JP2006300662A - Radiation detector and radiation inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation detector and a radiation inspection apparatus capable of improving spatial resolution and detection efficiency. <P>SOLUTION: The detector 11 is constituted by alternately and densely layering first detection substrates 14a having semiconductor detection elements 21-1 and second detection substrates 14b having semiconductor detection elements 21-2 in the direction of an X-axis to detect gamma-rays incident approximately in the direction of Y. First wiring boards 33 are provided with the semiconductor detection elements 21-1 on their tip parts 33a in such a way that incident planes 21 of gamma-rays may be oriented in the direction of -Y, and bent parts 33b are provided for the base side of the first wiring substrate 33 in such a way as not to be in contact with electrodes 23 of the semiconductor detection elements 21-2 on the lower side. The detector may be provided with a constitution in which two semiconductor detection elements are provided for one wiring board at different heights in the direction of the X-axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation detector and a radiation inspection apparatus, and more particularly to a radiation detector and a radiation inspection apparatus that detect gamma rays from a radioisotope in a subject.

  There is a positron tomography (PET) apparatus as an apparatus that can obtain precise information of a subject. In a diagnostic method using a PET apparatus, first, a test drug labeled with a positron (positron) nuclide is introduced into the body of a subject by injection or inhalation. The test drug introduced into the body is accumulated in a specific part having a function corresponding to the test drug. For example, when a saccharide test drug is used, it is selectively accumulated at sites with high metabolism such as cancer cells. At this time, positrons are emitted from the positron nuclide of the test agent, and when the emitted positrons and surrounding electrons are combined and annihilated, two gamma rays are emitted in the direction of about 180 degrees. Therefore, the two gamma rays are simultaneously detected by a gamma ray detector arranged around the subject, and processed by a computer or the like to obtain distribution image data of the radioisotope in the subject. The CT scan (computer tomography) apparatus used as a precision diagnostic apparatus can obtain structural information such as lesions in the body, whereas the PET apparatus can obtain functional information in the body of the subject, and thus various pathologies of intractable diseases. Elucidation is possible.

  In the PET apparatus, it is determined that the data is effective when a pair of gamma ray detectors sandwiching the subject simultaneously detect two gamma rays emitted from the positron nuclide in directions of about 180 degrees. If only one gamma ray incident at the same time is detected, it is discarded as invalid data.

  Conventionally, scintillators and photomultipliers have been used as gamma ray detectors (see, for example, Patent Document 1). A cell in which a scintillator and a photomultiplier are combined has an incident surface orthogonal to the incident direction of gamma rays of about 4 mm square. The spatial resolution of the gamma ray detector of the PET apparatus is improved as the incident surface is smaller. Spatial resolution refers to the minimum distance at which two positron nuclides that detect gamma rays can be detected separately when the two positron nuclides that generate gamma rays are close to each other in the subject. As the spatial resolution is improved, the position where the positron nuclide is present can be identified more precisely and precisely, and as a result, the function information of the subject can be obtained more accurately.

  However, since it is difficult to make the photomultiplier smaller than this, there is a limit to downsizing the cell. Therefore, in the case of such a gamma ray detector, there is a limit to improving the spatial resolution.

  Therefore, a semiconductor detection element that can be made smaller than a combination of a scintillator and a photomultiplier has been used (see, for example, Patent Document 2). The semiconductor detection element includes a pair of bias application electrodes and a signal extraction electrode on two opposing surfaces of a semiconductor crystal body such as CdTe. Electron hole pairs are generated by gamma rays incident on the semiconductor crystal body, and are induced by a bias electric field to extract a signal as a charge or voltage from the signal extraction electrode.

The semiconductor detection element can be reduced in size by cutting a semiconductor crystal body into a needle-like thin rectangular parallelepiped, providing an electrode on its side surface, and setting its end face as a gamma ray incident surface. It is expected that the spatial resolution of the gamma ray detector will be greatly improved by using such a semiconductor detection element.
JP-A-8-5746 JP 11-344568 A

  However, when a semiconductor detection element is mounted on a circuit board and a large number of circuit boards are stacked in the thickness direction, the gap between adjacent semiconductor detection elements in the thickness direction is a region where gamma rays cannot be detected, so-called dead. It becomes a space. When this gap is large, the proportion of gamma rays that cannot be detected among the incident gamma rays increases. That is, the detection efficiency (ratio of detectable gamma rays to incident gamma rays) decreases. In particular, when the semiconductor detection elements are downsized, the ratio of the total area of the gaps between adjacent semiconductor detection elements tends to increase with respect to the area of the gamma ray incident surface as the number of semiconductor detection elements increases. Then, there arises a problem that the detection efficiency is greatly lowered. Moreover, the problem that the spatial resolution of a gamma ray detector falls arises.

  In order to reduce this distance, a method of reducing the thickness of the circuit board or reducing the distance between the upper and lower circuit boards is conceivable. However, these methods have limitations in order to avoid the strength of the circuit board and electrical contact with the upper and lower circuit boards.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a radiation detector and a radiation inspection apparatus capable of improving spatial resolution and detection efficiency.

  According to one aspect of the present invention, there is provided a radiation detector that detects gamma rays incident from substantially a first direction, and is a plurality of detectors that are spaced apart from each other in a second direction orthogonal to the first direction. A first semiconductor detection element; and a second semiconductor detection element disposed at a position where gamma rays passing between the two first semiconductor detection elements adjacent in the second direction can enter. A featured radiation detector is provided.

