JPH09211131A - Positron ct device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain an image for specifying the position of a photographing region by taking out and arranging the data of an instructed angle out of collected simultaneous counting data, and making a planar image viewed from the direction of the angle. SOLUTION: Numeral 1 is added every address in correspondence with an angle θ and a distance (d) in a data collection memory 14. Such data collection is performed every slice. At the time of imaging, a signal designating a specified angle θ from a host computer 16 is transmitted to DSP(Digital Signal Processor) 15. Coefficients for dispersion correction of each detector have been written on the dram of DSP 15 with a host computer 16. Only the data of the designated angle θ out of data collected with the data collection memory 14 are successively corrected and calculated on the basis of the correction coefficients every address and the data after correction are transmitted to the computer 16 through a data bus.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positron CT
The present invention relates to an apparatus, and more particularly to a ring type positron CT apparatus.

[0002]

2. Description of the Related Art A positron CT apparatus uses a positron-emitting radionuclide and detects annihilation gamma rays to take a distribution image of the nuclide. For example, when a drug labeled with a positron-emitting radionuclide is administered to the human body, it accumulates in specific organs. At that time, gamma rays emitted outside the human body are detected by a detector arranged outside the human body to collect data. Since the annihilation gamma rays are emitted in the opposite direction of 180 °, it can be seen that nuclides are present on the line connecting the pair of detectors by detecting that they are incident on the pair of detectors at the same time. Therefore, the position information representing the line is determined in some form, and "1" is added to the address corresponding to the position information. The nuclide concentration distribution image at a predetermined cross section is reconstructed by processing the data collected by such counting for each position by a predetermined algorithm. This reconstructed image is used for diagnosis of a specific organ.

A scintillation detector or the like is used as a detector for detecting gamma rays outside the subject. In the ring type positron CT apparatus, a large number of this scintillation detectors are arranged in a ring type. Then, usually, the ring-shaped array of the detectors is stacked in a plurality of layers. Of the gamma rays from the nuclide on the plane where the detector ring type array of each layer is located, those emitted parallel to that plane are incident on one of the ring type detectors of that layer. To be detected. Therefore, the data on the plane (slice plane) of each layer of the subject is collected by the detector ring type array of each layer, and the concentration distribution image of the nuclide on these slice planes is obtained as a reconstructed image. It will be.

In such a positron CT apparatus,
It is necessary to specify the imaging site and position the subject before imaging. This positioning is easy when the position of the organ or the like can be identified from the outside. For example, when the head is imaged, the OM line, which is a line connecting the outer corner of the eye and the ear canal, which is recognizable from the outside, is used as a reference. If set, the first slice can be located at the fundus.

However, it is impossible to specify the position of organs such as the heart and the liver from the outside. Therefore, in such a case, it is necessary to separately capture a positioning image. A transmission image is used as the positioning image, for example. This transmission image is obtained by collecting data while rotating an external RI source around the trunk of the subject before administering the radioisotope (RI) to the subject and reconstructing the degree of transmission of gamma rays to obtain an image. It has been transformed.

[0006]

However, it takes time and effort to take a transmission transmission image for positioning in the case of taking an image of an organ whose position cannot be specified from the outside such as the heart or the liver. As a result, there is a problem that it is not practical. Therefore,
In the end, the actual situation is that the operator (doctor, etc.) empirically specifies the positions of the imaged parts or ultrasonic waves without taking the transmission images. .

In view of the above, an object of the present invention is to provide a positron CT apparatus improved so that an image for specifying the position of an imaged region can be easily obtained.

[0008]

In order to achieve the above object, in the positron CT apparatus according to the present invention, a large number of radiation detecting means are arranged in a ring shape, and the radiation detecting means in which the ring type arrangement is arranged in multiple layers. Corresponding to a multi-layered ring arrangement of means, a simultaneous detection means for detecting simultaneous output from two of the many radiation detection means in each slice, and a pair of radiation detection means for simultaneous output It is characterized in that it is provided with means for counting radiation events at an address to collect data, means for creating a plane image only from data of a designated angle, and image display means for displaying the plane image. There is.

By extracting and arranging data of a designated angle from the collected coincidence data, a plane image viewed from the angle direction can be created. This plane image is displayed by the image display means. Since such a planar image can be created by diverting the data collected for positron CT image reconstruction, positron CT
It can be created concurrently with image reconstruction, is extremely simple, and does not take much time. Alternatively, even when data is collected to create such a planar image separately from data collection for positron CT image reconstruction, data collection / image creation / display can be performed easily and in a short time.

[0010]

Next, embodiments of the present invention will be described in detail with reference to the drawings. In the positron CT apparatus according to the present invention, as shown in FIG. 1, a large number of radiation detectors 11 are arranged in a ring type, and the ring type arrangement 10 of the detectors 11 is formed in multiple layers (perpendicular to the plane of the drawing). In the same direction). A subject (patient) 30 is arranged in the multilayer ring-shaped array 10. A small amount of RI (the type depends on the organ to be imaged, for example, O-15) is administered to the subject 30. Alternatively, the line radiation source 21 arranged outside is rotated around the trunk of the subject 30.

