JP2006162293A - X-ray detector and x-ray ct device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector and an X-ray CT device capable of improving X-ray utilization efficiency. <P>SOLUTION: When a light emission part L1 is generated in a first scintillator layer 41, radiation light R1 is radiated. A first light parallelizing layer 51 converts the radiation light R1 into parallel light P1 and emits it. The parallel light P1 is transmitted through a second scintillator layer 42, and enters a second light parallelizing layer 52. The second light parallelizing layer 52 converts the parallel light P1 into focusing convergent light F1 and emits it. Though the convergent light F1 is spread after being focused, a most part thereof is received by a photodiode 61 in a corresponding channel after being spread. Since each scintillator layer which is not fractionated by a reflecting material or a slit is used, the X-ray utilization efficiency can be improved. Since each scintillator layer is thinned and each light parallelizing layer is provided between each scintillator layer, crosstalk can be suppressed. Since the whole scintillator layer is sufficiently thick, an X-ray can be detected in an X-ray energy range (wavelength range) as before. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray detector and an X-ray CT apparatus, and more particularly to an X-ray detector and an X-ray CT apparatus capable of improving X-ray utilization efficiency.

  Conventionally, in order to enable high-resolution imaging with an X-ray CT apparatus, many X-ray detectors (see, for example, Patent Document 1) provided with a plurality of photodiodes for each cell fractionated by a collimator, and many scintillators. An X-ray detector (see, for example, Patent Document 2) in which a reflecting material to be fractionated into cells is inclined has been proposed.

JP 2004-93489 A JP 2004-28815 A

In a conventional X-ray detector, in order to prevent light adjacent to a certain photodiode from receiving only a certain photodiode (hereinafter referred to as crosstalk), a scintillator is formed by a reflector or a slit. It was fractionated.
However, the presence of reflectors and slits has a problem of reducing X-ray utilization efficiency.
Accordingly, an object of the present invention is to provide an X-ray detector and an X-ray CT apparatus capable of improving the X-ray utilization efficiency.

In the first aspect, the present invention includes two or more stages of unfractionated scintillators, and radiation light generated by the scintillator at a certain stage is incident between the scintillator at a certain stage and the scintillator at the subsequent stage. An X-ray detector is provided that includes a collimating means for collimating the light and emitting it to the subsequent scintillator.
In the above configuration, “unfractionated scintillator” refers to a scintillator that is not fractionated into individual cells by a reflector or a slit.
Since the X-ray detector according to the first aspect uses a scintillator that is not fractionated by a reflector or a slit, the X-ray use efficiency is not reduced by the reflector or the slit, and the X-ray use efficiency can be improved. . In addition, since the collimating means is provided between the scintillators, it is possible to prevent the radiated light generated in a certain scintillator from further spreading in the subsequent scintillator and to reduce the thickness of the scintillator in one stage. Thus, it is possible to suppress the range in which the emitted light generated in a certain stage of scintillator spreads within the scintillator. Therefore, crosstalk can be suppressed. Furthermore, even if the thickness of a single scintillator is reduced, the X-ray can be detected within the same X-ray energy range as before by making the thickness of the scintillator for all stages equal to that of the conventional scintillator. Become.

In a second aspect, the present invention provides the X-ray detector according to the first aspect, wherein the collimating means has a structure in which a plurality of collimating lenses corresponding to channels are aligned in a plate shape. An X-ray detector is provided.
In the X-ray detector according to the second aspect, when radiation light generated by a scintillator at a certain stage is incident by a collimating lens corresponding to a channel, it can be collimated.

In a third aspect, the present invention provides the X-ray detector according to the second aspect, wherein the collimating lens has a focal length shorter than 3/4 of the thickness of the scintillator and 1 / th of the thickness of the scintillator. An X-ray detector characterized by being longer than 4 is provided.
For example, when the scintillator has three stages, the parallel light emitted from the collimating means between the first-stage scintillator and the second-stage scintillator is converted into the parallel light between the second-stage scintillator and the third-stage scintillator. It enters the means and is focused on the focal point, and then spreads.
Therefore, in the X-ray detector according to the third aspect, the focal length of the collimating lens is shorter than 3/4 of the thickness of the scintillator and longer than 1/4. As a result, when the scintillator has three stages, all or most of the light that is collected at the focal point of the collimating means between the second stage scintillator and the third stage scintillator and then spread is handled. Light can be received by the light receiving element of the channel. The same is true even if the scintillator has four stages.