  According to the present invention, the plurality of first semiconductor detection elements are spaced apart from each other in a second direction orthogonal to the first direction in which gamma rays are incident. The second semiconductor detection element is disposed at a position where gamma rays that have passed between two adjacent first semiconductor detection elements are incident. Therefore, the first and second semiconductor detection elements are densely arranged along the second direction. As a result, the ratio of the total area of the gamma ray incident surfaces of the first and second semiconductor detection elements to the total area of the virtual surface on which the gamma rays are incident (the incident surface effective ratio) increases. Therefore, the ratio of gamma rays that can be detected to the gamma rays incident on the radiation detector, that is, the detection efficiency of the radiation detector increases. Further, since the first and second semiconductor detection elements are densely arranged in the second direction, the spatial resolution of the radiation detector is improved.

  The first semiconductor detection element is provided on a first wiring board that supports and is electrically connected to the first semiconductor detection element, and the second semiconductor detection element is the second semiconductor A first wiring board, a first semiconductor detection element, a second wiring board, and a second semiconductor detection element provided on a second wiring board that supports and electrically connects the detection element; Are alternately arranged in the second direction, and the first semiconductor detection elements are arranged on the side where the gamma rays are incident on the first direction with respect to the second semiconductor detection elements. The semiconductor detection element may be configured to be disposed at a position corresponding to a gap between two adjacent first semiconductor detection elements in the second direction. By doing in this way, the gamma ray which passed between the two 1st semiconductor detection elements adjacent in the 2nd direction injects into a 2nd semiconductor detection element, Therefore The detection efficiency of a radiation detector increases.

  In addition, the first wiring board may be provided in a shape that avoids contact with a second semiconductor detection element adjacent in the second direction. Thus, an electrical short circuit between the electrode provided on the upper surface of the second semiconductor element and the wiring board can be prevented, and the first and second semiconductor detection elements are densely arranged in the second direction. Can be placed.

  The first semiconductor detection element and the second semiconductor detection element are provided on a third wiring board that supports and electrically connects the first semiconductor detection element and the second semiconductor detection element, The first semiconductor detection element is disposed on the side where the gamma rays are incident in the first direction with respect to the second semiconductor detection element, and the second semiconductor detection element is arranged at a height of the first semiconductor detection element. You may make it the structure provided on the convex part which has substantially the same height. By doing so, the incident surfaces of the first semiconductor detection element and the second semiconductor detection element are exposed as viewed from the first direction in which gamma rays are incident. This is because the effective rate of the incident surface is increased as compared with the case where one semiconductor detection element is provided on the wiring board and a plurality of detection boards are simply arranged in the second direction. Therefore, the radiation detector increases the detection efficiency and improves the spatial resolution.

  The first semiconductor detection element and the second semiconductor detection element include a plate-shaped semiconductor crystal having one end surface as an incident surface on which gamma rays are incident, a first main surface orthogonal to the thickness direction, and a first main surface. A first electrode portion and a second electrode portion provided on each of the two main surfaces, wherein the first electrode portion is formed so as to substantially cover the first main surface. The second electrode section may be composed of a plurality of electrodes arranged on the second main surface at substantially equal intervals along the incident surface, and a detection signal may be extracted from the electrodes.

  By adopting such a configuration, it is more dense to form a plurality of electrodes on the surface of the plate-like semiconductor crystal than to provide electrodes on individual semiconductor crystals that have been miniaturized and arrange them. Can be formed. Since the interval between the electrodes corresponds to the interval between one semiconductor detection element, one unit of the semiconductor detection element can be reduced in size. As a result, the spatial resolution of the radiation detector can be further improved. In addition, the radiation detector of the present invention can suppress damage to the semiconductor crystal body as compared with the case where electrodes are arranged on individual semiconductor crystal bodies and arranged them, and the S / N ratio and high frequency characteristics of the semiconductor detection element are deteriorated. Can be prevented.

  The semiconductor detection element is bonded to the second electrode portion side on the wiring substrate, the first wiring substrate, or the second wiring substrate via a bonding portion, and the bonding portion includes a low-temperature solder bump, a conductive paste, Alternatively, the structure may be any one of the group consisting of anisotropic conductive films. By using a low-temperature solder bump, a conductive paste, or an anisotropic conductive film for the joint, it is possible to suppress the adverse effects of stress and heat on the semiconductor detection element, for example, so-called polarization phenomenon. Therefore, it is possible to prevent deterioration of the S / N ratio and high frequency characteristics of the semiconductor detection element.

  According to another aspect of the present invention, the radiation detector according to any one of the above, wherein the radiation detector is disposed around the subject including the radioisotope so as to surround the subject and detects gamma rays generated from the radioisotope. There is provided a radiological examination apparatus comprising: a detection means having a first information processing means; and an information processing means for obtaining distribution information of the radioisotope in a subject based on detection data obtained from the detection means.

  According to the present invention, a radiation inspection apparatus having excellent spatial resolution and detection efficiency can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the radiation detector and radiation inspection apparatus which can improve detection efficiency while improving spatial resolution can be provided.

