Radiation image information capturing apparatus and method of detecting temperature of amplifier thereof

Amplifiers are mounted on flexible boards connected to a solid-state detector. A first temperature adjustment member is disposed near one of the surfaces of the amplifiers and the flexible boards, and a second temperature adjustment member is disposed near the other surface of the flexible boards. The first temperature adjustment member adjusts the temperature of the amplifiers themselves, and prevents heat from being transferred from the one of the surfaces of the flexible boards to the solid-state detector. The second temperature adjustment member prevents heat from being transferred from the other surface of the flexible boards to the solid-state detector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a radiation image information capturing apparatus for reading the radiation image information of a subject by converting the radiation image information into an electric signal, and a method of detecting the temperature of an amplifier of the radiation image information capturing apparatus.

2. Description of the Related Art

X-ray breast image capturing apparatus (mammographic apparatus) apply an X-ray radiation to a subject, i.e., a breast, to capture and record the radiation image of the subject in a radiation image recorder (solid-state detector), and read the recorded radiation image from the radiation image recorder by applying reading light from a reading light source to the radiation image recorder while moving the reading light source relatively to the radiation image recorder with a scanner to scan the radiation image recorder for thereby causing the radiation image recorder to emit light representing information depending on the recorded radiation image.

The radiation image recorder comprises a radiation solid-state detector made up of a matrix of photoelectric transducers and thin-film transistors (TFTs), and may be of the light reading type, the light conversion type, or the direction conversion type.

The radiation solid-state detector outputs an image signal in the form of an analog electric signal which represents a recorded radiation image. Since the output analog electric signal has a weak signal level, it is amplified by an amplifier.

The weak analog electric signal tends to be easily affected by temperature changes of the radiation solid-state detector and the amplifier. It is desirable to acquire radiation image information which is stable against temperature changes from the weak analog electric signal.

There is known a radiation image capturing apparatus disclosed in Japanese Laid-Open Patent Publication No. 2002-22841 (hereinafter referred to as “conventional art1”) for acquiring an image signal that is stable against temperature changes of an amplifier. As shown inFIG. 13of the accompanying drawings, the known radiation image capturing apparatus has a sensor substrate1having a matrix of pixels including photoelectric transducers and TFTs (converting means). The sensor substrate1is made of glass, and a fluorescent layer2is disposed on the sensor substrate1.

A detecting integrated circuit IC (amplifying means) is mounted on a surface of a flexible board3having an end electrically connected to the sensor substrate1and another end electrically connected to a signal processing circuit substrate4. A cooling fin unit5for radiating the heat generated by the detecting integrated circuit IC is held in contact with a heat transmitter6mounted on the detecting integrated circuit IC. The cooling fin unit5is coupled by sleeves9to an elastic plate7and a fixing plate8which are mounted on the opposite surface of the flexible board3that is remote from the detecting integrated circuit IC.

According to the conventional art1, the cooling fin unit5is positioned only on the side of the surface of the flexible board3on which the detecting integrated circuit IC is mounted. Therefore, the heat generated by the detecting integrated circuit IC tends to flow to the sensor substrate1along the opposite surface of the flexible board3that is remote from the detecting integrated circuit IC.

Japanese Laid-Open Patent Publication No. 2000-116633 (hereinafter referred to as “conventional art2”) discloses another radiation image capturing apparatus having a sensor substrate surrounded by a flexible circuit board. Upper and lower shield members are mounted respectively on upper and lower surfaces of the flexible circuit board with upper and lower heat insulators interposed therebetween. The lower shield member has a lower surface held against an inner frame, and the upper shield member has an upper surface held against an outer frame having a large volume.

According to the conventional art2, the flexible circuit board is vertically sandwiched by the upper and lower shield members. Heat from an amplifying means is not prevented from being transferred through the flexible circuit board to the sensor substrate.

Japanese Laid-Open Patent Publication No. 2000-37374 (hereinafter referred to as “conventional art3”) discloses still another radiation image capturing apparatus. As shown inFIG. 14of the accompanying drawings, the disclosed radiation image capturing apparatus has an image capturing device2avertically movably supported on a mount base1a. The image capturing device2aincludes a two-dimensional radiation detector3aand a signal converter4afor converting a signal from the two-dimensional radiation detector3ainto an image signal. The two-dimensional radiation detector3aand the signal converter4aare arranged successively from an X-ray tube, not shown.

