JP6692237B2 - Radiation detector - Google Patents

Description

  The present invention avoids performance degradation in a radiation detector composed of a plurality of semiconductor cells due to connecting a lead wire to a common electrode for applying a bias voltage to the semiconductor cells.

  In recent years, development of a photon counting CT (Computed Tomography) device equipped with a detector (photon counting type detector) adopting a photon counting method has been advanced. The photon counting type detector can individually count the radiation photons incident on the detecting element, unlike the charge integrating type detector employed in the conventional CT apparatus. This has the advantage that the energy of each incident radiation photon can be measured and more information can be obtained compared to the conventional CT device.

  The detection element of the photon counting type detector includes a semiconductor layer made of cadmium zinc telluride (CZT), cadmium telluride (CdTe), or the like, and each time a radiation photon is incident on the semiconductor layer, a corresponding charge is generated. Electrodes for collecting the generated charges are arranged to face the semiconductor layer, and a bias voltage is applied. The electrode arranged for reading out the charge for each pixel functions as an anode. One cathode side functions as a common electrode for a plurality of pixels. To apply a voltage to the common electrode, a lead wire for supplying a bias voltage is connected to the common electrode. By applying such a voltage, the charges generated in the semiconductor layer due to the incidence of radiation photons can be individually taken out from the electrode of each pixel.

  The detector having such a structure has a problem of connecting the lead wire for supplying the bias voltage to the common electrode without impairing the performance of the detector. Since a metal wire such as a copper wire is used for the lead wire for supplying the bias voltage, when the lead wire is arranged between the semiconductor layer and the radiation source, the lead wire absorbs the radiation and the lead wire is arranged. There is a difference in detection sensitivity between the spots and the spots that are not arranged. As a method of avoiding the occurrence of this difference in sensitivity, Patent Document 1 discloses a detector configuration in which a bias voltage feeding structure is provided at a position outside the radiation detection effective area.

JP, 2005-086059, A

  By the way, in recent CT apparatuses, there is a strong demand for increasing the width of the radiation detector in the body axis direction in order to shorten the imaging time. Therefore, it is necessary to configure a detector having a wider radiation detection effective area. On the other hand, it is generally difficult for the semiconductor layer used for the detection element of the photon counting type detector to have a necessary detector area with one crystal from the viewpoint of securing the crystal yield and dimensional accuracy. Therefore, a necessary detector area is secured by arranging a plurality of crystals adjacent to each other. At that time, when a plurality of detectors in which the lead wires for bias power supply are arranged outside the radiation detection effective area are arranged adjacent to each other as in Patent Document 1, the lead wires for bias power supply obstruct the close arrangement of the semiconductor layers. Therefore, a dead zone may be generated due to the gap between the semiconductor layers, or the lead wire for bias power supply power supply may interfere with the radiation detection effective area of the adjacent semiconductor layer, thereby impairing the radiation detection performance of the adjacent semiconductor layer. The problem arises. Therefore, even if the configuration of Patent Document 1 is directly applied to a photon counting type detector in which a plurality of semiconductor detection elements are arranged adjacent to each other, it is difficult to arrange the bias voltage feeding structure without impairing the radiation detection performance. ..

  The present invention has been made in view of the above circumstances, and when supplying a bias voltage to a plurality of adjacently arranged semiconductor layers, suppresses a difference in radiation detection performance on a radiation detection surface of each detection element and uniformizes detection sensitivity. The purpose is to improve sex.

In order to solve the above problems, the present invention provides the following means.
According to one embodiment of the present invention, a semiconductor layer which receives a photon of radiation to generate an electric charge, a common electrode which is formed on one surface of the semiconductor layer and applies a bias voltage to the semiconductor layer, and the other of the semiconductor layers A plurality of detection element modules in which the detection elements each having a pixel electrode formed on the surface are two-dimensionally arranged, and for power supply arranged at equal intervals on the surface of the common electrode of each detection element included in the detection element module There is provided a radiation detector including a plurality of lead wires and a scattered radiation removing member provided corresponding to the arrangement of the lead wires.

  According to the present invention, when supplying a bias voltage to a plurality of semiconductor layers arranged adjacent to each other, it is possible to suppress the difference in the radiation detection function on the radiation detection surface of each detection element and improve the detection sensitivity uniformity.

It is a block diagram which shows the outline of the X-ray CT apparatus which concerns on the 1st Embodiment of this invention. It is a perspective view which shows schematic structure of the X-ray detector of the X-ray CT apparatus which concerns on the 1st Embodiment of this invention. 1A is a plan view and FIG. 1B is a cross-sectional view taken along the line A-A ′ of FIG. 1A, relating to a detection element module used in an X-ray detector according to a first embodiment of the present invention. It is explanatory drawing which shows the example of the relationship of the X-ray irradiated from the X-ray source applied to the X-ray detector which concerns on the 1st Embodiment of this invention, a scattered radiation removal member, and an X-ray detector. (A) And (B) is explanatory drawing which shows the example of the arrangement | sequence of the detection element and pixel of the X-ray detector which concern on the 1st Embodiment of this invention. FIG. 10A is a plan view and FIG. 9B is a cross-sectional view taken along the line AA ′ of FIG. 9A, related to the detection element module used in the X-ray detector according to Modification 1 of the first embodiment of the present invention. .. FIG. 9A is a plan view and FIG. 8B is a cross-sectional view taken along the line A-A ′ of FIG. 9A, relating to a detection element module used in an X-ray detector according to a second embodiment of the present invention. FIG. 9A is a plan view and FIG. 9B is a cross-sectional view taken along the line A-A ′ in FIG. 9A, relating to a detection element module used in an X-ray detector according to a third embodiment of the present invention. FIG. 10A is a plan view and FIG. 8B is a cross-sectional view taken along the line AA ′ of FIG. 9A, relating to a detection element module used in an X-ray detector according to Modification 1 of the third embodiment of the present invention. .. The detection element module used in the X-ray detector according to the fourth embodiment of the present invention is (A) a plan view, (B) is a sectional view taken along the line AA ′ of (A), and (C). [Fig. 3] is a partially enlarged view of (A). FIG. 10A is a plan view of the detection element module used in the X-ray detector according to Modification Example 1 of the fourth embodiment of the present invention, FIG. 9B is a cross-sectional view taken along the line AA ′ of FIG. , (C) are partially enlarged views of (A). FIG. 13A is a plan view of a detection element module used in an X-ray detector according to Modification 2 of the fourth exemplary embodiment of the present invention, FIG. 9B is a cross-sectional view taken along the line AA ′ of FIG. , (C) are partially enlarged views of (A). The detection element module used in the X-ray detector according to the fifth embodiment of the present invention is (A) a plan view, (B) is a sectional view taken along the line AA ′ of (A), and (C). [Fig. 3] is a partially enlarged view of (A). FIG. 13A is a plan view of the detection element module used in the X-ray detector according to the first modification of the fifth embodiment of the present invention, FIG. 9B is a cross-sectional view taken along the line AA ′ of FIG. , (C) are partially enlarged views of (A). It is explanatory drawing which concerns on a circuit model for demonstrating the circuit setting of an X-ray detector.

