JP2010022667A - Cerebral blood flow analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably calculate a mean transit time of blood of a test site despite a time difference in contrast medium arrival times between the artery and a test region. <P>SOLUTION: This analyzer reconstructs a plurality of images with different imaging times collected by scanning a subject's site of interest where the contrast medium is administered, and analyzes the cerebral blood flow of the blood vessel in the brain tissue from the reconstructed image. This cerebral blood flow analyzer includes; a change curve creation means 26C for creating an artery curve and a test site curve indicating time-contrast medium density changes in the artery and the test site in the subject's brain tissue from a plurality of reconstruction images; a shift process means 26D shifting the created artery curve to the time axis negative direction closer than the test site curve; and a means 26E calculating the mean transit time of the blood flow of the test site from the artery curve and the test site curve after the shifting based on a blood flow transmission function model where a contrast medium arrival time in the test site is slower than the artery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for analyzing cerebral blood flow in brain tissue used in an X-ray CT apparatus, an MRI (magnetic resonance imaging) apparatus, and the like, and in particular, an analysis of cerebral blood flow generated by the arrival time of a contrast medium administered to a subject. The present invention relates to a cerebral blood flow analysis device that avoids the influence.

  Conventionally, when analyzing cerebral blood flow of blood vessels in a brain tissue of a subject (for example, a patient), after a contrast agent is administered to the subject, a predetermined interval (dynamic) is passed until the contrast agent passes through the region of interest of the subject. A method has been proposed in which dynamic scanning is performed at intervals), a plurality of continuous images are taken out, and cerebral blood flow analysis (CT-perfusion) is performed (Patent Document 1).

  In this cerebral blood flow analysis method, for example, the head (all examination regions) of a subject to which a contrast medium is administered is repeatedly imaged, and a plurality of continuous dynamic CT images are created. Then, a time-concentration (CT value) curve representing a time-dependent change in the CT value for each artery and each region to be examined, which is a region of interest on the subject's head, is obtained from the created dynamic CT images, and the brain This is a method for analyzing blood flow.

Here, as the cerebral blood flow analysis, using a CT value curve, cerebral blood flow (CBP: unit volume and blood flow per unit time in capillaries of brain tissue), cerebral blood volume (CBV: Cerebral Blood). Volume: blood volume per unit volume in brain tissue), mean transit time (MTT: Mean Transit Time: mean blood transit time of capillaries) and the like are calculated.
JP 2003-190148 A

  By the way, in the above cerebral blood flow analysis method, after a contrast agent is administered to a subject, a predetermined number of transmissions are continuously performed until the contrast agent passes through an artery and each examination site that are the subject's interest. Capture, reconstruct and display images. Then, as shown in FIG. 7 (a), the user designates a specific artery 101 in the head 100, and a time-concentration curve (arterial contrast image) representing the temporal change in the CT value of the artery shown in FIG. 7 (b). Agent concentration change curve: hereinafter referred to as arterial curve Ca) and time-concentration curve representing the time-dependent change in CT value of each site to be examined (contrast medium concentration change curve of site to be examined: hereinafter referred to as site curve Ci to be examined) ).

  At this time, the blood stained with the contrast medium normally passes through the heart and lungs, passes through the artery 101, and then flows into each of the inspected sites 102 in the brain tissue. An arterial curve Ca having a CT peak value with respect to each of the inspected sites 102 appears with a delay approximately equal to or later than the arterial curve Ca.

  Incidentally, when the average transit time MTT of blood in the brain tissue is represented by a transfer function from the relationship between the arterial curve Ca and the inspected site curve Ci in the brain tissue, it can be schematically represented as shown in FIG. .

  That is, when the cerebral artery curve Ca and the to-be-inspected curve Ci in the brain tissue rise with substantially the same CT value distribution immediately after the start of the administration of the contrast agent and then drop from substantially the same peak value, the pulse immediately after the start of the administration of the contrast agent Can be represented by a transfer function (see FIG. 8A). Further, when the cerebral artery curve Ca appears with substantially the same CT value distribution before the inspected site curve Ci in the brain tissue, it can be expressed by a pulse-like transfer function after a lapse of time from the administration start point of the contrast agent. (See FIG. 8B). Further, when both the curves Ca and Ci rise in the positive and negative directions immediately after the start of administration of the contrast agent and the CT peak value of the region curve Ci to be examined in the brain tissue becomes small, it becomes a low pulse accordingly. It can be expressed by a transfer function (see FIG. 8C).

