JP2009178185A - Medical imaging apparatus and medical imaging method - Google Patents

Abstract

In a medical imaging apparatus and a medical imaging method for imaging a mammary gland and a breast while compressing a breast with a compression plate, a mass portion is clarified by imaging an elastic property in a tissue.
The medical imaging apparatus includes an imaging table on which a subject is placed, a compression plate that compresses the subject between the imaging table, and a compression plate movement that moves the compression plate in a vertical direction or a horizontal direction. A pressure plate between the mechanism and first means for generating radiation or ultrasonic waves, detecting radiation that has passed through the subject or ultrasonic waves reflected by the subject and generating a signal; The compression plate moving mechanism is controlled so as to compress the sample in the vertical direction, and the compression plate moving mechanism is controlled so that the compression plate vibrates the subject in the horizontal direction, so that a signal generated by the first means is obtained. And a second means for generating an image signal representing the image of the subject.
[Selection] Figure 1

Description

  The present invention relates to a medical imaging apparatus and a medical imaging method for imaging a mammary gland and a breast while compressing a breast with a compression plate in order to diagnose breast cancer and the like.

  Conventionally, imaging methods using radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.) have been used in various fields, and especially in the medical field, it is the most important for diagnosis. It is one of the means. Radiographs obtained by mammary gland X-rays (X-ray mammography) performed to diagnose breast cancer are useful for detecting calcification, a precursor of cancer, depending on the age of the subject. May be difficult to find calcification. Therefore, it has been studied to make a diagnosis based on both a radiographic image and an ultrasonic image by using radiation and ultrasonic waves in combination. X-ray mammography and ultrasonic imaging each have the following characteristics.

  X-ray mammography is suitable for imaging calcification, which is one of the early symptoms of cancer, and can be detected with high resolution and high sensitivity. In particular, in the case of fat (so-called “fat breast”) in which mammary gland tissue begins to atrophy and is replaced with fat like a postmenopausal woman, more information is obtained by X-ray mammography. However, X-ray imaging has the disadvantage that the ability to detect tissue specificity (tissue properties) is low.

  In addition, in the X-ray image, since the mammary gland exhibits a uniform soft tissue concentration, in the case of a mammary gland in which the mammary gland has developed (so-called “dense breast”) like adolescent to premenopausal women Detecting a tumor becomes difficult. Furthermore, in X-ray mammography, only a two-dimensional image obtained by projecting a three-dimensional subject onto a plane can be obtained. Therefore, even if a tumor is found, information such as the position and size of the tumor in the depth direction is available. It is difficult to grasp.

  On the other hand, ultrasonic imaging can detect tissue specificity (for example, the difference between a cyst and a solid substance) and can also detect lobular cancer. It is also possible to observe an image in real time and generate a three-dimensional image. However, the accuracy of the ultrasonic imaging inspection often depends on the technique of an operator such as a doctor, and the reproducibility is low. In addition, it is difficult to observe minute calcification in an ultrasonic image.

  As described above, since the X-ray mammography examination and the ultrasonic imaging examination have advantages and disadvantages, it is desirable to perform both examinations in order to detect breast cancer with certainty. Since the X-ray mammography examination is performed in a state where the subject (breast) is compressed by the compression plate, in order to make a diagnosis based on the X-ray image and the ultrasonic image of the subject in the same state, ultrasonic imaging is performed. The examination must be performed in the same state as when the X-ray mammography examination is performed, that is, in a state where the subject (breast) is compressed by the compression plate. Furthermore, a medical imaging apparatus that performs imaging of the mammary gland and breast using radiation and ultrasound in combination has been studied.

  As a related technique, Patent Document 1 discloses a mammography apparatus for performing X-ray irradiation and ultrasonic irradiation for detecting the location of a lesion without moving a patient or readjusting the apparatus. Has been. This mammography apparatus includes an X-ray tube, an image receiver configured to receive X-rays emitted from the X-ray tube, an ultrasonic probe that can be manually moved by a user, and an X-ray It is provided between the tube and the receiver, and includes a compression plate that is transparent to X-rays and ultrasonic waves, and an ultrasonic probe position sensor for the apparatus. According to the mammography apparatus disclosed in Patent Document 1, it is possible to acquire corresponding X-ray images and ultrasonic images in one inspection. However, if ultrasound imaging is performed with the breast compressed, there is a demerit that the resolution in the thrust direction is reduced compared to ultrasound imaging under non-compression, so the corresponding X-ray image and ultrasound image can be reduced. Benefits are expected beyond getting.