An embodiment of the present invention will be described below with reference to the drawings.
A radiation imaging apparatus according to the present invention includes an X-ray source for irradiating X-rays, a detection unit in which pixels each including a plurality of detection elements for detecting the X-rays are two-dimensionally arranged, and a detection signal based on a detection signal from the detection elements. A signal processing unit that generates an output signal according to the intensity of X-rays, a signal addition unit, and an image generation unit are provided.
The signal addition unit adds the output signals of the detection elements belonging to the pixels to generate an X-ray count signal for each pixel. The image generation unit generates an image based on the X-ray count signal. At this time, based on the X-ray count signal of the pixel to be processed and the X-ray count signal of pixels located in the vicinity of the pixel to be processed, the non-uniformity of the X-ray incidence distribution of the pixel to be processed is estimated. A feature estimation unit is provided.

Hereinafter, embodiments of the present invention will be described more specifically.
<First Embodiment>
Hereinafter, an example of a radiation detector applied to, for example, an X-ray CT apparatus as a radiation detector according to the first embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the X-ray CT apparatus has an X-ray source 100, an X-ray detector 111, and a detection unit 104 (described later) of the X-ray source 100 and the X-ray detector 111, which are arranged to face each other and have a predetermined shape. Gantry rotating unit 101 rotating about the rotation axis, bed top 103 arranged in the opening of the gantry rotating unit 101, and a signal for processing a signal acquired by the X-ray detector 111 according to the operation of these imaging systems. And a processing unit 112.

  As the X-ray source 100, for example, an X-ray tube can be applied. The X-ray source 100 emits X-ray photons by colliding an electron beam accelerated by a tube voltage with a target metal such as tungsten or molybdenum and generating X-rays from the collision position (focus). The X-ray photons emitted from the X-ray source 120 are partially absorbed by the subject 102 according to the substance distribution in the subject after being subjected to adjustment of the flux and energy distribution by a filter (not shown), and partly Is transmitted through the subject 102 and detected by a detection unit 104 described later.

  The gantry rotating unit 101 arranges the X-ray source 100 and the detecting unit 104 so as to face each other, and rotates about a predetermined rotation axis. An opening into which the subject 102 is inserted is provided in the center of the gantry rotating unit 101, and a bed top 103 on which the subject 102 is laid down is arranged in this opening. The bed top plate 103 and the gantry rotating unit 101 are relatively movable in a predetermined direction.

  The X-ray detector 111 detects the incident X-ray photons, sorts them into a plurality of energy ranges and counts them, and employs a photon counting method, and a scattering unit provided on the X-ray incident side of the detector 104. The line removing member 28 (see FIG. 3B) and the signal collecting unit 108 that collects the projection image output from the detecting unit 104 are provided.

  The X-ray photons output by the detection unit 104 are processed and counted in the pulse mode by the signal acquisition unit 108. The counting here includes not only counting the detected X-ray photons but also acquiring energy information. If the X-ray scattered by the subject 102 is detected, it becomes an undesired signal. Therefore, the scattered X-ray removing member 28 is arranged in front of the detection unit 104 when viewed from the X-ray source 100 side, and the scattered X-ray is detected. Is shut off. Details of the detection unit 104 will be described later.

  The signal processing unit 112 includes a calculation unit 105 and a control unit 107, performs predetermined calculation processing on the signals collected by the signal collection unit 108, and creates a reconstructed image such as a multi-energy image, The generated image is displayed on the display unit (not shown).

Subsequently, the detection unit 104 of the X-ray detector 111 will be described.
As shown in FIG. 2, the detection unit 104 is configured by arranging a predetermined number of detection modules 10 in which a plurality of detection elements 20 are two-dimensionally arranged in the slice direction and the channel direction. The detection element module is arranged such that the channel direction thereof coincides with the rotation direction of the gantry rotation unit 101 and the slice direction thereof coincides with the rotation axis direction of the gantry rotation unit 111.

  As shown in FIG. 3B, each of the detection elements 20 included in the detection element module 10 includes a semiconductor layer 21 that receives a photon of radiation and generates an electric charge, and a semiconductor layer 21 formed on the upper surface of the semiconductor layer 21. A common electrode 22 to which a bias voltage is applied and a pixel electrode 23 formed to match the pixel pitch on the lower surface of the semiconductor layer are laminated. Each detection element 20 is a so-called photon counting type detection element, detects incident X-ray photons, and, for example, sorts into a plurality of energy ranges and performs counting.

  In the present embodiment, the detection elements 20 configured in this manner are arranged in four lines as shown in FIG. 3A (hereinafter, each detection element 20 will be referred to as 20A, 20B, 20C, 20D as necessary. A plurality of lead wires 24 (24A to 24D) for power supply are arranged at equal intervals on the surface of the common electrode 22 of the four detection elements 20A to 20D to form the detection element module 10.

  As shown in FIG. 3A, the lead wires 24 (24 </ b> A to 24 </ b> D) are on the surface of the common electrode 22 of each detection element 20 along the longitudinal direction of the detection element module 10, that is, the slice direction in the present embodiment. Are arranged at predetermined intervals to supply the bias voltage application power to each of the detection elements 20A to 20D.