In a fourth aspect, the present invention provides the X-ray detector according to the first aspect, wherein the collimating means is a structure in which a plurality of optical fibers are aligned in a plate shape. A featured X-ray detector is provided.
When a structure in which a plurality of optical fibers are aligned and integrated into a plate shape is used, light travels along the optical axis of the optical fiber regardless of the incident angle of light incident on one end side of the optical fiber. It can be regarded as parallel light. The spread of light emitted from the other end of the optical fiber can be suppressed by using an optical fiber having a large core diameter.

In a fifth aspect, the present invention provides an X-ray detector according to the fourth aspect, wherein the core at the end of the optical fiber is expanded.
By using an optical fiber having an enlarged core at the end, it is possible to suppress the spread of light emitted from the other end side of the optical fiber.

In a sixth aspect, the present invention provides the X-ray detector according to any one of the first to fifth aspects, wherein the collimating means has a thickness of 0.5 mm or less. A line detector is provided.
By suppressing the thickness of the collimating means to 0.5 mm or less, an increase in the thickness of the X-ray detector due to sandwiching the collimating means between the scintillators can be suppressed.

In a seventh aspect, the present invention provides the X-ray detector according to any one of the first to sixth aspects, wherein the scintillator has a thickness of 1.5 mm or less, and the combination has three or more stages. An X-ray detector is provided.
By suppressing the thickness of the scintillator to 1.5 mm or less, it is possible to suppress the range in which the radiated light generated in one stage of the scintillator spreads within the scintillator. Further, by setting the number of stages to three or more, the thickness of the scintillator including all the stages becomes equivalent to the conventional one, and X-rays can be detected in the same X-ray energy range as the conventional one.

In an eighth aspect, the present invention provides an X-ray CT apparatus comprising the X-ray detector according to any one of the first to seventh aspects.
In the X-ray CT apparatus according to the eighth aspect, since the X-ray detector having the above-described configuration is used, X-ray utilization efficiency can be improved.

  According to the X-ray detector and the X-ray CT apparatus of the present invention, X-ray utilization efficiency can be improved.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a plan view illustrating an X-ray CT apparatus 100 according to the first embodiment.
The X-ray CT apparatus 100 includes an operation console 1, a table device 10, and a scanning gantry 20.

  The operation console 1 includes an input device 2 that receives input from an operator, a central processing unit 3 that executes image reconstruction processing, a data collection buffer 5 that collects projection data acquired by the scanning gantry 20, and a projection data. A display device 6 for displaying the reconstructed CT image and a storage device 7 for storing programs and data are provided.

  The table device 10 includes a cradle 12 that puts a subject and puts it in and out of a bore (cavity) of the scanning gantry 20. The cradle 12 is moved up and down and linearly moved by a motor built in the table apparatus 10.

  The scanning gantry 20 includes an X-ray tube 21, an X-ray controller 22, a collimator 23, an X-ray detector 24, a DAS (Data Acquisition System) 25, and an X-ray tube that rotates around the body axis of the subject. A rotation controller 26 that controls the control unit 21, a tilt controller 27 that performs control when the scanning gantry 20 is tilted forward or backward of the rotation axis, and a control controller that exchanges control signals and the like with the operation console 1 and the table device 10. 29 and a slip ring 30 for transferring power, control signals, and collected data.

FIG. 2 is a side view of the main part of the X-ray detector 24 according to the first embodiment.
The X-ray detector 24 includes a first scintillator layer 41, a second scintillator layer 42 and a third scintillator layer 43, and a first collimating layer interposed between the first scintillator layer 41 and the second scintillator layer 42. 51, a second collimating layer 52 interposed between the second scintillator layer 42 and the third scintillator layer 43, and a photodiode array 60 in which a large number of photodiodes are arranged corresponding to the channels. Yes.

  The scintillator layers 41, 42, 43 are not fractionated into individual cells by reflectors, slits, etc., and the thickness is, for example, 1.5 mm.

  The collimating layers 51 and 52 are structures in which a plurality of collimating lenses corresponding to channels are integrated in a plate shape with their directions aligned, and are, for example, SELFOC (registered trademark) lens arrays. The thickness of the collimating layers 51 and 52 is, for example, 0.5 mm.

  The focal length of the collimating lens is, for example, 0.375 mm to 1.125 mm.

As shown in FIG. 3, when the light emitting part L1 is generated at the center of the first scintillator layer 41, the emitted light R1 is emitted from the light emitting part L1. The first parallel light layer 51 emits incident radiation R1 as parallel light P1.
The parallel light P <b> 1 passes through the second scintillator layer 42 and enters the second parallel light conversion layer 52. The second collimating layer 52 emits the incident parallel light P1 as convergent light F1 that converges on the focal point.
The convergent light F <b> 1 spreads after converging at the focal point, but even if spread, most of the light is received by the photodiode 61 of the corresponding channel and hardly received by the adjacent photodiode 62. Therefore, crosstalk can be suppressed.

