JPH0533985Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to improvement of a positron ECT device.

Conventional technology A positron ECT device administers a positron-emitting nuclide or its compound to a subject (patient), detects positron annihilation gamma rays emitted from the body, and processes the collected data using a computer. This is a device that reproduces the distribution of positron-emitting nuclides in the body as a digital image.

By the way, this positron ECT device (hereinafter referred to as
In order to detect gamma rays outside the patient's body, the PECT device uses a ring-shaped detector array in which a large number of radiation detectors are arranged in a ring shape around the patient. Usually, this ring-shaped detector array is stacked in multiple layers in the slice thickness direction so that multiple slice planes can be photographed simultaneously.

In this PECT apparatus, in order to increase the resolution of images, the aperture width of each of the many detectors has been reduced and these have been arranged in high density. This reduces the spatial sampling interval.

Problems to be Solved by the Invention However, simply reducing the aperture width of each detector and reducing the sampling interval as in the past causes a problem of reduced detection efficiency. Therefore,
Conventionally, there was a limit in terms of detection efficiency.

In other words, in the slice thickness direction, when arranging detectors in the slice thickness direction as described above and collecting data simultaneously for the number of detectors arranged, it is possible to reduce the aperture width of each detector in the slice direction. There is a limit to reducing the sampling interval in terms of detection efficiency, so
In reality, the sampling interval must be quite large, and as a result, the slice thickness of the reconstructed image cannot be reduced.

There is also a desire to increase the length of the slice in the thickness direction over which data can be collected at the same time. This can be done by widening the aperture width of each detector in the slice thickness direction to increase the slice thickness, or by increasing the number of detectors arranged in the slice thickness direction to increase the number of slices. In the former case, the resolution of the image decreases, resulting in deterioration in image quality, and in the latter case, there is a problem in that the cost is too high.

This invention improves the number of sampling points that can be collected substantially simultaneously across the slice thickness and the length of the slice through the thickness that can be collected substantially simultaneously without increasing cost. The purpose is to provide a PECT device.

Means for Solving the Problems According to this invention, there is a ring-shaped detector array consisting of a large number of radiation detectors arranged in a ring shape around the subject, and the positrons emitted from the subject are extinguished. The gamma rays are detected by each of the above detectors,
A PECT device that reconstructs a distribution image of positron-emitting nuclides within a subject by processing collected data by a computer, and includes a mechanism for reciprocating the ring-shaped detector array in the slice thickness direction. . Then, one data collection period is completed by repeatedly positioning the ring-shaped detector row alternately at at least two positions in the slice thickness direction using this reciprocating mechanism and collecting data. In other words, after all the data regarding one slice of the plurality of positions positioned above has been collected at a certain position of the ring-shaped detector array, the ring-shaped detector array is moved and the slice at that position is Rather than collecting data by setting one data collection period for each slice at the time before and after the movement, such as collecting all the data for a slice at a certain position, By repeating the process of collecting data, moving to another position and collecting a little data about other slices, we were able to collect all the necessary data for each slice at the end of one data collection period. In this way, simultaneity of data collection for multiple slices is obtained.

Operation The ring-shaped detector array is moved back and forth between two positions in the slice direction, and while data collection at each position is repeated alternately, a portion of the data for each slice is collected, resulting in one data collection. Once the period has elapsed, all necessary data has been collected for each of the multiple slices. Therefore,
The data for each slice was collected at substantially the same time. In other words, the number of sampling points from which data can be collected substantially simultaneously during one data collection period has increased in the slice thickness direction (the number of slices from which data can be collected substantially simultaneously has increased). Therefore, by increasing the number of slices that can virtually collect data simultaneously,
Images of many slices positioned over a wide range in the slice thickness direction can be obtained simultaneously, or images of many slices with small slice intervals can be obtained simultaneously. In the latter case, the slice interval (spatial sampling interval in the slice thickness direction) can be made smaller, but since the aperture width of each detector is not made smaller, the detection efficiency deteriorates (it takes less time to reconstruct one image). (Simply reducing the aperture width of each detector and increasing the array density will reduce detection efficiency and take time to collect data.)

Embodiment In FIG. 1, a ring-shaped array of radiation detectors 2 is placed around a subject (patient) 1. In this ring-shaped detector array 2, not only a large number of radiation detectors 3 are arranged in a ring shape in the circumferential direction, but also in the example shown in this figure, five radiation detectors 3 are arranged in the slice thickness direction. That is, the ring-shaped detector rows are stacked in five layers in the slice thickness direction.

