Radiation detection unit and radiographic inspection apparatus

Plural detection boards are stacked and fixed. The detection board has a wiring board, a semiconductor detection device fixed on an upper surface of the wiring board and configured to detect radiation, and a spacer fixed on the upper surface of the wiring board. Each of the detection boards is provided so that the semiconductor detection device and the spacer have a designated positional relationship. In addition, the spacers are stacked and matched in an X-Y plane surface with each other so that the detection boards are fixed by fixing members.

TECHNICAL FIELD

The present invention generally relates to radiation detection units having radiation semiconductor detection devices and radiographic inspection apparatuses using the radiation detection units. More specifically, the present invention relates to a radiation detection unit configured to detect gamma rays emitted from a radioisotope situated in a subject and a radiographic inspection apparatus using the radiation detection unit.

BACKGROUND ART

Recently, tomography apparatuses have been widely used in order to obtain information of the inside of a living organism (subject). There are an X-ray computed tomography (hereinafter “X-ray CT”) apparatus, a magnetic resonance imaging (MRI) apparatus, a single photon emission CT (hereinafter “SPECT”) apparatus, and a positron emission tomography (hereinafter “PET”) apparatus, as the tomography apparatuses. In the X-ray CT apparatus, X-ray beams having narrow widths are emitted to a certain cross section of the subject in multiple directions, X-rays permeating through the subject are detected, and a spatial distribution of the degree of abruption of the X-rays in the cross section is computed by a computer and imaged. Thus, dysplasia inside the subject such as a hemorrhagic area can be recognized by the X-ray CT.

On the other hand, since functional information in the subject can be obtained with high precision by the PET apparatus, development of the PET apparatuses has been progressing recently. In a diagnostic method using the PET apparatus, first, a medicine for inspection which is identified with a positron nuclide is introduced inside the subject by an injection, inhalation, or the like. The medicine for inspection introduced in the subject is stored in a specific portion having a function corresponding to the medicine for inspection. For example, in a case where a medicine for inspection of saccharide is used, the medicine is selectively stored in a portion where metabolism of a cancer cell or the like frequently occurs. At this time, a positron radiates from the positron nuclide of the medicine for inspection. At the time when the positron and an electron in the periphery of the positron are coupled and annihilated, two gamma rays (so-called annihilation gamma rays) are radiated in directions approximately 180 degrees relative to each other. These two gamma rays are simultaneously detected by a radiation detector provided surrounding the subject and an image is regenerated by a computer or the like, so that image data of the distribution of the radioisotopes (RI) of the subject are obtained. Thus, in the PET apparatus, since the functional information about the body of the subject is obtained, it is possible to elucidate the pathology of various intractable diseases.

As shown inFIG. 1, in a PET apparatus100, gamma ray detectors101are provided so as to surround a subject S 360 degrees. The gamma ray detector101includes a semiconductor detector102and a detection circuit103. Semiconductor detection devices (not shown inFIG. 1) are provided in the semiconductor detector102. The detection circuit103is configured to electrically detect the gamma rays entering the semiconductor detection devices. In addition, a generating position of the gamma ray is identified based on an output signal indicating that the gamma ray has entered from the detection circuit103and position information of the semiconductor detection device indicating where the gamma ray has entered. Furthermore, by detecting multiple gamma rays, an image of the distribution of the medicine for inspection in the subject S is regenerated.

Since the annihilation gamma rays are radiated from the subject in random directions, multiple semiconductor detection devices are arranged in the semiconductor detector102so that detection efficiency is improved. For example, as shown inFIG. 2, a radiation detection unit102where boards106having semiconductor detection devices105are provided in a housing104has been suggested (see, for example, Patent Document 1).

