JPH0949881A - Collimator of scintillation camera and data collection method for tomography image by using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image of tomography with a collimator of a scintillation camera which is simple in structure, producible with good accuracy, makes the uniformity of collected data good and has a small number of arch facts. SOLUTION: Combined are a collimator base member 18 forming a multitude of parallel slits 23 by arranging vertically a multitude of shielding plates constituted of radiation shield members and formed like a long and thin plate in horizontal direction with specific intervals, a support stage 19 standing up from one plane of the collimator base member 18 nearly vertically to the plane, and radiation shield rods 20 arranged in the direction perpendicular to the longitudinal direction of the parallel slits 23 of the collimator base member 18 supported detachably by the support stage 19. By this, a collimator with a simple structure and capable of accurately producing is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scintillation camera for detecting a radiation emitted from a radioactive substance distributed in a subject by a detector and taking a distribution image of the radioactive substance in the subject. The present invention relates to a collimator having a simple structure, which can be manufactured with high precision, can improve the uniformity of collected data, and can obtain a tomographic image with few artifacts, and a tomographic image data collecting method using the collimator. .

[0002]

2. Description of the Related Art A conventional scintillation camera is shown in FIG.
As shown in FIG. 7, a rotary disk 3 is rotatably attached to one side surface of a frame body 2 which stands upright from the detector stand 1 about a rotary shaft 4, and the rotary disk 3 protrudes from the front surface of the rotary disk 3.
The detector 6 is attached by the book support arms 5 and 5, and the collimator 7 is attached to the incident surface side of the detector 6. As shown in FIG. 7, the opening 8 formed in the center of the rotating disk 3 is provided so that the subject table 10 supported horizontally by the two columns 9 can be inserted. Has been. In this state, the detector 6 is rotated around the subject 11 laid on the subject table 10, and the radiation (gamma rays) emitted from the radioactive substance (radioisotope) distributed in the subject 11 is rotated. ) Is made incident on the detector 6 through the collimator 7 attached to the front surface of the detector 6, and the radiation emitted from the inside of the subject 11 is detected to capture the distribution image of the radioactive substance.

The collimator 7 of the detector 6 in the scintillation camera limits the direction of gamma rays incident on the detector 6 so that only the gamma rays useful for projecting the subject 11 on the detector 6 are limited. The parallel beam collimator 7 shown in FIG.
a and the fan beam collimator 7b shown in FIG. 9 are used. The parallel beam collimator 7a is shown in FIG.
As shown in the front sectional view and the side sectional view of FIG. 8B, a large number of parallel holes 13, 13, ... Are formed in the plate member 12 having a predetermined thickness in the direction orthogonal to the plate surface. Consists of As shown in the front sectional view of FIG. 9A, the fan beam collimator 7b extends radially so as to focus the plate member 12 having a predetermined thickness at a predetermined distance above the plate member 12 and As shown in the side sectional view of FIG.
2 a large number of holes 1 extending parallel to the direction orthogonal to the plate surface
4, 14, ... Are formed.

To collect the gamma rays emitted from the inside of the subject 11 using the fan beam collimator 7b shown in FIG. 9, for example, as shown in FIG.
While rotating the detector 6 around the body axis of 1 as indicated by arrow A, the regions 15a, 15b, 15 in the subject 11 are rotated.
Regarding the gamma rays generated from the radioisotopes distributed in c, ..., Only the gamma rays perpendicular to the incident surface of the detector 6 are made into holes 14a, 1 by the fan beam collimator 7b.
4b, 14c, ..., and the projection data 16 at that time was obtained.

[0005]

However, in the collimator 7 in such a conventional scintillation camera, the parallel beam collimator 7a shown in FIG.
As shown in FIG. 1, for example, a honeycomb structure is formed in a parallel porous type, the structure is complicated, and it is difficult to manufacture with high accuracy. Further, the fan beam collimator 7b shown in FIG. 9 extends radially so as to form a focal point F at an upper predetermined distance in the state seen in the front sectional view shown in FIG.
A large number of holes 14, 14, ... That extend parallel to the direction orthogonal to the plate surface in the state seen in the side sectional view shown in (b) are formed, and the structure is more complicated than that shown in FIG. In particular, the opening direction of the large number of holes 14, 14, ...
It was difficult to manufacture with high precision so as to concentrate on.
Therefore, in any of the above collimators 7a and 7b, if the manufacturing accuracy is not sufficient, the uniformity of the collected data is poor, which causes a ring-shaped artifact in the obtained tomographic image.

