JP2009160221A - X-ray computerized tomographic apparatus and three-dimensional image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quantitatively evaluate the movement of cardiac muscles. <P>SOLUTION: The X-ray computerized tomographic apparatus comprises an X-ray tube 101 for generating X rays; an X-ray detector 103 for detecting X rays transmitting the heart of a subject; a rotational driving part 107 for continuously rotating the X-ray tube around the subject together with the X-ray detector; a projection data generating part 106 for generating a plurality of temporally serial projection data sets based on the output from the X-ray detector; a reconstruction process part 114 for reconstructing a plurality of temporally serial three-dimensional images based on the plurality of generated projection data sets; a myocardial analysis part 118 for tracing a plurality of regions of the heart from the respective three-dimensional images and computing the momentum of each region based on the displacement of each traced region; and a three-dimensional display part 119 for displaying the computed momentum together with the three-dimensional images. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray computed tomography apparatus and a three-dimensional image processing apparatus for observing the movement of a myocardium using a three-dimensionally reconstructed moving image related to the heart of a subject.

  Conventionally, in order to observe the movement of the myocardium, there are a method of observing with an X-ray Angio apparatus or a method of observing an image reconstructed with CT. In the X-ray Angio apparatus, a very high-definition blood vessel structure can be depicted by injecting a contrast medium into a blood vessel using a catheter and continuously imaging the flow with X-rays. However, since the above method is not a visual evaluation index, it has not been possible to quickly grasp the state in an emergency such as surgery.

In addition, as a well-known document relevant to this application, there exist the following, for example.
JP 2002-330961 A

  As described above, conventionally, the movement of the myocardium has only been visually observed with an image reconstructed with an X-ray Angio apparatus or CT. For this reason, in the treatment of myocardial infarction, etc., the state could not be grasped quickly.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an X-ray computed tomography apparatus and a three-dimensional image processing apparatus that can quantitatively evaluate the movement of the myocardium.

  In order to achieve the above object, an X-ray computed tomography apparatus according to the present invention includes an X-ray tube that generates X-rays, an X-ray detector that detects X-rays transmitted through the heart of a subject, A projection that generates a plurality of temporally continuous projection data sets based on the rotation drive unit that continuously rotates the X-ray tube together with the X-ray detector around the subject and the output of the X-ray detector. A data generation unit, a reconstruction processing unit for reconstructing a plurality of temporally continuous three-dimensional images based on the generated plurality of projection data sets, and a plurality of portions of the heart from each of the three-dimensional images A tracking unit that tracks the amount of movement, a calculation unit that calculates the amount of movement of each part based on the displacement of each tracked part, and a display unit that displays the calculated amount of movement together with the three-dimensional image. Features.

  In addition, the three-dimensional image processing apparatus according to the present invention includes a storage unit that stores data of a plurality of temporally continuous three-dimensional images related to the subject's heart, and a plurality of portions of the heart from each of the three-dimensional images. Tracking means, tracking means for calculating the momentum of each part based on the tracked displacement of each part, and display means for displaying the calculated momentum together with the three-dimensional image. Features.

  As described above, according to the present invention, it is possible to realize an X-ray computed tomography apparatus and a three-dimensional image processing apparatus that can quantitatively evaluate the movement of the myocardium.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an X-ray computed tomography apparatus according to this embodiment. A tube voltage is applied from the high voltage generator 109 to the X-ray tube 101 via the slip ring 111, and a filament current is supplied. Thereby, X-rays are generated from the X-ray tube 101. As the X-ray detector 103, for example, a 256-slice multi-slice type is adopted. Note that the X-ray detector 103 may be a multi-slice type or single-slice type detector having another number of columns. The mechanism for converting incident X-rays into electric charge is an indirect conversion type in which X-rays are converted into light by a phosphor such as a scintillator, and the light is converted into electric charge by a photoelectric conversion element such as a photodiode, and in the semiconductor by X-rays. The generation of electron hole pairs and their transfer to the electrode, that is, the direct conversion type utilizing a photoconductive phenomenon, is the mainstream. Any of these methods may be employed as the X-ray detection element of the X-ray detector 103.

  The X-ray tube 101 and the X-ray detector 103 are mounted on an annular rotating frame 102 that is rotatably supported. The X-ray detector 103 is disposed at a position and an orientation facing the X-ray tube 101 with the opening 122 interposed therebetween. A subject placed on a couch top (not shown) is inserted into the opening 122. The X-ray detector 103 detects X-rays generated from the X-ray tube 101 and transmitted through the subject.