  Embodiments will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a PET apparatus according to the first embodiment of the present invention. Referring to FIG. 1, a PET apparatus 10 is arranged around a subject S, detects a gamma ray, and processes detection data from the detector 11. An information processing unit 15 that regenerates image data at the position of the positron nuclide RI, a display unit 16 that displays image data, a control unit 17 that controls movement of the subject S and the detector 11, and the information processing The terminal 15 and the control unit 17 are configured with a terminal that sends instructions, an input unit 18 including a printer that outputs image data, and the like.

The detector 11 introduces a test agent labeled in advance with the positron nuclide RI into the subject S, and detects gamma rays γ _a and γ _b emitted from the subject S. The detector 11 includes a plurality of detection substrates 14 provided with a semiconductor detection element 21 and a detection circuit 13. The semiconductor detection element 21 is disposed so as to face the subject S, and detects two gamma rays γ _a and γ _b generated simultaneously when the positron from the positron nuclide RI disappears. Since the two gamma rays γ _a and γ _b are emitted at an angle of about 180 degrees, they are incident on the semiconductor detection element 21 of the detector 11 facing each other with the subject S interposed therebetween. Each of the two semiconductor detection device 21 gamma gamma _a, is gamma _b incident sends gamma gamma _a, electrical signals generated by the incidence of the gamma _b (detection signal) to the detection circuit 13.

The detection circuit 13 determines the time (incident time) when the gamma rays γ _a and γ _b are incident on the detection element from the detection signal, and the incident time and the number of the semiconductor detection element 21 that detected the gamma rays γ _a and γ _b. (Detection data) is sent to the information processing unit 15.

  The information processing unit 15 performs coincidence detection and image data regeneration by an image regeneration algorithm based on the detection data. In the coincidence detection, when there are two or more pieces of detection data whose incident times substantially coincide with each other, it is determined that these pieces of detection data are valid and used as coincidence information. In the coincidence detection, detection data whose gamma ray incident times do not match is determined to be invalid and discarded. Then, based on the coincidence information, the detection element number included in the coincidence information, the position information of the detection element corresponding to the coincidence information, and the like, based on a predetermined image regeneration algorithm (for example, an Expectation Maximization method). Regenerate the image data. The display unit 16 displays the image data regenerated in response to a request from the input / output unit 18.

  With the above configuration and operation, the PET apparatus 10 detects gamma rays from the positron nuclide RI selectively located in the body of the subject S, and regenerates image data of the distribution state of the positron nuclide RI. The PET apparatus 10 according to the present embodiment is mainly characterized by the detector 11. Hereinafter, the detector 11 will be described in detail.

  FIG. 2 is a diagram schematically illustrating the arrangement of the detectors of the PET apparatus according to the first embodiment.

Referring to FIG. 2, the detectors 11 _{1 to} 11 ₈ of the PET apparatus are arranged around the subject S over 360 degrees. Each of the detectors 11 _{1 to} 11 ₈ is provided with a semiconductor detection element 21 on the subject S side. The detectors 11 _{1 to} 11 ₈ are arranged in this way to detect two gamma rays simultaneously emitted from the subject S. Here, the body axis direction of the subject S is defined as the Z-axis direction (Z and −Z directions). The detectors 11 _{1 to} 11 ₈ are arranged along the XY plane. The detector 11 may be movable in the Z-axis direction relative to the subject S. In FIG. 2, six detector boards 14 are stored in _eight detectors 11 _{1 to} 11 ₈ and one detector 11 _{1 to} 11 ₈ , but these numbers are merely an example. The number of detection substrates is appropriately selected.

FIG. 3 is a perspective view of a semiconductor detection element of the first example constituting the detector. Figure 3 shows as an example the semiconductor detection elements provided on the detector 11 ₁ shown in FIG. The X-axis, Y-axis, and Z-axis in FIG. 3 are the same as those shown in FIG.

Referring to FIG. 3, the semiconductor detection element 21 of the first example includes a thin plate-like semiconductor crystal body 22 and electrodes 23, 24 ₁ to 24 ₁ formed on surfaces orthogonal to the thickness direction (X-axis direction). It consists of 24 ₆ . Examples of the material of the semiconductor crystal 22 include cadmium telluride (CdTe), Cd _1-x Zn _x Te (CZT), and thallium bromide (TlBr) that are sensitive to gamma rays having an energy of 511 keV. . CdTe may be doped with Cl (chlorine) in terms of reducing leakage current. For example, the semiconductor crystal body 22 has dimensions of about 0.5 mm in thickness (X-axis direction), about 10 mm in depth (Y-axis direction), and about 10 mm in width (Z-axis direction). The longer the semiconductor crystal 22 is, the more preferable it is because the area of the incident surface of the gamma rays increases. However, it is preferable to set the semiconductor crystal 22 in a range of 5 mm to 30 mm for convenience of manufacturing such as manufacturability.

  The electrode 23 is made of a metal film that substantially covers one surface orthogonal to the thickness direction (X-axis direction) of the semiconductor crystal body 22. When the semiconductor crystal 22 is made of CdTe and the setting is made to apply the positive bias voltage Vb, the electrode 23 is In. As a result, a Schottky junction is formed between the electrode 23 and CdTe. The bias voltage Vb is a DC voltage and is set to 60 V to 1000 V, for example.

