram. The scatter sinogram created by the scatter projection data creation unit 25 is sent to the memory unit 9 via the controller 8. Then, the scattering sinogram is written and stored in the memory unit 9.

(Step S13) Generation of Inspection Data Step S13 in FIG. 7 is the same as step S3 in the first embodiment described above, and a description thereof will be omitted.

(Step S14) Scatter correction / reconstruction The image processing unit 7 (see FIG. 6) obtains a PET image as a reconstructed image by reconstructing while accumulating inspection data. At that time, the scattered sinogram is read out from the memory unit 9 and sent to the image processing unit 7 via the controller 8, and the scattered sinogram is incorporated into a successive approximation formula (in this embodiment, a successive approximation formula of 3D-OSEM method). Scatter correction is performed. Note that the scatter correction may be performed by converting the estimated distribution of scattered radiation from the inspection data and converting it into data in which the influence (bias) of the scattered radiation is eliminated. That is, scattering correction may be performed before reconstruction. The PET image after the scatter correction is sent to the memory unit 9 via the controller 8. Then, the PET image after the scattering correction is written and stored in the memory unit 9.

(Step S15) Display on Monitor Since step S15 in FIG. 7 is the same as step S5 in the first embodiment described above, description thereof is omitted.

  According to the mammo PET apparatus 1 according to the second embodiment, the detector 3 detects the radiation generated from the radiopharmaceutical in the subject M, and the coincidence counting circuit 6 calculates the inspection data from the radiation detected by the detector 3. (In each embodiment, a sinogram) is generated. On the other hand, the optical imaging means (3D scanner 12 in each embodiment) optically images a subject M (a breast in this embodiment 2) (a subject of nuclear medicine diagnosis) to acquire a three-dimensional image of the breast. In the model data imitating the inside of the outline of the three-dimensional image acquired by the optical imaging means (3D scanner 12), the probability that is the ratio of the number of detected radiation by scattered radiation to the total number of radiation events is simulated (for example, In the second embodiment, it is obtained by Monte Carlo simulation). The scatter projection data creation unit 25 creates scatter projection data (scatter sinogram in the second embodiment) representing the distribution of scattered radiation from the probability. Using the scattering projection data (scattering sinogram), the scattering correction means (image processing unit 7 in the second embodiment) scatter-corrects the inspection data (sinogram). As described in the above-described absorption correction of the first embodiment, the contour of the three-dimensional image acquired by the optical imaging means (3D scanner 12) does not depend on the distribution of the radiopharmaceutical. Therefore, it was obtained by simulation (Monte Carlo simulation) in model data imitating the outline of a 3D image taken by an optical imaging means (3D scanner 12) without using a CT image or MRI image (total radiation event). This is the case where the radiopharmaceutical is not distributed over the entire imaging region by using the scattered projection data (scattering sinogram) that represents the distribution of scattered radiation from the probability (the ratio of the number of radiation detected by scattered radiation to the number). However, the scattering correction can be performed accurately.

  Similar to the first embodiment described above, in this second embodiment, the imaging region is the breast. When the imaging region is a breast, the probability is obtained by simulation (Monte Carlo simulation) in model data assuming that the inside of the contour is water, and scatter projection data (scattering sinogram) is created from the probability.

  Since the parallel display and the superimposed display of the second embodiment are the same as those of the first embodiment, the description thereof is omitted. The operation and effect of the opening 2a (see FIG. 1 (a)) of the second embodiment are also the same as those of the first embodiment described above, and a description thereof will be omitted.

Next, Embodiment 3 of the present invention will be described with reference to the drawings.
FIG. 10 is a block diagram of a mammo PET apparatus according to the third embodiment. About the structure which is common in Example 1, 2 mentioned above, while attaching | subjecting the same code | symbol, the description is abbreviate | omitted and illustration is abbreviate | omitted.

  In the first embodiment described above, the absorption correction is performed using the optically photographed three-dimensional image, and in the second embodiment described above, the scattering correction is performed using the optically photographed three-dimensional image. On the other hand, in the third embodiment, body motion correction is performed using a three-dimensional image that has been optically photographed.

  A mammo PET apparatus 1 (see FIG. 1) includes a top plate 2 (see FIG. 1), a detector 3 (see FIG. 1), and a breast examination gantry 4 (see FIG. 1) similar to those of the first and second embodiments. And a base 5 (see FIG. 1). As shown in FIG. 10, the mammo PET apparatus 1 includes a coincidence circuit 6, an image processing unit 7, a controller 8, a memory unit 9, an input unit 10, a monitor 11, and a 3D scanner 12 similar to those in the first and second embodiments. And. Furthermore, in the third embodiment, the mammo PET apparatus 1 includes a change amount calculation unit 35 and a body motion correction unit 36. The coincidence circuit 6 corresponds to the inspection data generation means in the present invention, the image processing unit 7 of the third embodiment corresponds to the reconstruction means in the present invention, and the controller 8 includes the parallel display control means in the present invention and The 3D scanner 12 corresponds to the superimposing display control means, the optical imaging means in the present invention, the change amount calculation unit 35 corresponds to the change amount calculation means in the present invention, and the body motion correction unit 36 corresponds to the present invention. This corresponds to the body motion correcting means.

  The change amount calculation unit 35 uses the outline of the three-dimensional image acquired by the 3D scanner 12 to calculate a temporal change amount associated with body movement. The body motion correction unit 36 corrects the body motion of the examination data (sinogram) using the change amount obtained by the change amount calculation unit 35. The change amount calculation unit 35 and the body motion correction unit 36 are configured by a CPU or programmable device similar to the controller 8 or a GPU similar to the image processing unit 7. Specific functions of the change amount calculation unit 35 and the body motion correction unit 36 will be described in detail later.

  Next, a series of image processing including body movement correction according to the third embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart of a series of image processing including body movement correction according to the third embodiment, and FIG. 12A is a schematic diagram of breast images before and after body movement related to parallel movement, and FIG. ) Is a schematic diagram of each breast image before and after body movement related to rotational movement. As in Embodiments 1 and 2 described above, it will be described that the preparation for breast imaging has already been completed.

