JPH0636031B2 - Radiation type tomographic imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission type tomographic imaging apparatus for imaging a distribution image of a cross section of a radioactive isotope distributed in the body using a computer, and sometimes a double collimator. The present invention relates to a radiation type tomographic imaging apparatus capable of selecting three types of resolutions.

[Conventional technology]

Conventionally, a radiation type tomographic imaging device of this type has been disclosed in Japanese Patent Laid-Open No.
FIG. 6 shows a schematic front view of the structure, and FIG. 7 shows a schematic internal structure view of a portion AA of FIG. In each figure, the conventional emission type tomographic imaging apparatus has a large number of radiation detectors (1) arranged in a ring in a plane substantially perpendicular to the central axis 0-0 corresponding to the body axis of the subject (9). And is arranged inside the ring-shaped array of the radiation detector (1) and rotates about the central axis 0-0, and the directions with respect to the central axis 0-0 in the plane become various directions. The collimator (3a) having a large number of radiation incident direction defining apertures, which can rotate integrally with the collimator (3a) and slide in the central axis direction, can be retracted, and the central axis 0 in the plane. -0. A configuration including at least one layer of inner collimator (3b) having various directions in which the direction of the radiation incidence direction is defined and communicating with the opening of the collimator (3a) in a straight line. Is.

Next, the operation of the conventional device based on the above configuration will be described. The inner and outer collimators (3a) and (3b) are attached to the support linder (4
Gears of the support rings (4a) and (4b) supported by a) and (4b)
The gear (6) meshes with the gear (5), and the motor (7) rotates via the transmission mechanism such as the gear (6). Above inner support ring
(4b) is designed to rotate integrally with the outer support ring (4a) in this manner, but it can be slid backward and retracted as shown by the arrow in FIG. Has become.

In addition, there is another conventional radiation type tomographic imaging device shown in FIG. 8, which has three types of collimators (3a) for high resolution (HR), medium resolution medium sensitivity (MR), and high sensitivity (HS). ), (3b), (3c) are provided separately and independently, and these collimators (3a), (3b),
(3c) was rotated by a motor or manually in the direction of the arrow and inserted into the radiation detector (1) to change the resolution and sensitivity.

[Problems to be Solved by the Invention]

Since the conventional emission type tomographic imaging apparatus is configured as described above, even if the two kinds of resolutions can be appropriately selected by the two kinds of collimators, the two kinds of collimators are necessary to obtain the three kinds of resolutions. There was a problem that another collimator had to be added to the inside of the. In particular,
The configuration in which the collimator is divided into three layers must be formed to be extremely thin, which is difficult to manufacture and weak in mechanical strength, and it is difficult to adjust the three-layer collimator. there were.

Furthermore, other conventional emission type tomographic imaging devices can easily manufacture and adjust a collimator,
There is a problem in that a separate large-sized driving device is required for mounting each collimator on the radiation detector, and the operation becomes extremely complicated when manually performed.

The present invention has been made to solve the above problems,
An object of the present invention is to obtain an emission type tomographic imaging device capable of easily selecting three types of resolution and sensitivity with two types of collimators.

[Means for Solving the Problems]

The radiation type tomographic imaging apparatus according to the present invention has radiation detectors arranged on the circumference around the body axis of the subject, and the first collimator having a ring-shaped opening can be freely retracted inside the radiation detector. And a second collimator having a ring-shaped opening inside the first collimator is removably engaged with the first collimator, and both the first and second collimators are mounted inside the radiation detector. When rotating, the openings of both collimators communicate with each other and rotate integrally.

[Action]

The first and second collimators according to the present invention are mounted inside and outside the radiation detector so as to be retractable and retractable independently, and two types of collimators can be used individually or in combination to provide three types of resolution and sensitivity. It can be selected appropriately.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. This FIG. 1 is a schematic internal structural diagram corresponding to the AA part in FIG. 6 when both collimators of the radiation type tomographic imaging apparatus according to this embodiment are attached, and FIG. 2 shows the first collimator attached. And FIG. 3 shows a partial internal structure diagram when the second collimator is mounted.