A fan5aas a cooling means is mounted in an upper end of the image capturing device2a. An external air inlet port2bis defined in a lower end of the image capturing device2a. The signal converter4ais electrically connected by a cable6ato an image processor8aand a power supply9ain a controller7a.

The controller7a, which accommodates the image processor8aand the power supply9atherein, is positioned outside of the image capturing device2a. Therefore, the image capturing device2ais small in size, and the two-dimensional radiation detector3ais effectively cooled by the fan5a.

According to the conventional art3, however, since external air is directly introduced from the external air inlet port2binto the image capturing device2aby the fan5a, the temperature of a coolant, i.e., air, in the image capturing device2adepends on the ambient temperature around the image capturing device2a. Consequently, the temperature of the coolant drawn into the image capturing device2atends to vary, and the temperature in the image capturing device2acannot be controlled to a nicety.

In addition, the power supply9a, which includes a power supply unit for the signal converter4a, is disposed outside of and spaced from the image capturing device2a. As a result, the power transmission path along the cable6afrom the power supply9ato the signal converter4ais long enough to pick up external noise.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide a radiation image information capturing apparatus which is of a simple structure and capable of effectively controlling the temperature of an amplifier and reliably preventing heat from being transferred from the amplifier to a converter to efficiently obtain high-quality radiation image information, and a method of detecting the temperature of the amplifier.

A major object of the present invention is to provide a radiation image information capturing apparatus which is of a small size and capable of reliably controlling temperatures highly accurately without being affected by ambient temperatures to efficiently obtain high-quality radiation image information.

According to the present invention, there is provided a radiation image information capturing apparatus for reading the radiation image information of a subject by converting the radiation image information into an electric signal.

The radiation image information capturing apparatus has a converter for converting the radiation image information of the subject into the electric signal, an amplifier connected to the converter by a signal line for amplifying the electric signal produced by the converter, a first temperature adjustment member disposed near one surface of the amplifier and the signal line, and a second temperature adjustment member disposed near another surface of the signal line.

The first temperature adjustment member or the second temperature adjustment member may have a holder for holding the converter. The first temperature adjustment member or the second temperature adjustment member may comprise a Peltier device. Preferably, the radiation image information capturing apparatus further has a temperature detector for detecting the temperature of the amplifier.

The temperature detector may comprise a plurality of thermistors each of which is disposed on each side of the amplifier. The amplifier and the signal line may be controlled in a temperature range from 20° C. to 40° C. by the first temperature adjustment member and the second temperature adjustment member.

According to the present invention, there is also provided a method of detecting the temperature of an amplifier in a radiation image information capturing apparatus in which a converter for converting the radiation image information of a subject into an electric signal is connected by a signal line to the amplifier for amplifying the electric signal generated by the converter. The method comprises the steps of detecting temperatures respectively with first temperature detecting means disposed on one side of the amplifier and second temperature detecting means disposed on the other side of the amplifier, and setting (θJ+θJ+1)/2 as the temperature of the amplifier where θJrepresents the temperature detected by the first temperature detecting means and θJ+1represents the temperature detected by the second temperature detecting means.

According to the present invention, there is also provided a radiation image information capturing apparatus for reading the radiation image information of a subject by converting the radiation image information into an electric signal. The radiation image information capturing apparatus has a casing housing therein a converter for converting the radiation image information of the subject into the electric signal, an amplifier for amplifying the electric signal produced by the converter, a signal processor for processing the amplified electric signal, and a device power supply unit for supplying a power supply voltage at least to the converter, and a control power supply unit disposed outside the casing.

The casing has a space defined therein which is essentially closed from outside of the casing, and a heat exchanger is supported on the casing for adjusting the temperature of air in the space through a heat exchange with a heat medium outside the casing. The heat medium may be external air, an external coolant, an external heat transfer member, or the like.

The radiation image information capturing apparatus preferably further comprise a temperature measuring unit disposed in the casing for detecting the temperature in the space. The temperature in the space may be controlled in a temperature range from 20° C. to 40° C.

The heat exchanger may comprise a Peltier device. The heat exchanger may perform a heat exchange between air in the space and external air outside the casing. Alternatively, the heat exchanger may perform a heat exchange between air in the space and the casing.