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the meantime, in the PET apparatus, the position where the annihilation gamma ray is generated is identified based on the position information of the corresponding semiconductor detection device. Therefore, if the positional precision of the arrangement of the semiconductor detection devices is degraded, precision of the position information about where the gamma ray is generated is degraded so that spatial resolution may be degraded. In the above-mentioned patent document 1, as shown inFIG. 2, both end parts of the boards106of the semiconductor detector102are received in and fixed to grooves109aof guide rails109fixed on side walls of the housing104. Since the guide rails109are made of metal or resin, it is difficult to form the grooves109awith high precision, such limiting errors to less than several hundreds μm. In addition, arrangement errors of the guide rails109are generated. Furthermore, since the boards106are fixed by engaging side end parts of the boards106with the grooves109a, it is required that the external configuration of the board have good dimensional precision. As a result of this, the cost of the boards106is increased. In addition, positioning precision of the semiconductor detection devices105onto the board106is required.

Thus, there are dimensional errors and positioning errors of the boards106or the guide rails109, so it is difficult to arrange the semiconductor detection devices105with high precision.

Means for Solving Problems

Accordingly, embodiments of the present invention may provide a novel and useful radiation detection unit and radiographic inspection apparatus solving one or more of the problems discussed above.

More specifically, the embodiments of the present invention may provide a radiation detection unit where plural semiconductor detection devices are provided with high precision and a radiographic inspection apparatus using the radiation detection unit.

One aspect of the present invention may be to provide a radiation detection unit, including: a plurality of detection boards, the detection board having a wiring board; a semiconductor detection device fixed on an upper surface of the wiring board and configured to detect radiation; and a spacer fixed on the upper surface of the wiring board; and a fixing member configured to fix a built-up body where the plural detection boards are stacked, wherein the plural detection boards are arranged so that the semiconductor detection device and the corresponding spacer have a designated positional relationship; and the spacers have another designated relationship.

According to the embodiments of the present invention, plural detection boards are arranged so that the semiconductor detection device and the corresponding spacer have a designated positional relationship; and the spacers have another designated relationship. Hence, a positional relationship between semiconductor crystal devices arranged on different detecting boards is determined by only the positional relationship between the semiconductor crystal device and the spacer and dimensional precision of the spacer per se. Accordingly, the number of members for which high positioning precision is require in order to arrange semiconductor crystal devices is small, and there is a reduction in the number of the members requiring high dimensional precision. Therefore, it is possible to easily obtain high precision so that plural semiconductor detection devices with high precision can be realized.

The embodiments of the present invention may also provide a radiographic inspection apparatus, including: a radiation detection unit configured to detect radiation generated from a subject including a radioisotope, a detection circuit unit connected to the radiation detection unit; and an information processing part configured to process information about distribution in the subject of the radioisotope based on detected information including an entry time and an entry position of radiation obtained by the detection circuit unit.

According to the embodiments of the present invention, since plural semiconductor detection devices of the radiation detection unit are arranged with high precision, spatial resolution is improved so that inspection with high precision can be achieved.

EFFECT OF THE INVENTION

According to the embodiment of the present invention, it is possible to provide a radiation detection unit where plural semiconductor detection devices are provided with high precision and a radiographic inspection apparatus using the radiation detection unit. Other objects, features, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

EXPLANATION OF REFERENCE SIGNS

BEST MODE FOR CARRYING OUT THE INVENTION

A description is given below, with reference toFIG. 3throughFIG. 19, of embodiments of the present invention.

FIG. 3is a block diagram showing a structure of a PET apparatus of the embodiment of the present invention. As shown inFIG. 3, a PET apparatus10includes detectors11, an information processing part12, a display part13, a control part14, an input/output part15, and others. The detectors11are provided surrounding a subject S and configured to detect gamma rays. The information processing part12is configured to process detected data from the detectors11and regenerate image data of a position of positron nuclide RI in a body of the subject. The display part13is configured to display the image data and others. The control part14is configured to control movement of the detectors11and the subject S and others. The input/output part15is, for example, a terminal configured to transmit instructions to the image processing part12or the control part14, or a printer configured to output the image data.

