JPH0337588A - X-ray detector and x-ray ct scanner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Industrial Application Field) The present invention relates to an X-ray detector having a detection module in which X-ray detection elements including a scintillator and a photodiode are arranged in multiple channels; And Rotat using it
e/Rotate method.

5tationary/rotate type X-ray CT
(Computerized Ton+ography
) Relating to a scanner device.

(Prior Art) The general outline of this type of X-ray CT scanner device is as follows. That is, the X-ray detector and the X-ray source driven by the X-ray generator are arranged to face each other with an imaging area in between, and the subject is placed within the imaging area.

In the case of an X-ray CT scanner device called a Rotaie/Rotate method or a third-generation method, a pair of an X-ray source and an X-ray detector rotates around the subject, allowing multi-directional scanning. It is used to obtain X-ray projection data from
In the case of an X-ray CT scanner device called a world-wide type, only the X-ray source rotates around the subject to obtain X-ray projection data from multiple directions.

In this case, projection data based on transmitted X-rays from multiple directions to the subject obtained by rotating the pair of X-ray source and X-ray detector or the X-ray source is transmitted to the X-ray detector, I/V The data is collected by a data collector having a converter, an integrator, a multiplexer, an A/D converter, etc., and sent to the reconstruction processing system. The processed data is sent to a high-speed reconstruction unit, where it undergoes reconstruction processing to obtain a slice image, which is then displayed on a display system.

A detection module (hereinafter referred to as "channel") having a plurality of X-ray detection elements (hereinafter referred to as "channels") is used as an X-ray detector in such third-generation or fourth-generation X-ray CT scanner devices.
Hereinafter referred to as "module". ) is arranged (
Sometimes called a solid state detector. ) is used. In general, in addition to the solid-state detector type described above, an ion chamber type is also used for the X-ray detector and t7 in the third generation X1CT scanner, and the X-ray detector in the fourth generation
As the line detector, the above-mentioned solid state detector is used. For example, the current 4th generation X-ray CT scanner
The line detector has 96.1 modules and 2 modules.
4 channels, and the number of channels is 96x24-2
There are 304 items.

(Problems to be Solved by the Invention) On the other hand, the scanning mode of the X-ray CT scanner includes a mode such as a continuous scan mode in which the X-ray tube is continuously rotated and X-ray irradiation is performed.

In such a mode, the temperature rise of the X-ray tube, especially the anode, becomes extremely high. For this reason, forced air cooling, limb cooling, etc. are generally used to suppress the temperature rise of the anode, but in recent years, high-capacity X-ray tubes have begun to experience unprecedented temperature rises. There is. This temperature increase not only causes a reduction in the lifespan of the X-ray tube, as has been said in the past, but also the following problems have been clarified through research by the present inventors.

That is, as the temperature of the anode increases due to the temperature rise of the X-ray tube, the focal point of the tube moves, and the X-ray irradiation (incidence) position near the detector shifts from its original position.

In this type of X-ray CT scanner, due to the above-mentioned focus shift, the reconstructed image may have ring-shaped artifacts, making it unusable for clinical use. be.

Therefore, the present invention has been developed to prevent ring-shaped artifacts from appearing on reconstructed images even when the anode becomes hot due to an increase in the temperature of the X-ray tube and the focus of the tube moves.
An object of the present invention is to provide a ray detector and an X-ray CT scanner device.

[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 invention according to claim 1 provides an X-ray detector having a detection module in which X-ray detection elements including scintillators and photodiodes are arranged for a plurality of channels, wherein the scintillator section of the detection module is arranged for the plurality of channels. It is characterized in that the end face in the slicing direction is formed flat throughout.

Further, the invention according to claim 2 provides Rotate/Rot
As an X-ray detector for ate method X-ray CT scanner equipment,
The present invention is characterized in that the X-ray detector according to claim 1 is used.

(Function) According to the invention claimed in claim 1.2, the invention functions as follows. In other words, the inventor's research revealed that the cause of the variation in the sensitivity distribution in the slice direction for the plurality of channels in the scintillator section of the detection module of an X-ray detector is the non-flatness of the end surface of the scintillator section. did it. Therefore, by using a detection module that has a scintillator section with a flat end face in the slice direction, variations in the sensitivity distribution in the slice direction can be eliminated, thereby making it possible to obtain a reconstructed image without ring-shaped artifacts. .

(Embodiment) An embodiment of the X-ray detector according to the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a perspective view of a detection module according to this embodiment, and FIG. 2 shows a detection module in which the end surface in the slice direction of the scintillator section is formed flat (this embodiment) and a case in which the end surface in the slice direction is flat. Figures 3 to 5 show the sensitivity characteristics in the case where the
The figures are diagrams showing the method of manufacturing the scintillator part of the same example, in which Fig. 3 is a perspective view showing the situation in which the scintillator part is temporarily joined, and Fig. 4 is a diagram showing the scintillator part temporarily joined in Fig. 3. FIG. 5 is an exploded perspective view showing a state of final joining and a jig used therein, and FIG. 5 is a perspective view showing a state of flattening the end face in the slice direction of the scintillator portion which is finally joined in FIG. 4.