Therefore, the present invention addresses such a problem, has a simple structure and can be manufactured with high precision, improves the uniformity of collected data, and can obtain a tomographic image with few artifacts. And a tomographic image data collecting method using the same.

[0007]

In order to achieve the above object, a collimator for a scintillation camera according to the first aspect of the present invention comprises a large number of thin and thin shield plates made of a shield member for the radiation and having its plate surface. A collimator base member having a large number of parallel slits arranged in parallel vertically at a predetermined interval in the horizontal direction, a support stand rising from one surface of the collimator base member substantially vertically to the surface, and detachable from the support stand And a radiation shielding rod which is supported in the direction of the parallel slit of the collimator base member and is arranged in a direction orthogonal to the longitudinal direction.

Further, the shield bar may be supported on a support base in a height adjustable manner.

Further, two or more of the above-mentioned shield bars may be arranged on the support base in the lateral direction at arbitrary intervals.

A method of collecting tomographic image data according to a second invention as a related invention of the collimator is such that a detector is rotated around a subject lying on a subject table, and radioactive rays are distributed in the subject. As a collimator for a scintillation camera that causes radiation emitted from a substance to enter the detector through a collimator attached to the front of the detector, detects radiation emitted from the inside of the subject, and captures a distribution image of radioactive substances Using the collimator described in the above means, in the first imaging, remove the shield rod of the collimator and rotate the detector around the subject to detect the radiation from within the subject and collect the reference data, and then the next imaging Then attach the shield bar of the collimator and rotate the detector around the subject to detect radiation from the inside of the subject and collect shadow data. Calculated projection data by subtracting the shadow data from the reference data, and therefrom to create a tomographic image data.

The collimator of the scintillation camera configured as described above has a large number of parallel slits formed in the collimator base member and is orthogonal to the longitudinal direction of the parallel slits of the collimator base member which are detachably supported by the support base. The shield rods arranged in a direction act to limit the direction of the radiation emitted from within the subject and incident on the detector so that only radiation useful for projecting the subject is allowed to pass. According to the present invention, the collimator can be manufactured with high accuracy, and the uniformity of collected data can be improved and a tomographic image with few artifacts can be obtained. it can.

[0012]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 1 is a perspective view showing an embodiment of a collimator 17 of a scintillation camera according to the first invention, FIG. 2 is a front sectional view thereof, and FIG. 3 is a side sectional view thereof. A scintillation camera in which this collimator 17 is used detects a radiation (eg, gamma ray) emitted from a radioactive substance (eg, radioisotope) distributed in the subject and takes a distribution image of the radioisotope in the subject. The overall structure is the same as in FIGS. 6 and 7 showing the conventional example.

That is, a rotating disk 3 is rotatably attached to one side surface of a frame body 2 which stands upright from a detector stand 1 so as to be rotatable around a rotating shaft 4, and the rotating disk 3 projects from the front surface of the rotating disk 3.
The detector 6 is attached by the book support arms 5 and 5, and the collimator 7 is attached to the incident surface side of the detector 6. As shown in FIG. 7, the opening 8 formed at the center of the rotating disk 3 is provided so that the subject table 10 supported horizontally by the two columns 9 can be inserted. Has been. In such a state, the detector 6 is rotated around the subject 11 laid on the subject table 10, and gamma rays emitted from the radioisotopes distributed in the subject 11 are emitted from the front face of the detector 6. A radioisotope distribution image is captured by making the detector 6 incident on the detector 6 through a collimator 7 attached to the detector and detecting gamma rays emitted from the inside of the subject 11.

In the present invention, the collimator 7 is replaced with the collimator 17 shown in FIGS. The collimator 17 restricts the direction of gamma rays incident on the detector 6 and allows only the gamma rays useful for projecting the subject 11 to pass therethrough. As shown in FIG. , Support base 19,
It is formed by combining with the shield bar 20.

The collimator base member 18 serves as a base member of the collimator 17 of the present invention and also serves as one member for limiting the direction of incident gamma rays, and has a rectangular frame member 21, for example. As shown in FIG. 3, in a rectangular space surrounded by the member 21, a large number of shield plates 22, 22, ... Made of a shield member for shielding radiation such as lead or lead compound and formed on an elongated thin plate material are provided. The surfaces are arranged vertically and are arranged in parallel in the horizontal direction at predetermined intervals. Therefore, a large number of parallel slits 23 are formed at regular intervals between the large number of shield plates 22, 22 ,.
The parallel slits 23, 23, ... Selectively collect only gamma rays from a plane orthogonal to the rotation axis 4 shown in FIG.

