JPH0143278B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a radiation tomography apparatus.

2. Description of the Related Art Transmission-type and radiation-type computer tomography apparatuses have been known as so-called computerized tomography apparatuses that use radiation to obtain tomographic images of a human body sliced into rings. The transmission type irradiates the subject with radiation from the outside and detects data regarding the transmitted radiation intensity to construct an image of the radiation absorption rate distribution.The radiation type, on the other hand, uses RI (radioactive isotope) as a drug to inject into the human body. The present invention relates to the latter method, in which radiation emitted by RI is detected externally when RI is accumulated in a specific organ, and an RI distribution image is constructed.

Conventional radiation tomography equipment is configured to collect fan-shaped profile data that spreads out in a fan shape from many points on the circumference around the subject, so it is possible to select only parallel data from this data. There were problems such as the need for operations and the long data processing time.

An object of the present invention is to provide a radiation tomography apparatus that has a simple configuration and can obtain parallel profile data.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a donut-shaped collimator 3 is placed around the subject 1 at the center of the subject 10.
It is freely rotated around the center of rotation. In the embodiment shown in this figure, the collimator 3 is divided into four equal parts, and each part is provided with a number of parallel slits 4 facing in the direction of the subject 1.
This collimator has a specific structure as shown in FIG. 2, for example. That is, the elongated strips 32 made of radiation shielding material are attached at substantially right angles to the donut plate 31 made of radiation shielding material, and the strips 32 made of radiation shielding material are stacked in many layers to form a large number of parallel slits 4. This collimator 3 is driven by a motor 33 via a gear mechanism 34 and rotates as shown by the arrow.

A large number of radiation detectors 2 are arranged and fixed on the circumference around this collimator 3. Specifically, as shown in FIG. 1, the radiation detector 2 is attached to a donut-shaped frame 21, and this donut-shaped frame 21 is vibrated by rotating the rotating shaft 23 of the eccentric cam 22 at high speed in the direction of the arrow. It is now possible to do so. The radiation detector is
It can be composed of a crystal scintillator such as NaI or BGO, a photomultiplier tube, an amplifier, etc.

In the state shown in FIG. 1, of the radiation emitted from the subject 1, only the radiation traveling in the upward, downward, leftward and rightward directions passes through the parallel slit 4 and reaches the radiation detector 2. When the collimator 3 is rotated by 1/4 rotation by the motor 33, the radiation emitted in all directions reaches the radiation detector 2, and all the necessary data can be obtained. If the radiation is located within the dotted line 11, no matter which direction the radiation is emitted from, it will always be incident on one of the radiation detectors 2 during this 1/4 rotation, so the dotted line 11
The area indicated by is the image reconstruction area.

If the donut-shaped frame 21 is vibrated at high speed by the eccentric cam 22, and a large number of radiation detectors 2 are vibrated integrally, in the state shown in FIG. It will be possible to detect radiation even when it should not be present. That is, even if a large number of radiation detectors 2 are arranged closely together, there are restrictions in terms of their physical size, cost, etc., and it is not possible to arrange them so densely. The data sampling interval cannot be reduced because it depends on the arrangement density of the radiation detectors 2, but by moving the radiation detectors 2 a minute distance as described above, it is possible to Since it becomes possible to collect data at a certain position, it becomes possible to escape from the above-mentioned restrictions and make the sampling interval sufficiently small. Note that the minute movement of the large number of radiation detectors 2 as a whole can also be realized by other configurations, for example, by rotating the donut-shaped frame 21 alternately by a minute angle in the right and left rotation directions around the subject center 10. You can do it like this.

In Figure 1, the collimator 3 is divided into four equal parts,
It can be divided into 2, 3, 5, 6 equal parts, etc. As the number of equal fractions increases, the number of unusable radiation detectors (radiation detectors that are not located at the back of the parallel slit 4 and no radiation enters) decreases; however,
At the same time, the image reconstruction area 11 also becomes narrower.

As described above in the embodiments, according to the present invention, only the collimator rotates, so it is mechanically simple, but it is also possible to obtain profile data using parallel radiation, which is useful for later data processing. It is advantageous.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing one embodiment of the present invention, Figure 2 is a schematic diagram showing an embodiment of the present invention.
The figure is an enlarged perspective view of a part of the collimator 3 in FIG. 1. 1...Subject, 10...Subject center, 11...
Image reconstruction area, 2... Radiation detector, 21...
Donut-shaped frame, 22... Eccentric cam, 23...
... Rotating shaft, 3 ... Collimator, 31 ... Donut plate, 32 ... Long strip, 33 ... Gear mechanism, 34 ...
...Motor, 4...Parallel slit.

Claims (1)

[Claims] 1. The overall shape is a circular donut shape,
a collimator in which a large number of parallel slits are formed in each portion divided into an integral number of equal parts in the circumferential direction; a rotation mechanism that rotates the collimator about a central axis of the circular donut-shaped collimator; A radiation tomography apparatus comprising a large number of radiation detectors arranged and fixed to a frame that is a separate member from the collimator so as to be arranged on a circumference concentric with the collimator outside the collimator. 2. The radiation tomography apparatus according to claim 1, wherein the frame is moved by a small distance by a small distance moving mechanism.