  Patent Document 2 discloses that a displacement distribution can be estimated corresponding to a lateral displacement, and an elastic coefficient distribution can be reconstructed only from a strain distribution in the ultrasonic beam direction (axial direction). An intended ultrasound diagnostic system is disclosed. This ultrasonic diagnostic system includes an ultrasonic echo signal output unit that outputs an ultrasonic echo signal acquired by an ultrasonic probe that contacts a subject tissue, and an ultrasonic probe before and after compression of the ultrasonic probe with respect to the subject tissue. Orthogonal detection means for generating an envelope signal by orthogonally detecting a sound echo signal, and a correlation coefficient between the envelope signals before and after compression in the axial direction in the two-dimensional correlation window and in the lateral direction orthogonal to the axial direction, respectively. Correlation calculation means for calculating phase information that maximizes the correlation coefficient by calculating for each discrete scanning line by a predetermined value, and for calculating phase difference information between ultrasonic echo signals before and after compression at the position of the position information, and correlation calculation Displacement calculating means for obtaining displacement information in the axial direction and lateral direction in the subject tissue accompanying compression based on the position information and phase difference information obtained by the means, and the axial direction in the subject tissue Displacement information at each point in the horizontal direction and a distortion calculating means for calculating the strain distribution information by spatial differentiation. However, elastography as described in Patent Document 2 can be effectively used only in the vicinity of the epidermis of the subject at present due to the property of obtaining strain distribution information in the subject tissue.

Further, Patent Document 3 discloses MRI (magnetic resonance imaging) aimed at determining mechanical characteristics and / or elastic characteristics regardless of the distance from the surface at any position to be inspected. ) Elastography (magnetic resonance elastography: MRE) in the apparatus is disclosed. This device is a device for determining a mechanical parameter, particularly an elastic parameter, of an inspection object, and a) at least one device for determining a spatial distribution of magnetic particles in at least one inspection region of the inspection object. Means for generating a magnetic field having a spatial profile of magnetic field strength such that a first partial region having a low magnetic field strength and a second partial region having a higher magnetic field strength are generated in at least one examination region; Means for detecting a signal that is influenced by the spatial variation of the particles, in particular in the examination region, depending on the magnetization of the object to be examined, and information on the spatial distribution of the magnetic particles in the examination region, in particular temporally varying A device having means for evaluating the signal, and b) at least in and / or in the vicinity of the inspection area to be inspected. And at least one means for generating a Do least mechanical displacement. However, in the apparatus of Patent Document 3, real-time measurement is difficult due to the nature of MRI, and an electromagnet coil or the like is required, which makes the apparatus expensive and large.
JP 2003-260046 A (first page, FIG. 1) JP 2004-57652 A (page 1-2, FIG. 10) JP 2006-524086 A (1st page)

  Therefore, in view of the above points, the present invention provides a medical imaging apparatus and a medical imaging method for imaging a mammary gland and a breast while compressing a breast with a compression plate. The purpose is to clarify the part.

  In order to solve the above-described problem, a medical imaging apparatus according to one aspect of the present invention includes an imaging table on which a subject is placed, a first surface that presses the subject, and a first surface that faces the first surface. A compression plate that compresses the subject with the imaging table, and a compression plate that is substantially perpendicular to the first surface or a second direction that is substantially parallel to the first surface. A compression plate moving mechanism that moves in a direction, a first means that generates radiation or ultrasonic waves, detects radiation that has passed through the subject or ultrasonic waves reflected by the subject, and generates a signal; The compression plate moving mechanism is controlled so as to compress the subject in the first direction with the imaging table, and the compression plate moving mechanism is controlled so that the compression plate vibrates the subject in the second direction. A second means for generating an image signal representing an image of the subject based on the signal generated by the first means; To Bei.

  In addition, a medical imaging method according to one aspect of the present invention includes an imaging table on which a subject is placed, a first surface that presses the subject, and a second surface that faces the first surface. A compression plate that compresses the subject with the imaging table, and a compression plate that moves the compression plate in a first direction substantially perpendicular to the first surface or a second direction substantially parallel to the first surface. A medical imaging method used in a medical imaging apparatus having a plate moving mechanism, the step of controlling the compression plate moving mechanism so that the compression plate presses the subject in the first direction with the imaging table (a) And (b) controlling the compression plate moving mechanism so that the compression plate vibrates the subject in the second direction, and generating radiation or ultrasonic waves and reflecting by the radiation or subject passing through the subject. Detecting a generated ultrasonic wave to generate a signal (c), and generating a signal in step (c) Based on a signal, comprising the steps (d) to generate an image signal representing an image of the subject.

  According to the present invention, since the subject is imaged such that the subject is vibrated while the subject is compressed between the compression plate and the imaging table, the mass portion can be removed by imaging the elastic properties in the tissue. It can be clarified.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a block diagram showing a configuration of a medical imaging apparatus according to an embodiment of the present invention. The present invention can be applied to all medical imaging apparatuses that image breasts and breasts by irradiating radiation and / or ultrasound while compressing the breast with a compression plate. In the following, radiation is applied to the breast. The function of a radiation mammography device that generates radiation images by detecting radiation that passes through the breast, and generates ultrasound images by transmitting ultrasound to the breast and receiving ultrasound echoes reflected inside the breast A medical imaging apparatus having the function of an ultrasonic diagnostic apparatus will be described. Moreover, although the case where X-rays are used as radiation is described below, α rays, β rays, γ rays, electron beams, ultraviolet rays, and the like can also be used.

  As shown in FIG. 1, the medical imaging apparatus includes an X-ray tube 10, a filter 11, an X-ray detection unit 12 that detects X-rays generated by the X-ray tube 10 and transmitted through the subject 1, and the subject 1. A compression plate 13 for pressing the breast, a compression plate moving mechanism 14 for moving the compression plate 13, a pressure sensor 15 for detecting the pressure applied to the compression plate 13, and a plurality of ultrasonic waves for transmitting and receiving ultrasonic waves. An imaging unit including an ultrasonic probe 16 including an acoustic transducer, a probe moving mechanism 17 that moves the ultrasonic probe 16, and a position sensor 18 that detects the position of the ultrasonic probe 16. Have in.

