JPH0141950B2 - - 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 emission tomography apparatuses are constructed by arranging a large number of radiation detectors including scintillators and photoelectric detectors on the circumference, and therefore are inevitably expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved emission tomography apparatus that can reduce the cost by reducing the number of radiation detectors as much as possible while maintaining sensitivity and performance equivalent to conventional ones.

An embodiment of the present invention will be described below. 1st
As shown in the figure and FIG. 2, a collimator 2 is arranged around a subject 1. As shown in FIG. A plurality of collimators 2 (in this embodiment, 12
It is constructed by providing pinhole slits S1 to S12 at equal intervals. Around this collimator 2, there are a corresponding number (12 in this embodiment) of one-dimensional position detection type radiation detectors so that the radiation emitted from the subject 1 and radiated to the outside through each slit is incident respectively. Arranged. In this embodiment, as shown in the figure, the one-dimensional position detection type radiation detector is composed of arcuate scintillators D1 to D12 and photomultiplier tubes P1 to P24, with one photomultiplier at each end of each scintillator. The multiplier tubes are arranged to be optically coupled. Note that the scintillators D1 to D12 have a length that allows all of the radiation emitted from the imaging possible region 3 to be incident thereon.

When the radiation emitted from the object 1 passes through each slit and enters the rod-shaped scintillator, the output intensity of the photomultiplier tube increases as the incident position is _closer . ₂ , the characteristics will be as shown in Figure 3 A and B. Therefore, the radiation incident position can be determined from the mutual relationship between the output intensities of the photomultiplier tubes at both ends. A position determining circuit based on this principle is used in Unger type scintillation cameras and is well known.
The position determining circuit used here may have a similar configuration, so a detailed explanation will be omitted.

Therefore, from 12 sets of one-dimensional position detecting radiation detectors, 12 fan-shaped beams are detected with each slit position as the focal point.
Profile data of RI distribution can be obtained. Next, collimator 2, scintillators D1 to D1
2. The photomultiplier tubes P1 to P24 are rotated together by a minute angle ΔΘ about the center 10 of the subject 1, and 12 pieces of similar profile data are obtained again. In this way, all necessary data can be obtained by obtaining profile data at every minute angle ΔΘ and then rotating the angle formed by the adjacent pinhole slits (30° in this embodiment). Note that data may be obtained by further rotation and overlapping data may be collected. Further, instead of rotating by small angles ΔΘ, it may be rotated continuously, and data may be collected for each angle ΔΘ during the continuous rotation. The collimator 2, the scintillators D1 to D12, and the photomultiplier tubes P1 to P24 can be rotated about the center 10 of the subject 1 by using, for example, an appropriate rotating frame having a rotation center axis at the center 10. These collimator 2, scintillators D1 to D12, photomultiplier tube P
A configuration that holds 1 to P24 is conceivable. In other words, since a simple rotation mechanism is sufficient, a detailed specific explanation will be omitted.

Note that when attempting to obtain an RI distribution image using RI of a positron radionuclide with this apparatus, the collimator 2 is removed so that the radiation directly enters the one-dimensional position detection type radiation detector. In other words, when a positron annihilates, it emits two gamma rays in a 180° direction, so two opposing sets of one-dimensional position-detecting radiation detectors simultaneously detect these two gamma rays traveling in a 180° direction. This is because by doing so, the position of RI can be found.

As described above with respect to the embodiments, the radiation tomography apparatus according to the present invention includes a collimator that is arranged around a subject and is formed by providing a plurality of pinhole slits in a drum-shaped radiation shield, and an outer side of the collimator. An arcuate scintillator and a plurality of photoelectric detectors optically coupled to this scintillator are arranged concentrically in the circumferential direction at a plurality of one-dimensional position detection type radiation detectors comprising a position determining circuit that determines a one-dimensional radiation incident position in a direction; and rotation for rotating the collimator and the radiation detector together around the subject. mechanism, the number of radiation detectors can be reduced and the mechanism can be simplified while maintaining sensitivity and characteristics almost equivalent to conventional ones, making it possible to reduce costs. A radiation tomography device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of one embodiment of the present invention, and FIG.
The figure is a schematic cross-sectional view of the same, and FIG. 3 is a graph showing the relationship between the radiation incident position and the output intensity of the photomultiplier tube. 1... Subject, 2... Drum-shaped collimator, 3
...Shooting area, 10...Subject center, S1~
S12...Pinhole slit, D1~D12...
...Scintillator, P1-P24...Photomultiplier tube.

Claims (1)

[Claims] 1 A collimator consisting of a drum-shaped radiation shield with a plurality of pinhole slits arranged around the subject, an arcuate scintillator arranged concentrically in a circumferential direction outside the collimator, and this collimator. A plurality of photoelectric detectors optically coupled to the scintillator, and a position determination circuit that determines the one-dimensional radiation incident position in the longitudinal direction of the arcuate scintillator from the mutual relationship of the output intensities of these photoelectric detectors. A radiation tomography apparatus comprising: a plurality of one-dimensional position detection type radiation detectors; and a rotation mechanism that rotates the collimator and the radiation detector together with the object as a rotation center.