On the upper surface of the collimator base member 18, support stands 19, 19 are erected so as to face each other. This support base 19 supports a shield bar 20 which will be described later with respect to the collimator base member 18, and as shown in FIG. It is made of, for example, a triangular plate material that stands substantially vertically. The support base 19 is not limited to a triangular plate member, and may have any shape as long as it can support the shield bar member 20 at an appropriate distance from the upper surface of the collimator base member 18, for example, a quadrangle or a square shape. It may be a shape in which three or more mountain shapes are continuous.

A radiation shielding bar member 20 is supported on the supporting bases 19, 19. This shield bar 20
It is the other member that limits the direction of gamma rays emitted from the radioisotope in the subject and is formed of a radiation shielding member such as lead or lead compound in a round bar shape, as shown in FIG. The collimator base member 18 is arranged in a direction orthogonal to the longitudinal direction of the parallel slit 23, and is detachably supported at the apex of a triangle whose base is the length of the parallel slit 23.

Here, the operation of the shield rod 20 will be described with reference to FIG. In FIG. 4, FIG.
Collimator base member 18 of collimator 17 shown in FIG.
Are omitted, and the detector 6, the shield rod 20, and the subject 1 are omitted.
It shows the relationship with 1. In this case, the diameter of the shield bar 20 is the same as the diameter of the hole 13 shown in FIG. 8A or the diameter of the hole 14 shown in FIG. 9A, for example. In this state, the shield bar 20 is attached to the detector 6 and the subject 1
When it is arranged between the radioisotopes 1 and 1, the gamma rays generated from the radioisotopes distributed in the region 11 among the radioisotopes distributed in the subject 11 are blocked and not collected at the collection point a of the detector 6. . Therefore, in FIG. 4, by collecting the gamma ray data with and without the shield bar 20, and subtracting the latter from the former,
Gamma ray data can be collected only at the collection point a of the detector 6 where the shield bar 20 is located. Therefore, in FIG. 4, if the position of the shielding bar 20 is laterally shifted, gamma ray data at the collection points distributed over the entire surface of the detector 6 can be collected. Now, as shown in FIGS. 1 to 3, above the collimator base member 18, the shield bar 20 is provided at the apex of a triangle whose base is the length of the parallel slit 23.
9A and 9B as a whole by arranging
The collimator 17 having the same operation as the fan beam collimator shown in (1) can be constructed with an extremely simple structure.

In order to use the collimator 17 constructed as described above, in the scintillation camera shown in FIGS. 6 and 7, the bottom surface of the collimator base member 18 shown in FIG. Bar 20
The collimator 17 toward the subject table 10 side.
Is attached to the incident surface of the detector 6. Then, the detector 6 and the collimator 17 are rotated around the subject 11 laid on the subject table 10, and gamma rays emitted from radioisotopes distributed in the subject 11 are passed through the collimator 17 through the collimator 17. The gamma ray emitted from the inside of the subject 11 may be detected by the detector 6 and incident on the detector 6.

In FIG. 1, a plurality of mounting holes 24a, 24b, 24c are formed in the two opposing support bases 19, 19 at positions appropriately downward from the apexes of the triangles. The shield bar 20 may be supported on the support bases 19 and 19 such that the height thereof can be adjusted by using 24a to 24c. The means for adjusting the height of the shield bar 20 is not limited to the mounting holes 24 to 24c described above, and for example, the ends of the shield bar 20 may be attached to a plurality of positions on the inner surfaces of the support bases 19, 19 facing each other. A stopping means or other mounting means may be provided. Further, in FIG. 2, the shielding bar 20
Is not limited to one provided at the apex of a triangle having the length of the parallel slit 23 as the base, and as shown by reference numerals 20a and 20b, the support base 19 is provided at a constant height with an arbitrary interval in the lateral direction. You may arrange two or more. At this time, the support base 19 is, for example, a horizontally long quadrangle, and the shield bars 20a, 2
When a large number of 0b, ... Are arranged at a constant height over the length of the parallel slit 23 at a constant interval, as a whole, FIG.
The collimator 17 having the same operation as the parallel beam collimator shown in (a) and (b) can be constructed with an extremely simple structure.

Next, a method of collecting tomographic image data in a scintillation camera using the collimator 17 having the above-described structure will be described with reference to FIG. First, in the first photographing, in FIG. 5D, the shield bar 20 of the collimator 17 is removed from the support 19 and the detector 6 is rotated around the subject 11 in the direction of arrow B, for example.
The gamma ray from the inside of the subject 11 is detected and the result is shown in FIG.
The reference data 25 is collected as indicated by a broken line curve. Next, in the next imaging, in FIG. 5D, the shield bar 20 is attached to the support base 19, and the detector 6 is rotated around the subject 11 in the direction of the arrow B under the same conditions as described above. By detecting gamma rays from the inside of the subject 11, the
As shown by the solid curve in (c), the shielding bar 20
Of the shadow data 26 of FIG.