  Further, the medical imaging apparatus includes a movement control unit 20 that controls the compression plate moving mechanism 14 and the probe moving mechanism 17, a radiation imaging control unit 30, an ultrasonic imaging control unit 40, an image processing unit 50, Display units 61 and 62, console 70, control unit 80, and storage unit 90 are provided.

  FIG. 2 is a side view showing the appearance of the imaging unit of the medical imaging apparatus shown in FIG. As shown in FIG. 2, the imaging unit of the medical imaging apparatus includes an arm unit 2, a base 3 that holds the arm unit 2 movably in the vertical direction (Z-axis direction), and the arm unit 2 on the base 3. It has the axial part 4 to connect. The arm unit 2 is pressed between the X-ray tube 10, the filter 11, the X-ray detection unit 12, the imaging table 19 on which the subject 1 is placed, and the imaging table 19 to compress the subject 1. Plate 13, compression plate moving mechanism 14 for moving compression plate 13, ultrasonic probe 16, and probe movement for moving ultrasonic probe 16 in the X-axis, Y-axis, and Z-axis directions A mechanism 17 is provided.

  The X-ray tube 10 and the filter 11 constitute a radiation generation unit. The X-ray tube 10 generates X-rays when a tube voltage is applied. The filter 11 is made of a material such as molybdenum (Mo) or rhodium (Rh), and selectively transmits a desired wavelength component from among a plurality of wavelength components included in the X-ray generated by the X-ray tube 10. To do. The X-ray detector 12 is a flat panel detector (FPD) that captures an X-ray image by detecting X-rays that have passed through the subject 1 at a plurality of detection points in a two-dimensional region. By irradiating each detection point with X-rays emitted from the X-ray tube 10 and transmitted through the subject 1, a detection signal having a magnitude corresponding to the intensity of the X-rays is output from the X-ray detection unit 12. This detection signal is input to the radiation imaging control unit 30 (FIG. 1) via a cable.

  The compression plate 13 has a compression surface (lower surface in FIG. 2) that compresses the subject 1 along the X-ray irradiation direction, and a surface opposite to the compression surface (upper surface in FIG. 2). . The compression plate 13 is installed in parallel to the imaging table 19, and under the control of the movement control unit 20, the compression plate moving mechanism 14 moves the compression plate 13 in a direction substantially perpendicular to the compression surface (Z-axis direction). ) And / or in a direction substantially parallel to the compression surface (for example, the X-axis direction). The pressure sensor 15 detects the pressure applied to the compression plate 13, and the movement control unit 20 (FIG. 1) controls the compression plate moving mechanism 14 based on the detection result. When the subject (breast) 1 is sandwiched between the compression plate 13 and the imaging table 19, X-ray imaging and ultrasonic imaging are performed with the breast thickness uniform.

  Here, the compression plate 13 needs to be optically transparent in order to perform alignment and confirmation of the compression state when compressing the breast, and transmits X-rays emitted from the X-ray tube 10. At the same time, it is desirable to be formed of a material that easily propagates the ultrasonic wave transmitted from the ultrasonic probe 16. As the material of the compression plate 13, for example, a resin such as acrylic or polymethylpentene having a suitable value in the acoustic impedance that affects the reflectance of the ultrasonic wave and the attenuation coefficient that affects the attenuation of the ultrasonic wave can be used. .

  In the present embodiment, the movement control unit 20 controls the compression plate moving mechanism 14 so as to vibrate in a direction substantially parallel to the compression surface while the compression plate 13 compresses the subject 1 while receiving a preload. It is possible to image the vibrating subject 1. The frequency with which the compression plate 13 vibrates the subject 1 may be set in advance according to the resonance frequency of the cancer tissue, or imaging may be performed a plurality of times while sweeping the frequency. Alternatively, the compression plate 13 may apply an impulse or step-like vibration to the subject.

  The ultrasonic probe 16 includes a plurality of ultrasonic transducers arranged one-dimensionally or two-dimensionally. Each ultrasonic transducer transmits an ultrasonic wave based on an applied drive signal and outputs a reception signal by receiving an ultrasonic echo.

  Each ultrasonic transducer is, for example, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate), a polymer piezoelectric element represented by PVDF (polyvinylidene difluoride), or the like. It is comprised by the vibrator | oscillator which formed the electrode at the both ends of the material (piezoelectric body) which has the piezoelectricity. When a voltage is applied to the electrodes of such a vibrator by sending a pulsed or continuous wave electric signal, the piezoelectric body expands and contracts. By this expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by synthesizing those ultrasonic waves. Each vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. These electrical signals are output as ultrasonic reception signals and input to the ultrasonic imaging control unit 40 (FIG. 1) via a cable.

