Method of manufacturing light guide and method of manufacturing a radiation detector

According to a method of manufacturing a light guide of this invention, a shaping member is provided that covers a molding frame. In a releasing step, when the shaping member is lifted up in a direction apart from the molding frame, the light guide is lifted and pulled out from an aperture of the molding frame accordingly. As a result, there is no need to pull out the light guide by conventionally providing a pressing plug on a bottom of the molding frame and pressing the plug in a direction. In addition, there is no need to perform a grinding process to the light guide.

TECHNICAL FIELD

This invention relates to a method of manufacturing a radiation detector having a scintillator, a light guide, and a light detector that are optically coupled to one another in turn.

BACKGROUND ART

This type of radiation detector is used in emission computed tomography (ECT: Emission Computed Tomography) equipment to detect radiation (such as gamma rays) emitted from radiopharmaceutical that is administered to a subject and is localized to a site of interest for obtaining sectional images of the site of interest in the subject showing radiopharmaceutical distributions. Typical ECT equipment includes, for example, a PET (Positron Emission Tomography) device and an SPECT (Single Photon Emission Computed Tomography) device.

A PET device will be described by way of example. The PET device has a detector ring with block radiation detectors arranged in a ring shape. The detector ring is provided for surrounding a subject, and allows detection of gamma rays that are transmitted through the subject.

Such radiation detector arranged in the detector ring of the PET device is often equipped that allows position discrimination in a depth direction of a scintillator provided in the radiation detector for improved resolution. Particularly, such radiation detector is used, for example, in a PET device set for animals.FIG. 14is a perspective view showing a construction of a conventional radiation detector. Such radiation detector50has scintillation counter crystal layers52A,52B,52C, and52D in which scintillation counter crystals51of rectangular solid are accumulated in two dimensions, and a fluorescence detector53with a function of position discrimination that detects fluorescence irradiated from each of the scintillation counter crystal layers52A,52B,52C, and52D. Here, each of the scintillation counter crystal layers52A,52B,52C, and52D is laminated in a z-direction to form a scintillator52that converts incident radiation into fluorescence. Two or more reflectors54are provided in each of the scintillation counter crystal layers52A,52B,52C, and52D.

A light guide55is provided between the scintillator52and the fluorescence detector53to optically connect the scintillator52and the fluorescence detector53.

The light guide55has a solid resin through which fluorescence is transmitted. The solid resin includes inside thereof two or more reflectors55a. The reflectors55aare inserted in an aperture of a molding frame60, and a liquid thermosetting resin61is poured into the molding frame60, as shown inFIG. 15(a), for manufacturing the light guide55. The thermosetting resin61is cured, and thereafter a pressing plug62provided in the bottom of the molding frame60is pushed in a direction toward the aperture of the molding frame60as indicated by an arrow. As a result, the light guide55is removed from the molding frame60as shown inFIG. 15(b). Subsequently, grinding is performed to both surfaces63and64of the light guide55through which fluorescence is transmitted. When both surfaces63and64of the light guide55is flat, both surfaces63and64are polished, whereby the light guide55is completed (see, for example, Patent Literature 1).[Patent Literature 1]Japanese Patent Publication No. 2004-245592

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

However, the conventional method of manufacturing a radiation detector has the following drawbacks. Specifically, manufacturing of the conventional light guide55necessarily requires a process of grinding both surfaces63and64of the light guide55. Upon removal of the light guide55from the molding frame60, one end face63of the light guide in the aperture of the molding frame60always has a depression shape, and thus is not planar, which prevents the light guide from optically connecting the scintillation counter crystal layer52D and the fluorescence detector53under this state. The thermosetting resin61is a liquid when poured into the molding frame60. Consequently, the thermosetting resin61protrudes upward and a meniscus65appears at an end of the aperture of the molding frame60. The thermosetting resin61is to be cured while the meniscus65therein is kept in its shape. As a result, one end face63of the light guide is to have a depressed shape.

Moreover, upon removal of the light guide55from the molding frame60, other end face64of the light guide in the bottom of the molding frame60has a circular bulge66formed thereon, and thus is not planar, which prevents the light guide from optically connecting the scintillation counter crystal layer52D and the fluorescence detector53under this state. The molding frame60has the pressing plug62on the bottom thereof. Thus, when poured into the aperture of the molding frame60, the thermosetting resin61penetrates so as to fill a gap between the molding frame60and the pressing plug62. When the thermosetting resin61is cured under this state, a shape of a contact portion between the molding frame60and the pressing plug62is to be transferred on the other end face64of the light guide. Specifically, a circular bulge66is to be formed that shows a shape of the contact portion between the molding frame60and the pressing plug62.