(Step S21) Optical Photography Step S21 in FIG. 11 is the same as step S1 in the first embodiment described above and step S11 in the second embodiment described above, and therefore description thereof is omitted. However, unlike the first and second embodiments described above, in the third embodiment, optical imaging by the 3D scanner 12 (see FIGS. 1 and 2) is continued until reconstruction in step S23 described later is completed. Thus, the controller 8 (see FIG. 10) confirms whether or not a temporal change accompanying the body movement has occurred. In the third embodiment, a three-dimensional image of the breast acquired by the 3D scanner 12 is sent to the change amount calculation unit 35 (see FIG. 10) via the controller 8. Further, a three-dimensional image of the breast is also sent to the memory unit 9 (see FIG. 10) via the controller 8.

(Step S22) Generation of Inspection Data Step S22 in FIG. 11 is the same as step S3 in the first embodiment described above and step S13 in the second embodiment described above, and thus description thereof is omitted.

(Step S23) Reconstruction The image processing unit 7 (see FIG. 10) obtains a PET image that is a reconstructed image by reconstructing while accumulating examination data. Unlike the first and second embodiments described above, in the third embodiment, reconstruction by the image processing unit 7 is continued until the controller 8 determines that reconstruction has been completed in step S26 described later.

(Step S24) Body movement?
The controller 8 determines whether body movement has occurred in the breast of the subject M (see FIG. 1A). When the controller 8 determines that no body movement has occurred, the process proceeds to step S26, and when the controller 8 determines that body movement has occurred, the process proceeds to step S25. Since the body movement is limited to some extent at the opening 2a (see FIG. 1A), it will be described here as parallel movement, rotational movement, or a combination thereof for convenience of explanation.

(Step S25) Body Movement Correction When the controller 8 determines that body movement has occurred in step S24, the change amount calculation unit 35 uses the contour of the 3D image acquired by the 3D scanner 12 to perform body movement. The amount of change with time is calculated. Similar to the first and second embodiments described above, by binarizing the three-dimensional image of the breast acquired by the 3D scanner 12 by the threshold processing, the contour in the breast and the inside of the contour are “1”, the contour in the breast Is preferably set to “0”.

A breast image at a certain tomographic plane is acquired using a three-dimensional image of the breast after binarization processing. Motion by, as shown in FIG. 12 (a), the breast image P ₁₂ after body movement in the tomographic plane which is translated relative to the breast image P ₁₁ before the body motion in a certain tomographic plane is outputted. Assuming that the mapping conversion by translation is f ₁ , the change amount calculation unit 35 obtains the mapping conversion f ₁ . The mapping transformation f ₁ obtained by the change amount calculation unit 35 is sent to the body motion correction unit 36 (see FIG. 10) via the controller 8. By applying the inverse mapping transformation f ₁ ⁻¹ to the LOR inspection data orthogonal to the tomographic plane, the body motion correction unit 36 corrects the body motion of the LOR inspection data orthogonal to the tomographic plane. Here, LOR (Line Of Response) is a virtual line connecting two detectors that simultaneously count.

Similarly, the body movement, as shown in FIG. 12 (b), breast image P ₁₄ after body movement in the tomographic plane which is rotated and moved relative to the breast image P ₁₃ before the body motion in a certain tomographic plane is outputted Suppose. When mapping conversion by rotational movement and f _2, the change amount calculating unit 35 obtains the mapping transform f _2. The mapping conversion f ₂ obtained by the change amount calculation unit 35 is sent to the body motion correction unit 36 via the controller 8. The body motion correction unit 36 corrects the body motion of the LOR inspection data orthogonal to the tomographic plane by applying the inverse mapping transformation f ₂ ⁻¹ to the LOR inspection data orthogonal to the tomographic plane. In order to correct body motion more accurately, it is preferable to obtain mapping transformations on a plurality of different tomographic planes and to perform inverse mapping transformation on LOR inspection data orthogonal to the corresponding tomographic planes. The inspection data after the body movement correction is sent to the image processing unit 7 and the controller 8. Then, the process proceeds to step S26.

(Step S26) Is reconstruction complete?
When the controller 8 determines that body movement has occurred in step S24, the image processing unit 7 reconstructs the inspection data after the body movement correction by the body movement correction unit 36. If the controller 8 determines in step S24 that no body movement has occurred, the image processing unit 7 reconstructs the inspection data before the body movement correction. The controller 8 determines whether or not the reconstruction by the image processing unit 7 is completed. If the controller 8 determines that the reconfiguration has not been completed, the process returns to step S23, and steps S23 to S26 are looped and repeated until the controller 8 determines that the reconfiguration has been completed. If the controller 8 determines that the reconfiguration has been completed, the process proceeds to step S27. The PET image is sent to the memory unit 9 via the controller 8. Then, the PET image is written and stored in the memory unit 9.

(Step S27) Display on Monitor Since step S27 in FIG. 11 is the same as step S5 in the first embodiment described above and step S15 in the second embodiment described above, description thereof is omitted. However, when displaying a three-dimensional image of the breast obtained by optical imaging, a three-dimensional image of the breast before body movement or a three-dimensional image obtained by reconstructing a breast image after body movement correction is used.

  According to the mammo PET apparatus 1 according to the third embodiment, the detector 3 detects the radiation generated from the radiopharmaceutical in the subject M, and the coincidence circuit 6 uses the radiation detected by the detector 3 to obtain the inspection data. (In each embodiment, a sinogram) is generated. On the other hand, the optical imaging means (3D scanner 12 in each embodiment) optically images a subject M (a breast in this embodiment 3) (a subject of nuclear medicine diagnosis) to obtain a three-dimensional image of the breast. Using the contour of the three-dimensional image acquired by the optical photographing means (3D scanner 12), the change amount calculation unit 35 calculates a temporal change amount (mapping conversion in the third embodiment) accompanying the body movement. Then, the body motion correction unit 36 corrects the body motion of the examination data (sinogram) using the change amount (mapping conversion) obtained by the change amount calculation unit 35. As described in the above-described absorption correction in the first embodiment and the scattering correction in the second embodiment, the outline of the three-dimensional image acquired by the optical imaging unit (3D scanner 12) is not affected by the distribution of the radiopharmaceutical. Furthermore, the distribution of the radiopharmaceutical varies with time, but the contour of the three-dimensional image acquired by the optical imaging means (3D scanner 12) does not vary with time except for body movement. In other words, if there is a change in the contour of the three-dimensional image, the amount of change due to the change is considered to be due to body movement. Therefore, the temporal change amount (mapping conversion) accompanying the body movement is calculated using the contour of the three-dimensional image photographed by the optical photographing means (3D scanner 12) without using the CT image or the MRI image, By using the amount of change (mapping conversion), body movement correction can be performed accurately even when the radiopharmaceutical is not distributed over the entire imaging region.