  Further, as the contrast agent concentration peak arrival time between the cerebral artery curve Ca and the inspected site curve Ci in the brain tissue is separated, it is expressed by an ideal rectangular wave transfer function after a lapse of time from the administration start point of the contrast agent. (See FIG. 8D).

  However, when the cerebral artery curve Ca rises later than the inspected site curve Ci in the brain tissue, the transfer function model is not established (see FIG. 8E).

  This is because, when an abnormality occurs in the designated artery 101 for some reason, the examination site curve Ci related to the examination site 102 may appear first, and then the cerebral artery curve Ca of the designated artery 101 may appear.

  Originally, the average passage time MTT of blood in the region to be inspected 102 is calculated from the time difference between the arrival time at which the blood stained with the contrast medium reaches the artery 101 and the arrival time to reach a specific region to be inspected 102, As shown in FIG. 8E, when the curve Ca of the artery 101 appears later than the to-be-inspected part curve Ci of the to-be-inspected part 102, the analysis accuracy of the average passage time of blood in the to-be-inspected part 102 is greatly reduced, Analysis of blood flow becomes impossible.

  The present invention has been made in view of the above circumstances, and provides a cerebral blood flow analysis device that stably calculates the average passage time of blood in a region to be examined regardless of the time difference in contrast agent arrival time between the artery and the region to be examined. The purpose is to provide.

  In order to solve the above problems, a cerebral blood flow analysis device that analyzes blood flow in a brain tissue based on a plurality of images having different imaging times obtained by scanning a region of interest of a subject to which a contrast medium is administered And an arterial curve representing the time-contrast agent concentration change of the artery in the brain tissue that is the region of interest of the subject and the region to be examined from the plurality of images, and a change curve creating unit that creates the region to be examined, Arterial curve shift processing means for shifting the arterial curve created by the change curve creating means in the negative direction of the time axis with respect to the examination site curve, and blood flow whose contrast medium arrival time at the examination site is later than that of the artery A cerebral blood flow analysis device comprising: means for calculating an average transit time of blood flow of the examined region from the arterial curve after the shift and the examined region curve based on a transfer function model.

  According to the present invention, it is possible to stably calculate the average passage time of blood in a region to be examined regardless of the time difference in the contrast agent arrival time between the artery and the region to be examined.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing an embodiment of a cerebral blood flow analysis apparatus in an X-ray CT apparatus according to the present invention.

  This cerebral blood flow analysis device includes a subject region-of-interest image detection device 10 and a cerebral blood flow analysis device main body 20.

  The subject region-of-interest image detection apparatus 10 generates a plurality of continuous images in time series from the subject, and is not limited to a specific apparatus. For example, an X-ray CT apparatus (X Any one of a line computer tomography apparatus), a single photon emission tomography apparatus (SPECT apparatus), a positron emission tomography apparatus (PET apparatus), and an MRI apparatus is used. For convenience, an X-ray CT apparatus is used here. An example will be described.

  As the X-ray CT apparatus, a table 14 on which a subject 13 (patient) is placed is disposed between an X-ray generator 11 and an X-ray detector 12 having a two-dimensional detection channel. X-rays are irradiated from, for example, toward the head 13 a of the subject 13.

  Whether the two-dimensional X-ray detector 12 detects X-ray transmission data transmitted from the head 13a of the subject 13 two-dimensionally and sends it to the cerebral blood flow analyzer main body 20 as digital transmission data. Alternatively, digital transmission data is collected in accordance with a reading instruction from the cerebral blood flow analyzer main body 20.

  A high voltage generator 15 sets a desired tube voltage and tube current for the X-ray detector 12.

  That is, the subject region-of-interest image detection apparatus 10 is installed such that the X-ray generator 11 and the X-ray detector 12 face each other on a rotating ring and sandwich the head 13a of the subject 13 on the table 14. The X-ray transmission data transmitted through the head 13a is continuously detected in a two-dimensional manner while rotating the rotating ring at a high speed while the X-ray generator 11 is irradiated with the X-rays. A plurality of digital X-ray transmission data detected by the instrument 12 and corresponding to different projection directions are acquired.