As mentioned above, the conventional configuration requires a process of grinding the both faces63,64of the light guide55. That is, the both face63,64are not flat upon removal of the light guide55from the molding frame60. Therefore, a radiation detector cannot be manufactured with no grinding process performed.

A grinding process is performed through rubbing of the light guide55against a rotor disk. The grinding process is, however, complicated. Thus, shortened grinding process may ensure ease of manufacturing a radiation detector, which results in cost reduction of the radiation detector. Moreover, in the grinding process, the possibility increases that a corner of the light guide55is fractured, or excess grinding is performed of the corner of the light guide55. Considering from the light guide having a fractured corner that cannot be utilized as a product any more, the grinding process lowers manufacturing yield of the light guide.

This invention has been made regarding the state of the art noted above, and its object is to provide a method of manufacturing a radiation detector in which a light guide is manufactured with no grinding process performed thereto, whereby the possibility of fracturing a corner of the light guide is reduced to enhance manufacturing yield of the light guide, and a complicated grinding process is shortened to improve manufacture efficiency of the radiation detector for manufacturing a radiation detector of low price.

Means for Solving the Problem

This invention is constituted as stated below to achieve the above object. A method of manufacturing a light guide of this invention is a method of manufacturing a light guide provided in a radiation detector and allowing fluorescence to pass through. The method includes the steps of forming a lattice-like plate frame by fitting two or more first plates that extend along a first direction while being arranged in a second direction perpendicular to the first direction with two or more second plates that extend along the second direction while being arranged in the first direction for integration; inserting the plate frame into an aperture of a molding frame in a vertical direction; pouring a hardening resin pr to hardening to the aperture; placing, a shaping member with a planar bottom face on the aperture of the molding frame, thereby covering a liquid surface of the hardening resin with which the aperture is filled with the bottom face for making the liquid surface flat, and flooding out a part of the hardening resin from the aperture to form a bulge for covering a side edge in the bottom face of the shaping member; hardening the hardening resin with which the aperture is filled to form a light guide with a hardened solid resin embedded in the plate frame, and hardening the bulge to form a burr composed of the solid resin and connecting with the light guide, thereby integrating the light guide with the shaping member, releasing the light guide from the molding frame by lifting the shaping member and the integrated light guide upward in the vertical direction simultaneously; and separating the burr from the light guide to cancel the connection of the light guide and the shaping member.

In the releasing step in the method of manufacturing the light guide of this invention, the shaping member is lifted up in a vertical direction away from the molding frame. Accordingly, the light guide is lifted up from the aperture of the molding frame, and then pulled out therefrom. Therefore, there is no need to pull out the light guide by conventionally providing the pressing plug in the bottom of the molding frame and pressing the plug in a vertical direction. Consequently, a circular bulge that shows a shape of the contact portion of the pressing plug is not to be formed on a surface of the light guide that contacts the bottom of the molding frame.

Moreover, in the step of placing the shaping member, the bottom face of the shaping member covers the liquid surface of the thermosetting resin with which the aperture is filled. Here, the bottom face is planar, and accordingly the liquid surface is to be flat. That is, no meniscus appears on the liquid surface of the thermosetting resin. In other words, upon completion of removing the burr, the surface of the light guide that contacts the shaping member is already flat with no grinding process performed thereto. As a result, the grinding process for grinding the light guide may be eliminated in the construction of this invention.

A material of the first plate mentioned above is preferably selected from one of a material that reflects light, a material that absorbs light, and a material that transmits light.

Moreover, a material of the second plate mentioned above is preferably selected from one of a material that reflects light, a material that absorbs light, and a material that transmits light.

With the foregoing construction, more various light guides may be provided according to purposes. The plate provided in the light guide differs in its suitable material depending on a radiation detector. According to the foregoing construction, each material of the first plate and the second plate may appropriately be selected, whereby a situation increases where the light guide of this invention may be adopted.

Two or more grooves are formed along the vertical direction between each of the first plates and each of the second plates. It is more preferable, in the step of forming the plate frame, to fit the grooves in the first plates with the grooves in the second plates for forming the plate frame.

