JPH01292283A - Radiation detector - Google Patents

Abstract

PURPOSE:To prevent the deviation of the energy characteristics between channels by preventing the irradiation of the end part of a scintillator with scattered beam, by arranging a scattered beam preventing collimator at the center position between the collimators arranged in opposed relation to each other. CONSTITUTION:A scattered beam preventing collimator 13 is arranged at the center between opposed collimators 10, 10 so that the end part thereof is positioned at the intersecting point of the diagonal lines connecting the end parts of the opposed collimators 10. By this constitution, scattered X-rays impinge upon the end part of the scattered beam preventing collimator 13 but not against the end part of a scintillator 11 and, therefore, the generation of the deviation in the energy characteristics among channels can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a multichannel radiation detector used in an X-ray CT scanner device or the like.

(Prior Art) For example, in the case of a third generation XvACT scanner device, as shown in FIG. 2, an X-ray source 1 and a multichannel radiation detector 2 are arranged with a subject P in between. The pair of X-ray source 1 and multi-channel radiation detector 2 rotated around the subject P while facing each other, and irradiated X-rays from the X-ray source 1, passing through the subject P. X-rays are received by each channel of the multi-channel radiation detector 2, extracted as electrical signals, and sent to the signal processing system 4 via the data acquisition system 3, where reconstruction processing is performed. X between the X-ray source 1 and the multi-channel radiation detector 2
An image sliced in the line radiation direction is generated, and the display system 5
will be displayed.

In this case, solid state detectors are well known as multi-channel radiation detectors. That is, as shown in FIG. 3, collimators 10 made of heavy metals such as MO and W and used to prevent cyclotalk between channels are placed facing each other in a light-shielding box (not shown). A scintillator 11 and a photodiode 12 made of single crystal or polycrystal such as Cd WQ4 or Cs I are arranged behind the collimator 10. The X-rays whose incidence is restricted by the collimator 10 enter the scintillator 11 and emit visible light, and the emitted light is converted into a current signal by the photodiode 12 so that an output can be obtained as the current signal. It has become.

Here, the relationship between the collimator 10 and the scintillator 11 will be considered. That is, the collimator 10 is arranged to provide each channel with directivity and to prevent X-rays from directly hitting the ends of the scintillator 11.

In addition, the scintillator 11 is also called a crystal, but since there are variations in cutting precision during its production, the scintillator 11 should originally have a rectangular parallelepiped cross section.
In reality, for example, as shown in FIG. 3, there is a case where the left end (left end) is closer to the photodiode 12 and is narrower.

Here, in the scintillator 11 shown in FIG. 3, a case where the collimator 10 is arranged and a case where the collimator 10 is not arranged will be explained. As shown in FIG. 4, a collimator 1 is attached to a scintillator 11.
If the collimator 10 is not placed on the scintillator 11 as shown in FIG. X-rays do not directly hit the area, but scattered X-rays do.

In this case, when the scattered X-rays hit the end of the scintillator 11, the following problem occurs. That is, the scintillator 11 shown in FIG. 3 has a depth dimension (thickness dimension) at the end.
is smaller than the average, so this end has different energy characteristics than other parts. As a result, there is a deviation in the energy characteristics between each channel, which affects the detection signal, and as a result, ring-shaped artifacts occur in the image, leading to a decrease in image quality.

(Problem to be solved by the invention) In conventional radiation detectors, there is a deviation in energy characteristics between each channel due to scattered rays incident on the end of the scintillator. Although not taken into consideration, this also affected the detection signal, resulting in ring-shaped artifacts occurring in the image, resulting in a reduction in image quality.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a radiation detector that prevents scattered radiation from hitting the ends of the scintillator, thereby preventing deviations in energy characteristics between channels.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following means are taken to solve the above problems and achieve the objects.

That is, the present invention provides a radiation detector in which collimators are disposed facing each other along the direction of radiation incidence, and a scintillator and a photodiode are disposed behind the collimators, wherein the center of the opposed collimators is The present invention is characterized in that the collimator for preventing scattered radiation is arranged such that the end thereof is located at the intersection of diagonal lines of the ends of the opposing collimators.

(Function) According to this configuration, the end of the collimator for preventing scattered radiation is located at the intersection of the diagonal lines of the opposite ends of the collimators, so that the scattered radiation does not hit the end of the collimator for preventing scattered radiation. This prevents scattered radiation from hitting the ends of the scintillator.

(Example) An example of a solid-state detector as a radiation detector according to the present invention will be described below with reference to FIG.

That is, as shown in FIG. 1, collimators 10.10 are arranged facing each other along the X-ray incident direction, and a scintillator 11 and a photodiode 12 are arranged behind the collimators 10.10, and The anti-scattered radiation collimator 13 is located at the center of the opposing collimators 10, 10, and at the diagonal line f of the ends of the opposing collimators 10, 10.
l.

It is arranged so that its end is located at the intersection P of f2. Further, the length dimension of the anti-scattered radiation collimator 13 is set so that its end on the anti-intersection side is at the same surface position as the end on the incident side of the collimator 10°10.

According to such a configuration, the collimator 13 for preventing scattered radiation
Since the end of is located at the intersection P of the diagonals fl and f2 of the opposing ends of the collimators 10°10, the scattered X-rays will hit the end of the collimator 13 for preventing scattered rays, and the scintillator 11 Scattered X-rays will not hit the edges.

Therefore, there is no deviation in the energy characteristics between the channels, and it is possible to suppress the occurrence of ring-shaped arch-acts in the image, thereby preventing deterioration in image quality.

The length of the anti-scattered radiation collimator 13 may be any suitable length, and the length is set so that its end is below or above the same surface position as the incident side end of the collimator 10°10. You can leave it there.

The invention can be modified in various ways without departing from the gist of the invention.

[Effects of the Invention] As described above, in the present invention, the collimator for preventing scattered radiation is arranged such that the end thereof is located at the center of the opposing collimators and at the intersection of the diagonal lines of the ends of the opposing collimators. Due to this arrangement, the end of the collimator for preventing scattered radiation is located at the intersection of the diagonal lines of the ends of the opposing collimators, so the scattered radiation hits the end of the collimator for preventing scattered radiation, and the scintillator is Scattered rays will not hit the edges.

Therefore, according to the present invention, it is possible to provide a radiation detector in which the ends of the scintillator are prevented from being hit by scattered rays and the energy characteristics do not vary between channels.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of a radiation detector according to the present invention, FIG. 2 is a diagram showing the configuration of an X[CT scanner device, and FIG. 3 is a diagram showing the configuration of a conventional radiation detector. , 4th
The figure is a diagram for explaining problems with conventional radiation detectors. 10...Collimator, 11...Scintillator, 12
...Photodiode, 13...Collimator for preventing scattered radiation. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3 Figure 2

Claims (1)

[Claims] The collimators are arranged facing each other along the direction of radiation incidence,
In a radiation detector comprising a scintillator and a photodiode arranged behind the collimator, the ends thereof are located at the center of the opposed collimators and at the intersection of diagonal lines of the ends of the opposed collimators. A radiation detector characterized in that a collimator for preventing scattered radiation is arranged.