  The ultrasonic probe 16 may be moved while being in close contact with the compression plate 13 or moved away from the compression plate 13 by inserting an ultrasonic transmission medium such as echo jelly between the compression plate 13 and the ultrasonic probe 16. You may let them. More preferably, an ultrasonic transmission medium such as echo jelly is applied to the compression plate 13 and moved while the ultrasonic probe 16 is in contact with the compression plate 13. Further, the operator may move the ultrasonic probe 16, or the probe moving mechanism 17 may move the ultrasonic probe 16. In the following, the latter case will be described.

  The position of the ultrasonic probe 16 is detected by a position sensor 18 built in the ultrasonic probe 16. The movement control unit 20 grasps the position of the ultrasonic probe 16 based on the output signal of the position sensor 18 and controls the probe moving mechanism 17. While the probe moving mechanism 17 moves the ultrasonic probe 16, ultrasonic imaging is performed by the ultrasonic probe 16 transmitting and receiving ultrasonic waves.

The X-ray imaging system will be described with reference to FIG. 1 again.
The radiation imaging control unit 30 includes a tube voltage / tube current control unit 31, a high voltage generation unit 32, an A / D converter 33, a radiation image data generation unit 34, a subtraction unit 35, and an image data storage unit 36. Including.

  In the X-ray tube 10, the X-ray transmission is determined by the tube voltage applied between the cathode and the anode, and the amount of X-rays generated is determined by the time integral value of the tube current flowing between the cathode and the anode. The The tube voltage / tube current control unit 31 adjusts imaging conditions such as tube voltage and tube current according to the target value. The target values of the tube voltage and tube current can be manually adjusted by the operator using the console 70. The high voltage generator 32 generates a high voltage applied to the X-ray tube 10 under the control of the tube voltage / tube current controller 31.

  The A / D converter 33 converts the analog radiation detection signal output from the X-ray detection unit 12 into a digital signal (radiation detection data), and the radiation image data generation unit 34 performs a radiation image based on the radiation detection data. Generate data. The subtraction unit 35 temporarily stores the radiation image data generated by the radiation image data generation unit 34 in the image data storage unit 36, and stores radiation image data representing a plurality of radiation images stored in the image data storage unit 36. The subtraction process is performed to take the difference of the radiation image data obtained under a plurality of different conditions.

  FIG. 3 is a diagram showing elastic constants when various preloads are applied to various tissues in the breast. Here, the value of the preload is a portion that is compressed when preload is applied when the breast is compressed by applying preload in a predetermined direction and the thickness of the breast with no load in the predetermined direction is 100%. Is expressed as a percentage (%). Specifically, as shown in FIG. 2, when the breast is compressed between the compression plate 13 and the imaging table 19, the compression plate 13 and the imaging table in a state where the compression plate 13 is in contact with the breast (no load state). 19 is D1, and the distance between the compression plate 13 and the imaging table 19 in the pressurized state is D2, the value of the preload is {(D1-D2) / D1} × 100 (%) It is represented by

  As shown in FIG. 3, the elastic constants of fat and mammary gland are relatively small values less than 100 when the preload is 5% to 20%, and the preload is increased from 5% to 20% to increase the compression thickness (at the time of compression). Even if the thickness of the breast in the pressurizing direction is changed, the change in elastic constant is within twice. The elastic constant of the fiber structure is a relatively large value of about 107 when the preload is 5%. However, even if the preload is increased to 20% and the compression thickness is changed, it remains at about 233, which is about twice that. ing.

  On the other hand, the elastic constant of non-invasive breast cancer is a small value of about 25 when the preload is 5%, but when the preload is increased to 20% and the compression thickness is changed, it becomes about 301, which is about 12 times that. . The elastic constant of invasive breast cancer is about 93 when the preload is 5%, but when the preload is increased to 20% and the compression thickness is changed, the elastic constant becomes about 490, about five times that. Therefore, by increasing the preload to, for example, about 20% and detecting a portion having a large elastic constant in the breast, it can be diagnosed that the portion is likely to be cancerous tissue. Alternatively, by detecting a portion where the elastic constant at a relatively small preload (for example, about 5%) and the elastic constant at a relatively large preload (for example, about 20%) are detected, the portion may be a cancer tissue. Can be diagnosed as high.

  In order to detect cancer tissue by X-ray imaging, the subject is vibrated in a direction substantially orthogonal to the X-ray irradiation direction by utilizing the fact that the elastic constant of the cancer tissue increases when the preload is increased. It is effective to perform X-ray imaging while making it happen. That is, the portion having a large elastic constant is greatly displaced by vibration, so that the shadow in the X-ray image is thinned. By comparing this with an X-ray image of a stationary subject, a portion having a large elastic constant can be recognized.

  FIG. 4 is a diagram showing an image obtained by performing X-ray imaging on a mammo phantom as a subject. 4A is an image when X-ray imaging is performed without applying vibration to the subject, and FIG. 4B is an X-ray imaging while applying vibration of 47 Hz to the subject. This is an image when The mammo phantom contains particles that increase in elastic constant when the preload is increased, similar to cancer tissue. Hereinafter, a tissue or particle whose elastic constant increases when the preload is increased is referred to as “cancer tissue”. Comparing the two images, in the image when X-ray imaging is performed while applying vibration to the subject, the shadow of the cancer tissue is caused by the large displacement of the cancer tissue as shown by the arrow in FIG. It is fading.