With the foregoing construction, the plate frame may readily be formed. The plate frame of this invention is manufactured by fitting the grooves of the first plates and the second plates that intersects perpendicularly with each other, which ensures the plate frame having both plates integrated.

Moreover, the foregoing shaping member has a taper portion at the side end thereof having a thickness decreasing from the bottom face in the vertical direction so as to be adjacent to the side edge of the bottom face.

With the foregoing configuration, the taper portion in the shaping member has a thickness decreasing from the bottom face in a vertical direction, whereby it is ensured that the taper portion engages the burr. Accordingly, lifting up of the shaping member in a direction away from the frame in the vertical direction ensures lifting of the light guide from the aperture of the frame and pulling out therefrom.

In addition, the method of manufacturing the radiation detector having the light guide according to this invention further includes the steps of manufacturing a scintillator by arranging scintillation counter crystals that convert radiation into fluorescence in three dimensions; laminating the scintillator and the light guide in a given direction and coupled to each other; and coupling the light guide and a fluorescence detector that detects fluorescence in the given direction.

According to the foregoing construction, a radiation detector may be manufactured with no grinding process performed to the light guide. Upon completion of removing the burr, both surfaces of the light guide that transmits fluorescence are flat. Consequently, the light guide may be incorporated into the radiation detector by merely grinding the both surfaces thereof. In other words, the foregoing construction may shorten a complicated grinding process, which results in improved manufacturing efficiency of the radiation detector and provision of the radiation detector of low price.

Effect of the Invention

According to the method of manufacturing the light guide of this invention, a light guide may readily be manufactured with no grinding process performed thereto. With this invention, the light guide is not required for grinding. Consequently, the corner of the light guide may not be fractured through grinding of the light guide. Therefore, manufacturing yield of the light guide is enhanced, and a complicated grinding process is shortened to improve manufacture efficiency of the light guide and provide a light guide of low price.

DESCRIPTION OF REFERENCES

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of a method of manufacturing a radiation detector according to this invention will be described hereinafter with reference to the drawings.

Firstly, description will be given to a construction of a radiation detector according to Embodiment 1.FIG. 1is a perspective view of the radiation detector according to Embodiment 1. As shown inFIG. 1, the radiation detector1according to Embodiment 1 includes a scintillator2that is formed of scintillation counter crystal layers each laminated in order of a scintillation counter crystal layer2D, a scintillation counter crystal layer2C, a scintillation counter crystal layer2B, and a scintillation counter crystal layer2A, in turn, in a z-direction, a photomultiplier tube (hereinafter referred to as PMT)3having a function of position discrimination that is provided on an undersurface of the scintillator2for detecting fluorescence emitted from the scintillator, and a light guide4interposed between the scintillator2and the PMT3. Consequently, each of the scintillation counter crystal layers is laminated in a direction toward the PMT3. Here, the scintillation counter crystal layer2A corresponds to an incident surface of radiation in the scintillator2. Each of the scintillation counter crystal layers2A,2B,2C, and2D is optically coupled, and includes a transparent material t between each of the layers. The transparent material t passes through fluorescence generated in the scintillation counter crystal layers to guide the fluorescence into the PMT3. The transparent material t also adheres the scintillation counter crystals adjacent to one another in the z-direction. A thermosetting resin composed of a silicone resin may be used for the transparent material t. The scintillation counter crystal layer2A corresponds to a receiver of the gamma rays emitted from a radioactive source. The scintillation counter crystals in a block shape are arranged in a two-dimensional array with thirty-two numbers of the scintillation counter crystals in an x-direction and thirty-two numbers of the scintillation counter crystals in a y-direction relative to a scintillation counter crystal a (1, 1). That is, the scintillation counter crystals from a (1, 1) to a (1, 32) are arranged in the y-direction to form a scintillator crystal array. Thirty-two numbers of the scintillator crystal arrays are arranged in the x-direction to form a scintillation counter crystal layer2A. Here, as for the scintillation counter crystal layers2B,2C, and2D, thirty-two numbers of the scintillator counter crystals are also arranged in the x-direction and the y-direction in a matrix in a two-dimensional array relative to a scintillation counter crystal b (1, 1), c (1, 1), and d (1, 1), respectively. In each of the scintillation counter crystal layers2A,2B,2C, and2D, the transparent material t is also provided between the scintillation counter crystals adjacent to each other. Consequently, each of the scintillation counter crystals is to be enclosed with the transparent material t. The transparent material t has a thickness around 25 μm. Here, the PMT corresponds to the fluorescence detector in this invention. The x-direction and the y-direction correspond to the first direction and the second direction, respectively, in this invention. A gamma ray corresponds to radiation in this invention.