As shown in FIG. 1, a photodiode 2 is fixed onto a substrate 1 with an adhesive or the like, and the photodiode 2 is electrically connected to a conductive pattern provided on the substrate 1. As shown in FIG. On the photodiode 2, a scintillator section 5 formed by mutually bonding a thin rectangular scintillator 3 and a thin rectangular spacer 4 is fixed with an adhesive or the like.

The end surface 5A of the scintillator portion 5 in the slice direction is formed to have a flatness with a difference in unevenness of about 500 μm, for example, by a method described later. The illustrated arrow indicates the X-ray irradiation direction, and the illustrated broken line arrow indicates the arrangement direction of the detection modules.

Next, the operation of this embodiment configured as described above will be explained. That is, it is known that the ring-shaped artifact appearing on the reconstructed image is caused by variations in the sensitivity distribution of the X-ray detector in the slice direction.

However, it has not yet been elucidated in detail whether there is a correspondence between variations in sensitivity distribution and the X-ray detector and the single detection module that constitutes it. Therefore, the inventor clarified the above-mentioned relationship through research. First, the scintillator section 5 in the conventional example with variations in sensitivity distribution.
′ (the end face in the slice direction is not formed flat), the sensitivity characteristics when a narrow X-ray beam is incident on the scintillator section 5'' in the slice direction are as shown by the broken line curve in FIG. Regarding the incident position, it is asymmetrical from the center.

Therefore, the inventor assumed that the above-mentioned left-right asymmetry was the cause of variations in the sensitivity distribution, and performed several processes on the main body to make it symmetrical. was formed by polishing so that the difference in unevenness was about 500 μm, resulting in bilateral symmetry as shown by the solid curve in FIG.

Therefore, a plurality of detection modules each having a scintillator section 5 having a flat end face in the slice direction are arranged to perform X-ray CT.
When scanning an X-ray detector configured in a scanner device in a situation where the anode of the X-ray tube became hot due to an increase in the temperature of the tube and the focus of the tube shifted, a reconstructed image without ring-shaped artifacts was obtained. .

As described above, according to this embodiment, the end surface of the scintillator section 5 in the slice direction is made flat based on the result that the cause of the variation in the sensitivity distribution in the slice direction is the non-flatness of the end surface of the scintillator section. This eliminates variations in the sensitivity distribution in the slice direction, and as a result,
A reconstructed image without ring artifacts can be obtained.

Next, an example of the method for manufacturing the scintillator section 5 described above will be explained in the third section.
This will be explained with reference to FIGS. That is, as shown in FIG. 3, a strip-shaped scintillator 3 with a thickness of about 1 mm is used.
and a rectangular spacer 4 with a thickness of about 0.91 mm, for example, for 24 channels (24 scintillators, 24 spacers) by applying adhesive between them, and temporarily bonding the scintillator part. Get 5.

Next, as shown in FIG. 4, the temporarily joined scintillator section 5
are set in the main bonding jig 6 which has a fitting (=I) mechanism.
The side plate 6B (and the other side plate 6B2) are composed of an inverted-shaped upper block 6C, and rubber 7 is provided as an elastic pad in the part of these which comes into contact with the insulator part 5.
is provided.

Then, the scintillator section 5 is attached to the L-shaped lower block 6A.
is placed, m face plates 6B1 and side plates 6B2 are placed on both sides thereof, and an inverted-shaped top block 6C is placed so as to cover the top surface of the scintillator section 5, and these are connected by screws (not shown) as indicated by the broken line arrows in the figure. In particular, the scintillator portions 5 which are temporarily joined through the rubber 7 and are mutually tightened in the direction of
Scintillator 3. The spacer 4 is compressed in the stacking direction, and dimensioned in the slice direction and the slice width direction. Since scintillator 3 has weak mechanical strength,
Tightening shall be carried out in such a way as to prevent damage. Incidentally, the adhesive protrudes from the surface of the scintillator portion 5 which has been dimensioned by compression and finally joined as described above.

Next, as shown in FIG. 5, both sides of the scintillator part 5 are sandwiched between two small glass plates 8A and 8B, and the end surfaces are placed on a glass base on which particles 9 of cesium oxide or the like are scattered. 8C, the end of the scintillator part 5 sandwiched between the small glass plates 18A and 8B is moved in the direction of the arrow shown in the figure, and the end is polished.

Even during this polishing, the scintillator section 5 is moved in such a way that it is not damaged. Further, the adhesive that has protruded onto the surface of the scintillator portion 5 is also removed by polishing using the same method or a similar method. In addition, small glass plates 8A and 8B.