  Similar to the first and second embodiments described above, in this third embodiment, the imaging region is the breast. Since the parallel display and the superimposed display of the third embodiment are the same as those of the first and second embodiments, the description thereof is omitted. Further, since the operation and effect of the opening 2a (see FIG. 1A) of the third embodiment are also the same as those of the first and second embodiments, the description thereof is omitted.

Next, Embodiment 4 of the present invention will be described with reference to the drawings.
FIG. 13A is a schematic side view of the head PET device according to the fourth and fifth embodiments when the rail is provided, and FIG. 13B is a fourth embodiment when the rail is not provided. FIG. 14 is a schematic side view of such a head PET apparatus, and FIG. 14 is a block diagram of the head PET apparatus according to the fourth embodiment. In Example 4, including Example 5 described later, a head PET apparatus will be described as an example of a dedicated nuclear medicine diagnostic apparatus in which the imaging region is the head. FIG. 13 shows a configuration common to the fourth and fifth embodiments.

  As shown in FIG. 13A, the head PET device 41 receives a top plate 42 for placing the subject M on a horizontal surface in a supine position, and radiation (photons) generated from the radiopharmaceutical in the subject M. A head inspection gantry 44 on which the detector 3 to be detected is mounted, and a base 45 that supports the top plate 42 is provided. In addition, the head PET device 41 includes a coincidence circuit 6 (see FIG. 14), an image processing unit 7 (see FIG. 14), and a controller 8 (see FIG. 14) similar to those in the first to third embodiments. A memory unit 9 (see FIG. 14), an input unit 10 (see FIG. 14), a monitor 11 (see also FIG. 14), and an optical imaging gantry 46 (see also FIG. 14). Furthermore, in the fourth embodiment, the head PET device 41 includes an absorption coefficient map creation unit 47 (see FIG. 14). The coincidence circuit 6 corresponds to the inspection data generation means in the present invention, the image processing unit 7 of the fourth embodiment corresponds to the absorption correction means and the reconstruction means in the present invention, and the controller 8 corresponds to the parallel in the present invention. The optical imaging gantry 46 corresponds to display control means and superimposed display control means, the optical imaging gantry 46 corresponds to the optical imaging means in the present invention, and the absorption coefficient map creation unit 47 corresponds to the absorption coefficient map creation means in the present invention.

  The head inspection gantry 44 includes a ring-shaped housing 44 a that houses a plurality of detectors 3 arranged so as to surround the body axis of the subject M. The optical imaging gantry 46 optically captures the head of the subject M and acquires a three-dimensional image of the head. The optical imaging gantry 46 includes a light source 46a that irradiates infrared light and a camera 46b that performs optical imaging by detecting radiated light from the head. The light source 46a and the camera 46b are configured to rotate around the body axis of the subject M, and acquire a three-dimensional image of the head by optically photographing the light source 46a and the camera 46b while rotating. The head inspection gantry 44 and the optical imaging gantry 46 are provided so that the center of the housing 44a accommodating the detector 3 and the centers of the rotation paths of the light source 46a and the camera 46b coincide. A specific function of the optical photographing gantry 46 will be described later in detail.

  In the fourth embodiment, including the fifth embodiment described later, the base 45 is configured to move the top plate 42 up and down in the vertical direction, and the head of the subject M placed on the top plate 42. Is moved up and down to coincide with the center of the housing 44a of the head inspection gantry 44 and the center of the light source 46a of the optical imaging gantry 46 and the center of the rotation trajectory of the camera 46b. .

  As shown in FIG. 13A, the head inspection gantry 44 is moved together with the detector 3 and the housing 44a only on the rail R installed on the floor surface. The optical photographing gantry 46 is moved only on the rail R together with the light source 46a and the camera 46b. In addition, since the imaging | photography with the head test | inspection gantry 44 is performed after the optical imaging | photography with the optical imaging gantry 46, the optical imaging | photography gantry 46 is arrange | positioned in front of the subject M, and the head inspection gantry 44 is in the back of the subject M. It is arranged adjacent to the optical photographing gantry 46. The head R is designed so that the rail R is positioned directly below the central axis of the top plate 42 along the body axis of the subject M. As described in the first embodiment, the head inspection gantry 44 only on the rail R is used. By moving the optical imaging gantry 46, the top plate 42, the head inspection gantry 44, and the optical imaging gantry 46 are geometrically limited, so that the subject M and the apparatus can be properly aligned. it can.

  Specifically, first, the head inspection gantry 44 and the optical imaging gantry 46 are located away from the subject M, and the operator visually confirms that the subject M is placed on the top 42 in the supine position. After the confirmation, the head of the subject M coincides with the center of the casing 44a of the head inspection gantry 44, and coincides with the centers of the rotation paths of the light source 46a and the camera 46b of the optical imaging gantry 46. The top plate 42 is moved up and down in the vertical direction. Then, each gantry 44, 46 is moved on the rail R so as to be close to the head of the subject M. The movement of each gantry 44, 46 is movement in one direction (horizontal movement on the rail R), and the movement distance is determined. Therefore, as shown in FIG. 13A, it can be easily operated from the operation panel 10a of the input unit 10 (see FIG. 14) or the like at a position away from the subject M.