Next, from the above-mentioned reference data 25, shadow data 2
6 is subtracted to obtain the projection data 27 as shown in FIG.
Ask for. At this time, the gamma ray generated from the radioisotopes distributed in the regions 15a, 15b, 15c, ... Inside the object 11 shown in FIG.
By the action of the shield bar 20 of 7 and the parallel slit 23,
Only the gamma rays perpendicular to the plane of incidence of the detector 6 are collected at points a,
Area 1 in the subject 11 collected via b, c, ...
Data 15a 'corresponding to 5a, 15b, 15c, ...
15b ', 15c', ... Are obtained. Finally, FIG.
As shown in FIG. 5A, the projection data 27 shown in FIG.
By reversing the left and right of the projection data 16, projection data 16 similar to the conventional example shown in FIG. 10 can be obtained. The desired tomographic image can be obtained by reconstructing the image of the projection data 16 obtained in this way as in the conventional case.

[0023]

Since the present invention is constructed as described above,
Radiation from the inside of the subject with a large number of parallel slits formed in the collimator base member and a shield rod member that is detachably supported by the support base and that is arranged in a direction orthogonal to the longitudinal direction of the parallel slits of the collimator base member. Only the radiation useful for projecting the subject can be passed by limiting the direction of the radiation incident on the detector.
According to the present invention, the collimator can be manufactured with high accuracy, and the uniformity of collected data can be improved and a tomographic image with few artifacts can be obtained. it can.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a collimator of a scintillation camera according to the first invention.

FIG. 2 is a front sectional view of FIG.

FIG. 3 is a side sectional view of FIG.

FIG. 4 is a drawing for explaining the action of the shield bar.

5 is an explanatory view showing a tomographic image data acquisition method in a scintillation camera using the collimator shown in FIG.

FIG. 6 is a front view showing a scintillation camera used in the present invention and a conventional example.

FIG. 7 is a side view showing the scintillation camera.

FIG. 8 is a front sectional view and a side sectional view showing a conventional parallel beam collimator.

9A and 9B are a front sectional view and a side sectional view showing a conventional fan beam collimator.

FIG. 10 is an explanatory diagram showing collection of tomographic image data in a scintillation camera using a conventional fan beam collimator.

FIG. 11 is a perspective view showing a specific structure of a conventional parallel beam collimator.

[Explanation of symbols]

 6 Detector 10 Subject Table 11 Subject 16 Projection Data 17 Collimator 18 Collimator Base Member 19 Support 20, 20, 20a, 20b Shielding Rod 21 Frame Member 22 Shielding Plate 23 Parallel Slits 24a-24c Mounting Hole for Shielding Bar 25 Standard Data 26 Shadow data 27 Projection data

Claims (4)

[Claims] 1. A collimator base member in which a large number of thin and thin shield plates made of a radiation shield member are arranged in parallel in the lateral direction at predetermined intervals with the plate surface being vertical, and a plurality of parallel slits. , A support stand that rises from one surface of the collimator base member substantially perpendicularly to the surface, and a radiation stand that is detachably supported by the support stand and is arranged in a direction orthogonal to the longitudinal direction of the parallel slits of the collimator base member. A collimator for a scintillation camera, characterized by being combined with a shielding bar. 2. The collimator for a scintillation camera according to claim 1, wherein the shield bar is supported by a support so as to be adjustable in height. 3. The scintillation camera collimator according to claim 1, wherein two or more of the shield bars are arranged laterally at an arbitrary interval on a support base. 4. A detector is rotated around a subject lying down on a subject table, and radiation emitted from a radioactive substance distributed in the subject is passed through a collimator attached to the front face of the detector. The collimator according to claim 1 is used as a collimator of a scintillation camera which is made incident on the detector and detects radiation emitted from the inside of the subject to photograph a distribution image of a radioactive substance. Remove the rod and rotate the detector around the subject to detect the radiation from inside the subject and collect the reference data.In the next imaging, attach the shield rod of the collimator and attach the detector to the subject. It rotates around and detects radiation from the inside of the subject to collect shadow data, then subtracts the shadow data from the above reference data to obtain projection data. Tomographic image data acquisition method in a scintillation camera, characterized in that to create the over data.