The entire ring-shaped detector array 2 is then reciprocated in the slice thickness direction (in the left-right direction in the figure) relative to the subject 1. Various mechanisms such as a normal slide mechanism can be considered as the mechanism for this reciprocating movement. Note that this reciprocating movement only needs to be done relative to the subject 1, so move toward the subject 1 side (that is, toward the bed where the patient is sleeping).
It may be moved relative to the detector row 2.

In FIG. 1, the detector array 2 is moved back and forth between points A and B. Detector row 2 is placed at point A, data is collected at this position, then it is moved to point B, data is collected at this position, and then returned to point A, and so on. Then, reciprocating movement of the detector row 2 and data collection at each position A and B are repeated alternately, and data collection is performed in one data collection period. As a result, when looking at substantially the entire data collection period of one time, it can be seen that data collection was performed simultaneously using ten layers of ring-shaped detector arrays 2. In other words, the number of sampling points at which data can be collected simultaneously has doubled from 5 to 10 in the slice thickness direction, and in one data collection period, data for 10 slices can be collected at virtually the same time, allowing data to be collected at the same time. The length of the resulting slice in the thickness direction will also be doubled. Moreover, in this case, the number of detectors 3 arranged in the slice thickness direction does not increase, so the cost does not increase.

In this figure, the detector row 2 is reciprocated by the length of five detectors 3 in the slice thickness direction, thereby doubling the sampling point and data collection length in the slice thickness direction. However, as shown in FIG. 2, by setting the reciprocating distance to a length shorter than the thickness of one slice of the detector 3, the sampling pitch in the slice thickness direction can be made smaller. That is, in FIG. 2, the detector row 2 for three slices is moved back and forth between points C and D in the slice thickness direction, and the distance between points C and D is measured by the detector 3. The distance is half the thickness of one slice (the same is true even if it is an odd multiple), and the sampling pitch in the slice thickness direction is halved.

In other words, in both the embodiments shown in FIGS. 1 and 2, if the ring-shaped detector array 2 is stacked in five layers in the slice thickness direction, images of 10 slices can be obtained simultaneously in both cases. In the case of Fig. 1, the slice interval is 10, which corresponds to the array pitch of detector row 2 (array pitch in the slice thickness direction).
Data for slices can be obtained at the same time, and in the case of Figure 2, the slice interval is half the array pitch, which is 10.
Data for slices can be obtained simultaneously. In the former case, images of 10 slices positioned over a wide range in the slice thickness direction can be obtained simultaneously, and the length in the slice thickness direction over which data can be collected substantially at the same time can be expanded. In the latter case, data for each slice at a slice interval shorter than the actual array pitch of the detector row 2 can be collected simultaneously. Of course, if the aperture width (aperture width in the slice thickness direction) of each detector 3 is made smaller to increase the arrangement density in the slice thickness direction, the slice interval can be shortened, but in this case, the amount of light incident on each detector 3 per time As the number of gamma rays to be detected decreases, the detection efficiency deteriorates and it takes time to collect the data necessary to reconstruct one image. Since the detector 3 remains as it is and is simply moved, this inconvenience does not occur.

Effects of the invention According to this invention, the aperture width in the slice thickness direction of each detector is widened to increase the slice thickness, resulting in a decrease in image resolution and deterioration of image quality. By increasing the number of sampling points in the slice thickness direction at which data can be collected substantially simultaneously in one data collection period without increasing the number of arranged detectors and increasing the number of slices, thereby increasing the cost. The length in the slice thickness direction over which data can be collected substantially simultaneously during one data collection period can also be increased. Since simultaneous images of multiple slices can be obtained, changes in radioactive drug concentration over time can be tracked in multiple slices of the subject, making it possible to perform dynamic measurements in multiple slices that are truly useful for medical diagnosis. become.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of one embodiment of this invention, and FIG. 2 is a schematic diagram of another embodiment. 1...Object, 2...Detector row, 3...Detector.

Claims (1)

[Scope of utility model registration request] It has a ring-shaped detector array consisting of a large number of radiation detectors arranged in a ring shape around the subject, and each of the above detectors detects and collects positron annihilation gamma rays emitted from within the subject. A positron ECT device that reconstructs a distribution image of positron-emitting nuclides within a subject by processing the data by a computer, has a mechanism that reciprocates the ring-shaped detector array in the slice thickness direction. A positron ECT apparatus characterized in that one data collection period is completed by collecting data while repeating alternately positioning the ring-shaped detector array at at least two positions in the slice thickness direction.