The electrodes 24 _{1 to} 24 ₆ are provided on a surface facing the surface on which the electrode 23 is provided. The electrodes 24 _{1 to} 24 ₆ are striped, have a thickness (X-axis direction) of about 1 mm, and a depth (Y-axis direction) that is approximately the same length and width as the length of the semiconductor crystal body 22 in the Y-axis direction ( (Z-axis direction) has a width of about 0.3 mm. The distance L1 between the electrodes 24 _{1 to} 24 _{6 in} the Z-axis direction is set to about 0.5 mm. As the interval L1 is smaller, the detection position accuracy of the gamma ray is improved, and as a result, the spatial resolution of the detector is improved. However, it is preferably set in the range of 0.25 mm to 1.5 mm.

Electrodes 24 _{1 to} 24 ₆ are electrodes for taking out detection signals generated by the incidence of gamma rays. Each electrode 24 _{1 to} 24 ₆ is connected to a detection circuit (detection circuit 13 shown in FIG. 2) provided for each electrode 24. By arranging the electrodes 24 _{1 to} 24 ₆ in the Z-axis direction as described above, the gamma ray incident on the incident surface 21a of the semiconductor crystal body 22 (a surface parallel to the XZ plane of the semiconductor crystal body 22) in the Z-axis direction. Is determined. That is, the gamma rays γ _b incident on the semiconductor crystal 22 form a number of electron-hole pairs (charges) corresponding to the energy by photoelectric conversion. A bias voltage Vb is applied to the semiconductor crystal 22 so that the electrode 23 has a positive voltage with respect to the electrode 24. Due to the electric field generated by the bias voltage Vb, electrons move to the electrode 23, and holes move to _{one of} the electrodes 24 _{1 to} 24 ₆ closest to the incident position and are taken out as detection signals. For example, as shown in FIG. 3, when the gamma ray gamma _b is incident on the vicinity of the electrodes 24 _2, a detection signal is taken out from the electrode 24 _2. The detection signal is sent to the detection circuit, and the electrode 24 ₂ becomes detection data as position information together with the incident time of the gamma ray γ _b . Incidentally, gamma gamma _b is, for example, when incident on the incident surface 21a in the vicinity between the electrode 24 ₂ and the electrode 24 _3, the detection signal appears at both electrodes 24 ₂ and the electrode 24 _3. In this case, the information processing unit 15 shown in FIG. 1, one incident between the electrode 24 ₂ and the electrode 24 _3, or of the electrodes 24 ₂ and the electrode 24 _3, a detection signal output value higher Treated as incident on the electrode.

  Next, a method for forming the semiconductor detection element 21 of the first example will be described with reference to FIG. First, a semiconductor crystal is formed using a Bridgman method, which is a semiconductor crystal growth method, or a moving heating method, and is cut out in a predetermined crystal orientation to obtain a semiconductor crystal body 22.

Next, the electrodes 23 and 24 _{1 to} 24 ₆ are deposited on each surface of the semiconductor crystal body 22 by a vacuum deposition method or a sputtering method using a deposition source or a sputtering target of a Pt or In material. Next, the electrode 24 is patterned in a stripe shape by photolithography and etching. Thus, the semiconductor detection element 21 of the first example is formed.

The semiconductor detection element 21 of the first example is provided with a plurality of electrodes 24 _{1 to} 24 ₆ on the surface of a plate-like semiconductor crystal body 22, and a detection signal caused by an electron-hole pair generated by gamma rays incident from the incident surface 21 a. Is extracted from the electrode close to the incident position. In the semiconductor detection element 21, the detection position accuracy in the Z direction is improved as the electrode interval and the electrode width are reduced.

  On the other hand, a semiconductor detection element in which a pair of electrodes are provided on a rectangular parallelepiped as a needle-shaped rectangular parallelepiped and these are arranged can be considered without depending on the present invention. However, when arranging such a rectangular parallelepiped semiconductor crystal, an adhesive layer between the semiconductor crystals is required, which increases a dead space insensitive to gamma rays.

Therefore, in the semiconductor detection element 21 of the first example, one unit of the semiconductor detection element 21 can be made smaller than when the semiconductor crystal is downsized and a pair of electrodes are provided on each semiconductor crystal. As a result, the spatial resolution of the detector including such a semiconductor element can be improved.

In addition, since the method for forming the electrodes 23, 24 _{1 to} 24 ₆ of the semiconductor detection element 21 of the first example can reduce adverse effects such as damage to the surface of the semiconductor crystal 22, distortion occurs due to an impact such as CdTe. It is particularly preferable for the semiconductor crystal 22 that is easy to be used.

  Instead of the semiconductor detection element 22 of the first example, a semiconductor detection element of the second example described below may be configured.

  FIG. 4 is a perspective view of the semiconductor detection element of the second example. The semiconductor detection element of the second example is a case where a detection signal is taken out from the electrode side to which a positive voltage bias is applied. The X-axis, Y-axis, and Z-axis in FIG. 4 are the same as those shown in FIG.

Referring to FIG. 4, the semiconductor detection element 26 of the second example includes a thin plate-like semiconductor crystal body 22 and electrodes 23 ₁ to 23 ₆ formed on each of the surfaces orthogonal to the thickness direction (X-axis direction). , 24. The semiconductor crystal 27 is made of the same material as the semiconductor crystal 22 shown in FIG.

