JPH0142394B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a collimator used in camera rotation type ECT (Emission Computer Tomography).

[Conventional technology]

Camera rotation type ECT collects data by rotating a scintillation camera around a subject to whom RI (radioisotope) has been administered, and uses that data to perform image reconstruction processing on a computer. This method obtains a two-dimensional distribution image of RI within the subject's body on a slice plane parallel to the plane on which the rotational trajectory of the camera is. When performing ECT in this manner, conventionally, a collimator 1 as shown in FIG. 1 has been attached to a scintillation camera. In this collimator 1, square holes 2 are arranged in a straight line in the vertical direction (X direction) and also in a straight line in the horizontal direction (Y direction), and a partition wall 3 between the holes 2 The entire area is in the form of a grid.

[Problem to be solved by the invention]

Conventional collimators have a grid-like partition wall as shown above, and such collimators are used in ECT.
There is a problem in that the quality of the reconstructed image deteriorates when used for In other words, shadows of the partition walls appear in a checkerboard pattern both vertically and horizontally, and data is missing in the shadowed portions. For example, in the case of the AA line cross section in Figure 1,
As shown in FIG. 2, the gamma rays from the gamma ray source 5 are blocked by the partition wall 3 and cannot reach the scintillation camera 4 at any position in the Y direction. In the case of the BB line cross section in Figure 1, as shown in Figure 3,
Gamma rays from the gamma ray source 5 enter the scintillation camera 4 through the hole 2 and enter the partition wall 3.
Then it will not be incident. The position of the shadow (horizontal position) due to this partition wall 3 is the position of the BB line (vertical position)
Even if I shift it, it's the same. In other words, this third
It can be seen from the figure that the position information is scattered in the Y direction. Similarly, only discrete data can be obtained in the X direction. Therefore, regardless of whether the vertical or horizontal direction is perpendicular to the slice plane or within the slice plane, it is not possible to collect data in the portion corresponding to the shadow of the partition wall in the projection data in each direction. The projection data has a distribution in which the number of incident gamma rays is scattered in the positional direction, and the quality of the image reconstructed from this will deteriorate. An object of the present invention is to provide a collimator for ECT that can reduce deterioration in image quality of a reconstructed image when performing ECT by rotating a scintillation camera.

[Means to solve the problem]

In order to achieve the above object, this invention
In a collimator for ECT, a radiation shielding plate is provided with a large number of rectangular holes, and the partition formed between the rectangular holes is linear in one direction (vertical or horizontal) and linear in the other. The arrangement position of the rectangular holes is determined so that the rectangular holes are not linear in the direction, and the rectangular holes are mounted on the scintillation camera so that the direction in which the rectangular holes become linear is the direction of movement when the scintillation camera rotates. It has become a feature.

[Effect]