The detectors111through118are arranged 360 degrees around the subject S. Here, an axial direction of the subject S is defined as a Z-axial direction (Z and −Z directions). The detector11may be provided so as to move in the Z-axial direction relatively to the subject S. While eight detectors111through118are shown inFIG. 2, the present invention is not limited to this. The number of the detectors11can be properly selected.

The detectors11include semiconductor detecting units20and detection circuit units16. A medicine for inspection identified in advance by a positron nuclide RI is introduced in the subject S. The semiconductor detecting units20are provided so that surfaces where the gamma rays enter facing toward the subject S.

When positron generated from the positron nuclide RI is annihilated, two gamma rays γaand γbare simultaneously generated. Since two gamma rays γaand γbare radiated so as to form substantially 180 degrees relative to each other, the gamma rays γaand γbenter semiconductor detecting elements (indicated by a numerical reference25inFIG. 4) of the semiconductor detecting units20of the detectors11facing each other via the subject S. Each of the semiconductor detecting units20where one of the gamma rays γaand γbenter transmits an electric signal (detection signal) generated by entry of the one of the gamma rays γaand γbto the corresponding detection circuit unit16.

The detection circuit unit16includes a detection circuit (not shown). The detection circuit unit16is configured to determine a time (entry time) when the one of the gamma rays γaand γbenters the detecting element based on the detection signal supplied from the semiconductor detecting unit20. In addition, the detection circuit unit16transmits detected data such as entry time and entry position information (identifying number of the element detecting the gamma ray and others) to the information processing part12. The detection circuit of the detection circuit unit16is formed by a mixed circuit of an analog circuit and a digital circuit.

The information processing part12is configured, based on the detected data, to regenerate image data by detection of coincidence and use of an image regenerating algorithm. In the detection of the coincidence, if there are two or more detected data elements whose entry times are substantially the same, the detected data are determined as valid data so as to be regarded as coincident data. If the gamma rays entry times are not the same, the detected data elements are determined as invalid data so as to be destroyed. In addition, the image data are regenerated from the coincident information, a detection element number or the like included in the coincidence information, the position information of the detection element corresponding to this, and others, based on an image regenerating algorithm such as an expectation maximization method. The display part13is configured to display the image data regenerated based on a request of the input/output part15.

With the above-mentioned structure and operation, the PET apparatus10detects gamma rays from the positron nuclide RI selectively positioned in the body of the subject8so as to regenerate the image data of the positron nuclide RI distribution.

FIG. 4is a perspective view of the semiconductor detection unit20of the embodiment of the present invention. In other words,FIG. 4is a view seen in an entry direction of the gamma rays, that is, from a front surface of the semiconductor detection unit.

As shown inFIG. 4, the semiconductor detection unit20is a built-up body where plural detection boards22are stacked on the supporting base21. The built-up body is fixed in upper and lower directions by the fixing member23formed by four bolts23aand four nuts23b. A case where sixteen detection boards22are provided is shown in the example ofFIG. 4. The detection board22is formed by the wiring board24, the semiconductor detection device25, the connector26, the spacer28, and others. The spacers28of adjacent upper and lower detection boards22come in contact with each other so that the upper and lower detection boards22are stacked. The gamma rays radiated from the subject S enter the semiconductor detection device25so as to be converted to an electric signal. The electric signal is output from the connector26to the detection circuit board of the detection circuit unit indicated by a numerical reference16inFIG. 3via the flexible printed wiring board (FPC)29and others.

FIG. 5is a perspective view of the detection board22. For the convenience of explanation, illustration of the spacer28is omitted inFIG. 5.

As shown inFIG. 5, in the detection board22, the semiconductor detection device25and the connector26are fixed on the wiring board24. The wiring board24may be made of glass epoxy, polyimide, or the like. The semiconductor detection device25and the connector26are electrically connected to each other by the wiring patterns24aprovided on the wiring board24. There is no limitation of the type of the connector26. For example, a connector for a flat cable, where a flexible printed wiring board (FPC) or the like can be connected, can be used as the connector26.