The respective outputs of the detectors 11 for the respective layers are guided to the coincidence circuit 12, and it is detected that radiation is simultaneously incident on any two of the detectors 11 and the outputs simultaneously occur. And like this 2 at the same time
When an output is generated from one detector 11 and detected by the coincidence circuit 12, the output of the one set of detectors 11 from the coincidence circuit 12 is stored in a table.
The address signal is sent to the memory 13 and the address signal corresponding to the combination of the two detectors 11 is obtained. That is, the table memory 13 stores in advance a table to which addresses corresponding to various detector pairs are assigned.

This address is, for example, to represent a line connecting the detector pair as shown in FIG.
And the distance d from the center. Data collection memory 14
Then, "1" is added for each address according to the angle θ and the distance d. Such data collection will be performed for each slice.

On the other hand, a signal for designating a predetermined angle (corresponding to θ shown in the figure) from the host computer 16 in performing image pickup is sent through the data bus 17 to the DSP.
(Digital signal processor) 15.
Further, the host computer 16 writes the coefficient for correcting the variation of each detector 11 on the DRAM of the DSP 15. Of the data collected in the data collection memory 14, only the data at the designated angle is sequentially corrected and calculated for each address based on the correction coefficient, and the corrected data is the data bus 1
7 to the host computer 16.

The designated angle is designated as an arbitrary angle around the trunk. For example, the angle is set counterclockwise with the front as 0 degree. In that case, it is set to 90 degrees to obtain a sagittal plane image of the brain, 30 degrees to obtain a myocardial short-axis plane image, and the like.

If it is set to 30 degrees, θ is 3
Only 0 degree data (d takes various values) is sent to the host computer 16. When the data of only such a specified angle is fetched by the host computer 16 for all the slices, this data array becomes the object 3
A plane image viewed from the direction of 30 degrees counterclockwise from the front of 0 is configured. In the host computer 16,
After the data between the slices is linearly interpolated to match the pixel size, the image data is sent to the display device 18. As a result, a plane image of the subject 30 viewed from the direction of 30 degrees counterclockwise from the front is displayed.

In this case, if the data collection memory 14 is cleared and recollected at regular time intervals, plane images at constant time intervals will be sequentially displayed, which is a function equivalent to a so-called persistence scope of a gamma camera. Has become possible. This fixed time can be controlled by the host computer 16. Therefore, the subject 30
If the plane images as described above are sequentially obtained while slowly moving, it is possible to observe the plane image at each position of the movement, and it is possible to specify the imaged site from the image.

When the RI is administered to the subject 30 and the above-mentioned plane image is displayed, a memory that is not cleared separately from the memory space that is cleared at regular time intervals and that accumulates data. If data is once collected so that it can be used without being discarded, such as by providing a space, the data can also be used for positron CT image reconstruction. In that case, since data for positron CT image reconstruction can be obtained at the same time in the process of obtaining a planar image for positioning, positron CT image reconstruction can be performed in almost real time. Positron C
The reconstruction operation of the T image is performed in the host computer 16 or dedicated image reconstruction operation hardware (not shown) is used.

The above description is for one example of the embodiment, and it is needless to say that the specific configuration can be variously changed. For example, in the above, the data collection memory 14 collects data at all addresses, but it is limited to only obtaining a planar image for positioning, and the data collection may be performed only at addresses at designated angles. You can also Although the case where RI is administered to the subject 30 has been described above, the same thing can be done when the line source 21 is rotated around the subject 30 without collecting the RI. .

[0019]

As described above, according to the positron CT apparatus of the present invention, an image for positioning can be easily obtained, and by using this image, the imaged region can be specified accurately and in a short time. . In particular, since it is possible to monitor a plane image from an arbitrary angle, accurate positioning is possible even for organs that face different directions such as the heart and the brain. In addition, since the positioning image can be obtained in a short time with a simple operation, the burden on the patient is lightened and the throughput can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 10 detector ring array 11 detector 12 coincidence circuit 13 table memory 14 data collection memory 15 DSP 16 host computer 17 data bus 18 display device 21 line source 30 subject

Claims (1)

[Claims] 1. A multilayer ring array of radiation detecting means in which a large number of radiation detecting means are arranged in a ring shape, and the ring type arrangement is arranged in multiple layers, and two of the plurality of radiation detecting means in each slice. Detection means for detecting the simultaneous output of two radiation detectors, a means for counting radiation events at the addresses corresponding to the pair of radiation detection means for the simultaneous output, and collecting data, and data of a specified angle. A positron CT apparatus comprising: means for creating a plane image from only the image; and image display means for displaying the plane image.