As shown in FIG. 4, when the light emitting part L2 is generated at the center of the second scintillator layer 42, the emitted light R2 is emitted from the light emitting part L2. The second collimating layer 52 emits the incident radiation R2 as parallel light P2.
The parallel light P2 passes through the third scintillator layer 43, is mostly received by the photodiode 61 of the corresponding channel, and hardly received by the adjacent photodiode 62. Therefore, crosstalk can be suppressed.

  As shown in FIG. 5, when the light emitting part L3 is generated at the center of the third scintillator layer 43, the emitted light R3 is emitted from the light emitting part L3. Most of the emitted light R3 is received by the photodiode 61 of the corresponding channel, and hardly received by the adjacent photodiode 62. Therefore, crosstalk can be suppressed.

  According to the X-ray detector 24 and the X-ray CT apparatus 100 of the first embodiment, since the scintillator layers 41, 42, and 43 that are not fractionated by the reflecting material and the slit are used, the X-ray is used by the reflecting material and the slit. The efficiency is not lowered and the X-ray utilization efficiency can be improved. Moreover, since the parallel light layers 51 and 52 are provided between the scintillator layers 41, 42, and 43, crosstalk can be suppressed. Furthermore, since the combined thickness of the scintillator layers 41, 42, and 43 is 4.5 mm, X-rays can be detected in the same X-ray energy range (wavelength range) as that of the prior art.

Comparative example

FIG. 6 shows an X-ray detector 24 ′ having a structure in which the parallel light layers 51 and 52 are omitted from the X-ray detector 24 of the first embodiment.
In this X-ray detector 24 ′, since the emitted lights R 1 and R 2 are incident on the channels 62 and 63 adjacent to the corresponding channel 61, the crosstalk is increased.

FIG. 7 is a side view of the main part of the X-ray detector 24 according to the second embodiment.
The X-ray detector 24 has a configuration in which the third collimating layer 53 and the fourth scintillator layer 44 are added to the X-ray detector 24 of the first embodiment to form four scintillator layers.

  The radiated light R1 radiated from the light emitting portion L1 of the first scintillator layer 41 is converted into parallel light P1 by the first parallel light conversion layer 51 and converted into convergent light F1 by the second parallel light conversion layer 52. The collimated light layer 53 converts the light into parallel light P1 again. Most of the light is received by the photodiode 61 of the corresponding channel, and hardly received by the adjacent photodiode 62. Therefore, crosstalk can be suppressed.

  Similarly, the scintillator layer may have five or more stages, and conversely, the scintillator layer may have two stages.

FIG. 8 is a side view of the main part of the X-ray detector 24 according to the third embodiment.
The X-ray detector 24 includes a first scintillator layer 41, a second scintillator layer 42 and a third scintillator layer 43, and a first collimating layer interposed between the first scintillator layer 41 and the second scintillator layer 42. 51, a second collimating layer 52 interposed between the second scintillator layer 42 and the third scintillator layer 43, a third collimating layer 53 interposed after the third scintillator layer 43, And a photodiode array 60 in which a large number of photodiodes are arranged in correspondence with the channels.

  The scintillator layers 41, 42, 43 are not fractionated into individual cells by reflectors, slits, etc., and the thickness is, for example, 1.5 mm.

  The collimating layers 51, 52, and 53 are structures in which a plurality of optical fibers are aligned in a plate shape with the directions aligned, so to speak, a thin light guide. The thickness of the collimating layers 51, 52, 53 is, for example, 0.5 mm.

  As shown in FIG. 9, the optical fiber 50 of the collimating layers 51, 52, 53 has a larger ratio of the core 50a to the clad 50b as shown in FIG. It is preferable to use the one processed into 50c because the spread of the emitted light can be suppressed.

As shown in FIG. 11, when the light emitting part L1 is generated at the center of the first scintillator layer 41, the emitted light R1 is emitted from the light emitting part L1. The first parallel light layer 51 emits incident radiation R1 as parallel light P1. The parallel light P1 spreads a little after exiting the first parallel light layer 51, but does not spread as much as the radiated light R1, and most of the light passes through the second scintillator layer 42 and enters the second parallel light layer 52. .
The second collimating layer 52 emits incident light as parallel light. The parallel light spreads a little after exiting the second collimating layer 52, but does not spread as much as the radiated light R 2, and most of the light passes through the third scintillator layer 43 and enters the third collimating layer 53.
The third collimating layer 53 converts the incident light into parallel light and enters the photodiode 61 of the corresponding channel.