In each of the above drawings, the radiation type tomographic imaging apparatus according to the present embodiment has a large number of radiation detections arranged in a ring in a plane substantially perpendicular to the central axis 0-0 corresponding to the body axis of the subject (9). (1) and a large number of ring-shaped apertures for defining the radiation incident direction which sequentially differ from the central axis 0-0 in the plane in which the radiation detector (1) is arranged. First collimator (3a) that engages with and retracts inside the ring-shaped arrangement of the vessel (1) and rotates about the central axis 0-0
And the central axis in the plane where the radiation detectors (1) are arranged.
It has a large number of ring-shaped openings for defining the direction of incidence of radiation, which are sequentially different from 0-0, and is engaged with the inside of the first collimator (3a) in a retractable manner so that the central axis 0-0 A second collimator (3b) rotating as a center, and the first and second collimators (3a), (3b) are radiation detectors.
When it is positioned inside (1) and rotates, the openings of the first and second collimators (3a) and (3b) communicate with each other and rotate integrally.

The first collimator (3a) has a ring-shaped support ring (4a) integrally fixed to the back surface, and rail-shaped racks (41a) are attached to a plurality of inner sides of the support ring (4a). The rack (41a) slidably contacts a guide (81) of a rotary frame (8) described later and slides in and out of the radiation detector (1).
In addition, the second collimator (3b) has an annular support ring (4a) integrally fixed to the back surface, and the support ring (4b)
Rail-shaped racks (41b) are attached to multiple
It slides like the first collimator (3a).

The guide (81) that supports the sliding movement of the first and second collimators (4a) and (4b) is provided with bearings (81a) and (81b) from the tip to the middle upper and lower surface parts, and a motor (not shown). Also, the support rings (4a) and (4b) are smoothly slid by the speed reducer.

Next, the operation of the emission type tomographic imaging apparatus according to this embodiment based on the above configuration will be described. First, FIG. 1 shows the case where the collimator is used as a high resolution collimator. In the figure, the first and second collimators (3a) and (3b) slide integrally inside the radiation detector (1). By the sliding movement of the collimators (3a) and (3b), the openings of the collimators (3a) and (3b) are brought into communication with each other to form a single collimator. The opening of this single collimator has blades corresponding to the sum of the lengths of the blades forming the openings of the collimators (3a) and (3b). Since the length of the blade forming this opening is the main factor that determines the resolution and sensitivity together with the density of the blade, the opening through which the first and second collimators (3a) and (3b) communicate with each other has a high resolution ( It is suitable for low sensitivity). A state in which the openings of the first and second collimators (3a) and (3b) communicate with each other is shown in FIG. 4 as a front view of the collimator.

FIG. 2 shows the case where the collimator is used as a medium resolution / medium sensitivity collimator. In the figure, the first collimator (3a)
Slides away from the inside of the radiation detector (1) and only the second collimator (3b) is mounted inside the radiation detector (1).

Furthermore, FIG. 3 shows a case where the collimator is used as a highly sensitive collimator. In the figure, the second collimator (3b) slides away from the inside of the radiation detector (1), and only the first collimator (3a) is mounted inside the radiation detector (1).

In addition, the high resolution (HR), medium resolution (MR) and high sensitivity (H
The relationship between the resolution and the blade lengths of the collimators (3a) and (3b) in the case of (S) will be described with reference to FIGS. 5 (A), (B) and (C). FIG. 5 (A) is a view of the collimator blades viewed from the in-plane direction, FIG. 5 (B) is a view of the collimator blades viewed from the slice direction, and FIG. 5 (C) is the resolution of the parallel collimator. The aspect figure to demonstrate is shown.