  It is necessary to dispose the semiconductor layer 21 adjacently in the rotation direction (channel direction) of the detection unit 104. That is, since the detection element modules 10 are arranged adjacent to each other to form the detection unit 104, the lead wire 24 is generally led out in each detection element module 10 in the body axis direction (slice direction). Therefore, in FIG. 3, the lead wires 24A to 24D are for supplying a bias voltage from the lower bias voltage application terminal (not shown) in FIG. 3A to the common electrode 22 of the detection elements 20A to 20D. Wiring.

The lead wire 24A supplies a bias voltage to the detection element 20A, the lead wire 24B to the detection element 20B, the lead wire 24C to the detection element 20C, and the lead wiring 24D to the detection element 20D. The lead wirings 24 </ b> A to 24 </ b> D are covered with an insulating material 25 such as resin, and come into contact with the common electrode 22 at contacts 26. If a plurality of contacts 26 are provided for each detecting element 20, a voltage can be applied uniformly.
Further, in FIG. 3A and FIG. 3B, two lead wires 24 are arranged for each detection element 20, but one lead wire 24 is arranged for a plurality of detection elements 20. You may wire.

  Further, a scattered radiation removing member 28 is arranged on the upper surface of the X-ray detecting unit 104 so as to correspond to the arrangement of the lead wires 24. As shown in FIG. 3 (A), as the scattered radiation removing member 28, a one-dimensional slit collimator configured by vertically arranging a plurality of plate-shaped members at predetermined intervals can be applied. That is, the scattered radiation removing member 28 is composed of a plurality of rectangular plate-like members made of a substance containing molybdenum, tungsten or the like as a main component. The plurality of plate-shaped members are arranged at equal intervals in the channel direction so that the plate-thickness direction of the plate-shaped members is the channel direction and the positions of the lead wires 24 are matched.

Since the lead wire 24 is located below the scattered radiation removing member 28 by disposing the scattered radiation removing member 28, the lead wire 24 is covered and hidden by the scattered radiation removing member 28. However, in FIGS. For the sake of convenience, the lead wire 24 located below the scattered radiation removing member 28 is illustrated.
By disposing the scattered radiation removing member 28 on the X-ray incidence surface of the detection unit 104, most of the X-ray photons are incident on the region located below the scattered radiation removal member 28 on the X-ray incidence surface of the detection unit 104. Disappear. Therefore, substantially, the upper surface region of the X-ray detection unit 104 where the scattered radiation removing member 28 is not arranged becomes the effective area of the X-ray incident surface.

  As described above, by providing the scattered radiation removing member 28 in correspondence with the arrangement positions of the lead wires 24A to 24D and above the lead wires 24A to 24D, each lead is provided on the X-ray incident surface of the X-ray detection unit 104. The lines 24A to 24D are located below the scattered radiation removing member 28. Therefore, it is possible to suppress the influence of the change in the detection sensitivity due to the presence of the lead wires 24A to 24D in the effective area of the X-ray incidence surface of the detection elements 20A to 20D. By arranging and fixing the lead wirings 24A to 24D on the lower surface of the scattered radiation removing member 28, vibration of the lead wirings 24A to 24D when the detector 111 rotates is suppressed, and generation of electrical noise is suppressed. There is also an advantage of doing.

The positional relationship of the lead wires 24A to 24D with respect to the lower surface 28a of the scattered radiation removing member 28 will be described in more detail.
As shown in FIG. 4, the opening width in the channel direction of the plate member of the scattered radiation removing member 28 is a predetermined value PE, the distance between the focal point F of the X-ray and the lower surface 28a of the scattered radiation removing member 28 is D _ASG , and the lead It is assumed that the distance between the lines 24A to 24D and the scattered radiation removing member 28 in the stacking direction of the detection element is SY, and the margin between the lead wires 24A to 24D and the scattered radiation removing member 28 in the channel direction is SX.

In this case, by arranging the lead wires 24A to 24D so as to satisfy the following expression (1), the lead wires 24A to 24D are arranged at positions hidden from the focal point F. It is possible to suppress unevenness.
PE / 2 / D _ASG <SX / SY (1)

Furthermore, when considering the influence of scattered rays and the like due to the subject, the height of the scattered ray removing member 28 is set to H, and the lead wires 24A to 24D are arranged so as to satisfy the following expression (2). The lines 24A to 24D can be hidden behind the scattered radiation removing member 28, and unevenness in the detection sensitivity due to the lead lines 24A to 24D can be further suppressed.
PE / H <SX / SY (2)

By wiring the lead wires 24A to 24D in this manner, the resistance value of the lead wires 24A to 24D is a solid wiring (hereinafter, simply referred to as "layered wiring" that covers the effective area of the X-ray incident surface of the X-ray detection unit 104). It is higher than when it is called "solid wiring". However, since the resistance value of the semiconductor layer 21 is generally as high as about 1 MΩ, an increase in resistance value (for example, several Ω) due to the wiring of the lead wires 24A to 24D as described above can be sufficiently ignored.
This can be more generally confirmed by the following equation (3) using the resistance value RD of the semiconductor layer 21 and the resistance value RB of the solid wiring.
RB / RD << 1 ... Formula (3)

In addition, it is preferable that the arrangement interval of the lead wires 24A to 24D be set to match the pitch of pixels that detect X-ray photons as one unit of the X-ray detection unit 104, or an integral multiple thereof.
In order to improve the photon count rate, the semiconductor layer 21 may be configured to divide a pixel (pixel) P into a plurality of smaller subpixels SP and count the number of photons for each subpixel. As an example, FIG. 5A shows the case where the pixel is composed of 2 × 2 subpixels, and FIG. 5B is the case where the pixel is composed of 3 × 3 subpixels.

  In the case of FIG. 5A, the lead wires 24A to 24D are arranged every three pixels, and the contact point between the common electrode (not shown) on one pixel (pixel) of the semiconductor layer 21 and the lead wiring 24 is the contact 26, the pixel. The opening width is PE2. At this time, the pixel is P2, the subpixel is SP, the pixel pitch is DP2, and the subpixel pitch is DS. On the other hand, in the case of FIG. 5B, the pixel (pixel) is P3, the pixel pitch is DP3, and the pixel opening width is PE3 with respect to the same sub-pixel SP and sub-pixel pitch DS. In this way, for detectors that can adopt various pixel configurations, by setting the least common multiple of the number of sub-pixel divisions (for example, 6 for sub-pixel division numbers 2 and 3) that can take the arrangement interval of the lead wires. , The same lead wires 24A to 24D can support different sub-pixel division numbers.