  For example, the movement control unit 20 controls the compression plate moving mechanism 14 so that the compression plate 13 vibrates while compressing the subject with a relatively small preload (for example, about 5%). Further, the movement control unit 20 controls the compression plate moving mechanism 14 so that the compression plate 13 vibrates while compressing the subject with a relatively large preload (for example, about 20%). The radiation imaging control unit 30 may control each unit to perform X-ray imaging.

  In diagnosis, both images may be compared with the naked eye, and the subtraction unit 35 shown in FIG. 1 takes the difference between the radiation image data representing one image and the radiation image data representing the other image. You may detect a cancer tissue by processing. For example, the cancer tissue image obtained by the subtraction process is superimposed on the image of a stationary or vibrating subject as a color image, and the cancer tissue is displayed with emphasis.

Next, the ultrasonic imaging system will be described.
The ultrasonic imaging control unit 40 includes a scanning control unit 41, a transmission circuit 42, a reception circuit 43, an A / D converter 44, a signal processing unit 45, a B-mode image data generation unit 46, and an M-mode process. A unit 47, a Doppler processing unit 48, and an image composition unit 49 are included.

  The scanning control unit 41 sets the frequency and voltage of the drive signal applied to each ultrasonic transducer of the ultrasonic probe 16 from the transmission circuit 42 under the control of the movement control unit 20 and transmits the ultrasonic signal. Adjust the sound frequency and sound pressure. In addition, the scanning control unit 41 sequentially sets the transmission direction of the ultrasonic beam and sequentially sets and sets the transmission control function for selecting the transmission delay pattern according to the set transmission direction and the reception direction of the ultrasonic echo. And a reception control function for selecting a reception delay pattern according to the received reception direction.

  Here, the transmission delay pattern is applied to a plurality of drive signals in order to form an ultrasonic beam in a desired direction by ultrasonic waves transmitted from a plurality of ultrasonic transducers included in the ultrasonic probe 16. The reception delay pattern is a pattern of delay times given to a plurality of reception signals in order to extract ultrasonic echoes from a desired direction by ultrasonic waves received by a plurality of ultrasonic transducers. It is. The plurality of transmission delay patterns and the plurality of reception delay patterns are stored in a memory or the like.

  The transmission circuit 42 generates a plurality of drive signals respectively applied to the plurality of ultrasonic transducers. At that time, the transmission circuit 42 delays a plurality of drive signals based on the transmission delay pattern selected by the scanning control unit 41 so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers form an ultrasonic beam. The amount may be adjusted and supplied to the ultrasonic probe 16, or a plurality of drive signals may be ultrasonically transmitted so that ultrasonic waves transmitted from a plurality of ultrasonic transducers reach the entire imaging region of the subject. You may supply to the probe 16.

  The reception circuit 43 amplifies a plurality of ultrasonic reception signals respectively output from the plurality of ultrasonic transducers, and the A / D converter 44 converts the analog ultrasonic reception signal amplified by the reception circuit 43 into a digital ultrasonic signal. Convert to sound wave reception signal. Based on the reception delay pattern selected by the scanning control unit 41, the signal processing unit 45 gives respective delay times to the plurality of ultrasonic reception signals, and adds the ultrasonic reception signals, thereby receiving focus processing. I do. By this reception focus processing, a sound ray signal in which the focus of the ultrasonic echo is narrowed is formed.

  Further, the signal processing unit 45 corrects the attenuation due to the distance according to the depth of the reflection position of the ultrasonic wave by STC (Sensitivity Time gain Control) for the sound ray signal. Thereafter, an envelope detection process is performed by a low-pass filter or the like to generate an envelope signal.

  The B-mode image data generation unit 46 performs processing such as logarithmic compression and gain adjustment on the envelope signal to generate image data, and the image data is converted into image data according to a normal television signal scanning method. B-mode image data is generated by performing conversion (raster conversion).

  The M mode processing unit 47 pays attention to one sound ray in the cross section of the subject, and based on the sound ray signal subjected to the reception focus processing, represents the time-dependent change of the ultrasonic echo intensity from the sound ray. Mode image data is generated. FIG. 5 is a diagram illustrating an example of an image represented by M-mode image data. In FIG. 5, the horizontal axis represents time, and the vertical axis represents ultrasonic echo intensity.

  In M-mode imaging, the movement control unit 20 controls the ultrasonic plate imaging control by controlling the compression plate moving mechanism 14 so that the compression plate 13 vibrates the subject while compressing the subject with a relatively large preload (for example, about 20%). The unit 40 controls each unit and performs ultrasonic imaging. Here, since the movement control unit 20 sweeps the frequency for vibrating the subject, the horizontal axis of FIG. 5 also represents the vibration frequency of the subject.

  When the vibration frequency is swept, as shown in FIG. 5, the amplitude of the displacement of the object in the subject increases at a specific frequency due to resonance. The M mode processing unit 47 determines the magnitude of the displacement based on the change over time of the ultrasonic echo intensity, and determines that the vibration frequency when the magnitude of the displacement becomes the maximum is the resonance frequency.