  The rotating frame 102 is continuously rotated at a high speed of, for example, 0.4 seconds / rotation by driving of the rotation driving unit 107. The tube position detector is provided to detect the angle of the X-ray tube 101 and typically includes a rotary encoder. The angle of the X-ray tube 101 is typically detected as a displacement angle from the reference angle (0 °) when the X-ray tube 101 is at the uppermost position. The angle (180 °) corresponds to the lowest position.

  The X-ray detector 103 detects X-rays that have passed through the subject. The data acquisition circuit 104 is generally called a DAS (data acquisition system). The data acquisition circuit 104 amplifies the signal read for each channel from the X-ray detector 103 and further converts it into a digital signal. Data output from the data acquisition circuit 104 reflects the intensity of incident X-rays and is generally referred to as pure raw data. The projection data generation unit 106 performs pre-processing such as logarithmic conversion and sensitivity correction on the pure raw data received from the data collection circuit 104 via the non-contact data transmission unit 105, and immediately before the reconstruction process. Some so-called projection data (also called raw data) is generated. The projection data is stored in the data storage unit 112 in association with a time code representing the time when the projection data is collected and data regarding the angle of the X-ray tube 101 at the time of the collection. The projection data can be associated with the electrocardiogram by the time code.

  The reconstruction processing unit 114 employs a so-called half reconstruction method, and reconstructs image (single slice, multi slice, or volume) data based on projection data for (180 ° + fan angle) around the subject. Can be configured. For convenience of explanation, the projection data for (180 ° + fan angle) is referred to as a projection data set as one unit. Further, the angular position corresponding to the projection data set indicates any one of the start position, end position, and center position corresponding to (180 ° + fan angle) required for half reconstruction.

  The 3D image processing apparatus 1 includes an operation unit 115, a display unit 116, a control unit 117, a myocardial analysis unit 118, and a 3D display unit 119. The operation unit 115 includes input devices such as a keyboard and a mouse. The display unit 116 is a display device such as a CRT, a plasma display, or a liquid crystal display. The control unit 117 is a central processing unit (CPU) such as a microprocessor. The myocardial analysis unit 118 and the three-dimensional display unit 119 are control programs executed by the control unit 117, and details of the processing will be described later.

  Four-dimensional data of the heart region of the subject is imaged by the multi-slice CT imaging mechanism. Here, the 4th dimension indicates a 3D dimension with time added, that is, a 3D data moving image. The control unit 117 transfers the reconstructed moving image from the data storage unit 112 to the three-dimensional display unit 119 and displays the moving image.

  FIG. 2 shows an example of a GUI screen displayed on the display unit 16 by the three-dimensional display unit 119. As shown in FIG. 2, the GUI screen has a myocardial analysis icon ([Analyze] switch 21). When this switch is pressed by the operator, the control unit 117 starts analysis processing by the myocardial analysis unit 118.

(Myocardial analysis processing)
FIG. 3 is a flowchart showing a processing procedure of the myocardial analyzer 118. The analysis object is an image of the first frame, an image of the second frame, a second frame, a third frame,... Up to the above, sequential processing is performed using the previous and next frames (steps S3a to S3f).

  In FIG. 3, the myocardial analyzer 118 first extracts the myocardial wall from the N-frame image in step S3b. The following three types of methods can be used for the extraction method.

  In the first method, only the heart portion is manually cut out using a Cutting Tool on a three-dimensional image, and the myocardial wall is automatically extracted therefrom.

  In the second method, a point inside the heart and a contact point with the outside (starting part of the aorta, pulmonary artery, vena cava, and pulmonary vein) are specified on the three-dimensional image, and the heart region is then determined by the region growing method. Identify and extract the heart wall.

  In the third method, a three-dimensional model of the heart is stored in advance in a memory, the three-dimensional data of the heart that has been photographed is compared, and the three-dimensional photographed while deforming the 3D model (position, angle, diameter). Fit the data. Then, the wall closest to the myocardial wall of the three-dimensional model from the state where fitting is most suitable is taken as the myocardial wall of 3D data.

Next, in step S3c, the myocardial analysis unit 118 divides the extracted wall into minute regions, and sequentially performs correlation calculations while finely moving within the search region within a certain range from the same position on the N + 1th frame image. As a result, the lowest calculation result is determined as the corresponding position, and the movement vector to that position is stored. This process is performed on the entire wall of N frames, and a movement vector for each region is calculated. Here, the correlation calculation can be described as follows.