FIG. 6is a schematic cross-sectional view of the semiconductor detection device25. As shown inFIG. 6, the semiconductor detection device25is formed by a substantially plate shaped semiconductor crystalline substrate30, a first electrode part31, second electrode parts32, and others. The first electrode part31is formed on an upper surface of the semiconductor crystalline substrate30. The electrode parts32are formed on the lower surface of the semiconductor crystalline substrate30.

The semiconductor crystalline substrate30is made of, for example, cadmium telluride (CdTe) which is sensitive to gamma rays having energies of 511 keV, Cd1-xZnxTe (CZT), thallium bromide (TlBr), silicon, or the like. A dopant for controlling conductivity or the like may be included in these materials. Silicon is preferable as a material of the semiconductor crystalline substrate30because silicon has a higher mechanical strength than CdTe and crystal defect may not be formed in silicon during a processing. Semiconductor crystal is formed by a Bridgman method which is a crystal growth method of the semiconductor or a moving heating method and the semiconductor crystal is cut in a designated crystal orientation and in a plane plate manner so that the semiconductor crystalline substrate30is obtained.

The first electrode part31is made of a conductive film which substantially covers the upper surface of the semiconductor crystalline substrate30. A negative bias voltage Vb is applied to the first electrode part31so that the first electrode part31becomes a cathode. In a case where the semiconductor crystalline substrate30is made of CdTe, the first electrode part31is made of, for example, platinum (Pt). The bias voltage Vb is, for example, −60 V through −100 V DC.

The second electrode parts32are provided on the lower surface of the semiconductor crystalline substrate30so as to extend in a Y-axial direction. The second electrode parts32are made of plural conductive films separated from neighboring electrodes with a designated width in an x-axial direction. If the semiconductor crystalline substrate30is made of CdTe, the second electrode parts32, for example made of gold (Au) and indium (In), are supplied and diffused to the second electrode part32side of the semiconductor crystalline substrate30. Because of this, a Schottky barrier junction is formed between the second electrode parts32and the CdTe. A conductive film of each second electrode part32is fixed to the corresponding electrode24bprovided on the wiring board24via a conductive adhesion layer33such as a conductive paste or an anisotropic conductive adhesive. The electrode24bis connected to a wiring pattern indicated by a numerical reference24ashown inFIG. 5and connected to an electrical ground via a resistance. Hence, the second electrode part32is an anode. The electrode24bis connected to a preamp of the detection circuit of the detection circuit unit16via a condenser. In an example shown inFIG. 6, a single circuit connected to the second electrode part32is indicated and illustrations of circuits connected to other second electrode parts32are omitted.

Next, operations of the semiconductor device25are discussed. When the gamma rays enter the semiconductor crystalline substrate30, an electron-hole pair is formed stochastically. Since an electrical field is applied from the second electrode part32toward the first electrode part31in the semiconductor crystalline substrate30, the electron-hole pair is attracted to the second electrode part32so that an output signal is transmitted to the detection circuit of the detection circuit unit16.

FIG. 7is a perspective view of the spacer28. As shown inFIG. 7andFIG. 4, the spacer28includes a base part28A and a couple of arm parts28B. The plane plate shaped base part28A extends in the X-axial direction. The arm parts28B are provided at both side parts in the X-axial direction of the base part28A and extend in the Y-axial direction, namely an entry direction of the gamma rays. In the spacer28, a space opening to the gamma rays entry side is formed by the base part28A and the arm parts28B. The semiconductor detection device25is received in the space when the spacer28is fixed to the wiring board24. This space is greater in size than the semiconductor detection device25and therefore the semiconductor detection device25and the spacer28are prevented from contacting each other. Because of this, it is possible to easily position the semiconductor detection device25, compared to a case where the semiconductor detection device25and the spacer28contact each other.

The spacer28has a plane lower surface28c. In addition, the spacer28has an upper surface28dsituated in the highest position and a step part28esituated in a position lower than the upper surface28d. The upper surface28dof the spacer28is a plane surface. A position in upper and lower directions of the detection board22is defined by the upper surface28dand the lower surface28c.