The semiconductor crystal 27 has a recess 27a formed on the surface on the electrodes 23 ₁ to 23 ₆ side along the Y-axis direction. Electrodes 23 ₁ to 23 ₆ are formed on the surface of the semiconductor crystal body 27 (surfaces of the convex portions) between the adjacent concave portions 27a and the concave portions 27a. The distance L ₂ between the electrodes 23 ₁ to 23 _{6 in} the Z-axis direction is set to about 0.5 mm. Distance L ₂ is improved detection position accuracy of the small enough gamma rays, but improves the spatial resolution of the resulting detector is preferably set in a range of 0.25Mm～1.5Mm.

  The semiconductor crystal 27 has substantially the same size as the semiconductor crystal 22 shown in FIG. The thickness of the portion where the recess 27a is provided (the distance from the bottom surface of the recess 27a to the opposite surface) is preferably set in the range of 0.2 mm to 0.9 mm.

The electrodes 23 ₁ to 23 ₆ are made of In, and a positive bias voltage Vb is connected via a resistor and connected to a detection circuit provided for each electrode.

  The electrode 24 is a metal film made of, for example, Pt provided so as to substantially cover one surface of the semiconductor crystal body 22. The electrode 24 is grounded or electrically connected to a negative voltage power source.

The semiconductor detection element 26 of the second example has the same function as the semiconductor detection element of the first example. Furthermore, the semiconductor detection element 26 of the second example is provided with a recess 27a between the electrodes 23 ₁ to 23 ₆ , so that electrons generated by the incidence of gamma rays are more than the holes of the semiconductor detection element of the first example. Can be concentrated on one electrode. Therefore, in the semiconductor detection element 26 of the second example, the detection signal has a larger charge amount or output voltage than in the case of the semiconductor detection element of the first example. Therefore, the S / N ratio of the detection signal is improved, and for example, the incident time can be determined more accurately.

A method of forming the semiconductor detection element of the second example will be described with reference to FIG. First, a semiconductor crystal 27 is obtained in the same manner as described above. Next, a resist film is formed on one surface of the semiconductor crystal body 27, and openings are provided in stripes in the resist film along the Y-axis direction by photolithography. Next, an In film is formed by vacuum deposition or sputtering using an In material deposition source or sputtering target so as to cover the resist film and its opening. Next, the resist film is removed together with the In film formed thereon. In this manner, striped In electrodes 23 ₁ to 23 ₆ are formed.

Next, the semiconductor crystal 27 between the adjacent electrodes 23 ₁ to 23 _{6 is} selectively etched by the RIE method or the like to form the recess 27a. Note that a solid Pt film is formed on the other surface of the semiconductor crystal body 27 by vacuum evaporation or sputtering to form an electrode 23. Thus, the semiconductor detection element 27 of the second example is formed.

  The semiconductor detection element of the second example can achieve the same effect as the semiconductor element of the first example, that is, the size of one unit of the semiconductor detection element 26 can be reduced. Further, the semiconductor detection element of the second example can improve the S / N ratio of the detection signal as compared with the semiconductor element of the first example.

Note that the electrodes 24 _{1 to} 24 ₆ shown in FIG. 3 and the electrodes 23 ₁ to 23 ₆ shown in FIG. 4 show the case where there are six electrodes, but the number is not limited to six, and two to five may be used. Alternatively, it may be 7 or more, for example, 10 or 20.

FIG. 5 is a cross-sectional view of the main part of the detector, and FIG. 5 and 6 show as an example the detector 11 ₁ in FIG. The X axis, Y axis, and Z axis are set in the same direction as in FIG. That is, gamma rays from the subject are incident in the Y direction.

  5 and 6, the detector 11 includes a first detection substrate 14a provided with the semiconductor detection element 21-1 and a second detection substrate 14b provided with the semiconductor detection element 21-2. It is configured by alternately laminating in the axial direction.

  The first detection board 14a includes a semiconductor detection element 21-1, a first wiring board 33, and the like. The semiconductor detection element 21-1 is the semiconductor detection element of the first example described above. The first wiring board 33 includes, for example, a flexible wiring board, for example, a resin substrate such as polyimide, electrode pads 36 and 37, and a wiring layer (not shown).

  The semiconductor detection element 21-1 is provided on the distal end portion 33 a of the first wiring substrate 33 with the incident surface 21 a facing the −Y direction. A bent portion 33b is provided on the base side of the semiconductor detection element 21-1. The bent portion 33b is provided so as not to contact the electrode 23 of the semiconductor detection element 21-2 of the second detection substrate 14b on the lower side. The shape of the bent portion 33b is not limited as long as it is a shape that avoids the electrode 23 of the semiconductor detection element 21-2. Since the first wiring substrate 33 has flexibility, the bent portion 33b can be easily provided. The first wiring board 33 may not be a flexible wiring board when the bent portion 33b is formed in advance by molding or the like.

  The second detection board 14b includes a semiconductor detection element 21-2, a second wiring board 34, and the like. The semiconductor detection element 21-2 is the semiconductor detection element of the first example described above. Although the 2nd wiring board 34 is not specifically limited, For example, it consists of a single board | substrate ceramic board | substrate, a multilayer ceramic substrate, and a multilayer printed wiring board (for example, a glass cloth epoxy resin laminated board or a glass cloth polyimide resin laminated board). When the semiconductor crystal of the semiconductor detection element is CdTe, the second wiring substrate 34 is preferably a single plate or a multilayer substrate made of AlN when the semiconductor detection element is joined by heating. Thereby, since the thermal expansion coefficients of CdTe and AlN are approximately the same, the stress applied from the second wiring board 34 to CdTe after bonding can be reduced.