The resonance frequency f and the elastic constant K of a certain object have a relationship represented by the following equation (1).
Here, ρ represents the density of the object, and V represents the volume of the object. The elastic constant K is expressed using the resonance frequency f by the following equation (2).
K = 4π ² ρVf ² (2)

  Thus, since the elastic constant K is proportional to the square of the resonance frequency f, if it is assumed that the density ρ is constant in the subject, M-mode imaging is performed on each part of the subject. Thus, the M mode processing unit 47 can generate image data representing the difference in elastic constants in the subject.

  Alternatively, when the density ρ in the subject is known, the M-mode processing unit 47 generates image data representing the distribution of elastic constants by estimating the volume of each part based on the B-mode ultrasound image. can do. A portion having a large elastic constant can be diagnosed as having a high possibility of being cancerous tissue.

  Further, the M mode processing unit 47 obtains a ratio value between a measured value at a relatively small preload (for example, about 5%) and a measured value at a relatively large preload (for example, about 20%), and the ratio value is large. You may make it diagnose that a part has a high possibility of being a cancer tissue.

  On the other hand, the Doppler processing unit 48 uses the fact that the frequency of the ultrasonic echo changes due to the Doppler effect when the object in the subject is moving, to determine whether the object is approaching the ultrasonic probe. You can determine whether you are away. The Doppler processing unit 48 pays attention to one sound ray in the cross section of the subject, removes high frequency components from the sound ray signal subjected to the reception focus process, and then performs quadrature detection processing on the sound ray signal. As a result, Doppler image data representing the frequency distribution of the ultrasonic echo intensity from the sound ray is generated. FIG. 6 is a diagram illustrating an example of an image represented by Doppler image data. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents ultrasonic echo intensity.

  When performing Doppler imaging, the movement control unit 20 controls the compression plate moving mechanism 14 so that the compression plate 13 vibrates while compressing the subject with a relatively large preload (for example, about 20%), so that the ultrasonic imaging control unit. 40 controls each part and performs ultrasonic imaging. Here, since the movement control unit 20 sweeps the frequency at which the subject is vibrated, the amplitude of the displacement of the object in the subject increases at a specific frequency due to resonance. The Doppler processing unit 48 determines the magnitude of the displacement based on the magnitude of the frequency shift of the ultrasonic echo, and determines that the vibration frequency when the magnitude of the displacement becomes the maximum is the resonance frequency.

  Similarly to the above, when it is assumed that the density ρ is constant in the subject, the Doppler processing unit 48 causes the difference in elastic constants in the subject by performing Doppler imaging on each part of the subject. Can be generated.

  Alternatively, when the density ρ in the subject is known, the M-mode processing unit 47 generates image data representing the distribution of elastic constants by estimating the volume of each part based on the B-mode ultrasound image. can do. A portion having a large elastic constant can be diagnosed as having a high possibility of being cancerous tissue.

  Further, the M mode processing unit 47 obtains a ratio value between a measured value at a relatively small preload (for example, about 5%) and a measured value at a relatively large preload (for example, about 20%), and the ratio value is large. You may make it diagnose that a part has a high possibility of being a cancer tissue. The movement control unit 20 may control the compression plate moving mechanism 14 so that the compression plate 13 gives an impulse or step-like vibration to the subject. In that case, each part of the subject vibrates at each resonance frequency.

  Referring again to FIG. 1, the image composition unit 49 uses the B mode image data generated by the B mode image data generation unit 46, the M mode image data generated by the M mode processing unit 47, and the Doppler processing unit 48. One of the generated Doppler image data is selected and output as ultrasonic image data. Alternatively, the image composition unit 49 converts the image of the portion having a large elastic constant detected by the M mode processing unit 47 or the Doppler processing unit 48 into, for example, the image of the subject represented by the B mode image data. Ultrasonic image data may be generated by superimposing as a color image.

  The image processing unit 50 performs necessary image processing such as gradation processing on the radiation image data output from the radiation imaging control unit 30 and the ultrasound image data output from the ultrasound imaging control unit 40. Display image data is generated. Thereby, a radiographic image and an ultrasonic image are displayed on the display units 61 and 62, respectively.

  The console 70 is used by an operator to operate the medical imaging apparatus. The control unit 80 controls each unit based on the operation of the operator. In the above, the movement control unit 20, the radiation image data generation unit 34, the subtraction unit 35, the scanning control unit 41, the signal processing unit 45 to the image processing unit 50, and the control unit 80 are the central processing unit (CPU) and the CPU. Are configured with software (programs) for causing various processes to be performed, but may be configured with a digital circuit or an analog circuit. This software (program) is stored in a storage unit 90 configured by a hard disk or a memory. Further, the transmission delay pattern and the reception delay pattern selected by the scanning control unit 41 may be stored in the storage unit 90.

  INDUSTRIAL APPLICABILITY The present invention can be used in a medical imaging apparatus and a medical imaging method for imaging a mammary gland and a breast while compressing a breast with a compression plate in order to diagnose breast cancer and the like.