The scintillator2has scintillation counter crystals suitable for detection of gamma rays in a three-dimensional array. That is, the scintillation counter crystal is composed of Ce-doped Lu2(1-N)Y2×SiO5(hereinafter referred to as LYSO.) Each of the scintillation counter crystals is, for example, a rectangular solid having a width of 1.45 mm in the x-direction, a width of 1.45 mm in the y-direction, and a height of 4.5 mm regardless of the scintillation counter crystal layer. The scintillator2has four side end faces that are covered with a reflective film not shown. The PMT3is multi-anode type, and allows position discrimination of incident fluorescence in the x and y.

In the scintillation counter crystal layers2A,2B,2C, and2D of the scintillator2, first elongated reflectors r that extend in the x-direction are provided so as to be inserted between the scintillation counter crystals, and second elongated reflectors s that extend in the y-direction are provided as to be inserted between the scintillation counter crystals. The first reflectors r adjacent to each other are spaced apart by two scintillation counter crystals. The second reflectors r adjacent to each other are spaced apart by two scintillation counter crystals.FIG. 2is a plan view showing a construction of scintillation counter crystal layers in the radiation detector according to Embodiment 1. As shown inFIG. 2, each of the scintillation counter crystal layers2A,2B,2C, and2D differs from one another in inserting pattern of both reflectors. Specifically, the scintillation counter crystal layers2B has an inserting pattern of both reflectors that is shifted by one scintillation counter crystal in the y-direction from that of scintillation counter crystal layers2A. The scintillation counter crystal layers2C has an inserting pattern of both reflectors that is shifted by one scintillation counter crystal in the x-direction from that of scintillation counter crystal layers2A. The scintillation counter crystal layers2D has an inserting pattern of both reflectors that is shifted by one scintillation counter crystal in the xy-directions from that of scintillation counter crystal layers2A.

The light guide4is provided for guiding fluorescence emitted in the scintillation2into the PMT3. Consequently, the light guide4is optically coupled to the scintillator2and the PMT3. The construction of the light guide4will be described.FIG. 3is a plan view showing a construction of the light guide according to Embodiment 1. As shown inFIG. 3, the light guide4has thirty-one elongated first plates4aextending in the x-direction that are arranged in the x-direction so as to penetrate the light guide4in the z-direction. Moreover, the light guide4has thirty-one elongated second plates4bextending in the y-direction that are arranged in the y-direction so as to penetrate the light guide4in the z-direction. The first plates4aand the second plates4bform the plate frame6as shown inFIG. 4, when seen as a whole the light guide4. A resin block4cthat transmits light is inserted into each section that the plate frame6divides (seeFIG. 3.) The resin block4cis also provided on the side end of the light guide4. Consequently, each of the first plates4aand the second plates4bis interposed between the resin blocks4c. Here, the resin block4chas a same arrangement pitch as the scintillation counter crystal layers2A,2B,2C, and2D. As a result, each of resin blocks4cand scintillation counter crystals d that form the scintillation counter crystal layer2D is combined by one to one. The configuration of the plate frame6will be described in detail hereinafter.

The first plate4aand the second plate4bare composed of a reflector that reflects fluorescence emitted in the scintillator2. Consequently, the plate frame6(seeFIG. 4) does not permit fluorescence entering into the light guide4from the scintillator2to spread in the xy-directions. Fluorescence enters into the PMT3. Accordingly, the light guide4allows to pass on fluorescence from the scintillator2to the PMT3while maintaining a position where fluorescence is generated in the xy-directions.