  In FIG. 13A, the rail R is provided. However, as shown in FIG. 13B, the rail 42 is not provided. You may move horizontally along the body axis. That is, in FIG. 13A, only the gantry 44, 46 is moved while the top plate 42 is fixed, and the alignment is performed. However, in FIG. Only the plate 42 is moved for alignment. In the case of FIG. 13B, as in FIG. 13A, after the operator visually confirms that the subject M has been placed on the top 42 in the supine position, The top 42 is moved up and down so that the head coincides with the center of the housing 44a of the head inspection gantry 44 and coincides with the centers of the light source 46a and the camera 46b of the optical imaging gantry 46. Let Then, the top 42 is horizontally moved along the body axis of the subject M with respect to the base 45 so that the head of the subject M is brought close to the gantry 44 and 46.

  Moreover, you may combine the structure of Fig.13 (a) and the structure of FIG.13 (b). Further, as described in the first embodiment, a sensor or a contact sensor for detecting that a load is applied to the top plate 42 is installed on the top plate 42, or an optical image obtained by an optical camera is subjected to image processing. May be. It is preferable to control each gantry 44, 46 or the top plate 42 to move only when the subject M is placed on the top plate 42.

  A subject M to which a radiopharmaceutical has been administered in advance is placed on the couchtop 42 in a supine position. In order to image the head of the subject M, the operator visually confirms that the subject M has been placed on the top 42 in the supine position, and then the top 42 is moved up and down. After the head of the subject M coincides with the center of the housing 44a of the optical imaging gantry 46 of the head inspection gantry 44 and the center of the rotation trajectory of the light source 46a and the camera 46b, the top plate is as shown in FIG. Only the gantry 44, 46 is moved with the 42 being fixed, or only the top plate 42 is moved with the gantry 44, 46 being fixed as shown in FIG. The optical photographing gantry 46 is set so that the head is positioned, and optical photographing by the optical photographing gantry 46 is performed.

  After the optical imaging is completed, the head inspection gantry 44 is set so that the head is positioned, and imaging by the head inspection gantry 44 is performed. Specifically, the photon from the head set in the head inspection gantry 44 is counted by the detector 3 and sent to the coincidence circuit 6 (see FIG. 14) only when the photon is simultaneously counted. As a result, the head set in the head inspection gantry 44 is photographed.

  Next, as shown in FIG. 14, the coincidence data simultaneously counted by the coincidence circuit 6 is collected (generated) as inspection data including a sinogram as in the first embodiment. The generated inspection data is sent to the image processing unit 7 and the controller 8, and the image processing unit 7 reconstructs while accumulating the inspection data, thereby acquiring a PET image which is a reconstructed image. In the fourth embodiment, similarly to the first embodiment described above, using the absorption coefficient map (for example, absorption coefficient sinogram) created by the absorption coefficient map creating unit 47, the inspection data (sinogram) is reconstructed and corrected for absorption. .

  The absorption coefficient map creation unit 47 assumes an absorption coefficient value inside the contour of the three-dimensional image acquired by the optical imaging gantry 46, and creates an absorption coefficient sinogram representing the distribution of the assumed absorption coefficient value. To do. The absorption coefficient map creation unit 47 is configured by a CPU or programmable device similar to the controller 8 or a GPU similar to the image processing unit 7. A specific function of the absorption coefficient map creation unit 47 will be described later in detail.

  Next, a series of image processing including absorption correction according to the fourth embodiment will be described with reference to FIGS. 15 and 16. FIG. 15A is a flowchart of a series of image processing including absorption correction according to the fourth embodiment, FIG. 15B is a flowchart regarding creation of an absorption coefficient sinogram, and FIG. 16 shows each model data. It is a schematic diagram with which it uses for description regarding the deformation | transformation of. Note that the head of the subject M (see FIG. 13) to which the radiopharmaceutical was administered in advance has already been set in the optical imaging gantry 46 (see FIGS. 13 and 14), and preparation for imaging of the head has already been completed. It will be described as being.

(Step S31) Optical Imaging The light source 46a (see FIG. 13) of the optical imaging gantry 46 irradiates the head with infrared light from the light source 46a while rotating around the body axis of the subject M. In synchronization with the rotational movement of the light source 46a around the body axis, the camera 46b of the optical imaging gantry 46 performs optical imaging by detecting the emitted light from the head while rotating around the body axis. Then, a three-dimensional image of the head is acquired by optical imaging accompanying rotational movement around the body axis. The three-dimensional image of the head acquired by the optical imaging gantry 46 is sent to the absorption coefficient map creating unit 47 (see FIG. 14) via the controller 8 (see FIG. 14). Further, the three-dimensional image of the head is also sent to the memory unit 9 (see FIG. 14) via the controller 8.

(Step S32) Creation of absorption coefficient sinogram The absorption coefficient map creation unit 47 assumes an absorption coefficient value inside the contour of the three-dimensional image acquired by the optical imaging gantry 46, and each of the assumed absorption coefficient values. Create an absorption coefficient sinogram representing the distribution. As in the first to third embodiments described above, by binarizing the three-dimensional image of the head acquired by the optical imaging gantry 46 by threshold processing, the contour of the head and the inside of the contour are “1”, It is preferable to set the outside of the contour of the head to “0”. FIG. 15B is a more specific example of step S32 (generation of absorption coefficient sinogram) in FIG. Hereinafter, a description will be given with reference to FIG.

  In Examples 1 to 3 described above, the imaging region of the subject is the breast, but in Example 4, including Example 5 described later, the imaging region of the subject is the head. When the imaging region is a breast as in the first to third embodiments, the inside of the contour is assumed to be water and the water absorption coefficient value is uniformly determined. However, as in the fourth embodiment, the imaging region is determined. When the head is the head, it is determined by combining the air absorption coefficient value, the brain tissue absorption coefficient value, and the bone absorption coefficient value.

  Only the contour information cannot determine which part of the head corresponds to air, brain tissue, or bone. Therefore, in order to specify the inside of the head, the face information model, the skeleton model, the dentition model, and the like of the subject obtained in advance are combined with the contour information. At this time, it is preferable to prepare each model for each age, sex, and race. A model (such as a face surface model, a skeleton model, or a dentition model) corresponding to the age, sex, or race is selected from the subject to be imaged.