  Further, the semiconductor detection element 21-2 is provided on the tip end portion 34a of the second wiring board 34 with the incident surface 21a facing the -Y direction.

Although not shown in the drawings, the bases of the first detection substrate 33 and the second detection substrate 34 are provided with a semiconductor chip on which a detection circuit is mounted. The semiconductor chip is mounted with at least the same number of detection circuits as the number of electrodes 24 _{1 to} 24 ₆ for signal extraction of the semiconductor detection elements 21-1 and 21-2. The semiconductor chip is electrically connected to the semiconductor detection elements 21-1 and 21-2 through a wiring layer (not shown) provided on the first wiring board 33 or the second wiring board 34.

  The semiconductor detection element 21-1 of the first detection substrate 14a is provided on the side (−Y direction) where the gamma rays are incident with respect to the semiconductor detection element 21-2 of the second detection substrate 14b. The distance between the incident surfaces 21a of the semiconductor detection element 21-1 and the semiconductor detection element 21-2 is appropriately selected, but may be set longer than the depth (the length in the Y-axis direction) of the semiconductor detection element 21-1. preferable. Thereby, a bent portion 33b, which will be described in detail later, is provided, a space for arranging the semiconductor detection element 21-2 and the second wiring board 34 is secured, and the semiconductor detection element 21-1 and the semiconductor detection element 21- are arranged in the X-axis direction. 2 can be densely arranged.

  In addition, by separating the semiconductor detection element 21-1 and the semiconductor detection element 21-2, the gamma ray is detected depending on whether the gamma ray is detected by the semiconductor detection element 21-1 or the semiconductor detection element 21-2. There is a time difference in the incident time. This time difference may be corrected by the information processing unit 15 shown in FIG.

  Moreover, as shown in FIG. 6, the detector 11 is arrange | positioned so that each entrance plane 21a of the semiconductor detection elements 21-1 and 21-2 may be exposed to the side into which a gamma ray injects. Furthermore, it is preferable that the distance between the upper surface of the semiconductor detection element 21-1 of the first detection substrate 14 a and the lower surface of the first detection substrate 14 a thereabove is about the thickness of the semiconductor crystal body 22. Thereby, the whole incident surface 21a of the semiconductor detection element 21-2 can be effectively used without blocking the gamma rays incident on the first wiring board 33.

For example, the thickness of the first wiring board 33 is 0.5 mm, the thickness of the semiconductor crystal 22 of the semiconductor detection elements 21-1 and 21-2 is 0.5 mm, and the electrodes 23, 24 _{1 to} 24 ₆ of the semiconductor detection elements. Is 0.1 mm, and the thickness of the joint 35 is 0.1 mm, the effective ratio of the incident surface on which gamma rays are incident {(the total area of the incident surfaces 21a of the semiconductor detection elements 21-1 and 21-2). ) / (Area of the incident surface of gamma rays)} is 0.5 × 2 / (0.5 × 2 + 0.5 + 0.1 × 2 + 0.1) × 100 = 56 (%). It is apparent that the effective rate of the incident surface can be increased as compared with the case where only the first detection substrate 14a or the second detection substrate 14b is used for lamination. Accordingly, in the detector 11, the semiconductor detection elements 21-1 and 21-2 are densely arranged in the X-axis direction, so that the spatial resolution is improved. The calculation was made assuming that the Z-axis direction is 100%.

  As shown in FIG. 5, in order to apply a bias voltage to the electrode 23, the distance between the upper surface of the semiconductor detection element 21-2 of the second detection substrate 34 and the lower surface of the first wiring substrate 33 is about several hundred μm. Is preferably separated. Even in this way, the distance between the bent portions 33b of the first wiring board 33 can be adjusted, so that there is no effect on the arrangement of the semiconductor detection elements 21-1 and 21-2 in the X-axis direction. The effective rate of the surface does not decrease.

FIG. 7 is a plan view showing a state of joining of the semiconductor detection elements. Referring to FIG. 7 together with FIGS. 5 and 6, the semiconductor detection elements 21-1 and 21-2 are bonded to the first wiring board 33 or the second wiring board 34 on the electrodes 24 _{1 to} 24 ₆ side. Electrode pads 36 are provided on the surfaces of the first wiring board 33 and the second wiring board 34. The electrodes 24 _{1 to} 24 ₆ and the electrode pad 36 are bonded via the bonding portion 35. The joint 35 is not particularly limited, but it is preferable to use any one of a low-temperature solder bump, a conductive paste, and an anisotropic conductive film. By using these materials, adverse effects due to stress and heat applied to the semiconductor crystal body 22 during bonding can be suppressed.

  Examples of the low-temperature solder bump include Pb—Sn eutectic solder, Sn—Ag—In—Bi, and Sn—Zn—Bi as low melting point solder used for the bump. The conductive paste is obtained by kneading metal fine powder and resin, and exhibits an adhesive action and conductivity by drying and curing. Examples of the conductive paste include Ag epoxy paste.

The anisotropic conductive film is used by being sandwiched between the electrodes 24 _{1 to} 24 ₆ and the electrode pad 36. An anisotropic conductive film is an anisotropic conductive film in which conductive fillers are dispersed uniformly or oriented in a resin film, and adhesive action and conductivity are exhibited simultaneously by pressing, or pressing and heating. To do. Conductivity develops in the sandwiched direction.