The step part28eextends in the Y-axial direction of the spacer28. As shown inFIG. 8andFIG. 4, the step part28eis provided so that contact between the spacer28and the wiring board24of the detection board22stacked on the spacer28is prevented.

Opening parts28-1through28-3are provided so as to pierce the spacer28in the thickness direction of the spacer28. Two opening parts28-1are provided at each side in the X-axial direction of the base part28A. Bolts23aconfigured to fix the semiconductor detection unit20are inserted in the opening parts28-1. Internal diameters of the opening parts28-1are greater than the diameters of the bolts23a. Although two opening parts28-1are provided at each side in the X-axial direction of the base part28A, there is no limitation of the number of the opening parts28-1. A single or three or more opening parts28-1may be provided. In addition, the openings28-2and28-3are provided so that adhesives for fixing the spacer28and the wiring board24shown inFIG. 4are introduced in the openings28-2and28-3. There is no limitation of the number of the opening parts28-2and28-3. It is not always necessary to provide the opening parts28-2and28-3.

There is no limitation of a material of the spacer28as long as the material has a coefficient of elasticity so that the spacer28is not deformed due to a clamping force in upper and lower directions at the time when the semiconductor detection unit20is fixed. The material of the spacer28is selected from, for example, metal (alloy), a ceramic material, and others. It is preferable that the spacer28be made of ceramic material. In a case where ceramic material is used as the material of the spacer28, the spacer28is molded by a casting mold and the upper surface28dand the lower surface28care polished with high precision. In the case of the ceramic material, high surface smoothness with high dimensional precision is obtained by the polishing process. Hence, high dimensional precision of the spacer28can be obtained. Although it is relatively difficult to polish the step part28ecompared to the upper surface28dand the lower surface28c, the precision of the surface evenness or dimensional of the step part28emay be lower than that of the upper surface28dor the lower surface28c. Hence, it is easy to manufacture the spacer28.

Furthermore, each of the arm parts28B of the spacer28has a taper configuration where an outside edge28B-1is gradually tapered toward the inside in a Y-axial direction (a side of the subject in the gamma-ray entry direction). As discussed below, the semiconductor detection units20can be provided close-packed by arranging the outside edges28-1of the arm parts28B-1close to each other.

FIG. 8is a plan view of the semiconductor detection unit20shown inFIG. 4. As shown inFIG. 8, the detection boards22are arranged so that the semiconductor detection device25and the spacer28have a designated positional relationship. The designated positional relationship is, for example, distance and parallelization degree between a border in an X-axial direction of an external configuration of the semiconductor detection device25and an arm part head end surface28fof the spacer28and distance and parallelization degree between a border in a Y-axial direction of an external configuration of the semiconductor detection device25and an arm part head end surface28gof the spacer28f. By setting the designated positional relationships, the positional relationship between the semiconductor detection device25and the spacer28on an X-Y surface is determined.

FIG. 9is a schematic cross-sectional view of the semiconductor detection unit20shown inFIG. 4taken along a line A-A.FIG. 10is a schematic cross-sectional view of the semiconductor detection unit20shown inFIG. 4taken along a line B-B.FIG. 11is a schematic cross-sectional view of the semiconductor detection unit20shown inFIG. 4taken along a line C-C.

As shown inFIG. 9throughFIG. 11, the upper and lower detection boards22are stacked so that only the spacers28of the adjacent upper and lower detection boards22come in contact with each other. In other words, a lower surface28cof a spacer28of an upper detection board22comes in contact with an upper surface28dof a spacer28of a lower detection board22. A lower surface of the wiring board24of the upper detection board22does not come in contact with the upper surface of the lower detection board22because of a step part28eprovided at a lower spacer28. As a result of this, the positional relationship in the upper and lower direction of the detection boards22is determined by the distance between the upper surface28dand the lower surface28cof the spacer28, namely only the thickness of the spacer28.