It is a block diagram which shows the structure of the medical imaging device which concerns on one Embodiment of this invention. It is a side view which shows the external appearance of the imaging part of the medical imaging device shown in FIG. It is a figure which shows the elastic constant at the time of applying preload to the various structures | tissues in a breast. It is a figure which shows the image obtained by performing a X-ray imaging with respect to the mammo phantom as a subject. It is a figure which shows the example of the image represented by M mode image data. It is a figure which shows the example of the image represented by Doppler image data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subject 2 Arm part 3 Base 4 Axis part 10 X-ray tube 11 Filter 12 X-ray detection part 13 Compression board 14 Compression board moving mechanism 15 Pressure sensor 16 Ultrasonic probe 17 Probe movement mechanism 18 Position sensor 19 Imaging table 20 Movement control unit 30 Radiation imaging control unit 31 Tube voltage / tube current control unit 32 High voltage generation unit 33 A / D converter 34 Radiation image data generation unit 35 Subtraction unit 36 Image data storage unit 40 Ultrasound imaging control unit 41 Scan Control Unit 42 Transmitting Circuit 43 Receiving Circuit 44 A / D Converter 45 Signal Processing Unit 46 B Mode Image Data Generation Unit 47 M Mode Processing Unit 48 Doppler Processing Unit 49 Image Synthesis Unit 50 Image Processing Units 61 and 62 Display Unit 70 Console 80 Control unit 90 Storage unit

Claims (20)