  The material of the bonding portion 35 can further suppress the adverse effects of stress and heat applied to the semiconductor crystal body 22, and can prevent deterioration of the S / N ratio and high-frequency characteristics of the semiconductor detection elements 21-1 and 21-2. An anisotropic conductive film is particularly preferred.

  Further, as shown in FIG. 5, the electrode 23 is electrically connected to an electrode pad 37 provided on the first wiring board 33 or the second wiring board 34 using a conductive wire 38 by wire bonding or conductive paste. Is done.

The electrode 23 may be connected to the first wiring board 33 or the second wiring board 34 with the electrodes 24 _{1 to} 24 ₆ facing upward. In this case, each of the electrodes 24 _{1 to} 24 ₆ and the electrode pad 37 are electrically connected by wire bonding. Also in this case, the junction between the electrode 23 and the first wiring board 33 or the second wiring board 34 uses any one of a low-temperature solder bump, a conductive paste, and an anisotropic conductive film for the same reason as described above. It is preferable.

Although the example using the semiconductor detection element of the first example is given in FIGS. 5 to 7, the semiconductor detection element of the second example may be used instead of the semiconductor detection element of the first example. In this case, it is preferable that the semiconductor detection element joins the first wiring board 33 or the second wiring board 34 to the electrodes 23 ₁ to 23 ₆ shown in FIG.

  According to the present embodiment, the detector 11 alternately stacks the first detection board 14a and the second detection board 14b, and the first detection board 14a has a semiconductor detection of the second detection board 14b below it. A bent portion 33b for avoiding contact with the upper surface of the element 21-2 is provided. And the semiconductor detection element 21-2 is arrange | positioned in the back of the Y direction into which a gamma ray injects rather than the semiconductor detection element 21-1 of the 1st detection board | substrate 14a. By arranging in this way, the incident surfaces 21a of the semiconductor detection elements 21-1 and 21-2 can be densely arranged without blocking gamma rays. Therefore, the effective rate of the incident surface is improved. As a result, the detector 11 has improved spatial resolution and improved gamma ray detection efficiency.

  The detector 11 includes the semiconductor detection element 21 of the first example or the semiconductor detection element of the second example. In these semiconductor detection elements 21 and 26, one unit of the semiconductor detection element 21 can be reduced in size by a plurality of electrodes formed on one surface of the semiconductor crystal body 22. As a result, the spatial resolution of the detector 11 can be improved.

  In addition, the detector 11 uses any one of a low-temperature solder bump, a conductive paste, and an anisotropic conductive film for the joint portion 35 between the semiconductor detection elements 21 and 26 and the wiring boards 33 and 34, thereby providing a semiconductor crystal body. 22 can be further suppressed, and the S / N ratio and high-frequency characteristics of the semiconductor detection elements 21-1 and 21-2 can be prevented from deteriorating.

(Second Embodiment)
Next, a PET apparatus according to the second embodiment of the present invention will be described. The PET apparatus according to the second embodiment has the same configuration as the PET apparatus according to the first embodiment except for the detector.

  The PET apparatus according to the second embodiment has the configuration of the PET apparatus, the detector, and the semiconductor detection element according to the first embodiment shown in FIGS. 1 to 4 and 7. Therefore, the description of these points is omitted.

  FIG. 8 is a cross-sectional view of a principal part of the detector of the PET apparatus according to the second embodiment of the present invention. In the figure, portions corresponding to the portions described above are denoted by the same reference numerals, and description thereof is omitted. The wiring board in FIG. 8 is made of the same material as the second wiring board 34 in FIGS.

  Referring to FIG. 8, the detector 40 is configured by alternately stacking detection substrates 14c provided with two semiconductor detection elements in the X-axis direction. The detection board 14c includes semiconductor detection elements 21-1, 21-2, a wiring board 34, and the like. The semiconductor detection elements 21-1 and 21-2 are the semiconductor detection elements of the first example described above.

  In the detection substrate 14c, the semiconductor detection element 21-1 is provided on the distal end portion 34a of the second wiring substrate. Further, the detection substrate 14c is provided with a convex portion 42 on the base side of the semiconductor detection element 21-1, and the semiconductor detection element 21-2 is provided thereon. The convex part 42 is set to a height substantially equal to the height of the semiconductor detection element 21-1.

  In this manner, by disposing the semiconductor detection element 21-2 in the X-axis direction with respect to the semiconductor detection element 21-1 on the distal end portion 34a side, the detector 11 of the first embodiment shown in FIG. Similarly to the above, the effective rate of the incident surface on which gamma rays are incident can be improved. The convex portion 42 may be made of the same material as that of the second wiring board 34.

  In addition, the method of joining and electrically connecting the semiconductor detection elements 21-1 and 21-2 and the wiring board 34 or the convex portion 42 is the same as in the first embodiment.

  According to the present embodiment, two semiconductor detection elements 21-1 and 21-2 are provided on the wiring board 34, and the semiconductor detection element 21-2 is deeper in the Y direction where gamma rays are incident than the semiconductor detection element 21-1. And provided on the convex portion 42 having a height substantially equal to the height of the semiconductor detection element 21-1. By arranging in this way, the incident surfaces 21a of the semiconductor detection elements 21-1 and 21-2 can be densely arranged without blocking gamma rays. Therefore, the detector 40 has the same effect as that of the first embodiment, the effective rate of the incident surface is improved, and the spatial resolution and detection efficiency of the detector are improved.