The radiation image information capturing apparatus may further comprise a temperature adjuster disposed in the casing for adjusting the temperature of at least the amplifier. The radiation image information capturing apparatus may further comprise a heat insulating member disposed on an inner wall surface or an outer wall surface of the casing in enclosing relation to the space.

According to the present invention, the first temperature adjustment member adjusts the temperature of the amplifier itself and prevents heat from being transferred from the one surface of the signal line. The second temperature adjustment member prevents heat from being transferred from the other surface of the signal line. Accordingly, the temperature of the amplifier itself is effectively adjusted, and heat is prevented from being transferred from the amplifier to the converter through the signal line, with the simple structure. The converter is thus allowed to produce high-quality radiation image information efficiently.

The temperature of the amplifier is detected highly accurately and reliably based on the temperatures detected by the first temperature detecting means and the second temperature detecting means. Consequently, the temperature of the amplifier is controlled efficiently.

Furthermore, since the control power supply unit is disposed outside the casing, the casing is relatively small in overall size. Because the device power supply unit is housed in the casing, the power transmission path between the device power supply unit and the converter is so short that the power transmission path does not pick up unwanted external noise.

The essentially closed space is defined in the casing, and the air in the space is adjusted in temperature by the heat exchanger. Therefore, the temperature of the air in the space is not affected by the temperature of ambient air unlike the conventional system wherein external air is directly drawn into the casing. It is thus possible to control the temperature of the air in the casing easily and reliably with high accuracy for efficiently obtaining high-quality radiation image information.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows in perspective a mammographic apparatus10which is a radiation image information capturing apparatus according to a first embodiment of the present invention.

As shown inFIG. 1, the mammographic apparatus10has an upstanding base16, a vertical arm20fixed to a horizontal swing shaft18disposed substantially centrally on the base16, a radiation source housing unit24fixed to an upper end of the arm20and housing a radiation source for applying a radiation to a subject22, an image capturing base26fixed to a lower end of the arm20, and a compression plate28for compressing and holding an image capturing region, i.e., a breast, of the subject22against the image capturing base26. The image capturing base26houses a solid-state detector, to be described later, for detecting a radiation that has passed through the subject22to acquire radiation image information of the breast.

When the arm20, to which the radiation source housing unit24, the image capturing base26, and the compression plate28are secured, is angularly moved about the swing shaft18in the directions indicated by the arrow A, an image capturing direction with respect to the image capturing region of the subject22is adjusted. The compression plate28is connected to the arm20and disposed between the radiation source housing unit24and the image capturing base26. The compression plate28is vertically displaceable along the arm20in the directions indicated by the arrow B.

To the base16, there is connected a display controller30for displaying image capturing information including an image capturing region, an image capturing direction, etc. of the subject22which have been detected by the mammographic apparatus10and the ID information of the subject22, and setting these items of information when necessary.

FIG. 2shows internal structural details of the image capturing base26. InFIG. 2, the image capturing region of the subject22, i.e., a breast34, is shown as being placed between the image capturing base26and the compression plate28.

As shown inFIG. 2, the image capturing base26houses, in a casing26athereof, a solid-state detector (converter)36for storing radiation image information based on a radiation X emitted from the radiation source housed in the radiation source housing unit24and outputting an electric signal representative of the stored radiation image information, a reading light source38for applying reading light to the solid-state detector36to read radiation image information stored in the solid-state detector36, a scanner40for moving the reading light source38in the direction indicated by the arrow Y (seeFIG. 1) substantially parallel to a reading light scanning surface of the solid-state detector36, and an erasing light source42for applying erasing light to the solid-state detector36to remove unwanted electric charges accumulated in the solid-state detector36.

The solid-state detector36comprises a direct-conversion, light-reading radiation solid-state detector (converter). The solid-state detector36stores radiation image information represented by the radiation X that has passed through the breast34as an electrostatic latent image, and generates a current depending on the electrostatic latent image when the solid-state detector36is scanned by the reading light from the reading light source38.

As shown inFIG. 3, the solid-state detector36comprises a laminated assembly disposed on a glass substrate44and made up of a first electrically conductive layer46for passing the radiation X therethrough, a recording photoconductive layer48for generating electric charges upon exposure to the radiation X, a charge transport layer50which acts substantially as an electric insulator with respect to electric charges having latent image polarity developed in the first electrically conductive layer46and which acts substantially as an electric conductor with respect to electric charges having charge transport polarity which are of a polarity opposite to the electric charges having the latent image polarity, a reading photoconductive layer52for generating electric charges upon exposure to the reading light to be electrically conductive, and a second electrically conductive layer54which is permeable to the radiation X. An electric energy storage region56is provided in the interface between the recording photoconductive layer48and the charge transport layer50.