Here, fN (x, y, z) and fN + 1 (x, y, z) are images of the Nth frame and the (N + 1) th frame, respectively. CR _xyz (Δx _xyz , Δy _xyz , Δz _xyz ) is the result of the correlation operation at (x, y, z), and the position where the shift vector of (Δx _xyz , Δy _xyz , Δz _xyz ) is minimized is obtained. . Note that with this calculation alone, the heart wall at a different position in the Nth frame may correspond to the same position in the (N + 1) th frame. In order to prevent this problem, an optimum combination can be determined for the entire image as follows.

Here, (x _i , y _i , z _i ) and (x _{i + 1} , y _{i + 1} , z _{i + 1} ) indicate minute regions of adjacent heart walls.

When this association is completed, the velocity V _N (x, y, z) for each region and the length L _N (x, y, z) of the trajectory can be calculated as follows.

Here, Δt represents a standard time difference between the reconstructed image of the N frame and the reconstructed image of the (N + 1) th frame. Further, the position vector at that time (with the image center as the origin) is stored as P _N = (x, y, z).

The above processing is repeated from 1 frame to M-1 frames (assuming data of 1 frame M frames) (the last processing is processing of M-1 and M frames), and the speed and locus for each region are obtained. Further, | P _N | is calculated for each region, and normalized using the minimum and maximum values as follows.

(Analysis result display processing)
Next, analysis result display processing will be described. When the analysis processing is completed as described above, the control unit 117 enables selection of various radio switches 22 for displaying the analysis results provided on the GUI screen shown in FIG. FIG. 4 shows an example of a myocardial analysis result displayed on the display unit 6 by the three-dimensional display unit 119.

  When [Motion] is selected as the first analysis result, the three-dimensional display unit 119 calculates the total length of the trajectory for each minute region, and displays the same on the three-dimensional myocardial data. A part with a long total length displays red, and a part with a short total length displays blue.

  When [Velocity (Ave.)] is selected as the second analysis result, the three-dimensional display unit 119 calculates an average speed value for each minute region, and displays the three-dimensional myocardial data by changing the color. To do. A region with a high average value displays red, and a region with a low average value displays blue.

  When [Velocity (Max.)] Is selected as the third analysis result, the three-dimensional display unit 119 obtains the maximum value of the velocity for each minute region and displays it on the three-dimensional myocardial data while changing the color. . The region where the maximum value is large displays red, and the region where the maximum value is small displays blue.

  When [Velocity (Min.)] Is selected as the fourth analysis result, the three-dimensional display unit 119 obtains the minimum value of the velocity for each minute region and displays it on the three-dimensional myocardial data while changing the color. . The region where the minimum value is large displays red, and the region where the minimum value is small displays blue.

When [Phase] is selected as the fifth analysis result, the three-dimensional display unit 119 changes and displays the color on the three-dimensional myocardial data. The color is determined based on NP _{N. If} this value is close to 1, a red system is displayed, and if this value is close to 0, a blue system is displayed. In this case, unlike other analysis result displays, the color also changes when the phase is changed.

  As described above, in the above-described embodiment, a myocardial wall is extracted in each frame from a temporally continuous three-dimensional image of the heart, and a movement vector indicating a temporal displacement for each minute region of the extracted wall. Ask for. Based on the obtained movement vector, the momentum speed, trajectory length, and phase of each region are calculated and graphically displayed on the three-dimensional image with colors, brightness, and the like.

  Therefore, according to the above-described embodiment, the motion of the myocardium can be quantitatively evaluated, so that the surgeon can quickly grasp the state of the heart in an emergency such as surgery.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Specific examples of modifications are as follows.

  (1) Each function according to the present embodiment can also be realized by installing a program for executing the processing in a computer such as a workstation and developing the program on a memory. At this time, a program capable of causing the computer to execute the technique is stored in a recording medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), or a semiconductor memory. It can also be distributed.

  (2) In the above-described embodiment, the result of the entire heart wall is displayed. However, for example, an arbitrary position may be designated on a three-dimensional image, and data of only that part may be calculated and displayed. . In this case, the processing time can be shortened because the calculation amount is small. The calculation result may be displayed as a numerical value or may be displayed as a color as shown in FIG.

  (3) In the above embodiment, the speed and locus are used as they are, but there are individual differences in the size of the heart. Therefore, rather than simply using the absolute value to determine the color, individual differences may be considered and normalized by the size of the heart (for example, volume or length at the end diastole) may be displayed. Thereby, individual differences are absorbed to some extent, and objective comparison of data between different patients becomes possible.