In this way, by matching the pitch of the lead wires 24A to 24D with the pitch of the pixel, even if the pixel is divided into a plurality of subpixels, the sensitivity between the subpixels included in one pixel is increased. It is possible to suppress unevenness.
Further, although one lead wire 24 is configured to supply power to one semiconductor layer 21, it is also possible to configure to supply power to a plurality of semiconductor layers from one lead wire.

  As described above, according to the present embodiment, by making the wiring position of the lead wire 24 and the arrangement position of the scattered radiation removing member 28 substantially coincide with each other, the lead wire 24 does not block the incidence of X-rays. Further, by setting the positional relationship between the lead wire 24 and the scattered ray 28 at the position determined by the above-mentioned formulas (1) and (2), the exposure of the lead wire can be blocked by the scattered ray removing member 28. Therefore, in the detection module 10 including the plurality of adjacently arranged detection elements 20, when the bias voltage is supplied to the plurality of detection elements 20, that is, the semiconductor layer 21, the radiation detection performance of the radiation detection surface of each detection element 20 is improved. The difference can be suppressed and the detection accuracy can be improved.

  Although the detection element module 10 including the four detection elements 20 has been described in the above embodiment, the number of detection elements, the number of lead wires, the width, and the shape of the detection element module included in the detection element module can be appropriately changed.

(Modification 1 of the first embodiment)
In the above-described embodiment, the scattered radiation removing member 28 has a one-dimensional configuration, but the scattered radiation removing member 28 is not limited to one dimension, and the plate-shaped members are arranged in a lattice as shown in FIG. It is also possible to apply a two-dimensional rectangular collimator. Also in this case, it is preferable that the pixel for detecting the incident X-ray photon as one unit of the X-ray detection unit 104 and the pitch and shape of the two-dimensional rectangular collimator match. By matching the pitch and shape of a two-dimensional rectangular collimator with a pixel, even if the pixel is divided into a plurality of subpixels, it is possible to suppress sensitivity unevenness between subpixels included in one pixel. You can

<Second Embodiment>
In the above-described first embodiment and its modified example, the example in which the scattered radiation removing member is arranged in conformity with the arrangement of the lead wire with respect to the common electrode of the detection element module has been described. In the present embodiment, the scattered radiation removing member 28 is used as a part of the power feeding member in the same manner as the lead wire to supply the power for applying the bias voltage to the common electrode. different. In the following description, the same components as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  As shown in FIG. 7, the detection unit 104 is configured by arranging a predetermined number of detection element modules 12 in which a plurality of detection elements are two-dimensionally arranged in the slice direction and the channel direction. The detection element module is arranged so that the channel direction and the rotation direction are the same, and the slice direction and the rotation axis direction are the same.

  The detection element module has, for example, four detection elements 20A to 20D arranged in a line, and each detection element 20 has a semiconductor layer 21 that receives a photon of radiation and generates an electric charge, and an upper surface of the semiconductor layer 21. A common electrode 22 that applies a bias voltage to the formed semiconductor layer 21 and a pixel electrode 23 that is formed on the lower surface of the semiconductor layer are stacked. Each detection element 20 is a so-called photon counting type detection element, detects incident X-ray photons, and, for example, sorts into a plurality of energy ranges and performs counting.

  A scattered radiation removing member 28 is arranged on the upper surface of the X-ray detecting unit 104. As the scattered radiation removing member 28, for example, a two-dimensional rectangular collimator can be applied. The scattered radiation removing member 28 and the common electrode 22 are electrically connected via lead wires 29 (29A to 29D). By doing so, the scattered radiation removing member 28 is used as a part of the wiring material.

  That is, the scattered radiation removing member 28 is maintained at the bias voltage via the lead wiring 29 from the bias voltage feeding terminal (not shown). Next, by connecting the scattered radiation removing member 28 and the common electrode 22 of each of the detection elements 20A to 20D with lead wires 29A, 29B, 29C and 29D, a bias voltage is applied to the common electrodes 22A to 22D of each of the detection elements 20A to 20D. Can be powered. Although the lead wires 29A, 29B, 29C, and 29D have been described as an example here, the scattered radiation removing member 28 and the common electrodes 22A to 22D may be connected using a conductive material such as solder.

  As described above, according to the present embodiment, since the lead wire is not wired on the upper surface of the common electrode of the detection element module, the lead wire does not interfere with the X-ray detection surface of each detection element, and the radiation detection surface of each detection element is prevented. It is possible to suppress the difference in the radiation detection performance in and to improve the detection accuracy.

<Third Embodiment>
In the present embodiment, in order to supply a bias voltage to the common electrode of the detection element module, a plurality of strip-shaped conductive materials having a length extending from one end to the other end in the longitudinal direction of the detection element module are arranged. It is different from the first and second embodiments described above in that it is provided with. In the following description, the same components as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  The detection unit of the X-ray detector according to this embodiment is configured by arranging a predetermined number of detection modules 13 in which a plurality of detection elements are two-dimensionally arranged in the slice direction and the channel direction. The detection element module is arranged so that the channel direction and the rotation direction are the same, and the slice direction and the rotation axis direction are the same.

  As shown in FIG. 8, the detection element module 10 has, for example, four detection elements 20A to 20D arranged in a line, and each detection element 20 receives a photon of radiation and generates an electric charge. And a common electrode 22 formed on the upper surface of the semiconductor layer 21 for applying a bias voltage to the semiconductor layer 21, and a pixel electrode 23 formed on the lower surface of the semiconductor layer. Each detection element 20 is a so-called photon counting type detection element, detects incident X-ray photons, and, for example, sorts into a plurality of energy ranges and performs counting.

On the upper surface of the detection element module 10, that is, on the surface of the common electrode of each of the detection elements 20A to 20D, a lead wiring portion 31 for applying electric power for applying a bias voltage to the common through electrode is provided.
The lead wiring part 31 includes a plurality of plate-shaped wirings 30A, 30B, 30C, 30D made of a strip-shaped conductive material having a length extending from one end to the other end in the longitudinal direction of the detection element module at equal intervals in the channel direction. It is configured with a book arrangement. The plate-shaped wiring 30A supplies a bias voltage to the detection element 20A, the plate-shaped wiring 30B to the detection element 20B, the plate-shaped wiring 30C to the detection element 20C, and the plate-shaped wiring 30D to the detection element 20D.

