JPH06109853A - Positron ct device - Google Patents

Abstract

PURPOSE:To obtain a good image by automatically correcting body movement by performing correction so as to cancel the movement in linear and rotary directions of an examinee calculated from the displacement of the centers of gravity of two or more concerned areas set on an image. CONSTITUTION:The data stored in a memory 7 are read at every fixed time during the sampling of data to reconstitute an image by a computer 8 and the centers of gravity of two or more concerned areas are automatically calculated from the obtained image and the positional fluctuations of the centers of gravity are grasped by the comparison between successively obtained images. The movement and rotation of an examinee 1 are detected on the basis of the movement of the centers of gravity and the reconstituted image is moved in the opposite direction by the moving quantities (distances) in the X- and Y-directions of the centers of gravity by sending a command from the computer 8 to the memory 7 to negate the movement of the examinee 1 and, when the centers of gravity are rotated by an angle theta, the centers of gravity are rotated by the angle theta in the opposite direction to offset rotation. By this constitution, body movement can be automatically corrected on the image without imparting pain to a patient or applying labor to an operator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a positron CT apparatus for obtaining a concentration distribution image of a positron-emitting nuclide by calculation.

[0002]

2. Description of the Related Art A positron CT apparatus reconstructs a concentration distribution image of a positron-emitting nuclide (also called radioisotope, RI) by performing data processing using an electronic computer. A drug labeled with a positron-emitting nuclide is administered to a subject (patient), and gamma rays generated when the positron released from the positron-emitting nuclide in the body disappears are detected outside the body. Two of these gamma rays are simultaneously generated in the 180 ° direction. Therefore, a large number of radiation detecting detectors arranged in an annular shape so as to surround the subject are used. It is detected that two gamma rays are simultaneously incident on two of these detectors, and counting is performed for each combination of the incident detectors. Since the data (emission data) collected in this way can be regarded as projection data in each direction, it is possible to reproduce the concentration distribution image of the positron-emitting nuclide by backprojecting this.

In such a positron CT apparatus, if the subject moves during data collection, only data with a reduced spatial resolution can be obtained, and there is a situation in which measurement must be performed again. Therefore, conventionally, in many cases, the patient is strongly fixed so that body movement does not occur. In addition, the state of the patient may be visually monitored using a television camera, and when the body movement occurs, the operator may perform an operation of returning the patient with the body movement to the original position.

[0004]

However, if the patient is strongly fixed, there is a problem that the patient suffers, and it is laborious for the operator to restore the patient to its original position. Along with that, it is practically difficult to accurately restore the original position, which causes a problem in accuracy.

In view of the above, the present invention has been improved so that the body movement can be automatically corrected without causing pain to the patient or labor of the operator.
The purpose is to provide a T-device.

[0006]

In order to achieve the above object, in the positron CT apparatus according to the present invention, means for reconstructing an image based on the data at that time at fixed time intervals during the data acquisition time, A means for determining the center of gravity of at least two or more regions of interest set in advance on the image, and determining the movement of the subject in the linear direction and the rotation direction from the displacement, and correcting the movement so as to be finally canceled. It is characterized by including a correction means.

[0007]

When the subject moves, the center of gravity of the region of interest in the images obtained at regular intervals also moves. Since two or more regions of interest are set, movements of the subject in the linear direction and the rotational direction can be obtained from their displacements. Therefore, by directly changing the positional relationship between the gantry and the subject or changing the data writing position in the memory so that the movement in the linear direction and the rotational direction is canceled,
The deterioration of the spatial resolution of data due to body movement can be minimized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. In FIG. 1, the gantry 2 has an opening 3 in the center thereof, and a large number of detectors (not shown) for detecting radiation are arranged in an annular shape so as to surround the opening 3. By inserting the subject 1 into the opening 3, the data of the subject 1 is collected. The subject 1 is placed on the top plate 5 of the bed 4, and is moved into the opening 3 by the movement of the top plate 5.

The gantry 2 and the bed 4 are connected to the console 6 by a signal cable. Inside the console 6, a memory 7 for storing collected data and image data after reconstruction, a computer 8 for performing image reconstruction processing, an image display device 9 for displaying a reconstructed image, etc. are housed. There is.

In this embodiment, F-18-FDG (fluorodeoxyglucose), which has a small change in the RI distribution over time, is administered to the subject 1, and the subject 1
Is inserted into the opening 3 of the gantry 2 by moving the top plate 5, and the inspection is performed. In this case, the coincidence count data collected in the gantry 2 is added to the memory 7, but here, the data collection time before the data collection time set to reconstruct one image has elapsed. The data stored in the memory 7 is read out at regular intervals, and the computer 8 performs image reconstruction processing.