  (4) In the above embodiment, the multi-slice CT is imaged with a normal program. For example, it is easy to analyze by taking a fine image in a heart phase where motion is intense and coarse in a gentle region. Can be reduced. In order to achieve this, the gantry rotation of the multi-slice CT may be controlled, and the reconstruction time interval may be controlled by rotating the gantry in a phase where the motion is intense and rotating slowly in a phase where the motion is small.

  (5) Although an example using multi-slice CT has been described in the present embodiment, the present invention is not limited to the modality, and for example, an image reconstructed by an MRI apparatus, Cone Beam CT, or the like may be used. good. Further, a circulatory X-ray apparatus having a Biplane configuration can also be used. That is, as shown in FIG. 6, a moving image of a coronary (coronary artery) is taken, and a coronary image is reconstructed therefrom using Epipolar constraint conditions, and blood vessels are associated between N frames and N + 1 frames. Calculate the movement speed and movement trajectory length. After that, the Coronary on the heart model is matched with the reconstructed Coronary, and the calculated result is displayed superimposed on the Coronary of the heart model. Even in this way, the quantitative evaluation of the movement of the myocardium is possible as in the above embodiment.

  In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure which shows the structure of the X-ray computed tomography apparatus which concerns on one Embodiment of this invention. The figure which shows an example of the GUI screen displayed on a display part. The flowchart which shows the procedure of a process of a myocardial analysis part. The figure which shows an example of the myocardial analysis result displayed by a three-dimensional display part. The figure which shows the other example of the myocardial analysis result displayed by a three-dimensional display part. The figure which shows imaging | photography of the coronary artery by the X-ray apparatus for circulatory organs of a Biplane structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Three-dimensional image processing apparatus, 101 ... X-ray tube, 102 ... Rotating frame, 103 ... X-ray detector, 104 ... Data acquisition circuit, 105 ... Non-contact data transmission part, 106 ... Projection data generation part, 107 ... Rotation drive unit 109 109 high voltage generation unit 110 scan controller 111 slip ring 112 data storage unit 114 reconstruction processing unit 115 operation unit 116 display unit 117 electrocardiograph 118: Myocardial analysis unit, 119: Three-dimensional display unit.

Claims (10)

An X-ray tube that generates X-rays;
An X-ray detector for detecting X-rays transmitted through the heart of the subject;
A rotation drive unit that continuously rotates the X-ray tube around the subject together with the X-ray detector;
A projection data generator that generates a plurality of temporally continuous projection data sets based on the output of the X-ray detector;
A reconstruction processing unit for reconstructing a plurality of temporally continuous 3D images based on the generated plurality of projection data sets;
A tracking unit for tracking a plurality of portions of the heart from each of the three-dimensional images;
A calculation unit for calculating the momentum of each part based on the tracked displacement of each part;
An X-ray computed tomography apparatus comprising: a display unit that displays the calculated momentum together with the three-dimensional image.   The X-ray computed tomography apparatus according to claim 1, wherein the display unit further represents the calculated momentum by at least one of color, luminance, and numerical value.   The X-ray computed tomography apparatus according to claim 1, wherein the momentum is at least one of speed, locus length, and phase of each portion.   The X-ray computed tomography apparatus according to claim 5, wherein the calculation unit further normalizes the amount of exercise based on a size of the heart.   The X-ray computed tomography apparatus according to claim 1, wherein the projection data generation unit further changes a time interval of the projection data set according to the amount of exercise.   The X-ray computed tomography apparatus according to claim 5, wherein the rotation driving unit further changes a rotation speed according to the time interval. Storage means for storing data of a plurality of three-dimensional images that are temporally continuous with respect to the heart of the subject;
Tracking means for tracking a plurality of portions of the heart from each of the three-dimensional images;
Calculating means for calculating the momentum of each part based on the tracked displacement of each part;
A three-dimensional image processing apparatus comprising: display means for displaying the calculated amount of exercise together with the three-dimensional image.   The three-dimensional image processing apparatus according to claim 7, wherein the display unit represents the calculated amount of exercise with at least one of color, luminance, and numerical value.   The three-dimensional image processing apparatus according to claim 7, wherein the momentum is at least one of speed, trajectory length, and phase of each portion.   The three-dimensional image processing apparatus according to claim 7, wherein the calculation unit further normalizes the amount of exercise based on a size of the heart.

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