  Further, a conductor sheet 33 having the same material and the same thickness as the plate-shaped wiring 30 is provided in the gap between the plate-shaped wirings 30 in the lead wiring portion 31. The conductor sheet 33 is coated with an insulator 25B such as resin. The conductor sheet 33 is preferably made of the same material as the plate wirings 30A to 30D, but may be made of another material having substantially the same X-ray attenuation characteristics.

  Here, since the lead wiring portion 31 plays a role of supplying a predetermined potential to the common electrode 22, it is necessary when the detection element 20 is inspected, that is, in the initial stage of the production of the detection element module 10. At this time, since there is a concern that the detection element 20 has a low yield, if there is a defect in the detection characteristics, the lead wiring portion 31 is peeled off and replaced with another detection element 20, thereby reducing the production yield of the detection element module 10. Can be improved.

  On the other hand, the conductor sheet 33 is arranged to suppress uneven detection sensitivity. Since the bonding surface of the conductor sheet 33 is large, it is desirable that the conductor sheet 33 is not bonded at the initial stage of the production of the detection element module 10, but is bonded at the completion of the inspection and arrangement of the detection elements 20, that is, at the final stage of the production of the detection element module 10. .. By considering the manufacturing process of such a detection element module 10 and configuring the lead wiring portion 31 and the conductor sheet 33 as separate parts, there is an effect of improving the production yield of the detection element module 10.

More specifically, as shown in FIG. 8A, the conductor sheet 33 is arranged so as to fill the gap in the lead wiring portion 31. At this time, a slight gap can be provided between the conductor sheet 33 and each of the plate-shaped wirings 30A to 30D of the lead wiring portion 31 in consideration of an alignment error. However, it is desirable that this gap be equal to or smaller than the pixel pitch DP.
In the present embodiment, the lead wiring portion 31 and the conductor sheet 33 are coated with an insulator 25A such as resin for the purpose of easy handling and protection. Further, the conductor sheet 33 and the lead wiring portion 31 are separate components and have a layered structure.

  As described above, according to the present embodiment, by providing the conductor sheet 33 in the gap in the lead wiring portion 31, unevenness in the X-ray detection sensitivity caused by the lead wiring portion on the X-ray incident surface is greatly suppressed. be able to.

  When adopting this configuration, the potential of the conductor sheet 33 can be appropriately selected from ground or bias voltage. When the potential of the conductor sheet 33 is set to the ground, it is difficult for a user or the like to come into contact with the bias voltage, which has the effect of enhancing the safety of the detector. On the other hand, when the potential of the conductor sheet is set to the bias potential, there is an effect of enhancing the stability of the lead wiring with respect to load fluctuation.

(Modification 1 of the third embodiment)
In this modification, as shown in FIG. 9, instead of the conductor sheet provided in the gap between the plate-shaped wirings 30 of the lead wiring portion 31 in the above-described third embodiment, the detection element is provided on the surface of the lead wiring portion. A conductor layer 34 is provided that uniformly covers the entire common electrode of the module.
The conductor layer 34 is preferably made of the same material as that of the lead wiring portion 31, but may be made of another material capable of obtaining equivalent X-ray attenuation characteristics. Further, the conductive layer may be coated with an insulating material 25B such as a resin for the purpose of improving the easiness of handling and protecting. Further, as in the third embodiment, coating the lead wiring portion 31 with another insulator 25A to form a separate component has the effect of improving the production yield of the detection element module 10.
As described above, it is possible to greatly suppress the unevenness of the X-ray detection sensitivity caused by the lead wiring portion on the X-ray incident surface of the detection unit 104.

<Fourth Embodiment>
Like the radiation detector according to the third embodiment described above, the present embodiment has a length from one end to the other end in the longitudinal direction of the detection element module for supplying a bias voltage to the common electrode of the detection element module. Is provided with a plurality of strip-shaped conductive materials having a lead wiring portion. As shown in FIG. 10, in the present embodiment, the plate-like wiring of the lead wiring portion is a mesh, and the mesh pattern of the mesh is inclined with respect to the array direction of the detection elements, which is the third embodiment described above. Different from In the following description, the same components as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  As shown in FIG. 10, the detection element module 10 has, for example, four detection elements 20A to 20D arranged in a line, and each detection element 20 receives a photon of radiation and generates an electric charge. And a common electrode 22 formed on the upper surface of the semiconductor layer 21 for applying a bias voltage to the semiconductor layer 21 and a pixel electrode 23 formed on the lower surface of the semiconductor layer and provided to match the pixel pitch. It is configured. Each detection element 20 is a so-called photon counting type detection element, detects incident X-ray photons, and, for example, sorts into a plurality of energy ranges and performs counting.

A lead wiring portion 41 that supplies electric power for applying a bias voltage to the common electrode is provided on the upper surface of the detection element module 10, that is, the surface of the common electrode of each of the detection elements 20A to 20D.
The lead wiring portion 41 includes plate-shaped wirings 42A, 42B, 42C, 42D made of a strip-shaped conductive material having a length extending from one end to the other end in the longitudinal direction of the detection element module 10 in the channel direction. A plurality of them are arranged at intervals. As shown in FIG. 10, in the present embodiment, four plate-shaped wirings 42A to 42D are arranged, the plate-shaped wiring 42A to the detection element 20A, the plate-shaped wiring 42B to the detection element 20B, and the plate-shaped wiring 42B. The wiring 42C supplies a bias voltage to the detection element 20C, and the plate-shaped wiring 42D supplies a detection element 20D with a bias voltage. The plate-like wirings 42A, 42B, 42C, 42D are covered with an insulator 25 such as resin, and contact the common electrode 22 at a contact 26. If a plurality of contacts 26 are provided for each semiconductor layer 21, a voltage can be applied uniformly.

  Each plate-shaped wiring 42A, 42B, 42C, 42D of the lead wiring portion is a mesh in which a lead wire having a wiring width W1 is woven, and the mesh pattern of the mesh is inclined with respect to the arrangement direction of the detection elements. More specifically, as shown in the enlarged view of FIG. 10C, in the plate-shaped wiring, the lead wires having the wiring width W1 are arranged in the lateral direction (longitudinal direction of the detection module) pitch PX1 in FIG. 10A. 10 (A), the mesh shape is woven so as to have a pitch PY1 in the vertical direction (short direction of the detection module).