The data to be read may be all of the data gradually accumulated in the memory 7 at the time of reading, but the data newly accumulated from the time of the previous reading is preferable. Therefore, in addition to the data collecting area at all data collecting times, an area for accumulating data to be read in the middle is provided in the memory 7,
In that area, new data is stored after erasing at each read time point. Alternatively, in that area, it is also possible to perform a new data writing while sequentially erasing the previously written data so that the data is always stored for a certain time from the present time. Further, reading while writing data can be performed if the writing cycle and the reading cycle are separated, or a memory that can simultaneously read while writing may be used.

In this way, an image can be obtained at fixed time intervals during data acquisition, and the variation in the position of the center of gravity of the region of interest can be captured from the image. That is, in this embodiment, data acquisition for obtaining an image for positioning is performed in advance prior to data acquisition, an image is reconstructed from the obtained data, and the image is displayed, for example, as shown in FIG. It is displayed on the screen 11 of the display device 9. And this screen 1
1, a plurality of regions of interest 21, 22,
Set 23. Here, the head tomographic image 12 is displayed on the screen 11, and the regions of interest 21 to 23 are set on the displayed head tomographic image 12.

Then, the computer 8 calculates the centroids of the regions of interest 21 to 23 in the images obtained at regular time intervals.
Automatically ask by. This center of gravity is obtained as points 31 to 33 on the coordinates of the screen 11 as shown in FIG.

The center of gravity position is compared by the computer 8 between images obtained one after another at regular intervals.
The center of gravity 31 is for the region of interest 21, and since the region of interest 21 is the entire image, it is the center of gravity of the entire image. Therefore, the fact that the position of the center of gravity 31 has changed means that the entire subject 1 has moved. Also, the centers of gravity 32, 33 are smaller regions of interest 22, 2,
Since it is the center of gravity of 3, the rotation of the subject 1 can be evaluated by the moving distance and the moving direction of the two center of gravity 32, 33.

Therefore, since the movement and rotation of the subject 1 can be known by grasping the movement of the centers of gravity 31 to 33, this can be corrected. That is, a command is sent from the computer 8 to the memory 7 and X of the center of gravity 31 is sent.
If the reconstructed image is moved in the opposite direction by the amount of movement (distance) in the Y and Y directions, the movement can be canceled, and if the image is rotated by the angle θ, it is rotated by θ in the opposite direction. Can be canceled.

The correction of the distance direction and the rotation direction may be performed by moving the reconstructed image data on the memory 7 (changing the writing address of the image data), or on the memory 7 of the raw data. Change the write address of. Such a correction can be performed completely by software. Further, in addition to the operation on the memory 7, the positional relationship between the gantry 2 and the subject 1 may be directly changed. In this case, the computer 8 issues a command to the gantry 2 or the bed 4 in accordance with the calculated movement distance, direction, or rotation angle, and the gantry 2 or the top plate 5 is moved or rotated so as to cancel it. It is also possible.

By such a correction, it is possible to minimize the deterioration of the spatial resolution due to the body movement.

In the above, the body movements of the subject 1 in the horizontal / vertical direction and the rotation direction in the plane perpendicular to the body axis of the subject 1 are corrected, but the plane parallel to the body axis (for example, sagittal) is corrected. It is also possible to correct the movement and inclination of the subject 1 in the plane (that is, the body movement in the horizontal / vertical direction and the rotation direction in the plane). In that case, a tomographic image in the body axis direction (for example, a sagittal image) may be obtained one after another at regular time intervals, and the variation of the center of gravity of the region of interest may be similarly captured.

If a plurality of point radiation sources (not shown) are attached to the subject 1 and regions of interest are set for these, the movements and rotations of the point radiation sources can be captured, so that they can be reproduced more accurately. It is possible to correct body movements with high flexibility.

[0020]

According to the positron CT apparatus of the present invention, the body motion of the subject can be automatically detected, and the motion is corrected accordingly, so that the patient is distressed or the operator is not affected. It is possible to obtain a good image while minimizing the deterioration of the spatial resolution of the data due to body movements without labor.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an embodiment of the present invention.

FIG. 2 is a diagram showing a region of interest on a screen.

FIG. 3 is a diagram showing the position of the center of gravity on the screen.

[Explanation of symbols]

 1 subject 2 gantry 3 opening 4 bed 5 top plate 6 console 7 memory 8 computer 9 image display device 11 screen 12 head tomographic image 21-23 region of interest 31-33 centroid

Claims (1)

[Claims] 1. A means for reconstructing an image based on the data at that time at fixed time intervals during the data acquisition time, and determining the center of gravity of at least two or more regions of interest preset on the image, and A positron CT apparatus comprising: means for obtaining movements of a subject in a linear direction and a rotation direction from displacements; and correction means for correcting such movements so as to be finally canceled.