  The cerebral blood flow analysis device main body 20 is constituted by a computer device, and various functional units are connected to an interface 21 and a bus 22 connected to the interface 21 in terms of hardware.

  This functional unit includes an operation unit 23 such as a keyboard or pointing device for inputting transmission data collection instructions, image reconstruction instructions, setting of various data necessary for blood flow analysis processing in brain tissue, and other various control instructions. A storage device 24 that collects and stores a plurality of continuous X-ray transmission data, an image display unit 25 that displays a reconstructed image of the acquired X-ray transmission data and various processed images, and a blood flow in the brain tissue The image analysis processing unit 26 includes a CPU that executes analysis processing, a ROM 27, a RAM 28, and the like.

  Based on a plurality of images of the region of interest (for example, the head 13 a) of the subject 13 stored in the storage device 24, the image analysis processing unit 26 performs tissue blood at the site according to a blood flow analysis processing program for brain tissue. It analyzes flow (perfusion) dynamics.

  The ROM 27 stores a blood flow analysis processing program for brain tissue. The RAM 28 temporarily stores images and information such as processing results during the analysis processing of blood flow in the brain tissue processed by the image analysis processing unit 26.

  As shown in FIG. 2, the image analysis processing unit 26 functionally collects a plurality of continuous X-ray transmission data and displays the transmission data collection means 26A, and collects the collected X-ray transmission data. A reconstruction processing means 26B for reconstructing an image based on the image, a specific arterial curve designated by the user (a time-concentration curve representing a temporal change in the CT value of the artery), and each inspected site curve in the brain tissue (each CT value curve creating means 26C as a change curve creating means for creating a time-concentration curve representing a time-dependent change in CT value of a region to be inspected, and an arterial curve created by this CT value curve creating means 26C is negative on the time axis. Arterial curve shift processing means 26D that shifts in the direction and blood flow rate calculation means 26E are provided.

  If the subject region-of-interest image detection apparatus 10 is, for example, an X-ray CT apparatus, the X-ray CT apparatus itself executes the transmission data collection means 26A and the reconstruction processing means 26B, and the cerebral blood flow analysis apparatus main body 20 May obtain a reconstructed image.

  Next, the operation of the cerebral blood flow analysis apparatus configured as described above will be described with reference to FIG.

  First, the subject region-of-interest image detection apparatus 10 performs a dynamic scan on a desired cross section of the subject 13, for example, the head 13a. At the time of this scan, an X-ray contrast agent having no cerebral vascular permeability is rapidly administered to the subject 13. This contrast agent flows into the cerebral artery via the heart and lungs, and flows out from the arterial flow to each cerebral vein through each examination site in the brain tissue.

  Here, when the user inputs a collection instruction from the operation unit 23, the image analysis processing unit 26 executes the transmission data collection unit 26A.

  The transmission data collection unit 26A collects X-ray transmission data (raw data) corresponding to different projection directions in the desired cross section of the head 13a of the subject 13 by the above-described dynamic scan at regular time intervals or continuously. The data is sequentially stored in the storage device 24 (S1).

  After collecting the X-ray transmission data, the reconstruction processing means 26B is executed. The reconstruction processing means 26B reconstructs using the collected X-ray transmission data in accordance with the reconstruction processing program, creates a dynamic CT image for cerebral blood flow analysis, and stores it in a predetermined area of the storage device 24 (S2). ).

  The series of processes in steps S1 and S2 is performed when the dynamic blood flow image (reconstructed image) is created on the subject region-of-interest image detection apparatus 10 side. It is assumed that a predetermined number (for example, 40) of dynamic CT images consecutive in different times are collected and stored in a predetermined area of the storage device 24. This dynamic CT image is an image reflecting the behavior information (change information with time) of the contrast agent in the desired cross section. Note that the dynamic CT image may be an image corresponding to a three-dimensional spatial region as well as an image of one cross section.

  When the conditions necessary for the analysis of the cerebral blood flow of the blood vessels in the cerebral tissue are satisfied, the image analysis processing unit 26 reads the blood flow analysis processing program from the ROM 27 when receiving a cerebral blood flow analysis instruction from the user. After writing in the storage device 24, the CT value curve creating means 26C is executed in accordance with the blood flow analysis processing program.