Each of the first electrically conductive layer46and the second electrically conductive layer54provides an electrode. The electrode provided by the first electrically conductive layer46comprises a two-dimensional flat electrode. The electrode provided by the second electrically conductive layer54comprises a plurality of linear electrodes54aspaced at a predetermined pixel pitch for detecting the radiation image information to be recorded as an image signal. The linear electrodes54aare arranged in an array along a main scanning direction, and extend in an auxiliary scanning direction, which is the same as the direction indicated by the arrow Y, perpendicular to the main scanning direction.

The reading light source38has, for example, a line light source comprising a linear array of LED chips and an optical system for applying a line of reading light emitted from the line light source to the solid-state detector36. The linear array of LED chips extends perpendicularly to the direction in which the linear electrodes54aof the second electrically conductive layer54of the solid-state detector36extend. The line light source moves along the direction in which the linear electrodes54aextend to expose and scan the entire surface of the solid-state detector36.

The erasing light source42should preferably comprise a light source which can emit and quench light in a short period of time and which has very short persistence. For example, the erasing light source42may comprise a plurality of external-electrode rare-gas fluorescent lamps extending perpendicularly to the direction of the array of LET chips of the reading light source38and arranged in an array along the direction of the array of LET chips of the reading light source38(seeFIG. 2).

As shown inFIG. 3, flexible boards (signal lines)60are connected to the respective linear electrodes54aof the second electrically conductive layer54of the solid-state detector36. Amplifiers62are mounted on the respective flexible boards60near the linear electrodes54a. The flexible boards60are electrically connected to various boards through an A/D converter, to be described later.

As shown inFIGS. 3 and 4, a first temperature adjustment member64is disposed near one of the surfaces of the amplifiers62and the flexible boards60, and a second temperature adjustment member66is disposed near the other surface of the flexible boards60. The first temperature adjustment member64and the second temperature adjustment member66are secured together by bolts, not shown, for example.

The first temperature adjustment member64is made of a metal having a high thermal conductivity and has a substantially L-shaped cross section. The first temperature adjustment member64has a recess68defined in a surface thereof facing the amplifiers62. The amplifiers62are partly disposed in the recess68. A temperature adjusting means such as a Peltier device70, for example, is mounted on a lower horizontal ledge of the first temperature adjustment member64. A heat sink72is mounted on the Peltier device70.

The Peltier device70may be dispensed with, and the heat sink72may be mounted directly on the first temperature adjustment member64. Further alternatively, a heat transfer means such as a heat pipe or the like may be connected to the first temperature adjustment member64.

The second temperature adjustment member66is made of a metal having a high thermal conductivity. The second temperature adjustment member66has an upper surface (holder)66afor directly holding an end of the solid-state detector36thereon. An end of an attachment74is placed on the upper surface66aof the second temperature adjustment member66. The other end of the attachment74is placed on an upper surface of the solid-state detector36. The attachment74is fastened to the upper surface66aof the second temperature adjustment member66by bolts76(seeFIG. 4).

As shown inFIGS. 3 and 5, a temperature detector78for detecting temperatures of the amplifiers62is disposed on the second temperature adjustment member66. The temperature detector78comprises a plurality of thermistors (temperature detecting means)80, adjacent two of which are positioned on each side of each of the amplifiers62. If there are n of amplifiers62, then (n+1) of thermistors80are disposed on the second temperature adjustment member66(seeFIG. 5).

FIG. 6shows in block form a control circuit of the mammographic apparatus10.

As shown inFIG. 6, the control circuit comprises the solid-state detector36, a high-voltage supply unit82for supplying a high voltage to the solid-state detector36, the amplifiers62for amplifying analog electric signals output from the respective linear electrodes54aof the solid-state detector36which is supplied with the high voltage from the high-voltage supply unit82, an A/D converter84for converting the amplified analog electric signals into digital electric signals, and a signal processing board86for processing the digital electric signals.

Operation of the mammographic apparatus10will be described below.

