JPH03295493A - Detector for x-ray ct - Google Patents

Abstract

PURPOSE:To reduce the size and weight of the detector by providing a filter which covers the end part of the X-ray incidence surface of each scintillator element and a grid which prevents the incidence of scattered ray on the scintillator on the X-ray incidence surface of the scintillator. CONSTITUTION:The filter 6 which covers the end part of the X-ray incidence surface 2c of each scintillator element 2a and the grid for preventing the incidence of scattered rays on the scintillator 2 are provided on the X-ray incidence surface 2c of the scintillator 2. A tungsten filter which absorbs X rays greatly and a grid are used for the filter 6 to reduce the size and weight of the detector greatly. Then the incidence of X rays on the scintillator element end part is prevented without trouble to prevent scattered rays from being made incident on the scintillator.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention is a method for detecting X-rays that are used in an X-ray CT device and transmitting through a subject to obtain a tomographic image of the subject. Related to X-ray CT detector that outputs video signals (prior art) Conventionally, as this type of X-ray CT detector, there is one shown in FIG. 6, for example. In the figure, this detector 100
1.0 is a visible light emitting surface 1.0 of a scintillator 101 in which a plurality of scintillator elements 101a that emit visible light according to the amount of incident X-rays are arranged and bonded via spacers 102.
A photodiode 103 as a photoelectric conversion means is bonded to lb, and the photodiode 103 is attached to an insulating substrate 1.05. Photodiode 103
A plurality of photodiode elements 103b are formed on one semiconductor substrate 103a, and a scintillator 101
and photodiode 103 are bonded together so that each channel is aligned.

Here, if X-rays are incident on the side edge of each scintillator element 101a, for example, the joint portion with the spacer]-02, detection accuracy will decrease, so in order to prevent X-rays from incident on this edge, and In order to prevent scattered rays from entering the scintillator 101, the X-ray entrance surface 10 of the scintillator 101
A collimator 106 is provided at 1c.

In the collimator 106, a plurality of collimator plates 106a arranged on the spacer 102 are supported by frame plates (not shown) provided on the front side and the rear side in FIG. 6. The collimator plate 106a is the scintillator element 101a.
In order to prevent X-rays from entering the ends, the width (thickness) of the spacer 102 and the scintillator element 101a is set to cover the ends, and in order to obtain the grid ratio necessary to remove scattered rays, The length in the X-ray incident direction is made sufficiently long.

Then, the X-rays are directed toward the scintillator 101 in the direction of the arrow in FIG.
When the X-rays are incident on the scintillator element 101
a emits visible light according to the amount of incident X-rays, this visible light enters the photodiode element 103b corresponding to this scintillator element 101a, and the photodiode 103 converts the X-ray detection information obtained for each channel into an electrical signal. It is converted and output to a signal processing system (not shown).

(Problem to be solved by the invention) However, in the case of the above-mentioned prior art, the collimator plate 106a requires a sufficient thickness iI'f in order to prevent X-rays from entering the end of the scintillator element 101a. It also requires a sufficient length to obtain the grid ratio necessary to prevent scattered radiation. Therefore, collimator], 0
6, the size and weight of detector 1. This was an obstacle to making the OO smaller and lighter.

The present invention has been made to solve the problems of the prior art described above, and its objectives are to significantly reduce the size of the
An object of the present invention is to provide an X-ray CT detector that can be made lightweight.

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, in the present invention, the incident X
In an XvACT detector, a photoelectric conversion means is bonded to the visible light emitting surface of a scintillator in which a plurality of scintillator elements that emit visible light according to the dose are arranged and bonded. It is characterized in that it is provided with a filter that covers the end of the X-ray incident surface of the scintillator element, and a grid for preventing scattered rays from entering the scintillator.

(Function) The X-ray CT detector of the present invention having the following configuration includes a filter for preventing X-rays from entering the scintillator element end, and a grid for preventing scattered rays from entering the scintillator. If the filter is shaped to cover the end of the scintillator element, it is possible to prevent X-rays from entering the end of the scintillator element, even if the thickness is thin, and the grid also prevents scattered rays. Grid required for
If the scintillator has a sand ratio, it is possible to prevent scattered radiation from entering the scintillator even if the scintillator is thin. Therefore, there is no need to use a collimator that is large in size and weight, and by using a thin filter and grid, the size and weight of the detector can be reduced.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing the configuration of an X-ray CT detector according to an embodiment of the present invention.

In the figure, this X-ray CT detector 1 includes a plurality of scintillating elements 2 that emit visible light according to the amount of incident X-rays.
A photodiode 4 as a photoelectric conversion means is adhered to the visible light emitting surface 2b of the scintillator 2, which is arranged and bonded to the scintillator 2 with spacers 3 interposed therebetween, and the photodiode 4 is attached to an insulating substrate 5. Photodiode 4 is 1
A plurality of photodiode elements 4 on one semiconductor substrate 4a
b is formed, and the scintillator 2 and photodiode 4 are bonded together so that each channel is aligned.

Further, the X-ray entrance surface 2c of the scintillator 2 is provided with a filter 6 that covers the end of the X-ray entrance surface 2c of each scintillator element 2a, and a grid 7 for preventing scattered radiation from entering the scintillator 2. ing.