(Step S33) Does the contour of the head match the selected face surface layer model?
The controller 8 determines whether or not the contour of the head matches the selected face surface layer model. When the controller 8 determines that the contour of the head matches the selected face surface model, the process proceeds to step S34. When the controller 8 determines that the contour of the head does not match the selected face surface model, Proceed to step S36.

(Step S34) Determination of each position When the controller 8 determines in step S33 that the contour of the head matches the selected face surface model, by selecting the skeleton model, the dentition model, etc. The skeleton position corresponding to the skeleton inside the contour and the dentition position corresponding to the dentition inside the contour are respectively determined.

(Step S35) Assignment of each absorption value Then, a bone absorption value is assigned to the skeleton position and the dentition position, and an absorption coefficient value of water or air is assigned to a position other than the skeleton position / dentation position and the face surface layer position. A map representing the distribution of the bone resorption coefficient values and the water or air absorption coefficient values assigned to each position is created as an absorption coefficient sinogram. Refer to References 3 to 6 for a method for specifying the internal structure of a contour by combining a facial surface model, a skeleton model, a dentition model, and the like of a subject obtained in advance with contour information (Reference 3). : Special table 2004-512919, Reference 4: JP 2003-044873 A, Reference 5: Kijima Kiyoshi, three others, “skeletal extraction from MRI images and high-fidelity skeletal and joint motion capturing”, Information Processing Society of Japan Research Report, 2005/3/4, 2005-CV IM-148 (13), p. 101-108, Reference 6: Sadahiro Kan, “Feature Point Extraction from 3D Human Body Scan Data “Applications”, Keio University Graduate School of Science and Engineering, Department of Open Environmental Science, 2008, p.21-25). The absorption coefficient sinogram created by the absorption coefficient map creation unit 47 is sent to the memory unit 9 via the controller 8. Then, the absorption coefficient sinogram is written and stored in the memory unit 9.

(Step S36) Deformation of the selected model When the controller 8 determines in step S33 that the contour of the head does not match the selected face surface model, as shown in FIG. 16, the selected face surface layer is selected. model _{S 10} in accordance with the contour _{S 0} of the head is deformed. When mapping conversion by deformation and _{f 3,} by performing mapping transform _{f 3} to the face surface model _{S 10,} to the face surface model _{S 10} in accordance with the contour _{S 0} of the head is deformed to _{S 20.} Similarly, the skeleton model S ₁₁ and dentition model S ₁₂ at that time is also deformed to fit the contour S ₀ of the head. By performing skeleton model _{S 11} and dentition model _{S 12} to the mapping transform _{f 3,} respectively, thereby to fit the contour _{S 0} of the head deforming the skeleton model _{S 11} and dentition model _{S 12} to _{S 21, S 22} . Then, the process returns to step S34.

In performing step S34, S35 after the deformation in step S36, it determines deformed skeleton position corresponding to the skeleton model S ₂₁ and deformed dentition position corresponding to the dentition model S _22, respectively. Then, bone resorption values are assigned to the skeleton position and the dentition position, water or air absorption coefficient values are assigned to positions other than the skeleton position / dentition position and the face surface layer position, and assigned to each position. A map representing the distribution of the absorption coefficient value of bone and the absorption coefficient value of water or air is created as an absorption coefficient sinogram. In the following, description will be given returning to FIG.

(Step S37) Generation of Examination Data Subsequently, the detector 3 detects radiation (photons) generated from the radiopharmaceutical in the head of the subject M, and is simultaneously counted by the coincidence counting circuit 6 (see FIG. 14). The coincidence data is collected (generated) as inspection data consisting of a sinogram. The generated inspection data is sent to the image processing unit 7 (see FIG. 14) and the controller 8.

(Step S38) Absorption Correction / Reconstruction Step S38 in FIG. 15A is the same as step S4 in the first embodiment described above, and a description thereof will be omitted.

(Step S39) Display on Monitor Since step S39 in FIG. 15A is the same as step S5 in the first embodiment, the description thereof is omitted. However, in Examples 1 to 3 described above, the imaging region of the subject is the breast, whereas in Example 4, including Example 5 described later, the imaging region of the subject is the head. Therefore, the three-dimensional image of the head obtained by optical imaging and the PET image are arranged on the same monitor 11 (see FIGS. 13 and 14) for display control (parallel display control), or the head obtained by optical imaging. Display control (superimposition display control) is performed by superimposing the three-dimensional image of the part and the PET image.

  In the first embodiment described above, the imaging region of the subject is the breast, whereas in this fourth embodiment, the imaging region of the subject is the head, except for the head PET according to the fourth embodiment. Since the operations and effects relating to the absorption correction of the device 41 are the same as those in the first embodiment, the description thereof will be omitted.

  In the fourth embodiment, the imaging part is the head. When the imaging region is the head as in the fourth embodiment, the absorption correction is performed by combining the air absorption coefficient value, the brain tissue absorption coefficient value, and the bone absorption coefficient value. In the case of brain tissue, since it is regarded as an area that can be approximated by water, the absorption coefficient value of water is used. Specifically, from the model data composed of the face surface model, skeleton model, and dentition model of the subject M obtained in advance, the face surface layer position corresponding to the contour face surface layer, and the skeleton position corresponding to the skeleton inside the contour And the dentition position corresponding to the dentition in the inside of the contour is determined. Then, bone resorption values are assigned to the skeleton position and the dentition position, water or air absorption coefficient values are assigned to positions other than the skeleton position / dentition position and the face surface layer position, and assigned to each position. A map representing the distribution of the absorption coefficient value of bone and the absorption coefficient value of water or air is created as an absorption coefficient map (an absorption coefficient sinogram in the fourth embodiment). As described above, the absorption coefficient value of water (absorption coefficient value of brain tissue) is known, the absorption coefficient value of bone and the absorption coefficient value of air are also known, and the face surface model of the subject M obtained in advance. By using model data composed of a skeletal model and a dentition model and assigning a bone absorption coefficient value and a water or air absorption coefficient value to each position, the absorption correction can be easily performed.

  Since the parallel display and the superimposed display of the fourth embodiment are the same as those of the first to third embodiments, description thereof is omitted.