Using a console and an ID card (not shown), the operator sets ID information and an image capturing method of the subject22. The ID information represents the name, age, sex, etc. of the subject22. The image capturing method includes information representing an image capturing region, an image capturing direction, etc. specified by the doctor. The ID information and the image capturing method can be entered by the operator from the console. This information can be displayed for confirmation on the display controller30of the mammographic apparatus10.

Thereafter, the operator places the mammographic apparatus10into a certain state according to the specified image capturing method. For example, the breast34may be imaged as a cranio-caudal view (CC) taken from above (seeFIG. 2), a medio-lateral view (ML) taken from the side of the chest, or a medio-lateral oblique view (MLO) taken from an oblique view. Depending on a selected one of these image capturing views, the operator turns the arm20about the swing shaft18.

Then, the operator places the subject22into a specified image capturing state with respect to the mammographic apparatus10. For example, if a left breast34of the subject22is to be imaged as a cranio-caudal view (CC), then the operator places the left breast34on the image capturing base26, and thereafter lowers the compression plate28to hold the breast34between the image capturing base26and the compression plate28, as shown inFIG. 2.

Then, the operator energizes the radiation source housed in the radiation source housing unit24to capture radiation image information. Specifically, the radiation X emitted from the radiation source passes through the breast34held between the compression plate28and the image capturing base26, and is applied to the solid-state detector36housed in the image capturing base26. Before a radiation image is captured, the entire surface of the solid-state detector36is irradiated with the erasing light from the erasing light source42to remove unwanted electric charges from the solid-state detector36.

After the radiation X has passed through the breast34, the radiation X carries radiation image information of the breast34. When the radiation X which carries the radiation image information of the breast34is applied to the solid-state detector36while a high voltage is being applied between the first electrically conductive layer46and the second electrically conductive layer54by the high-voltage supply unit82, pairs of positive and negative electric charges are generated in the recording photoconductive layer48of the solid-state detector36, and the negative electric charges are stored in the electric energy storage region56that is provided in the interface between the recording photoconductive layer48and the charge transport layer50. The amount of the stored negative electric charges, i.e., the amount of electric charges having latent image polarity, is substantially proportional to the dose of the radiation X that has passed through the breast34. The positive electric charges generated in the recording photoconductive layer48are attracted to the first electrically conductive layer46in which they are combined with the negative electric charges supplied from the high-voltage supply unit82and are eliminated.

After the radiation image information is captured, the reading light source38is moved in the direction indicated by the arrow Y by the scanner40while applying the reading light to the solid-state detector36.

In the solid-state detector36, pairs of positive and negative electric charges are generated in the reading photoconductive layer52, and the positive electric charges are attracted to the negative electric charges (latent image polarity electric charges) stored in the electric energy storage region56and move in the charge transport layer50. The positive electric charges are then coupled to the negative electric charges in the electric energy storage region56and are eliminated. The negative electric charges generated in the reading photoconductive layer52are coupled to the positive electric charges supplied from the high-voltage supply unit82to the second electrically conductive layer54and are eliminated.

In this manner, the negative electric charges stored in the solid-state detector36are eliminated by the charge coupling, and a current is generated in the solid-state detector36due to the movement of the electric charges for the charge coupling. Small electric charges generated in the linear electrodes54aof the second electrically conductive layer54are amplified by the amplifiers62mounted on the flexible board60as analog electric signals. The analog electric signals are sent to the A/D converter84and converted thereby into digital electric signals. The digital electric signals are processed by the signal processing board86to produce radiation image information of the breast34.

According to the first embodiment, as shown inFIGS. 3 and 4, the flexible boards60connected to the respective linear electrodes54aof the solid-state detector36extend toward the distal end of the image capturing base26in the direction indicated by the arrow Y and are sandwiched between the first temperature adjustment member64and the second temperature adjustment member66. Therefore, as shown inFIG. 1, the solid-state detector36can be positioned as closely to the subject22as possible.

The first temperature adjustment member64is disposed near one of the surfaces of the amplifiers62and the flexible boards60, and the second temperature adjustment member66is disposed near the other surface of the flexible boards60. The first temperature adjustment member64is effective to adjust the temperature of the amplifiers62, e.g., to cool the amplifiers62, and also to prevent heat from being transferred from the one of the surfaces of the flexible boards60to the solid-state detector36. The second temperature adjustment member66is effective to prevent heat from being transferred from the other surface of the flexible boards60to the solid-state detector36.