  At this time, the amount of change in detection sensitivity between pixels due to the mesh wiring can be suppressed by adjusting the wiring width W1 of the mesh wiring and the horizontal pitch PX1, or the wiring width W1 of the mesh wiring and the vertical pitch PY1. it can. For example, by setting the horizontal pitch PX1 and the vertical pitch PY1 to be the same size, and setting the wiring width W1 to the vertical pitch PX1, 10% of the horizontal pitch PY1, and less than or equal to the pixel pitch (DP), X-ray incidence On the surface, the amount of change in the X-ray detection sensitivity caused by the lead wiring portion can be suppressed to about 20% of that in solid wiring.

If this is generalized, when the target amount of change in detection sensitivity is R%,
W1 / PX1 + W1 / PY1 <R% and W1 <DP (4)
By setting a constant that defines the mesh of the plate-shaped wiring so as to satisfy the above condition, the amount of change in the detection sensitivity due to the presence or absence of the lead wiring portion can be suppressed to about R%. For the sake of simplicity, in Expression (4), the change amount of the detection sensitivity is approximated by the change amount of the aperture ratio, and the influence of the overlapping portion of the mesh portion is ignored.

  By the way, similarly to the above-described first embodiment, the resistance value of the mesh wiring is higher than that of the solid wiring. However, since the resistance value of the semiconductor layer is generally as high as about 1 MΩ, an increase in resistance value (for example, several Ω) due to the application of mesh material wiring to the plate-shaped wiring can be sufficiently ignored. This can be confirmed by the equation (3) described above.

  The detection element module shown in FIG. 10 is an example, and the number of detection elements, the width and shape of the mesh of the plate-shaped wiring, the mesh-shaped wiring and the detection element connection position, and the like may be appropriately changed. Further, the end of the mesh wiring may be shunted by using a conductor having a wiring width smaller than the pixel pitch, may be opened without shunting, or may be thinned out within a range that does not significantly impair the performance.

(Modification 1 of the fourth embodiment)
Like the radiation detector according to the fourth embodiment described above, the present embodiment has a length from one end to the other end in the longitudinal direction of the detection element module for supplying a bias voltage to the common electrode of the detection element module. And a lead wiring portion in which a plurality of mesh-shaped plate-shaped wirings are arranged. As shown in FIG. 11, in the present embodiment, a total of eight plate-shaped wirings of the lead wiring portion are arranged. In the following description, the same components as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  The plate-shaped wirings 42A, 42B, 42C, 42D, 42E, 42F, 42G, 42H of the lead wiring portion 41 supply a bias voltage from a bias voltage application terminal (not shown) to the common electrodes of the detection elements 20A to 20D. The plate-shaped wires 42A and 42B are connected to the detection element 20A, the plate-shaped wires 42C and 42D are connected to the detection element 20B, the plate-shaped wires 42E and 42F are connected to the detection element 20C, and the plate-shaped wires 42G and 42H are connected to the detection element 20C. A bias voltage is supplied to each of the detection elements 20D. That is, in the detection element module according to this modification, power can be supplied to one detection element by two plate-shaped wirings.

  Further, the lead wiring portion 41 is covered with an insulator 25 such as a resin, and contacts the common electrode 22 at a contact 26. If a plurality of contacts 26 are provided for each semiconductor layer 21, a voltage can be applied uniformly. In FIG. 11, one plate-shaped wiring supplies power to one semiconductor layer 21. However, one plate-shaped wiring may supply power to a plurality of semiconductor layers.

  The plate-shaped wirings 42A to 42H in the present modified example are woven with lead wires having a predetermined wiring width and have a mesh pattern in the arrangement direction of the detection elements 20A to 20D, similarly to the plate-shaped wiring according to the above-described fourth embodiment. It is a mesh that is slanted. More specifically, as shown in the enlarged view of FIG. 11C, in the plate-shaped wiring, the lead wires having the wiring width W2 have a pitch in the horizontal direction (short direction of the detection module) in FIG. 11A. PX2 has a mesh shape woven so as to have a pitch PY2 in the vertical direction (longitudinal direction of the detection module) in FIG. 11A.

The amount of change in the detection sensitivity due to the mesh-shaped plate-shaped wirings 42A to 42H can be suppressed by adjusting the wiring width W2, the horizontal direction PX2, and the vertical direction pitch PY2. For example, the relationship between the vertical pitch PX2, the horizontal pitch PY2, the wiring width W2, the pixel pitch (DP), and the change amount of the detection sensitivity with R% is as follows.
W2 / PX2 + W2 / PY2 <R% and W2 <DP ... Formula (5)
For the sake of simplicity also in the equation (5), the change amount of the detection sensitivity is approximated by the change amount of the aperture ratio, and the influence of the overlapping portion of the mesh portion is ignored.

  As described above, according to this modification, it is possible to suppress the amount of change in the X-ray detection sensitivity caused by the lead wiring portion on the X-ray incident surface. Further, by dividing the number of plate-like wirings in the lead wiring portion and connecting to the common electrode of the detection element at a plurality of locations, it is possible to suppress the voltage distribution inside the common electrode and to make the power supply redundant. it can.

(Modification 2 of the fourth embodiment)
In this modification, the plate-shaped wiring 42 of the lead wiring portion 41 is a mesh, and the mesh pattern of the mesh is a lattice shape that matches the arrangement direction of the detection elements. Different from Example 1. In the following description, the same components as those of the other embodiments described above are designated by the same reference numerals, and the description thereof will be omitted.

  The plate-shaped wiring 42 of the lead wiring portion 41 in the present modification 2 is a lattice-shaped mesh that matches the array direction of the detection elements. As shown in FIG. 12, the mesh-like plate-shaped wiring is formed by weaving lead wires having a wiring width W3, and having a horizontal pitch (short direction of the detection module) PX3 and a vertical pitch (longitudinal direction of the detection module) PY3. By adjusting these, it is possible to suppress a change in detection sensitivity due to the mesh-shaped plate wiring.