Next, Embodiment 5 of the present invention will be described with reference to the drawings.
FIG. 17 is a block diagram of a head PET apparatus according to the fifth embodiment. Constituent elements common to the above-described fourth embodiment are denoted by the same reference numerals, description thereof is omitted, and illustration is omitted.

  In Example 4 described above, the absorption correction was performed using a three-dimensional image that was optically photographed. On the other hand, in the fifth embodiment, scattering correction is performed using a three-dimensional image optically photographed.

  The head PET device 41 (see FIG. 13) includes a top plate 42 (see FIG. 13), a detector 3 (see FIG. 13), and a head inspection gantry 44 (see FIG. 13) similar to those in the fourth embodiment. And a base 45 (see FIG. 13). As shown in FIG. 17, the head PET device 41 includes a coincidence circuit 6, an image processing unit 7, a controller 8, a memory unit 9, an input unit 10, a monitor 11, and an optical imaging gantry 46, which are the same as those in the fourth embodiment. And. Furthermore, in the fifth embodiment, the head PET apparatus 41 includes a scatter projection data creation unit 51. The coincidence circuit 6 corresponds to the inspection data generation means in the present invention, the image processing unit 7 of the fifth embodiment corresponds to the scattering correction means and the reconstruction means in the present invention, and the controller 8 corresponds to the parallel in the present invention. The optical imaging gantry 46 corresponds to display control means and superimposed display control means, the optical imaging gantry 46 corresponds to optical imaging means in the present invention, and the scattered projection data creation unit 51 corresponds to scattered projection data creation means in the present invention.

  In the fifth embodiment, similarly to the second embodiment described above, using the scatter projection data (for example, scatter sinogram) created by the scatter projection data creation unit 51, the inspection data (sinogram) is reconstructed and scatter correction is performed.

  The scatter projection data creation unit 51 simulates the probability that is the ratio of the number of radiation detected by scattered radiation to the total number of radiation events in the model data imitating the contour of the three-dimensional image acquired by the optical imaging gantry 46. The scattering sinogram representing the distribution of scattered radiation is obtained from the probability. The scattered projection data creation unit 51 is configured by a CPU or programmable device similar to the controller 8 or a GPU similar to the image processing unit 7. A specific function of the scattered projection data creation unit 51 will be described later in detail.

  Next, a series of image processing including scattering correction according to the fifth embodiment will be described with reference to FIG. FIG. 18A is a flowchart of a series of image processing including scattering correction according to the fifth embodiment, and FIG. 18B is a flowchart regarding creation of a scattering sinogram. As in the above-described fourth embodiment, it is assumed that the preparation for photographing the head has already been completed.

(Step S41) Optical Photography Step S41 in FIG. 18A is the same as step S31 in the above-described fourth embodiment, and a description thereof will be omitted. In the fifth embodiment, a three-dimensional image of the head acquired by the optical imaging gantry 46 (see FIGS. 13 and 17) is converted into a scatter projection data creation unit 51 (see FIG. 17) via the controller 8 (see FIG. 17). 17). Further, the three-dimensional image of the head is also sent to the memory unit 9 (see FIG. 17) via the controller 8.

(Step S <b> 42) Scattering sinogram creation The scatter projection data creation unit 51, in model data imitating the outline of a three-dimensional image acquired by the optical imaging gantry 46, detects the number of radiation detected by scattered radiation with respect to the total number of radiation events. The probability that is the ratio of the above is obtained by simulation, and a scattering sinogram representing the distribution of scattered radiation is created from the probability. As in the first to fourth embodiments described above, by binarizing the three-dimensional image of the head acquired by the optical imaging gantry 46 by threshold processing, the contour of the head and the inside of the contour are “1”, It is preferable to set the outside of the contour of the head to “0”. FIG. 18B is a more specific example of step S42 (creation of a scattering sinogram) in FIG. Hereinafter, a description will be given with reference to FIG.

  In Examples 1 to 3 described above, the imaging region of the subject is the breast, but in Example 5 as in Example 4 described above, the imaging region of the subject is the head. Therefore, when the imaging region is the breast as in Example 2 and the scatter correction is performed, the probability is obtained by simulation in the model data assuming that the inside of the contour is water, and a scatter sinogram is created from the probability. On the other hand, when the imaging region is the head and scatter correction is performed as in the fifth embodiment, the face surface layer model, skeleton model, and dentition of the subject obtained in advance as in the fourth embodiment. The inside of the head is specified by combining the model and the contour information.

  Specifically, from the model data consisting of the face surface model, skeleton model and dentition model of the subject obtained in advance, the face surface layer position corresponding to the contour face surface layer, the skeleton position corresponding to the skeleton inside the contour, and The model data simulating the contour is reconstructed by determining the dentition position corresponding to the dentition in the contour. For this purpose, as described in the fourth embodiment, a model (such as a face surface model, a skeleton model, or a dentition model) corresponding to age, sex, or race is selected from the subject to be imaged.

(Step S43) Does the contour of the head match the selected face surface layer model?
Since step S43 in FIG. 18B is the same as step S33 in the fourth embodiment described above, description thereof is omitted.

(Step S44) Determination of Each Position Step S44 in FIG. 18B is the same as step S34 in the above-described fourth embodiment, and therefore description thereof is omitted.

(Step S45) Assignment of each absorption value Then, the bone absorption value is assigned to the skeleton position and the dentition position, and the water or air absorption coefficient value is assigned to the position other than the skeleton position / dentation position and the face surface layer position. The map representing the distribution of the bone resorption coefficient value and the water or air resorption coefficient value assigned to each position is used as the reconstructed model data. A probability is obtained by simulation in the reconstructed model data, and a scattering sinogram is created from the probability. As described in the second embodiment, for example, a scattered ray model (see FIG. 8) used in the ESSE method for obtaining a scattered ray component by applying Monte Carlo simulation is replaced with reconstructed model data.

  The method of obtaining the probability by the ESSE method in the reconstructed model data is omitted because the water absorber in Example 2 is simply replaced with the reconstructed model data. The scattering component in the projection data estimated by the ESSE method is created as a scattering sinogram. The scatter sinogram created by the scatter projection data creation unit 51 is sent to the memory unit 9 via the controller 8. Then, the scattering sinogram is written and stored in the memory unit 9.

