JPS6252479A - Ring spect apparatus - Google Patents

Abstract

PURPOSE:To make it possible to simultaneously pick up and display a flat image while data for a tomographic image is sampled, by arranging a cylindrical collimator equipped with a large number of pinholes to the inner peripheral part of a cylindrical MWPC detector and rotating the same. CONSTITUTION:A controller 2 is cylindrical and has a large number of pinholes 21 arranged thereto. This collimator 2 is concentrically arranged inside a cylindrical MWPC 1 and rotated by a rotating/driving apparatus 22. An examinee 3 is introduced into the cylindrical collimator 2. The visual field containing the examinee 3 is projected to the inner cylindrical side surface of the cylindrical MWPC detector 1 by each pinhole 21 of the cylindrical collimator 2. If the collimator 2 is stopped to accumulate data, an RI distribution flat image wherein the examinee 3 has been looked from a large number of circumferential directions can be observed. This data can be also used as one for reconstituting a tomographic image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a nuclear medicine diagnostic device, and in particular to a ring S system that administers a single photon-emitting nuclide (RI) (radioisotope) to a human body and obtains a tomographic image of its distribution. P E
CT (Single Photon Emissi)
onComputed Tomography) device.

2. Description of the Related Art A conventional ring SPECT device has a configuration that can also be called a multiple scintillator type ring SPECT device, in which a detector consisting of a combination of a scintillator and a photomultiplier tube is arranged in a multiple ring configuration.

Problems to be Solved by the Invention However, the conventional multiple scintillator type ring SPE
CT equipment has extremely poor spatial resolution in the axial direction of the body, and also does not cover the field of view in the axial direction sufficiently, so it is difficult to obtain a planar image of the RI distribution projected onto a single plane, as can be obtained with a scintillation camera. It is difficult, and even if possible, it is impossible in real time, requiring a large software burden and computational time.

This invention is capable of capturing and displaying planar images while collecting data for tomographic images.
The purpose is to provide equipment.

Means for Solving the Problems The ring SPECT device according to the invention has a cylindrical MW
It consists of a PC detector (multi-wire proportional counter detector) and a rotating cylindrical collimator with a plurality of pinholes placed on the inner circumference of the PC detector.

Operation The cylindrical MWPC detector has positional resolution in both its circumferential and axial directions. On the other hand, since the collimator is provided with a pinhole, a planar image is obtained when the RI distribution is projected through this pinhole. In other words, a planar image is projected onto the inner peripheral surface of the cylindrical MWPC detector through the pinhole. Therefore, if the plane image projected in this way is displayed as it is, a plane image similar to that taken with a normal scintillation camera can be obtained. That is, it is possible to capture and display a planar image at the same time as collecting data for tomographic imaging.

Embodiment In FIG. 1, the cylindrical MWPC detector l is a MWPC
The detector is cylindrical. That is, MWPC
The detector consists of a cathode surface with a large number of cathode wires arranged on one surface in a chamber in which an inert gas with a high atomic number (for example, Xe, etc.) and a quenching gas (such as CH4) are sealed at high pressure. are arranged on two sides of an anode surface with a large number of anode wires arranged on one surface, and this chamber, two cathode surfaces, and seven node surfaces are each cylindrical. It is made into a cylinder by arranging them concentrically. By using the resistance division method or the delay line method, position discrimination can be performed in the direction in which the cathode wires are arranged, so by arranging the wires on two cathode surfaces so that they intersect between those surfaces, two-dimensional detection on the side surface of the cylinder can be performed. positioning, that is, positioning in the circumferential direction and the body axis direction. In addition, 1 with only two cathode surfaces and one anode surface.
Although it may be a layer MWPC detector, in this embodiment,
By making the layers formed by two cathode surfaces and one anode surface into multiple layers, that is, by stacking them in the radial direction (arranging them concentrically), a multilayer MWPC detector is created (as shown in Figure 2, the inner , the first layer, the second layer, etc.). Further, the positioning accuracy of the positioning circuit in each layer is made to be rougher as the layers are closer to the outer periphery.

The collimator 2 has a cylindrical shape and has many pinholes 21.
In the example of the if diagram, they are arranged on one circumference. This collimator 2 is placed concentrically inside the cylindrical MWPC detector l and is rotated by a rotary drive 22.

