JPH036480B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ring-shaped collimator used in a radiation type computer tomography apparatus in which a large number of radiation detectors are arranged in a ring shape.

There are two types of radiation computer tomography devices: one type that rotates a scintillation camera around the subject, and the other type that arranges a large number of radiation detectors in a ring shape and places the subject inside this ring-shaped arrangement to take images. There is.

In this latter type of radiation computerized tomography apparatus, a ring-shaped collimator is used.
Conventionally, what is called a turbofan collimator has been used as this ring-shaped collimator. This turbofan collimator is made by arranging a large number of radiation shielding thin plates in a ring shape and hardening them with radiolucent resin so that they can rotate while maintaining the ring-shaped arrangement, so that the direction of the thin plates changes little by little. It is tilted. In other words, the radiation incident direction defined by the elongated gap between the thin plates changes slightly at each position in the circumferential direction. Therefore, this turbo uncollimator
When placed inside a ring-shaped array of radiation detectors and rotated, the direction of the radiation incident on a single radiation detector will change one after another according to the rotation, and the required angle This will allow you to scan a range.

By the way, in a turbo uncollimator like this, increasing the spacing between the thin plates of the radiation shielding will result in higher sensitivity but lowering the resolution, and conversely, making the spacing narrower will improve the resolution but lower the sensitivity. As such, sensitivity and resolution are incompatible.

Therefore, in the past, various types of turbofan collimators were prepared depending on the sensitivity and resolution, typically two types of turbofan collimators: a high-sensitivity type with wide spacing between the thin plates of the radiation shield and a high-resolution type with narrow spacing.
They are used by changing them depending on the purpose.

However, replacing the collimators one by one depending on the purpose is not only cumbersome, but also poses problems in terms of the effort required to manage the collimators that are not in use and the space required to store them.

In view of the above, it is an object of the present invention to solve problems such as the trouble of replacement and management, and the problem of storage space, by realizing a high-sensitivity type and a high-resolution type in one turbofan collimator.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figures 1 and 2 are
It shows a ring-shaped collimator for a radiation type computer tomography apparatus according to an embodiment of the present invention,
As shown in these figures, a thin plate 1 of radiation shielding material such as lead or tungsten defines the direction of radiation incidence (in this case, the direction of incidence changes gradually with respect to the center position O). A large number of them are arranged, and radiation transparent foamed resin 2 is filled and solidified between these thin plates 1 as spacers.
The foamed resin 2 is made of a material such as polyurethane foamed resin that has good adhesion to the thin plate 1, and each thin plate 1 is held in its position by the solidified foamed resin 2. It is integrated with the foamed resin 2 and has a ring shape as a whole.

The thin plates 1 are provided so that sparsely arranged parts and densely arranged parts are alternately repeated in the arrangement direction (in this case, in the circumferential direction). This repetition interval corresponds to the arrangement interval of the radiation detectors 3. Assuming that 2π/θ radiation detectors 3 are arranged at a constant angle θ (radian) as shown in FIG.
It is. Areas with sparse arrangement density are high sensitivity areas, and areas with dense arrangement areas are high resolution areas.

This ring-shaped collimator is intermittently rotated at every angle θ from the state shown in FIG. By rotating 360 degrees, data from incident radiation from various angular directions within a certain range can be obtained from each radiation detector 3, and the concentration distribution image of RI (radioisotope) can be reconstructed. . In this case, each radiation detector 3 functions as a high-resolution collimator because a high-resolution section is always located therein. Furthermore, if the ring-shaped collimator is rotated by an angle θ/2 from the state shown in Fig. 1 (this state is shown in Fig. 3) and then rotated intermittently at every angle θ, this collimator can be used as a highly sensitive collimator. It turns out. Note that the plurality of thin plates 1, each corresponding to one radiation detector 3, are tilted toward the center position O (that is, inward), but doing so is advantageous in terms of the directivity characteristics of the incident radiation. (Theoretically, the plurality of thin plates 1 corresponding to each radiation detector 3 may be parallel, but
In this case, the directivity becomes broader, and since the plurality of thin plates 1 corresponding to the adjacent radiation detectors 3 are parallel between them, a dead space is required to adjust the angle in the adjacent parts).

This collimator is extremely easy to manufacture because it can be manufactured by pouring foamed resin 2 in a ring shape into a ring-shaped array of a large number of thin plates 1 that are positioned and arranged and solidifying the foamed resin 2.

In the above example, the high-sensitivity part and the high-resolution part are provided by changing the arrangement density of the thin plate 1, but it is also possible to change the length of the thin plate 1 or change the inclination angle with respect to the center position O. These two parts can also be made by

As described above with respect to the embodiments, according to the present invention, it is possible to easily convert from high resolution to high sensitivity (or vice versa), and there is no need for space for a replacement collimator. It has a simple structure, is easy to manufacture, and can be lowered in price.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an embodiment of the present invention seen from the front, Fig. 2 is a partially enlarged perspective view of the same embodiment, and Fig. 3 is a schematic diagram of a part of the embodiment seen from the front showing another state of use. It is a diagram. 1... Thin plate of radiation shielding material, 2... Foamed resin,
3... Radiation detector.

Claims (1)

[Claims] 1 Arranged in a ring shape, the direction of which changes slightly at each position in the circumferential direction,
In a ring-shaped collimator for a radiation-type computer tomography apparatus, which is composed of a large number of radiation shielding thin plates and a radiation-transparent spacer arranged between these thin plates to hold the above-mentioned large number of thin plates together, The sparse portions and dense portions are alternately repeated in the circumferential direction, and the repeating interval is equal to the array spacing of the radiation detectors arranged in a ring shape. A ring-shaped collimator for a radiation computer tomography apparatus, characterized in that it is correspondingly provided.