Description will be given to a process of discriminating a fluorescence generating position in the x-direction in the radiation detector1according to Embodiment 1. As shown inFIG. 2, each of the scintillation counter crystal layers2A,2B,2C, and2D that forms the scintillator2differs from one another in inserting positions of the first reflectors r and the second reflectors s.FIG. 2shows a portion of the scintillator2according to Embodiment 1, and (a), (b), (c) and (d) in the drawing illustrate configurations of the scintillation counter crystal layers2A,2B,2C, and2D, respectively. Directing attention to the scintillation counter crystals a (2, 2), b (2, 2), c (2, 2), and d (2, 2) on (2, 2), all of the four have two sides adjacent to each other that are covered with the reflectors. The scintillation counter crystals on (2, 2) differ from one another in direction where the reflectors are provided. Thus, four scintillation counter crystals that are identical to one another in the xy-positions have different optical conditions. The fluorescence generated in the scintillation counter crystal reaches the PMT3while spreading in the xy-directions. Providing the reflectors leads to addition of directivity to the spreading. Moreover, comparing fluorescence generated in the four scintillation counter crystals having the same xy positions, they differ from one another in direction of spreading. That is, differences in position of generating fluorescence in the z-direction in the scintillator2are to be converted into differences of fluorescence in the xy-directions. The PMT3may detect a slight deviation of the fluorescence in the xy-directions due to the differences in the position in the z-direction, and may calculate the position of generating fluorescence in the z-direction from it.

Description will be given to a method of manufacturing such a radiation detector noted above. Particularly, description will be given to a method of manufacturing a light guide in Embodiment 1.

FIG. 5is a perspective view showing a process of manufacturing the plate frame according to Embodiment 1. The first plates4aare arranged in the y-direction for manufacturing a plate frame according to Embodiment 1. As shown inFIG. 5, the first plate4ais a strip member having a long side direction along the x-direction, a short side direction along the z-direction, and a thickness direction along the y-direction. The first plate4ahas two or more grooves5aalong the z-direction. Directing attention to a single first plate4a, the grooves5aare arranged approximately at equal intervals, and have openings provided in a uniform direction with respect to the z-direction. Moreover, as shown inFIG. 5, the second plate4bis a strip member having a long side direction along the y-direction, a short side direction along the z-direction, and a thickness direction along the x-direction. The second plate4bhas two or more grooves5balong the z-direction. Directing attention to a single second plate4b, the grooves5bare arranged approximately at equal intervals, and have openings provided in a uniform direction with respect to the z-direction. In the plate frame manufacturing step, the second plates4bapproach the first plates4aalong the z-direction, thereby fitting the grooves5aand5bof both plates4aand4bto one another. Thus, the second plates4bare arranged in the x-direction. The first plates4aand the second plates4bare integrated with each other to manufacture a plate frame6having both plates4a,4barranged in a lattice shape as shown inFIG. 4.

Next, the plate frame6is inserted into the molding frame7. Prior to explanation on the plate frame insertion step, description will be given to the configuration of the molding frame7.FIG. 6is a perspective view showing a configuration of the molding frame according to Embodiment 1. The molding frame7of Embodiment 1 has an aperture7aupward in the z-direction. The aperture7ais rectangular seen in the z-direction, and has a depth in the z-direction approximately identical to a thickness in the z-direction of the light guide according to Embodiment 1. The bottom of the aperture7ain the z-direction constitutes a close end surface7bin s planar shape. The close end face7bis not always required for providing a pressing plug, etc. The molding frame7may be composed of, for example, fluorocarbon polymers.

FIG. 7is a sectional view showing a step of inserting the plate frame according to Embodiment 1. As shown inFIG. 7, in the plate frame insertion step, the plate frame6is inserted into the aperture7ain the z-direction. Here, the aperture7ahas a length in the x-direction approximately same as that in the long side direction of the first plate4a, and a length in the y-direction approximately same as that in the long side direction of the second plate4b. As a result, four side ends of the plate frame6abut the four side end faces of the aperture7a. As shown inFIG. 7, the plate frame6is inserted into the aperture7aof the molding frame7. A release agent is applied in advance to the aperture7aof the molding frame7for releasing the cured thermosetting resin. InFIG. 7, the number of the plates that form the plate frame6is omitted. Likewise, the number of the plates is to be omitted in the subsequent drawings.FIGS. 7 to 11are sectional views in the zx-plane. Embodiment 1 has a similar yz-plane in its sectional view. The z-direction here corresponds to the vertical direction in this invention.

Subsequently, the liquid thermosetting resin is poured into the aperture7a.FIGS. 8 and 9are sectional views each showing the pouring step according to Embodiment 1. As shown inFIG. 8, the liquid thermosetting resin8is poured into the aperture7aof the molding frame7in the z-direction. The thermosetting resin8prior to curing is liquid. Thus, the aperture7amay readily be filled with the thermosetting resin8. Moreover, degassing process is performed in advance to the thermosetting resin8. When cured, the thermosetting resin8is changed into a transparent solid resin so as to transmit fluorescence. In the pouring step, the plate frame6inserted into the aperture7agoes-down into the thermosetting resin8. Accordingly, an upper end of the plate frame6in the z-direction is covered with the thermosetting resin8. The thermosetting resin8is raised from the aperture7adue to a surface tension when seen as a whole the molding frame7. Here, the thermosetting resin corresponds to the hardening resin in this invention. Specifically, an epoxy resin may be used, for example.