Accordingly, the temperature of the amplifiers62is effectively controlled, and heat is prevented from being transferred from the amplifiers62to the solid-state detector36through the flexible boards60, with the simple structure. The solid-state detector36is thus allowed to produce high-quality radiation image information efficiently.

Furthermore, the distal end of the solid-state detector36is directly placed on the upper surface66aof the second temperature adjustment member66and retained on the upper surface66aby the attachment74. The image capturing base26is not unduly large in size in the direction indicated by the arrow Y, but remains effectively small in size as a whole.

The Peltier device70, for example, is mounted as a temperature adjusting means on the first temperature adjustment member64, and the heat sink72is mounted on the Peltier device70. The Peltier device70combined with the heat sink72improves the temperature adjusting capability of the first temperature adjustment member64for reliably adjusting the temperature of the amplifiers62to a desired temperature. A heat transfer means such as a heat pipe or the like may be employed instead of the Peltier device70to improve the temperature adjusting capability of the first temperature adjustment member64.

As shown inFIG. 5, the thermistors80are mounted on the second temperature adjustment member66such that adjacent two of the thermistors80are positioned on each side of each of the amplifiers62. Therefore, the dimension (thickness) of the second temperature adjustment member66in the direction indicated by the arrow Y is smaller than if the thermistors80are directly mounted on the amplifiers62, making the image capturing base26relatively small in overall size.

If the temperatures measured by the respective thermistors80that are positioned on each side of each of the amplifiers62are indicated by θJ, θJ+1, respectively, then the temperature of the amplifier62disposed between the thermistors80is indicated by (θJ+θJ+1)/2. By controlling the Peltier device70based on the calculated temperatures of the thermistors80, the actual temperatures of the amplifiers62can be controlled in a desired temperature range, e.g., in a temperature range from 20° C. to 40° C. in terms of temperatures measured at the positions of the thermistors80.

In the first embodiment, the solid-state detector36is employed as a converter. The solid-state detector36may comprise a device handling small electric charges such as thin-film transistors (TFTs), highly sensitive CCDs (Charge-Coupled Devices), or the like.

FIG. 7shows in perspective a mammographic apparatus100which is a radiation image information capturing apparatus according to a second embodiment of the present invention.FIGS. 8 through 10show details of the radiation image information capturing apparatus according to the second embodiment. Those parts of the mammographic apparatus100which are identical to those of the mammographic apparatus10according to the first embodiment are denoted by identical reference characters, and will not be described in detail below. Similarly, identical parts of mammographic apparatus according to third and fourth embodiments to be described below will not be described in detail below.

As shown inFIG. 8, the casing26aof the image capturing base26has a space102defined therein which is essentially closed from outside the casing26a. The casing26asupports thereon a heat exchanger104for adjusting the temperature of air in the space102through a heat exchange with a heat medium outside the casing26a.

The heat exchanger104is disposed remotely from the subject22, e.g., on a portion of the casing26aclose to the base16. The heat exchanger104comprises a temperature adjusting means, e.g., a Peltier device106, mounted on an inner wall surface of the casing26a. A heat sink108which mainly serves to absorb heat is positioned in the space102and fixedly mounted on the Peltier device106. Another heat sink110which mainly serves to radiate heat is fixedly mounted on an outer wall surface of the casing26ain alignment with the heat sink108.

The image capturing base26incorporates a structure for circulating air in the space102or a structure for producing a forced convective flow of air in the space102for allowing the Peltier device106to uniformly control the temperature in the space102as a whole.

For example, as shown inFIG. 9, a wall plate112is disposed in the space102to provide a circulatory passage114defined between the wall plate112and the inner wall surface of the casing26a. A fan116is disposed in the circulatory passage114. The wall plate112comprises a metal plate having a high thermal conductivity. When the fan116rotates to generate an air flow in the circulatory passage114, the air flow is cooled and/or heated by the heat sink108under temperature control of the Peltier device106. The temperature-controlled air exchanges heat with the air in the space102while flowing through the circulatory passage114, thereby adjusting the temperature in the space102as a whole.

FIG. 10shows in block form a control circuit housed in the image capturing base26of the mammographic apparatus100.