The filter 6 is made of a metal such as tungsten or molybdenum that has high X-ray absorption, and has a plurality of rectangular entrance windows 6a and a light shielding part 6b corresponding to the X-ray incident surface of each scintillator element 2a, as shown in FIG. . The width d2 between the entrance windows of the light shielding part 6b is the distance d between the ends of the scintillator elements 2a,
The length L2 in the vertical direction (longitudinal direction) of the entrance window 6a is made shorter than the length in the vertical direction (longitudinal direction) of the X-ray entrance surface of the scintillator element 2a. Thereby, the light shielding part 6b is connected to the scintillator element 2.
By covering the longitudinal and lateral ends of the X-ray entrance surface a, it is possible to prevent X-rays from entering the four side edges of the scintillator element 2a. The width a1 of the entrance window 6a is determined by the formula aH=P-d from the channel pitch P and the width d2 between the entrance windows.
2.

As shown in FIG. 3, the grid has a grid ratio equal to that of the conventionally used collimator 1-06. That is, the distance between the collimator plates 106a is a2, the length in the X-ray incident direction is L3, the width of the X-ray transparent portion 7a of the grid 7 is a3, and the length of the X-ray shielding portion 7b in the X-ray incident direction is t. As shown in FIG. 4, the scintillator 2 is formed in an arc shape centered on the focal point of the X-ray tube of the X-ray CT device to which this detector is applied, and the scintillator 2 is formed in an arc shape centered on the focal point of the X-ray tube of the X-ray CT device to which this detector is applied. 7 is formed into an arc shape along the arc-shaped scintillator 2, and is adhered to the X-ray incident surface 2C of the scintillator so as to cover the end of the filter 6 or scintillator element 2a.
Furthermore, a grid 7 is bonded thereon.

When photographing a subject with an X-ray CT apparatus to which this detector 1 is applied, as shown in FIG.
irradiates the object P with X-rays, and the X that passes through the object P
A ray is incident on the detector 1. At this time, in the detector] 8, the X-rays enter the scintillator element 2a in the direction of the arrow in the figure.
The scintillating element 2a upon which X-rays have entered emits visible light corresponding to the amount of X-rays to the corresponding photodiode element 4b, and an electrical signal as a video signal is emitted from the photodiode 4 to the information processing section 11. Ru.

In the information processing section 11, the preprocessing section 1-2 performs preprocessing such as signal processing on the video signal, and the image reconstruction section 13 reconstructs the image. Then, an image signal containing this reconstructed image is sent from the information processing section 11 to a display 14 such as a CRT, and a tomographic image of a predetermined cross section of the subject P is displayed on the screen of the display 14.

In the X11 CT detector 1 of this embodiment, since the thin filter 6 and the grid 7 are used together, there is no need to use a collimator that is large and heavy, and the detector 1 is significantly miniaturized. Lighter. Also, filter 6
The scintillator element 2a is made of a metal with high X-ray absorption.
Since the end portion is closely covered by the light shielding portion 6b, it is possible to reliably prevent X-rays from entering the end portion of the scintillator element 2a.
The thin thickness does not impede its functionality.

The grid 7 is a collimator 10 whose grid ratio is necessary for preventing the incidence of scattered radiation.
Since the grid ratio is set equal to 6, it is possible to reliably prevent scattered radiation from entering the scintillator 2, and its thin thickness does not impede its function.

Furthermore, in the detector of this embodiment]-, the grid 7
When providing this on the X-ray entrance surface 2C of the scintillator, the combination accuracy of the grid 7 and the scintillator 2 is not required.

On the other hand, conventional X-ray CT detectors are equipped with a collimator, and in order to reliably prevent X-rays from entering the end of the scintillator element, precision in the combination of the collimator plate and scintillator element is required. It was time consuming. Therefore, the detector 1 of this embodiment is easier to manufacture than the conventional one, and productivity can be improved.

[Effects of the Invention] The X-ray CT detector of the present invention has the above-described configuration and function, and by using a filter and a grid in combination instead of a collimator, detection can be performed using a thin filter and a grid. It is possible to significantly reduce the size and weight of the device. Then, the X to the end of the scintillator element is
It is possible to prevent radiation from entering the scintillator and prevent scattered radiation from entering the scintillator.

Further, when providing a grid, unlike the case of a collimator, there is no need for precision in the combination of a grid and a scintillator, which simplifies the manufacture of the detector and improves productivity.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the configuration of a detector for XIICT according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the shape of a filter in the same embodiment, and FIG. Explanatory diagram for explaining the grid ratio of the grid, 4th
The figure is an explanatory diagram showing the scintillator, filter, and grid in the same embodiment, and FIG. 5 is an explanatory diagram showing the scintillator, filter, and grid in the same embodiment. FIG. 6 is an explanatory diagram showing the electrical configuration of an X-ray CT apparatus to which a CR detector is applied, and FIG. 6 is a longitudinal sectional view showing the configuration of a conventional X-ray CT detector. 1...X-ray CT detector 2...Scintillator 2a
...Scintillator element 2b...Visible light emission surface 2c.
...X-ray entrance surface 4...Photodiode 4a...Semiconductor substrate 4b
...Photodiode element 6...Filter 7...
·grid

Claims (1)

[Scope of Claims] An X-ray CT detector in which a photoelectric conversion means is bonded to the visible light emitting surface of a scintillator in which a plurality of scintillator elements that emit visible light according to the amount of incident X-rays are arranged and bonded, An X-ray CT characterized in that the scintillator is provided with a filter that covers the end of the X-ray entrance surface of each scintillator element and a grid for preventing scattered rays from entering the scintillator. detector.