Subsequently, the shaping member9is placed so as to cover the aperture7aof the molding frame7. First, description will be given to the configuration of the shaping member9. As shown inFIG. 9, the shaping member9has a bottom face9ain a planar shape. The bottom face9ahas a length in the x-direction longer than that of the first plate4ain the long side direction. Likewise, the bottom face9ahas a length in the y-direction longer than that of the first plate4ain the long side direction. Accordingly, the bottom face9aof the shaping member9is larger than the aperture7aof the molding frame7. The molding frame7may be formed of a fluorocarbon resin, for example. The taper portion9bis provided adjacent to the side edge9cin the bottom face9aof the side ends in the shaping member9that has a thickness decreasing from the bottom face9ain the vertical direction.

In the shaping member placing step, the bottom face9aof the shaping member9is placed on the molding frame7, thereby covering the liquid surface of the thermosetting resin8with which the aperture7aof the molding frame7is filled. In the covering process, it is preferable to place the shaping member9on the molding frame7over a sufficient period of time such that no bubble is contained between the liquid surface of the thermosetting resin8and the bottom face9a. Moreover, in this step, the liquid surface of the thermosetting resin8is covered with the bottom face9a. Here, the bottom face9ais planar, and accordingly the liquid surface is to be flat. In addition, the bottom face9ais rectangular, and larger than the aperture7aof the molding frame7in size in the xy-directions. Consequently, upon completion of the shaping member placing step, the aperture7ais entirely covered with the shaping member9, when seen the molding frame7in the z-direction. In other words, the aperture7ais entirely covered with the bottom face9a. A release agent is applied in advance to the bottom face9aof the shaping member9for releasing the cured thermosetting resin.

In the shaping member placing step, the shaping member9is pressed against the molding frame7. Accordingly, the bottom face9aof the shaping member9is parallel to the close end face7b.FIG. 10is a sectional view showing the shaping member placing step according to Embodiment 1. Particularly, the configuration is shown upon completion of the pressing mentioned above. As shown inFIG. 10(a), the shaping member9is pressed for supporting the molding frame7. The thermosetting resin8is raised from the aperture7ain the previous step. When pressed with the shaping member9, the thermosetting resin8overflows outward from the aperture7aby a volume over the aperture7a. Consequently, as shown inFIG. 10(a), a bulge10composed of the overflowed thermosetting resin8is formed on the side edge9cof the bottom face9a. The bulge10is formed along the side edge of the shaping member9, and has a square shape when seen as a whole the molding frame7. When pressing of the shaping member9is cancelled, the thermosetting resin8is to flow between the shaping member9and the molding frame7.

FIG. 10(b) is an enlarged sectional view of the side edge. As shown inFIG. 10(b), the bulge10has a raised portion10athat is raised from the aperture7aand a channel portion10bthat connects the raised portion10aand the thermosetting resin8with which the aperture7ais filled. Here inFIG. 10(b), the channel portion10bis shown highlighted as if the shaping member9is apart from the molding frame7. Actually, the channel portion10bis filmy.

Next, the molding frame7is put into an oven maintained at a predetermined temperature with the shaping member9placed thereon for curing the thermosetting resin. The light guide4with the plate frame6embedded into a solid resin11is to be formed inside the aperture7aof the molding frame7. Simultaneously, the bulge10is cured on the side edge9cof the bottom face9ain the shaping member9to form the burr12of the solid resin. The burr12has a raised portion12athat is raised from the aperture7aand a channel portion12bthat connects the raised portion12aand the light guide4extending in the aperture7a. The state is like that inFIG. 10(b). Here, the numeral number10in the drawing is to be interpreted as the numeral number12. The shaping member9here is supported on the shaping member9via a film channel12b.