In the same figure (A), the blades of the first and second collimators (3a) and (3b) when viewed from the in-plane direction are inclined obliquely with respect to the inner side, and the opening width d between the blades is gradually narrowed to the inner side. and that _{(d 1> d 2> d} 3> d 4). The resolution and sensitivity in this case are specified by the aperture width of the blade. The calculation results of this resolution and sensitivity are shown in Table 1.

In addition, the blade lengths of the first and second collimators (3a) and (3b) viewed from the slice thickness direction in FIG.
The blade length a ₁ of the collimator (3a) is longer than the blade length a ₂ of the second inner collimator. Due to this difference in blade length, when the first and second collimators (3a) and (3b) communicate with each other to obtain a blade length (a ₁ + a ₂ ), a high resolution (HR) is obtained, and a second collimator is used. Medium resolution (MR) when only (3b) is installed and blade length is a _2, and high sensitivity when only the first collimator (3a) is installed and blade length is a _1.
(HS).

That is, the reason why the resolution differs due to the difference in blade length is obtained by the following equation (see FIG. 5 (c)).

Here, a + b + c = const., D = const. Therefore, if the blade length a is constant, the resolution is also constant, and the blade length a is changed in order to change this resolution.

In the above embodiment, the first and second collimators (3a) and (3b) are slid together as a unit in the case of high resolution (HR), but the first and second collimators ( It is also possible to have a configuration in which 3a) and (3b) are slid separately and independently.

Although the collimator blades have different configurations with respect to the central axis in the above embodiment, the collimator blades may be divided into a plurality of regions and the collimator blades in this one region may be parallel to each other. .

〔The invention's effect〕

As described above, according to the present invention, the first and second collimators that slidably move into and out of the radiation detector are engaged with each other, and both collimators rotate when the collimators rotate inside the radiation detector. Since the openings of the two are in communication with each other and rotate integrally, it is possible to form a collimator by combining or combining two types of collimators, and two types of collimators can be used with three types of resolution and sensitivity as appropriate. The effect is that it can be selected. Further, since the two types of collimators are slidably slidably moved, the exchange mechanism can be extremely simplified and downsized, and the operation can be performed easily and safely, and the cost can be reduced. Have.

[Brief description of drawings]

FIG. 1 is a schematic internal structure diagram when both collimators of an emission type tomographic imaging apparatus according to an embodiment of the present invention are mounted, and FIG. 2 is mounted only the first collimator of the embodiment in FIG. FIG. 3 is a schematic internal structure diagram in the case where only the second collimator of the embodiment in FIG. 1 is attached, and FIG. 4 is a first and second schematic diagram in FIG.
FIG. 5 is a front view when the collimator of FIG. 2 is engaged and rotating, FIG. 5 is a γ-ray incident mode diagram of the relationship between the first and second collimators and the half width, and FIG. 6 is a general emission type tomographic imaging apparatus. FIG. 7 is a schematic sectional view of a conventional emission type tomographic imaging device in FIG. 6AA, and FIG. 8 is a schematic configuration diagram of another conventional device. (1) ...... Radiation detector, (3a) …… First collimator, (3b) …… Second collimator, (4a), (4b) …… Support ring, (8) …… Rotating frame, ( 41a), (41b) ... rack, (81) ... guide, (9) ... subject. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A large number of radiation detectors arranged in a ring shape in a plane substantially perpendicular to a central axis corresponding to a body axis of an object, and a ring shape in a plane in which the radiation detectors are arranged. A first collimator which has a large number of openings for defining the radiation incident direction, and which is engaged with the inside of the ring-shaped array of the radiation detectors so as to be retractable and rotatable about the central axis;
A large number of ring-shaped openings for defining the radiation incident direction are provided in a plane in which the radiation detectors are arranged, and the openings are retractably engaged with the inside of the first collimator to rotate about the central axis. And a second collimator for
When the first and second collimators are located inside the radiation detector and rotate, the openings of the first and second collimators communicate with each other and rotate integrally with each other. Imaging device.