The glass base 8C was selected because it is made of a material that has the same degree of hardness as the scintillator 3 so that the scintillator 3 sandwiched between them will not break, but it is also possible to use a material made of other materials. You can.

As described above, a scintillator section 5 having a flat end face in the slice direction is manufactured, and this is assembled as a detection module shown in FIG. 1. A plurality of detection modules each having a scintillator section 5 having a flat end face in the slice direction are arranged, and as shown in FIG. Configure.

That is, as shown in FIG. 6, two beds (not shown) and a gantry 10 including a bed control device are arranged to sandwich an X-ray source 12 and a subject 14 placed within an imaging area with respect to the X-ray source 12. Multi-channel X-ray detector 16 of the present invention
It has Here, the pair of X-ray source 12 and multi-channel X-ray detector 16 can rotate at high speed in a circular orbit.

Projection data, which is the output of each channel of the X-ray detector 16, is collected by a pig collector 18 having channels such as an I/V converter, an integrator, a multiplexer, an A/D converter, etc., and the collected data is reconstructed. The image is sent to a processing system 20, where it undergoes reconstruction processing to obtain a slice image, and is displayed on a display system 22.

Further, the X-ray source 12 is supplied with a high voltage controlled by an X-ray generator 24, and the gantry 10 is supplied with a high voltage controlled by the gantry/bed controller 2.
6. The X-ray generator 24 and the gantry/bed controller 26 are under the control of a system controller 28, which uses a console 30 and a display system 22 to set scan conditions and display messages. etc. can be controlled. The system controller 28 is
An X-ray control signal based on set scan conditions is given to the X-ray generator 24, and a reconstruction control signal based on the set scan conditions is given to the reconstruction processing system 20.

According to the X-ray CT scanner device with such a configuration, when scanning is performed in a situation where the anode of the X-ray tube becomes hot due to the temperature rise of the X-ray tube and the focus of the tube moves, a reconstructed image without ring-shaped artifacts can be obtained. can get.

The present invention is not limited to the above-mentioned embodiments, but can also be applied to a fourth-generation X-ray CT scanner device, for example, by configuring a circular X-ray detector using the above-described detection module. In addition, various modifications can be made without departing from the gist of the present invention.

[Effect of the invention] As described above, the invention according to claim 1 provides a scintillator,
In an X-ray detector having a detection module 4 formed by arranging X-ray detection elements including photodiodes for a plurality of channels, the scintillator section of the detection module has an end face in a slice direction that is flat over the plurality of channels. The invention according to claim 2 is characterized in that the Rotate/R
An X-ray CT scanner characterized in that the X-ray detector according to claim 1 is used as an rotated X-ray CT scanner device.
It is a T-scanner device.

Therefore, according to the inventions according to claims 1 and 2, the inventor's research has revealed that the cause of the variation in the sensitivity distribution in the slice direction is the non-flatness of the end face of the scintillator portion. Therefore, by using a detection module that has a scintillator section with a flat end face in the slice direction, variations in the sensitivity distribution in the slice direction can be eliminated, thereby making it possible to obtain a reconstructed image without ring-shaped artifacts. .

Therefore, according to the present invention, even if the anode becomes hot due to an increase in the temperature of the X-ray tube and the tube focus moves, the The present invention can provide a ray detector and an X-ray CT scanner device.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a detection module according to an embodiment of the X-ray detector of the present invention, and FIG. 2 is a perspective view of the detection module in which the end surface of the scintillator section in the slice direction is formed flat (this example). FIGS. 3 to 5 are diagrams showing the method of manufacturing the scintillator section of the same example, and FIGS. Fig. 3 is a perspective view showing the state in which the scintillator parts are temporarily joined, Fig. 4 is an exploded perspective view showing the state in which the scintillator parts temporarily joined in Fig. 3 are permanently joined, and the jig used for this, and Fig. 5 The figure is a perspective view showing the situation in which the end face in the slice direction of the finally joined scintillator part is formed flat in Figure 4, and Figure 6 is a third generation X-ray CT scanner using the X-ray detector of the present invention. FIG. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Photodiode, 3...Scintillator, 4...Spacer, 5...Scintillator part, 66...Main bonding jig, 7...Rubber, 8A, 8B...
Small glass plate, 8C...Glass base, 9...and grains, 1
0... Frame, 12... X-ray source, 14... Subject,
16... Multi-channel X-ray detector, 18... Data collector, 20... Reconstruction processing system, 22... Display system, 24... X-ray generator, 26... Frame - Bed controller, 28... system controller, 30... system controller.

Claims (2)

[Claims] (1) In an X-ray detector having a detection module formed by arranging X-ray detection elements including scintillators and photodiodes for multiple channels, the scintillator section of the detection module extends in the slice direction over the multiple channels. An X-ray detector characterized by having a flat end face. (2) An X-ray CT scanner device characterized in that the X-ray detector according to claim 1 is used as an X-ray detector of a Rotate/Rotate type X-ray CT scanner device.