In each of the detection boards22, the upper surface of the wiring board24is fixed to the lower surface28cof the spacer28via the adhesive layer35. In other words, the position in the Z-axial direction of the semiconductor detection element25is determined based on the lower surface28cof the spacer28as a reference point. The position in the Z-axial direction of the detection board22is also determined by the lower surface28cof the spacer28. Hence, the position in the Z-axial direction of the semiconductor detection device25is determined by the spacer28. Only thickness in the spacer28need be formed with high precision. Since the thickness precision of the spacer28can be easily controlled, the position in the Z-axial direction of the semiconductor detection element25can be set with high precision. In addition, the spacers28come in contact with each other by only areas of both side parts in the X-axial direction of the arm part28B and the base part28A. Hence, the positioning precision of the spacers28is improved.

The adhesive35is formed between the lower surface28cof the spacer28and the upper surface of the wiring board24so that the spacer28and the wiring board24are fixed to each other. Although there is no limitation of the material of the adhesive layer35, epoxy resin, for example, can be used as the material of the adhesive layer35. The thickness of the adhesive layer35is, for example, 20 μm and extremely thinner than a gap between upper and lower detection boards22. Hence, the thickness of the adhesive layer35does not influence the positioning precision. InFIG. 9throughFIG. 11, the thickness of the adhesive layers35is illustrated magnified compared to those of other members.

The spacers28may be fixed to each other by introducing the adhesive into the opening parts28-2and28-3shown inFIG. 8. As a result of this, the adhesive layer35can be thinner such as 0 (zero).

FIG. 12is a view showing the arrangement of the semiconductor detection units20shown inFIG. 4of the PET apparatus10. In the PET apparatus10, the semiconductor detection units20are arranged on a surface perpendicular to the body axis of the subject S.FIG. 12is a view seen in the body axial direction (plan view).

As shown inFIG. 12, the semiconductor detection units20are arranged so that the subject S is surrounded by the semiconductor detection devices25. The arm parts28B of the spacers28of the neighboring semiconductor detection units20are close to each other. The arm part28B of one semiconductor detection unit20is substantially parallel to the arm part28B of a neighboring semiconductor detection unit20. The arm parts28B of a spacer28have a taper configuration where an outside edge28B-1is gradually tapered toward the inside in a Y-axial direction (a side of the subject in the gamma-ray entry direction). Hence, it is possible to closely arrange the neighboring semiconductor detection units20. As a result of this, the distance between the neighboring semiconductor detection devices25can be shortened so that the gamma rays going out between the semiconductor detection devices25and not detected can be reduced. Therefore, it is possible to improve detection efficiency of the PET apparatus. Furthermore, by properly selecting a taper angle of the outside edge28-1, it is possible to arrange the semiconductor detection units20in a circumferential direction of the subject S where the body axis of the subject S is a center.

According to the embodiment of the present invention, the positional relationship of the semiconductor detection devices25provided on the different detection boards22of the semiconductor detection unit20is determined by the positional relationship of the semiconductor detection device25and the spacer28of each detection board22and by dimensional precision of the spacer28per se. Therefore, members for which precision is required in order to arrange the semiconductor detection devices25with high precision are only the semiconductor detection device25and the spacers28. In other words, the number of the members for which precision is required is small. In addition, dimensions whose precision is required for these members are the external configuration of the semiconductor detection devices25, parts indicated by numerical references28gand28finFIG. 8for positioning the spacer28, and the thickness of the spacer28. Accordingly, since the dimensions whose precision is required are limited, it is possible to easily obtain good precision. Hence, it is possible to arrange plural semiconductor detection devices25of the semiconductor detection unit20with high precision.