In addition, although the example which used the semiconductor detection element of the 1st example was given in FIG. 8, you may use the semiconductor detection element of a 2nd example instead of the semiconductor detection element of a 1st example. In this case, the semiconductor detection element preferably bonds the electrodes 23 ₁ to 23 ₆ shown in FIG. 4 and the wiring board.

  Further, instead of the convex portion 42 shown in FIG. 8, the wiring substrate 34 between the semiconductor detection element 21-1 and the semiconductor detection element 21-2 is provided with a bent portion similar to the bent portion 33b shown in FIG. The substrate 34 may have a shape equivalent to the height of the convex portion 42. By doing in this way, while having the same effect as the detector 40, the convex part 42 can be abbreviate | omitted.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the present invention described in the claims. It can be changed.

  For example, in the first and second embodiments described above, the PET apparatus has been described as an example, but the detection circuit of the present invention can be applied to a SPECT (Single Photon Emission Computed Tomography) apparatus.

It is a block diagram which shows the structure of the PET apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows typically arrangement | positioning of the detector of the PET apparatus which concerns on 1st Embodiment. It is a perspective view of the semiconductor detection element of the 1st example which constitutes a detector. It is a perspective view of the semiconductor detection element of the 2nd example. It is principal part sectional drawing of a detector. It is the figure which looked at the principal part of the detector from the incident side of the gamma ray. It is a top view which shows the mode of joining of a semiconductor detection element. It is principal part sectional drawing of the detector of the PET apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 PET apparatus 11 Detector 13 Detection circuit 14, 14c Detection board 14a 1st detection board 14b 2nd detection board 15 Information processing part 16 Display part 17 Control part 18 Input / output part 21, 21-1, 21-2, 26 Semiconductor Detection element 22, 27 Semiconductor crystal body 27a Recess 23, 23 ₁ to 23 ₆ , 24, 24 _{1 to} 24 ₆ Electrode 33 First wiring substrate 34 Second wiring substrate 35 Joint portion 36, 37 Electrode pad 42 Convex portion Vb Bias voltage

Claims (11)

A radiation detector for detecting gamma rays incident from a substantially first direction,
A plurality of first semiconductor detection elements disposed apart from each other in a second direction orthogonal to the first direction;
A radiation detector, comprising: a second semiconductor detection element disposed at a position where gamma rays passing between two first semiconductor detection elements adjacent in the second direction can enter. The first semiconductor detection element is provided on a first wiring substrate that supports and electrically connects the first semiconductor detection element;
The second semiconductor detection element is provided on a second wiring substrate that supports and electrically connects the second semiconductor detection element,
The first wiring board and the first semiconductor detection element, and the second wiring board and the second semiconductor detection element are alternately arranged in a second direction,
The first semiconductor detection element is arranged on the side where the gamma rays are incident with respect to the second semiconductor detection element in the first direction,
The radiation detector according to claim 1, wherein the second semiconductor detection element is arranged at a position corresponding to a gap between two adjacent first semiconductor detection elements in the second direction. .   The radiation detector according to claim 2, wherein the first wiring board is provided in a shape that avoids contact with a second semiconductor detection element adjacent in the second direction.   The first semiconductor detection element and the second semiconductor detection element are arranged to be separated from each other in the first direction by a distance larger than the length of the first semiconductor detection element along the first direction. The radiation detector according to any one of claims 1 to 3.   The radiation detector according to claim 1, wherein the first wiring board is more flexible than the second wiring board. The first semiconductor detection element and the second semiconductor detection element are provided on a third wiring board that supports and electrically connects the first semiconductor detection element and the second semiconductor detection element,
The first semiconductor detection element is disposed closer to the side on which the gamma rays are incident in the first direction than the second semiconductor detection element;
The radiation detector according to claim 1, wherein the second semiconductor detection element is provided on a convex portion having a height substantially equal to the height of the first semiconductor detection element. The first semiconductor detection element and the second semiconductor detection element include a plate-shaped semiconductor crystal having one end surface as an incident surface on which gamma rays are incident, a first main surface orthogonal to the thickness direction, and a first main surface. A first electrode portion and a second electrode portion provided on each of the two main surfaces,
The first electrode portion is made of a metal film formed so as to substantially cover the first main surface,
The second electrode section is composed of a plurality of electrodes arranged at substantially equal intervals along the incident surface on the second main surface, and a detection signal is taken out from the electrodes. 6. The radiation detector according to claim 1.   The radiation detector according to claim 7, wherein the second main surface is substantially flat.   The radiation detector according to claim 7, wherein a plurality of recesses are formed at substantially equal intervals along the incident surface on the second main surface, and the electrodes are provided between adjacent recesses. The first semiconductor detection element and the second semiconductor detection element are bonded to the first wiring board, the second wiring board, or the third wiring board through a bonding portion on the second electrode portion side. ,
The radiation detector according to any one of claims 2 to 8, wherein the joint portion is made of any one of a group consisting of a low-temperature solder bump, a conductive paste, and an anisotropic conductive film. The radiation detector according to claim 1, wherein the radiation detector is disposed around the subject including the radioisotope so as to surround the subject and detects gamma rays generated from the radioisotope. Detection means;
An information processing unit that acquires distribution information of the radioisotope in a subject based on detection data acquired from the detection unit.

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