As shown inFIG. 10, the control circuit comprises the solid-state detector36, a device power supply unit118for supplying a high power supply voltage to the solid-state detector36, the amplifiers62for amplifying analog electric signals output from the respective linear electrodes of the solid-state detector36which is supplied with the high voltage from the device power supply unit118, the A/D converter84for converting the amplified analog electric signals into digital electric signals, the signal processing board86for processing the digital electric signals, the heat exchanger104, a first temperature adjuster (the first and second temperature adjustment members64,66)120, a second temperature adjuster122for adjusting the temperature of the A/D converter84, and a temperature measuring unit (temperature sensor)124for detecting the temperature in the space102. The second temperature adjuster122may be of the same arrangement as the first temperature adjuster120.

The signal processing board86, the reading light source38, the erasing light source42, the heat exchanger104, the first temperature adjuster120, the second temperature adjuster122, and the temperature measuring unit124are supplied with a power supply voltage from a control power supply unit126disposed outside the image capturing base26. The control power supply unit126is housed in the base16, for example, as shown inFIG. 7.

According to the second embodiment, as shown inFIG. 10, since the control power supply unit126is disposed outside the casing26aof the image capturing base26, the casing26amay be relatively small in size. The casing26ahouses the device power supply unit118therein. Therefore, the power transmission path between the device power supply unit118and the solid-state detector36is short enough not to pick up unwanted external noise.

The essentially closed space102is defined in the casing26a, and the air in the space102is adjusted in temperature by the heat exchanger104. Therefore, the temperature of the air in the space102is not affected by the temperature of ambient air unlike the conventional system wherein external air is directly drawn into the casing26a. It is thus possible to control the temperature of the air in the casing26aeasily and reliably with high accuracy for efficiently obtaining high-quality radiation image information.

According to the second embodiment, as shown inFIGS. 8 and 9, the heat exchanger104has the Peltier device106disposed on the inner wall surface of the casing26a. The heat sink108is positioned in the space102and fixedly mounted on the Peltier device106, and the heat sink110is fixedly mounted on the outer wall surface of the casing26a.

The heat sink108mainly serves to absorb heat, and the heat sink110mainly serves to radiate heat. When the heat sink108cools the air in the space102, the heat sink110radiates the heat through a heat exchange with the external air. An air blower such as a fan or the like is disposed outside the casing26ato allow the heat sink110to radiate the heat more effectively based on a forced convective flow of the external air.

Similarly, as shown inFIG. 9, a forced convective flow of air is generated in the space102to allow the heat sink108to absorb the heat quickly from the air in the space102. Accordingly, the cooling capability of the space102is increased.

As shown inFIG. 10, the temperature measuring unit124is disposed in the space102for detecting the temperature in the space102. Based on the temperature detected by the temperature measuring unit124, the Peltier device106is energized to control the temperature in the space102highly accurately. The first temperature adjuster120and the second temperature adjuster122are associated respectively with the amplifiers62and the A/D converter84which generate heat. The amplifiers62and the A/D converter84can thus be adjusted in temperature individually and effectively.

FIG. 11shown in block form a control circuit housed in an image capturing base130of a mammographic apparatus according to a third embodiment of the present invention.

As shown inFIG. 11, the entire outer wall surface of the casing26ais covered with a heat insulating member132of resin. The space102in the casing26ais effectively and reliably thermally insulated from the ambient environment by the heat insulating member132to permit the temperature of the air in the space102to be adjusted with higher accuracy. The heat insulating member132may be disposed on the inner wall surface of the casing26a.

FIG. 12shows in sectional side elevation an image capturing base140of a mammographic apparatus according to a fourth embodiment of the present invention.

As shown inFIG. 12, the casing26aof the image capturing base140supports a heat exchanger142thereon. The heat exchanger142comprises a Peltier device106mounted on an inner wall surface of the casing26aand a coating layer144of aluminum, for example, disposed on the inner wall surface of the casing26a.

According to the fourth embodiment, when the Peltier device106is energized for temperature control, a natural convective flow of air is generated in the space102through the coating layer144to control the temperature of the air in the space102. Heat is radiated from the Peltier device106based on the thermal conductivity of the casing26aitself. Therefore, the temperature of the air in the space102can be controlled highly accurately with a simple and economical arrangement.

In the second through fourth embodiments, as described above, the Peltier device106is employed as the temperature adjusting means. However, the temperature adjusting means should not be limited to the Peltier device106, but may be of any of various other structures. For example, a pipe for circulating a heat medium may be disposed in the space102and a radiator may be mounted on the casing26a, so that a heat exchange may take place between the heat medium and the external air or external cooling water.