In addition, the lower surface28cand the upper surface28dof the spacer28are plane. Hence, even if the spacer28is formed of ceramic having high mechanical strength, it is possible to control thickness with high precision and provide high surface evenness by a mechanical polishing method. Accordingly, it is possible to easily obtain high dimensional precision of the spacer28and make the spacer28thin. Hence, the distance between the upper and lower semiconductor detection devices25of the semiconductor detection unit20can be shortened so that detection error can be reduced and detection efficiency can be improved. In addition, it is possible to make the size of the semiconductor detection unit20small.

Next, a manufacturing method of the semiconductor detection unit20is discussed with reference toFIG. 13andFIG. 14.

FIG. 13is a first view of manufacturing steps of the semiconductor detection unit20.FIG. 14is a second view of the manufacturing steps of the semiconductor detection unit20. Steps of assembling the semiconductor detection unit20are discussed with reference toFIG. 13,FIG. 14andFIG. 4.

In a step shown inFIG. 13, the semiconductor detection device25and the connector26are provided and fixed on the wiring board24. The semiconductor detection device25may be provided with positional precision so as to be consistent with the electrodes24bshown inFIG. 6.

Next, in a step shown inFIG. 14, the spacer28is positioned relative to the semiconductor detection device25shown inFIG. 13and the lower surface of the spacer28and the upper surface of the wiring board24are fixed to each other by the adhesive. More specifically, positioning of the spacer28is done by reading two sides25aand25bof the semiconductor detection device25with an image analysis apparatus and fixing the spacer28so that the arm part head end surface28fand the step part side surface28gare parallel with the sides25aand25bat designated distances LXand LY, respectively. As a result of this, the positional relationship between the semiconductor detection device25and an X-Y surface of the spacer28is determined.

Next, the detection boards22are stacked as shown inFIG. 4. Furthermore, while the side surfaces of the spacers28are controlled in the X-axial direction and Y-axial direction, the bolts23aare inserted in the opening parts (not shown) of the supporting base and the opening parts28-1of the spacer28. More specifically, for example, the side surface28sin the X-axial direction and the arm part head end surface28fof the spacer28shown inFIG. 14are controlled and the spacer28is pushed so that these surfaces become consistent with each other. As a result of this, the side surfaces of the spacers28are controlled in the X-axial direction and Y-axial direction. Since the spacers28have the same configurations, positions of the spacers28are consistent with each other. Next, the detection boards22are fixed by the nuts23b. Although the detection board22is directly fixed to the supporting base21, the detection boards22may be fixed to each other and then the detection boards22may be fixed to the supporting base21. Thus, the semiconductor detection unit20is formed.

According to the above-mentioned manufacturing method, the semiconductor detection device25of each of the detection boards22and the spacer28are fixed to each other by positioning them in a designated positional relationship, and the detection boards22are fixed to each other by arranging the position of the spacers28. Hence, the semiconductor detection devices25can be provided with high precision.

As an example of the fixing method of the detection board22, the spacers28may be positioned by using the image analysis apparatus when the detection boards22are stacked and then the spacers28may be fixed by the adhesive. As a result of this, since the projection boards are stacked while the projection boards are being positioned, all of the semiconductor detection devices25of the semiconductor detection unit20can be arranged and fixed with high precision. In this case, it is not necessary to provide a fixing member having the bolts23aand the nut23bshown inFIG. 4.

Next, modified examples of the semiconductor detection unit of the embodiment of the present invention are discussed.FIG. 15is a plan view of a first modified example of the semiconductor detection unit40.FIG. 16is a plan view of a second modified example of the semiconductor detection unit45. InFIG. 15andFIG. 16, parts that are the same as the parts shown inFIG. 1throughFIG. 14are given the same reference numerals, and explanation thereof is omitted.

Referring toFIG. 15andFIG. 16, the semiconductor detection units40and45have the same structures as that of the semiconductor detection unit20except spacers41and46are different from the spacer28. Surfaces and positions for positioning of the spacers41and46are different from those of the spacer28.

