JPH0521033Y2 - - Google Patents

Description

[Detailed explanation of the invention] Industrial application field This invention is a ring type single photon ECT.
Regarding equipment.

Conventional technology A ring-type single photon ECT device arranges a large number of radiation detection detectors in a ring shape to obtain a tomographic image of the concentration distribution of single photon-emitting nuclides. It is configured as follows. In FIG. 3, detectors 1 for detecting radiation are arranged in a ring shape, and a ring-shaped collimator 2 is placed inside the detectors 1.
rotates. In the case of the figure, this collimator 2 is 4
The parallel collimator in each direction allows projection data in four angular directions to be obtained simultaneously.

Considering projection data in a certain angular direction, for example, the vertical direction, as shown in Figure 3, the vertical projection data is generated by an upper detector group and an opposing lower detector group. However, the data sampling points are at each position of the detector 1.

By the way, the conventional ring type single photon
In the ECT device, the number of detectors 1 is set to an even number such as 2 or 8 times for reasons such as facilitating computer processing. Therefore, in the upper detector group and the lower detector group, the position of the detector 1 in the linear direction is the same, that is, the linear sampling point is the same on the upper side and the lower side. This is true for all directions other than the vertical direction; in any angular direction, the linear position of the detectors in the opposing detector groups is the same, and the linear sampling is the same by the opposing detector groups. Point data is obtained.

Therefore, for each of the projection data in all angular directions, the linear sampling width is
is equal to the array spacing of

On the other hand, a ring-type single photon ECT device requires high spatial resolution. To achieve this, the length of the radiation shielding thin plates in the collimator 2 is increased and the intervals between them are narrowed to improve the spatial resolution of the collimator 2.
However, in order to reproduce this spatial resolution on the reconstructed image, the linear sampling width of the projection data in each angular direction must be set to 1/2 or less of the half-width of the spatial resolution of the collimator 2. Therefore, even if the spatial resolution of the collimator 2 is increased, it is meaningless unless the linear sampling width of the projection data is reduced.

Therefore, in order to increase the spatial resolution,
In order to reduce the linear sampling width of projection data, the size of each detector 1 is reduced to increase the arrangement density and narrow the spacing between the detectors 1.

Further, the ring-shaped arrangement of the detector 1 as a whole is subjected to minute rotation or wobbling (swaying motion). That is, the entire ring-shaped array of detectors 1 is rotated by a small radius to shift the position of each detector 1.

Problems to be Solved by the Invention However, the conventional structure of reducing the size of the detector and increasing the arrangement density has the disadvantage of being expensive because it requires a large number of expensive detectors. Further, in the case of a configuration that allows minute rotation or wobbling, a special mechanism is required for that purpose, making the mechanism complicated.

The purpose of this invention is to provide a ring-type single photon ECT device that has a simple mechanism, is inexpensive, and can achieve high spatial resolution by making the linear sampling width smaller than the detector spacing. purpose.

Means to solve the problem Ring type single photon according to this invention
The ECT device includes an odd number of detectors fixedly arranged in a ring along one circumference, and a rotating ring-shaped collimator placed inside the ring arrangement of the detectors. configured.

Effect If the number of detectors fixedly arranged in a ring shape along one circumference is odd, one side and the other side facing each other by 180 degrees will have a direction perpendicular to the opposite direction. In this case, the position of each detector is staggered. In other words, the center of the detector on the other side is located in the middle of the interval between the detectors on one side facing each other by 180 degrees. Therefore, when projection data in one angular direction is collected on one opposing side and the other side, the number of linear sampling points is doubled, and the linear sampling width becomes 1/2 of the detector spacing.
Therefore, spatial resolution is improved.

Embodiment In FIG. 1, detectors 1 for detecting radiation are arranged in a ring shape, and a ring-shaped collimator 2 is placed inside the detectors 1, and this collimator 2 rotates. This configuration is similar to the conventional one (FIG. 3), but is characterized by the fact that the number of detectors 1 is an odd number.

In this case, for example, considering projection data in the vertical direction, as shown in Figure 1, the sampling points of the projection data collected by the upper detector group and the lower The sampling points of the projection data collected by the detector group are staggered and located in the middle of each other. In other words, by arranging an odd number of detectors 1 in a ring shape along one circumference, when looking at the opposing parts, the position of the upper detector 1 is on the lower side in the direction perpendicular to the opposing direction. This is because it is located between the positions of the detector 1 and the position of the detector 1. Therefore, the number of linear sampling points for vertical projection data is twice as many as before due to the upper detector group and lower detector group. The linear sampling width of the data is 1/2 of the interval between the detectors 1.

And this is true not only for projection data in the vertical direction but also for projection data in all angular directions, so for projection data in all angular directions, simply by setting an odd number of detectors, each projection data The linear sampling width of can be set to 1/2 of the spacing of the detectors 1.

Note that the sampling point is determined by the position where the detector 1 is arranged and does not depend on the collimator 2. Therefore, no matter what collimator is used, the linear sampling interval of each projection data is set to 1/2 of the interval of the detector 1. It can be done. For example, a ring-shaped collimator 3 having parallel collimators in three directions as shown in Fig. 2 may be used, or a turbofan-shaped collimator in which the holes (radiation transmission paths) of the collimator are not parallel may be used. .

Detector 1 is typically one per scintillator.
Although it is possible to use a combination of several photomultiplier tubes, it is not limited to this. For example, light from many scintillators is guided to a few photomultiplier tubes, and radiation is incident on which scintillator. Any individual item can be used, such as a type that distinguishes whether the item has been used or not.

Effects of the invention According to this invention, there is no need to arrange a large number of small detectors, so it is inexpensive, and there is no need for complicated mechanisms for micro-rotation or wobbling, and the ring-shaped arrangement of detectors can be fixed. Therefore, while the mechanism is simple, the linear sampling width can be made smaller than the detector interval, and the spatial resolution can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of one embodiment of this invention, FIG. 2 is a schematic diagram of another embodiment, and FIG. 3 is a schematic diagram of a conventional example. 1...Detector, 2, 3...Ring type collimator.

Claims (1)

[Scope of utility model registration request] Ring type single photon ECT having an odd number of detectors fixedly arranged in a ring shape along one circumference and a rotating ring type collimator placed inside the ring arrangement of the detectors. Device.