(Step S46) Deformation of the selected model Step S46 in FIG. 18B is the same as step S36 in the above-described fourth embodiment, and a description thereof will be omitted. Hereinafter, the description will be made with reference back to FIG.

(Step S47) Generation of Inspection Data Step S47 in FIG. 18A is the same as step S37 in the above-described fourth embodiment, and thus description thereof is omitted.

(Step S48) Scattering Correction / Reconstruction Step S48 in FIG. 18A is the same as step S14 in the second embodiment described above, and a description thereof will be omitted.

(Step S49) Display on Monitor Since step S49 in FIG. 18A is the same as step S39 in the above-described fourth embodiment, description thereof is omitted.

  In the second embodiment described above, the imaging region of the subject is the breast. In this fifth embodiment, except that the imaging region of the subject is the head, the head PET according to the fifth embodiment. Since the operations and effects relating to the scattering correction of the device 41 are the same as those in the second embodiment described above, the description thereof is omitted.

  In the fifth embodiment, the imaging part is the head. When the imaging site is the head as in the fifth embodiment, the face surface layer position corresponding to the contour face surface layer is obtained from model data including the face surface model, skeleton model, and dentition model of the subject obtained in advance. The model data imitating the contour is reconstructed by determining the skeleton position corresponding to the skeleton inside the contour and the dentition position corresponding to the dentition inside the contour. In the reconstructed model data, a probability is obtained by simulation (Monte Carlo simulation), and scattering projection data (scattering sinogram) is created from the probability.

  Since the parallel display and the superimposed display of the fifth embodiment are the same as those of the first to fourth embodiments, the description thereof is omitted.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In each of the above-described embodiments, the PET apparatus has been described as an example of the nuclear medicine diagnosis apparatus. However, the present invention is also applied to a SPECT (Single Photon Emission CT) apparatus that detects a single radiation. be able to.

  (2) In each of the above-described embodiments, the data format is a sinogram, but is not limited to a sinogram. If it is projection data, for example, the data format may be a histogram. Therefore, in Examples 1 and 4 described above, the absorption coefficient map is an absorption coefficient sinogram, but the absorption coefficient map may be an absorption coefficient histogram. Further, in the above-described Examples 2 and 5, the scatter projection data is a scatter sinogram, but the scatter projection data may be a scatter histogram.

  (3) In Examples 1 to 3 described above, the imaging region of the subject was the breast, and in Examples 4 and 5 described above, the imaging region of the subject was the head. As described in the section of “Means”, the imaging region is not particularly limited. However, the imaging target is preferably a local part such as a breast or a head. When the imaging region is the head as in the fourth and fifth embodiments described above, the absorption correction of the fourth embodiment is performed by combining the face surface layer model, the skeleton model, the dentition model, and the like of the subject obtained in advance with the contour. Or the scattering correction of the fifth embodiment. The body motion correction of the third embodiment may be applied to the head.

  (4) In the first to third embodiments described above, as shown in FIGS. 1 (a) and 1 (b), a plurality of detectors 3 are accommodated in a ring-shaped casing 4a so as to surround the breast. In the fourth and fifth embodiments described above, as shown in FIG. 13, the plurality of detectors 3 are accommodated in the ring-shaped housing 44a so as to surround the body axis of the subject M. Is not particularly limited. For example, a compression type in which a mammogram is performed by pressing a breast with a flat plate incorporating a detector.

  (5) In each of the above-described embodiments, the optical photographing means is an optical photographing gantry including a 3D scanner that emits infrared light or a light source that emits infrared light. It is not limited. For example, visible light may be used. However, in the case of irradiating visible light, there is a possibility that light from the outside may be erroneously detected. Therefore, it is preferable to configure surrounding equipment so as to shield the outside. In particular, when the imaging region of the subject is the breast as in the first to third embodiments described above, a casing (gantry) that shields the outside is provided on the floor surface, and the casing (gantry) is provided with the casing shown in FIG. The top plate 2 of a) is mounted. This also has the effect of blocking the breast from the outside and making it difficult to see.

  (6) In Examples 1 to 3 described above, the breast of the subject was photographed in the prone position, and in Examples 4 and 5 described above, the head of the subject was photographed in the supine position. As a structure of the apparatus, it is not always necessary to provide a top plate for placing the subject on a horizontal surface in a lying position. For example, when the breast is photographed by pressing the breast with a flat plate with a built-in detector as in the modification (4), it is performed in the sitting position.

  (7) In Embodiments 1 to 3 described above, the 3D scanner 12 (see FIGS. 1 and 2) is used as an optical imaging unit, and the breast that is the imaging site is irradiated with infrared light, and the radiation emitted from the breast The three-dimensional image of the breast was acquired using the triangulation method, but it is not limited to the 3D scanner for optically photographing the breast. For example, the light source 46a and the camera 46b (both see FIG. 13) that rotate around the body axis of the subject around the head that is the imaging region are applied to the breast as in the fourth and fifth embodiments described above. May be. Specifically, as shown in FIG. 19, the mammo PET apparatus 1 may include a light source 46a and a camera 46b that rotate around the breast.

  (8) In the first to third embodiments described above, the left and right breasts are photographed, but if there are special circumstances, only one breast may be photographed. In addition, the left and right breasts were respectively guided through one opening 2a (see FIG. 1 (a)), and the left breast was guided through the right breast. You may have two openings which guide and pass below.

  (9) In the scattering correction of the second and fifth embodiments described above, the simulation is a Monte Carlo simulation, but is not limited to the Monte Carlo simulation. For example, a single scattering simulation (SSS) method may be used.

  (10) In the above-described scattering correction in the second and fifth embodiments, the inside of the outline of the three-dimensional image acquired by the optical photographing means (the 3D scanner 12 in the second embodiment and the optical photographing gantry 46 in the fifth embodiment) is simulated. In the model data, the probability, which is the ratio of the number of detected radiations with scattered radiation to the total number of radiation events, was obtained by simulation, and from this probability, scattered projection data representing the distribution of scattered radiation was created. As shown in FIG. 5, LOR that crosses the outside of the contour (see the two-dot chain line in FIG. 20) may be due to scattering inside the imaging region, and LOR that crosses the outside of the contour may be excluded.