As shown inFIG. 15, a couple of notch parts41hformed by two surfaces41gand41fperpendicular to each other is formed at head end parts of a pair of the arm parts41B of the spacer41. Positions in the X-axial direction and the Y-axial direction of the spacer41are determined by standard surfaces41gand41fof each of a couple of the notch parts41h, and the spacer41is positioned against the semiconductor detection device25in this example as well as the example shown inFIG. 14. As a result of this, the spacer41can be arranged with high precision against the semiconductor detection element25by forming the notch parts41hwith high precision.

There is no need to provide two notch parts41h. Only a single notch part41hmay be provided. In this case, positions in the X-axial direction and the Y-axial direction of the spacer are determined by the surfaces41gand41f.

In addition, as shown inFIG. 16, three standard marks46k1through46k3are formed on the arm parts46B. Positions in the X-axial direction and the Y-axial direction of the spacer are determined by a line connecting the standard marks46k1and46k2to each other and a line connecting the standard marks46k1and46k3to each other as standard lines. Because of this, only by forming the standard marks46k1through46k3with high precision, it is possible to provide the spacer46against the semiconductor detection device25with high precision.

FIG. 17is a plan view of a third modified example of the semiconductor detection unit. InFIG. 17, parts that are the same as the parts shown inFIG. 1throughFIG. 16are given the same reference numerals, and explanation thereof is omitted.

As shown inFIG. 17, the structure of the semiconductor detection unit50is the same as that of the semiconductor detection unit20shown inFIG. 4throughFIG. 11(hereinafter “FIG. 4and other figures”) except that a lower surface52cof the spacer28is narrower than the upper surface52din the X-axial direction. The upper surface of the wiring board24is fixed to the step part52e. While the semiconductor detection unit50can achieve the same effect as that achieved by the semiconductor detection unit20shown inFIG. 4and other figures, the position in the Z-axial direction of the semiconductor detection device25is related to distance between the lower surface52cof the spacer28and the step part52e. The lower surface52cof the spacer28may be polished so that the distance between the lower surface52cof the spacer28and the step part52ebecomes a designated distance.

FIG. 18is a plan view of a fourth modified example of the semiconductor detection unit.FIG. 19is a view showing an arrangement of the semiconductor detection units shown inFIG. 18of the PET apparatus. InFIG. 18andFIG. 19, parts that are the same as the parts shown inFIG. 1throughFIG. 17are given the same reference numerals, and explanation thereof is omitted.

As shown inFIG. 18andFIG. 19, the semiconductor detection unit60has the same structure as that of the semiconductor detection unit20shown inFIG. 4except a plane surface configuration of the spacer68and a plane surface configuration of the wiring board64. The wiring board64is narrower facing the entry direction of the radiation. More specifically, the wiring board64has a configuration where both sides of the outside edges64B are substantially consistent with virtual lines extending from the corresponding outside edge68B-1of the arm parts68B of the spacer68. Because of this, as shown inFIG. 19, neighboring semiconductor detection units60are provided so that the outside edges64B of the wiring boards64are adjacent to each other. Accordingly, it is possible to closely arrange the neighboring semiconductor detection units60. As a result of this, it is possible to further reduce the distance between the neighboring semiconductor detection devices25. Hence, in the semiconductor detection unit60compared with the semiconductor detection unit20shown inFIG. 12, it is possible to reduce the ratio of the gamma rays going out from the semiconductor detection devices25that are not detected. Hence, it is possible to further improve detection efficiency of the PET apparatus.

For example, although the PET apparatus is discussed as an example of the present invention in the above-discussed embodiments, the present invention is not limited to this. The present invention can be applied to an SPECT (single photon-emission computed tomography) apparatus.

This patent application is based on Japanese Priority Patent Application No. 2005-355134 filed on Dec. 8, 2005, the entire contents of which are hereby incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a radiation detection unit having radiation semiconductor detection devices and a radiographic inspection apparatus using the radiation detection units; more specifically, to a radiation detection unit configured to detect gamma rays emitted from a radioisotope situated in a subject and a radiographic inspection apparatus using the radiation detection unit.