Subsequently, the shaping member9is lifted up in the z-direction apart from the molding frame7(seeFIG. 11.) A taper portion9bprovided in the shaping member9has a thickness decreasing from the bottom face9ain the z-direction, and thus the taper portion9bis engaged with the raised portion12a. When the shaping member9is lifted up in the z-direction apart from the molding frame7, the raised portion12ais also simultaneously lifted up together with the shaping member9. The raised portion12ais connected to the light guide4via the channel12b. Consequently, as shown inFIG. 11, when the shaping member9is lifted up in the z-direction apart from the molding frame7, the light guide4is pulled out from the aperture7aof the molding frame7accordingly to release the light guide4from the molding frame7.

Thereafter, the burr12connected to the light guide4is separated therefrom. Specifically, the channel12bis separated from the light guide4. Here, the channel12bis filmy, and thus no tool is particularly required for the separation.

Finally, a grinding process is performed to both of a surface of the light guide contacting the shaping member9and that contacting the close end face7bof the molding frame7in the light guide4, thereby completing the light guide according to Embodiment 1.

With the method of manufacturing the light guide according to Embodiment 1, the thermosetting resin8is poured enough during the pouring step to be raised from the aperture7adue to a surface tension, which ensures formation of the bulge10in the latter shaping member placing step. Moreover, in the latter releasing step, when the shaping member9is lifted up in the z-direction apart from the molding frame7, the light guide4is certainly lifted and pulled out from the aperture7aof the molding frame7accordingly. As a result, there is no need to pull out the light guide4by conventionally providing the pressing plug62as shown inFIG. 15on the bottom of the molding frame7and pressing the plug62in the z-direction. Therefore, no circular bulge66is to be formed on the light guide4that shows a shape of the contact portion in the pressing plug62.

The close end face of the aperture7ain the molding frame7is planar. Accordingly, the thermosetting resin8poured into the aperture7ais to be planar. That is, the surface of the light guide4that contacts the close end face7bis already flat without performing a grinding process at the time when the light guide4is pulled out from the molding frame7. Consequently, the grinding step of grinding the light guide4may be eliminated in the construction of Embodiment 1.

Moreover, in the shaping member placing step, the bottom face9acovers the liquid surface9aof the thermosetting resin8with which the aperture7ais filled. Here, the bottom face9aof the shaping member9is planar, and accordingly the liquid surface is to be flat. That is, no meniscus65appears on the liquid surface of the thermosetting resin8. In the resin curing step, the thermosetting resin8is to be cured while maintaining the shape of the liquid surface thereof. Thus, the surface of the light guide4that contacts the shaping member9is already flat without performing a grinding process at the time when separation of the burr is completed. Consequently, the grinding step of grinding the light guide4may be eliminated in the construction of Embodiment 1.

The taper portion9bprovided in the shaping member9has a thickness decreasing from the bottom face9ain the z-direction. Thus, the taper portion c is certainly engaged with the raised portion12a. As a result, when the shaping member9is lifted up in the z-direction apart from the molding frame7, the light guide4is certainly lifted and pulled out from the aperture7aof the molding frame7accordingly.

As mentioned above, with the method of manufacturing the light guide according to Embodiment 1, the light guide may readily be manufactured with no grinding process performed thereto. According to Embodiment 1, the light guide4is not required for grinding. Consequently, the corner of the light guide4may not be fractured through grinding of the light guide4. Therefore, manufacturing yield of the light guide4is enhanced, and a complicated grinding process is shortened to improve manufacture efficiency of the light guide4, which results in manufacturing of the light guide4of low price.

Next, description will be given to a method of manufacturing a radiation detector as Embodiment 2.FIGS. 12 and 13are perspective views each showing a method of manufacturing a radiation detector according to Embodiment 2.

First, in order to manufacture a radiation detector1of the construction described in Embodiment 1, scintillation counter crystals are arranged in two dimensions to form a scintillation counter crystal layer. Specifically, first reflectors r and second reflectors s are assembled to form a reflector lattice frame21. A container22is prepared having a recess22athat allows accommodation of the reflector lattice frame21. As shown inFIG. 12(a), the recess22ais laid with a film23, and then the reflector lattice frame21ais placed thereon. Thereafter, the scintillation counter crystal24is inserted after another in each section divided by the reflector lattice frame21a, whereby a single scintillation counter crystal layer2A is formed. Here inFIG. 12, the number of the reflectors that constitute the reflector lattice frame21is omitted. Likewise, the number of the reflectors is to be omitted in the subsequent drawings.FIGS. 12 and 13are sectional views in a zx-plane. Embodiment 2 has a similar yz-plane in its sectional view.