  (11) The absorption correction, scattering correction, and body movement correction of the above-described embodiments may be combined with each other. Absorption correction, scattering correction, and body motion correction may all be combined, absorption correction and scattering correction may be combined, scattering correction and body motion correction may be combined, or absorption correction and scattering correction may be combined. Also good.

  As described above, the present invention is suitable for a nuclear medicine diagnostic apparatus for imaging a local region such as a breast-only nuclear medicine diagnostic apparatus or a head-only nuclear medicine diagnostic apparatus.

DESCRIPTION OF SYMBOLS 1 ... Mammo PET apparatus 2 ... Top plate 2a ... Aperture 3 ... Detector 6 ... Simultaneous counting circuit 7 ... Reconstruction means 8 ... Controller 12 ... 3D scanner 15, 47 ... Absorption coefficient map creation part 25, 51 ... Scattering projection data Creation unit 35 ... change amount calculation unit 36 ... body motion correction unit 41 ... head PET device 46 ... optical imaging gantry P ₁ ... three-dimensional image of breast (obtained by optical imaging) P ₂ ... PET image M ... subject

Claims (10)

A nuclear medicine diagnostic device,
A detector for detecting radiation generated from a radiopharmaceutical in the subject;
Inspection data generating means for generating inspection data from radiation detected by the detector;
Optical photographing means for optically photographing the subject to obtain a three-dimensional image of the subject;
An absorption coefficient map creating means for assuming an absorption coefficient value inside the contour of the three-dimensional image acquired by the optical photographing means, and creating an absorption coefficient map representing the assumed distribution of the absorption coefficient value;
Using an absorption coefficient map created by the absorption coefficient map creating means, and an absorption correction means for absorbing and correcting the inspection data,
Nuclear medicine diagnostic equipment. A nuclear medicine diagnostic device,
A detector for detecting radiation generated from a radiopharmaceutical in the subject;
Inspection data generating means for generating inspection data from radiation detected by the detector;
Optical photographing means for optically photographing the subject to obtain a three-dimensional image of the subject;
In the model data imitating the inside of the contour of the three-dimensional image acquired by the optical imaging means, a probability that is the ratio of the number of detected radiation by scattered radiation to the total number of events of the radiation is obtained by simulation, and from the probability Scattered projection data creating means for creating scattered projection data representing the distribution of scattered radiation;
Scatter correction means for correcting scatter of the inspection data using the scatter projection data created by the scatter projection data creation means,
Nuclear medicine diagnostic equipment. A nuclear medicine diagnostic device,
A detector for detecting radiation generated from a radiopharmaceutical in the subject;
Inspection data generating means for generating inspection data from radiation detected by the detector;
Optical photographing means for optically photographing the subject to obtain a three-dimensional image of the subject;
A change amount calculating means for calculating a temporal change amount associated with body movement using the contour of the three-dimensional image acquired by the optical photographing means;
Body movement correction means for correcting body movement of the examination data using the amount of change obtained by the change amount calculation means,
Nuclear medicine diagnostic equipment. The nuclear medicine diagnosis apparatus according to claim 1,
When the imaging region of the subject is a breast, the inside of the contour is assumed to be water, and the water absorption coefficient value is uniformly determined, and a map showing the distribution of the water absorption coefficient value is used as the absorption coefficient The map creation means creates the absorption coefficient map.
Nuclear medicine diagnostic equipment. The nuclear medicine diagnosis apparatus according to claim 1,
When the imaging region of the subject is the head, from the model data comprising the subject's face surface model, skeleton model and dentition model obtained in advance, the face surface layer position corresponding to the face surface layer of the contour, The skeleton position corresponding to the skeleton inside the contour and the dentition position corresponding to the dentition inside the contour are respectively determined, and bone resorption values are assigned to the skeleton position and the dentition position, and the skeleton position / tooth Assign a water or air absorption coefficient value to a position other than the row position and the face surface layer position, and a map showing the distribution of the bone absorption coefficient value and the water or air absorption coefficient value assigned to each position. A coefficient map creating means creates the absorption coefficient map.
Nuclear medicine diagnostic equipment. The nuclear medicine diagnosis apparatus according to claim 2,
When the imaging region of the subject is a breast, the probability is obtained by simulation in the model data assuming that the inside of the contour is water, and the scatter projection data creation means creates the scatter projection data from the probability To
Nuclear medicine diagnostic equipment. The nuclear medicine diagnosis apparatus according to claim 2,
When the imaging region of the subject is the head, from the model data comprising the subject's face surface model, skeleton model and dentition model obtained in advance, the face surface layer position corresponding to the face surface layer of the contour, The model data imitating the contour is reconstructed by determining the skeleton position corresponding to the skeleton inside the contour and the dentition position corresponding to the dentition inside the contour, and the reconstructed model The probability in the data is obtained by simulation, and the scattered projection data creating means creates the scattered projection data from the probability.
Nuclear medicine diagnostic equipment. In the nuclear medicine diagnostic apparatus according to any one of claims 1 to 7,
Reconstructing means for generating a reconstructed image by reconstructing the inspection data;
A parallel display control means for displaying the reconstructed image generated by the reconstructing means and the three-dimensional image acquired by the optical photographing means side by side on the same monitor;
Nuclear medicine diagnostic equipment. In the nuclear medicine diagnostic apparatus according to any one of claims 1 to 8,
Reconstructing means for generating a reconstructed image by reconstructing the inspection data;
Superimposing display control means for superimposing and displaying the reconstructed image generated by the reconstructing means and the three-dimensional image acquired by the optical photographing means,
Nuclear medicine diagnostic equipment. In the nuclear medicine diagnostic apparatus according to any one of claims 1 to 9,
When the imaging region of the subject is a breast,
The subject is placed on a horizontal surface in a prone position, and includes a top plate having an opening through which the breast is guided downward,
The opening of the top plate is configured with a size that allows both the left and right breasts to be inserted,
The detector is provided below the opening of the top plate.
Nuclear medicine diagnostic equipment.

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