  That is, the CT value curve creating means 26C reads a plurality of (for example, 40) dynamic CT images from the storage device 24 (S3), performs noise removal, and displays them on the image display unit 25 (S4).

  Then, for a plurality of dynamic CT images, the user determines whether or not the artery 31 is designated via the operation unit 23 (S5), and if designated, the CT value (contrast agent concentration) for the designated artery 31 is designated. Value) for each image in a time-series manner to create an arterial curve Ca that is a time-contrast agent concentration curve representing a time-dependent change in the CT value of the designated artery, and similarly, brain tissue of the head 14 that is the region of interest. After creating a region-of-inspection curve Ci that is a time-contrast medium concentration curve representing a time-dependent change in CT value of each region to be examined (S6), the arterial curve shift processing means 26D is executed.

  The arterial curve shift processing unit 26D analyzes the arterial curve Ca and the inspected site curve Ci created by the CT value curve creating unit 26C, respectively, and at least a contrast agent is designated from the arterial curve Ca and the inspected site curve Ci. The rise time (start time) ta of the arterial curve Ca reaching the artery 31 and the rise time (start time) ti of the test site curve where the contrast medium reaches the test site are calculated (S7).

  In addition, the rise time of the inspected part curve Ci is calculated by calculating the time when the inspected part curve Ci (t) or the differential value dCi (t) in the time direction of the curve Ci (t) is larger than a predetermined set value. The rise time ti may be used. Further, the rising time ti may be calculated by performing smoothing in the time axis direction, or by applying the whole curve to be inspected or a part of the curve to a polynomial or a gamma function.

  When obtaining the region-of-inspection curve Ci (t), it may not be a contrast agent concentration change curve in a specific pixel (pixel), and for example, an average value of a plurality of pixels in a certain setting region may be used.

  The rise of the arterial curve Ca (t) may be calculated by the same method as in the case of the inspected site curve Ci.

  Further, the arterial curve shift processing means 26D calculates the rise time (start time) ta, ti, and then shifts the arterial curve Ca by the following shift method.

(1) When the rise time ta of the arterial curve Ca is compared with the rise time ti of the examination site curve, and it is determined that the rise time ta of the arterial curve Ca is later than the rise time ti of the examination site curve Ci The parallel movement amount ts is calculated so that the curve Ca rises from a certain time in the negative direction of the time axis relative to the rise time ti of the inspected site curve Ci (S8).

  Then, the arterial curve Ca is shifted (translated) by the parallel movement amount ts in the negative direction in time, thereby creating a shifted arterial curve Ca ′ as shown in FIG. 4A (S9).

(2) Further, as another shift method, the rise time ta of the arterial curve Ca is set in advance as the rise time ti of the inspected site curve Ci in software, or the time axis ti is shifted in the negative direction of the time axis. Such processing may be performed. In this way, when the rise time of the arterial curve Ca is shifted in the negative direction of the time axis by td (≧ 0) from the rise time ti of the site curve Ci, the shift amount ts (when <0) of the arterial curve Ca is , Ts = ti−td−ta.

  That is, when it is determined in advance that the rise time of the arterial curve Ca before the shift is softly shifted in the negative direction of the time axis until the rise time of the inspected site curve Ci or the imaging start time, the artery before the shift is determined. The parallel movement amount that shifts the curve Ca in parallel in the negative direction of the time axis until the rise time of the inspected site curve Ci or the contrast agent administration start time is calculated. Shift in the negative direction and create the arterial curve after this shift.

  When ts ≧ 0, ts = 0 and the arterial curve Ca does not have to be shifted. When the arterial curve Ca (t) is shifted by ts in the time axis direction, Ca ′ (t) = Ca (t−ts).

  Further, the image analysis processing unit 26 executes a blood flow rate calculation unit 26E. This blood flow rate calculation means 26E is based on a blood flow transfer function model (see FIG. 4B) in which the contrast medium arrival time at the site to be examined is later than that of the artery, and is examined in the brain tissue by a deconvolution operation. The average transit time MTT of the part curve Ci is calculated, and the blood flow rate is calculated using a conventionally known calculation method (S10).

  As a deconvolution considering the delay of the contrast agent, a method that does not define the shape of the transfer function such as the SVD method is used, or when applying to the transfer function model, the delay time delay is transmitted as a parameter as shown in FIG. Analysis may be performed by incorporating the function model.