For example, the relationship between the vertical pitch PX3, the horizontal pitch PY3, the wiring width W3, the pixel pitch (DP), and the change amount of the detection sensitivity with R% is as follows.
W3 / PX3 + W3 / PY3 <R% and W3 <DP ... Formula (6)
For the sake of simplicity also in Expression (6), the change amount of the detection sensitivity is approximated by the change amount of the aperture ratio, and the influence of the overlapping portion of the mesh portion is ignored.
As described above, according to the present modification, the amount of change in the X-ray detection sensitivity caused by the lead wiring portion on the X-ray incident surface can be suppressed, and the wiring pattern creation cost of the plate-shaped wiring can be reduced. effective.

<Fifth Embodiment>
The present embodiment includes a lead wiring portion that is uniformly arranged on the surface of the detection element module for supplying a bias voltage to the common electrode of the detection element module. In the present embodiment, as shown in FIG. 13, the lead wiring portion includes a plurality of lead wires each having a length from one end to the other end in the longitudinal direction, and each lead wire is on the surface of the common electrode. It is arranged at intervals. In the following description, the same components as those of the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

  The detection element module 10 has, for example, four detection elements 20A to 20D arranged in a line, and each detection element 20 has a semiconductor layer 21 that receives a photon of radiation and generates an electric charge, and an upper surface of the semiconductor layer 21. The common electrode 22 formed on the semiconductor layer 21 for applying a bias voltage to the semiconductor layer 21 and the pixel electrode 23 formed on the lower surface of the semiconductor layer so as to match the pixel pitch are laminated. Each detection element 20 is a so-called photon counting type detection element, detects incident X-ray photons, and, for example, sorts into a plurality of energy ranges and performs counting.

  On the upper surface of the detection element module 10, that is, on the surface of the common electrode of each detection element, a lead wiring portion 51 including a plurality of lead wires 52A to 52D for supplying power to the common electrode is provided. As shown in FIG. 13, each of the lead wires 52A to 52D has a length extending from one end to the other end of the detection element module, and is evenly spaced on the surface of the common electrode while being inclined with respect to the arrangement direction of the detection elements. The lead wires 52A to 52D are arranged in a uniform arrangement with respect to the X-ray incidence surface of each detection element 20.

  The lead wire 52A supplies a bias voltage to the detecting element 20A, the lead wire 52B supplies a detecting element 20B, the lead wire 52C supplies a detecting element 20C, and the lead wiring 52D supplies a detecting element 20D with a bias voltage.

As shown in FIG. 13C, assuming that the lead wire has a wiring width W4 and the lateral direction (short side direction of the detection element module) pitch PX4, the amount of change in detection sensitivity due to the arrangement of the lead wires is the wiring width W4 and the lateral direction. It can be suppressed by adjusting PX4. For example, the relationship between the lateral pitch PX4, the wiring width W4, the pixel pitch (DP), and the change amount of the detection sensitivity with R% is as follows.
W4 / PX4 <R% and W4 <DP ... (7)
In addition, also in the formula (7), the change amount of the detection sensitivity is approximated by the change amount of the aperture ratio for simplicity.

The lead wiring HVL is covered with an insulator 25 such as resin, and contacts the common electrode 22 at a contact 26. If a plurality of contacts 26 are provided for each semiconductor layer 21, a voltage can be applied uniformly.
Further, in FIG. 13, one lead wire (HVL) supplies power to one detection element, but one lead wire (HVL) supplies power to a plurality of semiconductor elements (D). It can also be wired to supply. In this embodiment, the lead wiring is diagonal wiring, which has the effect of reducing the wiring pattern creation cost.

(Modification 1 of the fifth embodiment)
In this modification, as shown in FIG. 14, as in the fifth embodiment described above, the lead wiring portion includes a plurality of lead wires each having a length from one end to the other end in the longitudinal direction. The lead wires are arranged at equal intervals on the surface of the common electrode. In the present embodiment, each lead wire is not inclined and is wired in parallel with the array direction of the detection elements.

As shown in FIG. 14C, assuming that the lead wire has a wiring width W5 and a lateral (short side of the detection element module) direction pitch PX5, the amount of change in the detection sensitivity due to the arrangement of the lead wire is the wiring. It can be suppressed by adjusting the width W5 and the lateral direction PX5.
For example, the relationship between the vertical pitch PX5, the wiring width W5, the pixel pitch (DP), and the change amount of the detection sensitivity with R% is as follows.

W5 / PX5 <R% and W5 <DP (8)
Note that, also in the formula (8), the change amount of the detection sensitivity is approximated by the change amount of the aperture ratio for simplicity.
As described above, in this modification, the lead wires are arranged in a comb shape, so that the cost for forming the wiring pattern can be reduced.

  It should be noted that each of the above-described embodiments and the modifications thereof are examples, and the number of detection elements constituting the detection element module, the lead wire, the width and shape of the plate-shaped wiring, the detection element connection position, the material of the conductor sheet, etc. are appropriately changed. can do. Further, it may be combined with periodic wiring. In addition to copper, the conductor used in the lead wiring portion and the conductor sheet is made of aluminum or iron having a smaller atomic number, which has the effect of further reducing the difference in sensitivity.

The constant setting of the circuit will be described below.
As shown in FIG. 15, the semiconductor layer 21, the common electrode 22, and the pixel electrode 23 form a detection element, and the voltage VHV is applied to the common electrode 22 using the lead wire 24. A capacitor CVH for stabilization is connected in parallel to the voltage VHV.

  At this time, when the current induced in the semiconductor layer 21 by the photons is ID, the inductance of the lead wiring 24 as a typical parasitic component is LHV, and the equivalent series resistance ESR of the stabilizing capacitance is considered to represent an equivalent circuit. , As shown in FIG. In such a circuit, anti-resonance occurs due to a change in the specific frequency of the current ID, and a phenomenon occurs in which the voltage applied to the common electrode 22 changes. The frequency F is expressed by the following equation (9) using the parasitic inductance LHV of the lead wiring 24 and the stabilizing capacitance CHV.

  That is, when the current ID has this frequency component, the voltage applied to the semiconductor layer 21 changes, and the detector response to photons becomes unstable. Therefore, the parasitic inductance LHV of the lead wiring 24 and the stabilizing capacitance CHV are appropriately adjusted so as to be separated from the main frequency of the current ID. As an example of the frequency of the current ID, the one caused by the change in capacitance due to the vibration of the lead wiring due to the rotation of the CT scanner (1 Hz to 5 Hz), and the one caused by the change in the X-ray attenuation depending on the subject. (1 kHz to 10 kHz) and the like are possible.