As shown in FIG. 12, when the light emitting part L2 is generated at the center of the second scintillator layer 42, the emitted light R2 is emitted from the light emitting part L2. The second collimating layer 52 emits the incident radiation R2 as parallel light P2. The parallel light P2 spreads a little after exiting the second parallel light layer 52, but does not spread as much as the radiated light R1, and most of the light passes through the third scintillator layer 43 and enters the third parallel light layer 53. .
The third collimating layer 53 converts the incident light into parallel light and enters the photodiode 61 of the corresponding channel.

  As shown in FIG. 13, when the light emitting part L3 is generated at the center of the third scintillator layer 43, the emitted light R3 is emitted from the light emitting part L3. The third collimating layer 53 emits incident radiation R3 as parallel light P3. The parallel light P3 is received by the photodiode 61 of the corresponding channel.

  According to the X-ray detector 24 and the X-ray CT apparatus using the same according to the third embodiment, the scintillator layers 41, 42, and 43 that are not separated by the reflecting material and the slit are used. The X-ray utilization efficiency is not reduced, and the X-ray utilization efficiency can be improved. Moreover, since the parallel light layers 51 and 52 are provided between the scintillator layers 41, 42, and 43, crosstalk can be suppressed. Furthermore, since the combined thickness of the scintillator layers 41, 42, and 43 is 4.5 mm, X-rays can be detected in the same X-ray energy range (wavelength range) as that of the prior art.

FIG. 14 is a side view of the main part of the X-ray detector 24 according to the fourth embodiment.
The X-ray detector 24 has a configuration in which the third collimating layer 53 is omitted from the X-ray detector 24 of the third embodiment.

  Since the X-ray detector and the X-ray CT apparatus of the present invention do not perform fractionation with a reflector or a slit, the channel interval can be shortened and can be used for high-resolution imaging.

1 is an explanatory diagram illustrating a configuration of an X-ray CT apparatus according to Embodiment 1. FIG. 1 is a side view of an essential part showing an X-ray detector according to Embodiment 1. FIG. FIG. 6 is a first explanatory diagram illustrating an operation of the X-ray detector according to the first embodiment. FIG. 6 is a second explanatory diagram illustrating the operation of the X-ray detector according to Embodiment 1. FIG. 6 is a third explanatory diagram illustrating the operation of the X-ray detector according to Embodiment 1. It is a principal part side view which shows the X-ray detector which concerns on a comparative example. FIG. 6 is a side view of a main part showing an X-ray detector according to Embodiment 2. FIG. 6 is a side view of a main part showing an X-ray detector according to Embodiment 3. 6 is a cross-sectional view illustrating a first example of an optical fiber according to Example 3. FIG. 6 is a cross-sectional view showing a second example of an optical fiber according to Example 3. FIG. FIG. 10 is a first explanatory diagram illustrating the operation of the X-ray detector according to Embodiment 3. FIG. 10 is a second explanatory diagram showing the operation of the X-ray detector according to Embodiment 3. FIG. 10 is a third explanatory diagram illustrating the operation of the X-ray detector according to Embodiment 3. FIG. 9 is a side view of a main part showing an X-ray detector according to Embodiment 4.

Explanation of symbols

24 X-ray detector 41, 42, 43 Scintillator layer 51, 52, 53 Collimating layer 60 Photodiode array 70 Collimator 100 X-ray CT apparatus

Claims (8)

  Two or more stages of non-fractionated scintillators are provided, and when radiation light generated by the scintillator of a certain stage is incident between the scintillator of a certain stage and the scintillator of the succeeding stage, the light is collimated to the scintillator of the subsequent stage. An X-ray detector characterized by interposing a collimating means for emitting light.   2. The X-ray detector according to claim 1, wherein the collimating means is a structure in which a plurality of collimating lenses corresponding to channels are integrated in a plate shape with the directions aligned. .   3. The X-ray detector according to claim 2, wherein a focal length of the collimating lens is shorter than 3/4 of the thickness of the scintillator and longer than 1/4 of the thickness of the scintillator. Detector.   2. The X-ray detector according to claim 1, wherein the collimating means is a structure in which a plurality of optical fibers are integrated in a plate shape with the directions aligned.   5. The X-ray detector according to claim 4, wherein a core at an end of the optical fiber is expanded in diameter.   6. The X-ray detector according to claim 1, wherein the collimating means has a thickness of 0.5 mm or less.   The X-ray detector according to any one of claims 1 to 6, wherein the scintillator has a thickness of 1.5 mm or less, and the combination has three or more stages. vessel.   An X-ray CT apparatus comprising the X-ray detector according to any one of claims 1 to 7.

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