  Therefore, according to the embodiment as described above, when at least the rise time of the arterial curve Ca is later than the rise time of the inspected site curve Ci, the arterial curve Ca is time in the negative direction of the time axis from the inspected site curve. Shift to move parallel to get up from. Since the average transit time MTT of the region curve Ci to be examined in the brain tissue is calculated based on the blood flow transfer function model in which the contrast agent arrival time of the region to be examined is later than that of the artery, the contrast between the artery and the region to be examined is calculated. Regardless of the time difference in the agent arrival time, the contrast agent average passage time MTT of each site to be inspected can always be calculated stably.

  Incidentally, when the arterial curve Ca is in a non-shift state although the rise time of the arterial curve Ca is later than the rise time of the region curve Ci to be examined, an analysis of cerebral blood flow is performed as shown in FIG. The left side of the image becomes unanalyzable and becomes a red map (light black in the figure), but when the arterial curve Ca is shifted, a normal analysis image can be obtained as shown in FIG. .

In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

The block diagram which shows one Embodiment of the cerebral blood-flow analysis apparatus which concerns on this invention. The figure which shows the function structure of the image analysis process part of FIG. The figure explaining the flow of a series of processes of the image analysis process part of FIG. The transfer function model figure obtained from the relationship between the arterial curve after a shift, and a to-be-inspected part curve. The transfer function model figure which represented delay time delay as a parameter. The figure which shows the blood-flow analysis image of the state which shifted the arterial curve to the state without a shift. The figure explaining the relationship between the site | part of interest of the subject explaining a prior art example, the arterial curve which is the said site of interest, and a to-be-examined site | part curve. The typical transfer function model figure represented from the relationship between an arterial curve and a to-be-inspected part curve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Subject interest part image detection part, 11 ... X-ray generator, 12 ... X-ray detector, 13 ... Subject, 13a ... Head part which is a part of interest, 20 ... Cerebral blood flow analysis apparatus main part, 23 ... Operation unit, 24 ... storage device, 25 ... image display unit, 26 ... image analysis processing unit, 26A ... transmission data collection unit, 26B ... reconstruction processing unit, 26C ... CT value curve creation unit, 26D ... arterial curve shift processing unit 26E: Blood flow rate calculation means.

Claims (3)

In a cerebral blood flow analysis device that analyzes blood flow in brain tissue based on a plurality of images with different imaging times obtained by scanning a region of interest of a subject to which a contrast agent is administered,
An arterial curve representing a time-contrast agent concentration change of an artery in a brain tissue that is a region of interest of the subject and a region to be examined from the plurality of images, and a change curve creating unit that creates a region to be examined;
Arterial curve shift processing means for shifting the arterial curve created by the change curve creating means in the negative direction of the time axis rather than the examination site curve;
Based on a blood flow transfer function model in which the contrast agent arrival time of the examination site is later than that of the artery, the average transit time of the blood flow of the examination site is calculated from the arterial curve and the examination site curve after the shift. A cerebral blood flow analysis device comprising: a calculating means. The cerebral blood flow analysis device according to claim 1,
The arterial curve shift processing means includes a rise time calculating means for calculating a rise time between the arterial curve before the shift and the region curve to be examined, and a rise of the arterial curve before the shift calculated by the rise time calculating means. When it is determined that the time is later than the rise time of the examination region curve, the amount of movement by which the arterial curve before the shift is shifted in parallel in the time axis negative direction from the rise time of the examination site curve is calculated. A cerebral blood flow analysis apparatus comprising: means; and means for shifting the arterial curve before the shift in the negative direction of the time axis in accordance with the calculated movement amount, and calculating the arterial curve after the shift. The cerebral blood flow analysis device according to claim 1,
When the arterial curve shift processing means is determined in advance to shift the rise time of the arterial curve before the shift in the negative direction of the time axis until the rise time of the examination site curve or the imaging start time, Means for calculating a movement amount that shifts the arterial curve before the shift in parallel in the negative direction of the time axis until the rise time of the examination site curve or the contrast agent administration start time, and the pre-shift according to the calculated movement amount And a means for calculating the arterial curve after the shift in the negative direction of the time axis.

Images