In this collimator for ECT, the arrangement positions of the rectangular holes are determined so that the partition wall portion is not linear in one of the vertical and horizontal directions. Therefore, the collimator is attached to the scintillation camera and rotated so that the direction in which the collimators are arranged in a straight line is the direction of movement when the scintillation camera rotates, that is, the direction within the slice plane, and the collimator is rotated to collect data. Then, the linear striped shadows of the partition wall are arranged in a direction perpendicular to the slice plane. That is,
Rotation information within the slice plane is not lost; only position information in the direction perpendicular to the slice plane is lost. Since the slice plane is generally thicker than several rectangular holes, even if positional information in a direction perpendicular to the slice plane is lost, this only results in a decrease in sensitivity. Therefore, deterioration in image quality of the reconstructed image can be reduced.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In the collimator 6 according to one embodiment, a large number of square holes 7 are provided in the radiation shielding plate in an arrangement as shown in FIG. In other words, the arrangement position of the holes 7 is adjusted so that the partition wall 8 does not form a straight line in one direction of the X or Y direction (the X direction in this figure), but by shifting it little by little in the other direction (the Y direction in this figure). It is determined. Further, in a collimator 11 according to another embodiment, as shown in FIG. so as not to form a straight line in the long side direction of hole 9 (X direction in this figure).
Short side direction of rectangular hole 9 (Y direction in this figure)
The arrangement positions of the holes 9 are determined by shifting them little by little. These collimators 6 and 11 are arranged so that this Y direction is
It is attached to the scintillation camera so that it is in the direction of movement of the scintillation camera when the ECT rotates. Then, the X direction is a direction perpendicular to the slice plane, and the Y direction is a direction within the slice plane. In the collimators 6 and 11 shown in FIGS. 4 and 5, striped shadows extending linearly in the Y direction are produced as shadows of the partition walls 8 and 10, but the shadows are not linear in the Y direction. become. In other words, these fourth
The shadows extending in the horizontal direction in the figures and FIG. 5 are linear, but the shadows extending in the vertical direction sway from side to side in a zigzag shape. Therefore, regarding the position information in the X direction,
Parts corresponding to the linear shadows extending in the horizontal direction are missing, and only discrete data can be obtained. On the other hand, regarding position information in the Y direction, the shadow extending in the vertical direction sways left and right in a zigzag shape, so even if position information is missing in a place with a shadow, the missing Position information will be obtained at the locations above and below the location, and as a result, the position information in the Y direction will not be missing and will be obtained continuously. In ECT, such collimators 6,
11 is attached to the scintillation camera as described above, rotates, and stops at every minute angle to allow gamma rays to be incident thereon to obtain projection data at each position. Here, the projection data in one direction for a certain slice plane is the distribution of the number of incident gamma rays in the Y direction, and from the two-dimensional data spread over the entire field of view of the scintillation camera, a predetermined X direction corresponding to the slice plane is This is obtained by extracting only the data belonging to the range and arranging it in the Y direction. The slice thickness is not so thin, but is usually at least as thick as several holes 7 and 9. Therefore, data in the Y direction is not missing as described above, and continuous data is obtained, so that sufficient projection data can be obtained. Therefore, by obtaining such projection data from multiple directions and reconstructing the image from them,
A tomographic image of excellent image quality can be obtained. In the case of the collimator 11 shown in FIG. 5, the hole 9 is long in the X direction and short in the Y direction. Therefore,
The gamma ray incident direction regulation function (aperture function) is
The positional resolution is high in the Y direction and low in the X direction, and the positional resolution is high in the Y direction and low in the X direction. The Y direction is within the slice plane, and high positional resolution in that direction is effective in improving the spatial resolution of the reconstructed image. On the other hand, the X direction is the slice thickness direction, and high positional resolution is not required. The fact that the hole 9 is long in the X direction means that the shadow area is reduced accordingly, and the sensitivity can be improved. In other words, the sensitivity is increased by taking advantage of the fact that positional resolution is not required in the X direction. After all, with this collimator 11, it is possible to obtain ECT data with high positional resolution and to increase sensitivity.

【Effect of the invention】

According to the collimator for ECT of the present invention, although it has a simple configuration, by attaching it to the scintillation camera when performing ECT by rotating the scintillation camera, it is possible to reduce deterioration in image quality of reconstructed images.

[Brief explanation of drawings]

Figure 1 is a partially cutaway enlarged front view of the conventional example, Figure 2 is a sectional view taken along line AA in Figure 1, and Figure 3 is a BB in Figure 1.
4 is a partially cutaway enlarged front view of one embodiment of the present invention, and FIG. 5 is a partially cutaway enlarged front view of another embodiment. 1, 6, 11... collimator, 2, 7, 9... hole,
3, 8, 10... partition part, 4... scintillator, 5...
Gamma ray source.

Claims (1)

[Claims] 1. A radiation shielding plate is provided with a large number of rectangular holes, and a partition formed between the rectangular holes is linear in one of the vertical and horizontal directions, The ECT is mounted on the scintillation camera so that the rectangular holes are arranged so that they are not linear in other directions, and the direction in which the rectangular holes are linear is the direction of movement when the scintillation camera rotates. Collimator for use. 2. The rectangular hole is formed in a rectangular shape so that one direction of the vertical or horizontal direction in which the partition wall portion is not linear is the long side, and the other direction is the short side. A collimator for ECT according to claim 1.