A subject 3 is placed inside this cylindrical collimator 2.

As shown in FIG. 2, each pinhole 21 of one cylindrical collimator 2 allows the field of view 3 including the subject 3 to be shaped like a cylindrical MW.
It is projected inside the cylindrical side of the PC detector l. Therefore, when the cylindrical MWPC detector 1 is expanded, the plane images projected by each pinhole 21 are arranged in the circumferential direction as shown in FIG. Note that the positions of the pinholes 21 are determined so that these plane images do not overlap with each other.

Therefore, if the collimator 2 is kept stationary for a while and data is accumulated, as many plane images as there are pinholes 21 can be obtained.
RI distribution plane images viewed from multiple directions around the area can be observed. Since this data can also be used as data for tomographic image reconstruction, data for tomographic images can be collected at the same time as plane images are taken.

In order to reconstruct a tomographic image, it is necessary to collect data at every minute angle around the subject 3 and increase the sampling density, so data collection at one position of the collimator 2 is performed as described above. After completing this, the collimator 2 is rotated by a small angle and kept stationary at that position, and similar data collection is performed. If this operation is repeated within the angle of the arrangement interval of the pinholes 21, all necessary data will be collected.

When collecting data for tomographic images in this way.

The only mechanical movement is the collimator 2, and the single cylindrical MWPC detector 1 remains stationary to obtain sufficient sampling density. Therefore, the cylindrical MWPC detector 1 can be kept completely stationary, and stable operation of the MWPC detector 1 can be ensured. Therefore, it is extremely important to be able to keep the cylindrical MWPC detector l stationary.

By the way, as mentioned above, in this example, the cylindrical MW
The PC detector 1 is a multilayer MWPC detector, and the positioning accuracy of the positioning circuit in each layer is made to be rougher as the layers are located on the outer periphery.

This is to suppress parallax errors due to the finite aperture of the pinhole 21 of the collimator 2. In other words, since the outer layer contains more parallax errors due to the finite aperture of the pinhole 21, the accuracy of one positioning is made coarser in proportion to the distance from the pinhole 21, and in the obtained position information, the parallax error in the outer layer is larger than that in the innermost layer ( This is made to match the parallax error in the first layer). Then, if the number of pixels in the effective field of view is the same for each layer and the position information obtained from each layer is simply added on one image, the image obtained from each outer layer can be reduced and obtained from the innermost layer. This means that it is superimposed on top of the original image.

Thereby, the parallax error due to the finite aperture of the pinhole 21 can be minimized (the parallax error of the innermost layer).

Although the pinholes 21 of the collimator 2 are arranged in one row on one circumference in the above, the detection surface of the MWPC detector 1 can be effectively utilized by devising this arrangement. For example, when the pinholes 41 of the collimator 4 are arranged alternately on two circumferences as shown in FIG. appear alternately on the two columns, so that the proportion of the area occupied by the projected images in the detectable plane of the MWPC detector 1 increases, and as a result the ring SPE
The sensitivity of the entire system of the CT apparatus is improved.

Further, the count rate characteristics can be improved by dividing the cathode surface and the anode surface in the circumferential direction or the body axis direction and providing a positioning circuit for each of them.

Effects of the Invention According to the present invention, it is possible to simultaneously capture plane images from multiple directions while collecting data for tomographic images. Also, MWP
Since no mechanical movement of the C detector is required, stable operation can be achieved.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of one embodiment of the present invention, Fig. 2 is a cross-sectional view of a part of the same embodiment, Fig. 3 is an exploded view of a cylindrical MWPC detector, and Fig. 4 is another embodiment. FIG. 5 is an exploded view of a cylindrical MWPC detector for explaining a plane image obtained by the collimator of FIG. 4. l... Cylindrical MWPC detector 2.4... Collimator 21.41... Pinhole 22... Rotation drive device 3... Subject 31...
field of view

Claims (2)

[Claims] (1) A ring SPECT device consisting of a cylindrical MWPC detector and a rotating cylindrical collimator with a plurality of pinholes placed on the inner circumference of the MWPC detector. (2) The cylindrical MWPC detector is composed of multilayer MWPC detectors stacked in the radial direction, and the positioning accuracy of each layer is made rougher as the outer layer increases. Ring SPECT device according to item 1.