A further reflector lattice frame21bis placed on the scintillation counter crystal layer2A, and thereafter, the scintillation counter crystal24is inserted in each section divided by the reflector lattice frame21b, whereby a single scintillation counter crystal layer2B is formed. Thus, a scintillation counter crystal layer is successively formed after another, whereby four scintillation counter crystal layers2A,2B,2C, and2D, for example, are formed inside the recess22a. As noted above, the scintillation counter crystals are arranged in three dimensions, as shown inFIG. 12(b).

Next, as shown inFIG. 13(a), the both ends of the film23are folded toward inside of the container22for enclosing the counter crystal layers2A,2B,2C, and2D. Thereafter, the whole film23is pulled out from the recess22a. A release agent is applied inside of the recess22a, and then a degassed thermosetting resin26is poured into the recess22aof the container22. Next, as shown inFIG. 13(a), a group of the scintillation counter crystals enclosed the film23is again inserted into the recess22a, and goes down with the thermosetting resin26. Thereafter, folding of the film23is cancelled, and the end of the film23is pulled as shown inFIG. 13(b) for pulling out the film23from recess22a. Accordingly, the recess22ahas the group of the scintillation counter crystals remained therein that is sunk in the thermosetting resin26. Subsequently, the thermosetting resin26is cured and the group of the scintillation counter crystals is pulled out, whereby a scintillator2may be obtained in which the scintillation counter crystals are arranged in three dimensions. Here, the scintillator2has a hardened solid resin interposed between the adjacent scintillation counter crystals, which corresponds to the foregoing the transparent material t.

<Lamination Step and Fluorescence Detector Coupling Step>

Next, the light guide4according to Embodiment 1 is adhered to the completed scintillator2with an adhesive, thereby realizing lamination thereof in the z-direction and optical coupling of the scintillator2and the light guide4. Here, each of resin blocks4cin the light guide4and each of the scintillation counter crystals d in the scintillator are combined by one to one. Finally, a fluorescence detection surface of the PMT3is adhered to the light guide4with the adhesive, thereby realizing lamination thereof in the z-direction and optical coupling to the light guide4. Through the step, the light guide4allows to pass on fluorescence generated from the scintillator2to the PMT3. As mentioned above, the radiation detector according to Embodiment 2 is completed. Here, the z-direction corresponds to the given direction in this invention.

With the method of manufacturing the radiation detector according to Embodiment 2 as mentioned above, the radiation detector may be manufactured with no grinding process performed to the light guide4. The surface of the light guide4contacting the close end face7band that contacting the shaping member9are flat at the time when separating of the burr is completed. Consequently, the light guide4may be incorporated into the radiation detector by merely grinding the both surfaces of the light guide4. Therefore, with the method of manufacturing the radiation detector according to Embodiment 2, a complicated grinding process in the light guide manufacturing step is shortened, which results in improved manufacture efficiency of the radiation detector and provision of a radiation detector of low price.

This invention is not limited to the foregoing embodiments, but may be modified as follows.

(1) In each of the foregoing embodiments, the scintillation counter crystal is composed of LYSO. Alternatively, the scintillation counter crystal may be composed of other materials, such as GSO (Gd2SiO5), which may be used in this invention. According to this modification, a method of manufacturing a radiation detector may be provided that allows provision of a radiation detector of low price.

(2) In each of the foregoing embodiments, the scintillator2has four scintillation counter crystal layers. This invention is not limited to this embodiment. For instance, the scintillator formed of one scintillation counter crystal layer may be applied to this invention. Moreover, the scintillation counter crystal layer may be freely adjusted in number depending on applications of the radiation detector.

(3) The fluorescence detector in each of the foregoing embodiments is formed of the PMT. This invention is not limited to this embodiment. A photodiode or an avalanche photodiode, etc. may be used instead of the PMT.

(4) In each of the foregoing embodiments, the first plate and the second plate are formed of a reflector that reflects fluorescence. This invention is not limited to this embodiment. A material of the first plate may be selected from one of a material that reflects light, a material that absorbs light, and a material that transmits light. Likewise, a material of the second plate may be selected from one of a material that reflects light, a material that absorbs light, and a material that transmits light. According to this modification, the first plate and the second plate may freely vary in material depending on applications of the radiation detector.

INDUSTRIAL UTILITY

As described above, this invention is suitable for a radiation detector for use in a medical field.