An imaging table on which the subject is placed;
A compression plate that has a first surface that compresses the subject and a second surface that faces the first surface, and that compresses the subject between the imaging table;
A compression plate moving mechanism for moving the compression plate in a first direction substantially perpendicular to the first surface or in a second direction substantially parallel to the first surface;
First means for generating radiation or ultrasound, detecting radiation that has passed through the subject or reflected by the subject, and generating a signal;
The compression plate moving mechanism is controlled such that the compression plate compresses the subject in the first direction with the imaging table, and the compression plate vibrates the subject in the second direction. Second means for controlling the compression plate moving mechanism to generate an image signal representing an image of the subject based on the signal generated by the first means;
A medical imaging apparatus comprising: The first means includes a radiation generation unit that generates radiation, and an X-ray detection unit that detects the radiation generated by the radiation generation unit and passed through the subject and outputs a detection signal,
An image signal representing a radiographic image based on a detection signal generated when the second means detects a radiation that has passed through a vibrating subject and a movement control unit that controls the compression plate moving mechanism. A radiation imaging control unit for generating
The medical imaging apparatus according to claim 1.   The second means generates a first image signal representing a first radiation image based on a detection signal generated by detecting radiation that has passed through a vibrating subject, and vibrates. Generating a second image signal representing a second radiation image based on a detection signal generated by detecting radiation that has passed through a non-subject, and based on the first and second image signals, The medical imaging apparatus according to claim 2, wherein a part having a large elastic coefficient is detected.   The second means controls the compression plate moving mechanism so that the compression plate vibrates while compressing the subject with the first preload, and the subject vibrates while being compressed with the first preload. A first image signal representing a first radiation image is generated based on a detection signal generated by detecting the radiation that has passed through the compression plate, and the compression plate causes the subject to differ from the first preload. The detection signal generated by detecting the radiation that has passed through the subject vibrating while being compressed with the second preload by controlling the compression plate moving mechanism to vibrate while being compressed with the preload of 2. Based on the difference in the thickness of the subject in the pressurizing direction during compression by the compression plate based on the first and second image signals based on the second image signal representing the second radiation image The part where the elastic modulus changes greatly Detecting, medical imaging apparatus according to claim 2, wherein.   The medical imaging apparatus according to any one of claims 1 to 4, wherein the second means controls the compression plate moving mechanism such that the compression plate sweeps a frequency at which the subject vibrates. The first means includes an ultrasonic probe that transmits an ultrasonic wave according to a drive signal, receives an ultrasonic echo, and outputs a received signal while moving along the second surface of the compression plate. ,
Based on the movement control unit that controls the compression plate moving mechanism and the received signal generated by receiving the ultrasonic echo reflected by the vibrating subject, the second means An ultrasonic imaging control unit for obtaining information on an elastic constant in a desired portion of
The medical imaging apparatus according to claim 1.   The second means controls the compression plate moving mechanism so as to sweep the frequency at which the compression plate vibrates the subject, and receives the ultrasonic echo reflected by the vibrating subject. 7. The medical device according to claim 6, wherein a resonance frequency in a desired portion in the subject is obtained based on an amplitude change of the generated reception signal, and information relating to an elastic constant in the desired portion in the subject is obtained based on the resonance frequency. Imaging device.   The second means obtains a resonance frequency in a desired portion in the subject based on a Doppler shift of a reception signal generated by receiving an ultrasonic echo reflected by the subject that is vibrating, and the resonance frequency The medical imaging apparatus according to claim 6, wherein information relating to an elastic constant at a desired portion in the subject is obtained based on the information.   9. The medical imaging apparatus according to claim 8, wherein the second means controls the compression plate moving mechanism so that the compression plate gives an impulse or step-like vibration to the subject.   The second means controls the compression plate moving mechanism so that the compression plate vibrates while compressing the subject with the first preload, and the subject vibrates while being compressed with the first preload. A first resonance frequency in a desired portion in the subject is obtained based on a reception signal generated by receiving the ultrasonic echo reflected by the target, and a desired resonance frequency in the subject is determined based on the first resonance frequency. Determining the first information on the elastic constant in the portion, and controlling the compression plate moving mechanism so that the compression plate vibrates the subject with a second preload different from the first preload, Determining a second resonance frequency at a desired portion in the subject based on a reception signal generated by receiving an ultrasonic echo reflected by the subject vibrating while being compressed with a preload of 2. By obtaining the second information relating to the elastic constant in a desired portion in the subject based on the resonance frequency of 2, the portion having a large change in the elastic coefficient due to the difference in preload is obtained based on the first and second information. The medical imaging device according to any one of claims 6 to 9, wherein the medical imaging device is detected. An imaging table on which the subject is placed, a first surface that compresses the subject, and a second surface that faces the first surface, and compresses the subject between the imaging table. Medical imaging used in a medical imaging apparatus having a plate and a compression plate moving mechanism that moves the compression plate in a first direction substantially perpendicular to the first surface or a second direction substantially parallel to the first surface A method,
Controlling the compression plate moving mechanism so that the compression plate compresses the subject in the first direction with the imaging table;
(B) controlling the compression plate moving mechanism so that the compression plate vibrates the subject in the second direction;
(C) generating radiation or ultrasonic waves, detecting radiation passing through the subject or ultrasonic waves reflected by the subject and generating a signal;
Generating an image signal representing an image of the subject based on the signal generated in step (c); and
A medical imaging method comprising: Step (c) includes generating radiation using a radiation generation unit, detecting radiation generated by the radiation generation unit and passing through a subject using an X-ray detection unit, and outputting a detection signal. ,
Step (d) includes generating an image signal representing a radiation image based on a detection signal generated by detecting radiation that has passed through the vibrating subject;
The medical imaging method according to claim 11.   Step (d) is a step (d1) of generating a first image signal representing a first radiation image based on a detection signal generated by detecting radiation that has passed through a vibrating subject. Generating a second image signal representing a second radiation image based on a detection signal generated by detecting radiation that has passed through a non-vibrated subject, the first and first The medical imaging method according to claim 12, further comprising a step (d3) of detecting a portion having a large elastic coefficient based on the image signal 2. Step (b) is a step (b1) of controlling the compression plate moving mechanism such that the compression plate vibrates the subject while compressing the subject with the first preload, and the compression plate applies the first preload to the subject. And (b2) controlling the compression plate moving mechanism to vibrate while being compressed with a second preload different from
Step (d) is a first image signal representing a first radiographic image based on a detection signal generated by detecting radiation that has passed through a subject that is vibrating while being compressed with a first preload. And a second radiation image representing a second radiation image based on a detection signal generated by detecting radiation that has passed through the subject that is vibrating while being compressed with the second preload (d1). A step (d2) of generating an image signal of step (d2), and a step (d3) of detecting a portion having a large change in elastic modulus due to a difference in preload based on the first and second image signals.
The medical imaging method according to claim 12.   The medical imaging method according to claim 11, wherein step (b) includes controlling the compression plate moving mechanism so that the compression plate sweeps a frequency at which the subject vibrates. The step (c) transmits an ultrasonic wave according to the drive signal while moving the ultrasonic probe along the second surface of the compression plate, receives an ultrasonic echo, and outputs a received signal. Including
Step (d) includes determining information relating to an elastic constant at a desired portion in the subject based on a received signal generated by receiving an ultrasonic echo reflected by the subject being vibrated. ,
The medical imaging method according to claim 11. Step (b) includes controlling the compression plate moving mechanism to sweep the frequency at which the compression plate vibrates the subject;
Step (d) obtains a resonance frequency at a desired portion in the subject based on the amplitude change of the received signal generated by receiving the ultrasonic echo reflected by the subject that is vibrating, and the resonance frequency Determining information on an elastic constant at a desired portion in the subject based on
The medical imaging method according to claim 16.   Step (d) obtains a resonance frequency at a desired portion in the subject based on the Doppler shift of the received signal generated by receiving the ultrasonic echo reflected by the vibrating subject, and sets the resonance frequency to The medical imaging method according to claim 16, further comprising: obtaining information on an elastic constant in a desired portion in the subject based on the information.   The medical imaging method according to claim 18, wherein step (b) includes controlling the compression plate moving mechanism so that the compression plate applies an impulse or step-like vibration to the subject. Step (b) is a step (b1) of controlling the compression plate moving mechanism such that the compression plate vibrates the subject while compressing the subject with the first preload, and the compression plate applies the first preload to the subject. And (b2) controlling the compression plate moving mechanism to vibrate while being compressed with a second preload different from
Step (d) includes a first step in a desired portion of the subject based on a received signal generated by receiving an ultrasonic echo reflected by the subject that is vibrating while being compressed with the first preload. (D1) which obtains the first resonance frequency and obtains first information on the elastic constant in a desired portion in the subject based on the first resonance frequency, and the object which is vibrating while being compressed by the second preload. A second resonance frequency at a desired portion in the subject is obtained based on a reception signal generated by receiving the ultrasonic echo reflected by the subject, and the desired resonance in the subject is determined based on the second resonance frequency. The step (d2) for obtaining the second information relating to the elastic constant in the portion of (ii), and detecting the portion where the change in the elastic modulus due to the difference in preload is large, based on the first and second information Step (d3) and a,
The medical imaging method according to any one of claims 16 to 19.