  For these frequencies, if the parasitic inductance of the lead wire 24 is 100 nH and the stabilizing capacitance CHV is 47 μH, the resonance frequency F becomes 73.4 kHz, which can be kept away from the main frequency component of the current ID. As another means, the equivalent series resistance ESR can be increased to some extent (the Q value can be lowered) to quickly attenuate the resonance generated at the frequency and suppress the influence of voltage fluctuation.

20, 20A, 20B, 20C, 20D ... Detecting element, 21 ... Semiconductor layer, 22 ... Common electrode, 23 ... Pixel electrode, 24, 29 ... Lead wiring, 25 ... Insulator, 2 ... ..Contact, 28 ... Scattered radiation removing member, 30 ... Plate wiring, 31 ... Lead wiring portion, 33 ... Conductor sheet, 34 ... Conductor layer, 41 ... Lead wiring portion , 42 ... Plate wiring, 51 ... Lead wiring portion, 52 ... Lead wire

Claims (16)

A semiconductor layer that generates a charge by receiving a photon of radiation that has passed through a subject, a common electrode that is formed on a surface of the semiconductor layer on the subject side, and applies a bias voltage to the semiconductor layer; A plurality of detection element modules in which detection elements having a pixel electrode formed on a surface opposite to the surface on the subject side are two-dimensionally arranged,
A plurality of lead wires for power supply arranged at a predetermined interval on the surface of the common electrode of each detection element included in the detection element module;
Arranged closer to the subject than the lead wire, and having a scattered radiation removing member for blocking the radiation scattered by the subject,
The scattered radiation removing member includes a plurality of plate-shaped members that are erected at predetermined intervals, and the plate-shaped members are respectively arranged at positions corresponding to the arrangement of the lead wires and erected above the lead wires. A radiation detector characterized by being provided.   The radiation detector according to claim 1, wherein the scattered radiation removing member is a one-dimensional collimator having a plurality of plate-shaped members provided upright corresponding to the arrangement of the lead wires.   The radiation detector according to claim 1, wherein the scattered radiation removing member is a two-dimensional collimator having plate-shaped members arranged in a grid pattern corresponding to the arrangement of the lead wires.   The radiation detector according to claim 2 or 3, wherein a pitch of the plate-shaped member matches a pitch of pixels of the detection element module.   2. The grid according to claim 1, wherein the scattered radiation removing member forms a grid by a plurality of plate members in a channel direction arranged corresponding to the arrangement of the lead wires and a plate member in a slice direction orthogonal to the plate members in the channel direction. Radiation detector. A semiconductor layer that generates a charge by receiving a photon of radiation that has passed through a subject, a common electrode that is formed on a surface of the semiconductor layer on the subject side, and applies a bias voltage to the semiconductor layer; A plurality of detection element modules in which detection elements having a pixel electrode formed on a surface opposite to the surface on the subject side are two-dimensionally arranged,
A scattered radiation removing member that is disposed on the surface of the detection element on the subject side and that blocks radiation scattered by the subject; and a wiring that connects the scattered radiation removing member and the common electrode,
The scattered radiation removing member includes a plurality of plate-shaped members erected at predetermined intervals,
A radiation detector for supplying power to the common electrode via the scattered radiation removing member and the wiring. A radiation detector disposed with a radiation source and a predetermined rotation axis interposed therebetween, which rotates around the rotation axis together with the radiation source,
A semiconductor layer that generates charges upon receiving photons of radiation, a common electrode that is formed on one surface of the semiconductor layer and applies a bias voltage to the semiconductor layer, and a pixel electrode that is formed on the other surface of the semiconductor layer. A plurality of detection element modules in which the detection elements having and are two-dimensionally arranged,
And a lead wire for power supply arranged on a surface of said common electrode of said respective detection elements included in the detection element module,
A radiation detector in which the lead wiring portion is formed by arranging a plurality of strip-shaped plate-shaped wirings at predetermined intervals in a channel direction which is the direction of rotation .   The radiation detector according to claim 7, wherein each plate-shaped wiring of the lead wiring portion is a mesh, and the mesh pattern of the mesh is inclined with respect to the arrangement direction of the detection elements.   The radiation detector according to claim 7, wherein each plate-shaped wiring of the lead wiring portion is a mesh, and the mesh pattern of the mesh is a lattice shape that matches the arrangement direction of the detection elements.   The radiation detector according to claim 7, wherein each conductive material of the lead wiring portion has a mesh shape in which lead wires having a wiring width smaller than a pixel pitch of the detection element are woven.   The radiation detector according to claim 7, wherein a conductor sheet made of a material having substantially the same X-ray attenuation characteristics as that of the conductive material is provided in a gap between the conductive materials in the lead wiring portion.   The radiation detector according to claim 7, wherein a conductor layer covering the entire common electrode is provided on the surface of the lead wiring portion.   The radiation detector according to claim 11 or 12, wherein the lead wiring portion and the common electrode are protected by different insulators. A radiation detector disposed with a radiation source and a predetermined rotation axis interposed therebetween, which rotates around the rotation axis together with the radiation source,
A semiconductor layer that generates charges upon receiving photons of radiation, a common electrode that is formed on one surface of the semiconductor layer and applies a bias voltage to the semiconductor layer, and a pixel electrode that is formed on the other surface of the semiconductor layer. And a plurality of detection element modules in which a plurality of detection elements having and are two-dimensionally arranged,
And a plurality of lead wires for power supply arranged on a surface of said common electrode of said respective detection elements included in the detection element module,
The plurality of lead wires are arranged so as to extend from one end to the other end in the slice direction, which is the rotation axis direction of the detection element module,
On the surface of the common electrode, the wiring width (W) of the lead wire is smaller than the pitch (PX) of the pixel electrodes in the channel direction, which is the direction of rotation, and the ratio W / PX of the two is predetermined. The radiation detector is arranged to be smaller than the value of .   The radiation detector according to claim 14, wherein the plurality of lead wires are arranged so as to be inclined with respect to the arrangement direction of the detection elements.   15. The radiation detector according to claim 14, wherein the plurality of lead wires are arranged in parallel to the arrangement direction of the detection elements.

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