JP5196728B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus, and more particularly, to an X-ray CT apparatus designed to reduce heat and radiation noise generated by a circuit device provided in a gantry rotating unit.

  In recent X-ray CT apparatuses, CT image data (hereinafter referred to as image data) can be displayed in real time by increasing the speed and performance of an X-ray detection unit and arithmetic processing unit. And the development of the multi-slice method has made it possible to collect image data and three-dimensional image data on a plurality of slice planes in a short time.

  In particular, it is necessary to collect three-dimensional image data such as volume rendering image data by a multi-slice method using an X-ray detector in which a plurality of X-ray detection elements are arranged in the slice direction (the body axis direction of the subject). Time has been drastically reduced, diagnostic efficiency has been greatly improved, and the load on the operator and subject has been reduced.

  In the X-ray CT apparatus, X-rays emitted from the X-ray generation unit and transmitted through the subject are detected by an X-ray detection unit disposed behind the subject, and this detection signal is transmitted to a data acquisition unit (hereinafter referred to as DAS). (referred to as a “data acquisition system” unit) to generate projection data. Then, image data is generated by reconstructing a plurality of projection data collected while rotating the above-described X-ray generation unit, X-ray detection unit, and DAS unit around the subject at high speed.

  In the multi-slice X-ray detection unit, a plurality of X-ray detection elements constituted by scintillators and photodiodes are two-dimensionally arranged, and the detection signals output from each of these X-ray detection elements are bundled in data. Signal processing is performed by a multi-channel current / voltage converter, an A / D converter, or the like provided in the DAS unit. Therefore, the above-mentioned X-ray detection unit and DAS unit are composed of an extremely large number of X-ray detection elements and circuit elements as compared with conventional X-ray CT apparatuses, and these elements generate unacceptable levels of heat and radiation noise. It has a new problem to do.

  That is, the heat generated by the above-described elements deteriorates its circuit characteristics, and radiation noise generated by these elements not only deteriorates the image quality of generated image data but also EMC (electro-magnetic compatibility). Conformance to standards may be difficult.

In order to reduce the heat generated by the X-ray detection unit, a method using a cooling fan or a heat pump has already been attempted. In addition, cooling devices and heat pipes composed of Peltier elements are arranged at a plurality of locations on the metal cover having high thermal conductivity covering the above-described X-ray detection unit and DSA unit, and this metal cover is grounded at a high frequency. Thus, a method of reducing heat and radiation noise generated by the X-ray detection unit has also been proposed (see, for example, Patent Document 1).
JP 2002-34968 A

  However, the above-described method cannot efficiently reduce heat generation and radiation noise. In particular, a method using a heat pipe is effective for countermeasures against heat generation. However, a grounded heat pipe may act as an antenna and increase radiation noise.

  Furthermore, in order to increase the frame rate of the image data and improve the time resolution, it is necessary to rotate the X-ray detection unit, the DSA unit, and the X-ray generation unit together with the gantry rotation unit at high speed around the subject. When a heat pipe or cooling device described in Patent Document 1 is attached to an X-ray detection unit or DAS unit that performs high-speed rotation, for example, an extremely large centrifugal force of 13G to 40G is applied to the heat pipe or cooling device. There is a risk of acting and breaking.

  That is, a method for efficiently reducing both the heat and radiation noise generated by the X-ray detection unit and the DAS unit provided in the gantry rotation unit rotating at high speed has not been proposed.

  The present invention has been made in view of the above-described problems, and its purpose is to cover a circuit device provided in a gantry rotating unit that rotates at high speed around a subject with a shield box having a heat dissipation function. An object of the present invention is to provide an X-ray CT apparatus capable of effectively reducing heat and radiation noise generated by a circuit device.

One aspect of the present invention provides an X-ray generation unit that generates X-rays to a subject, and a projection data collection unit that includes a plurality of chip devices that detect X-rays transmitted through the subject and collect projection data. Rotation means for rotating the X-ray generation means and the projection data collection means at high speed around the body axis of the subject, and image data generation means for reconstructing the projection data to generate image data. relates to X-ray CT apparatus comprising Te, said projection data collecting means, fixed heat conductor mounted on the back for each respective chip devices mounted on its own circuit board, the thermal conductor to the chip device shielding means having a first shielding box which in the state of being covered with the chip device and the heat conductor, and a second shielding box which covers apart the first shielding box, the It is characterized in that it comprises.

  According to the present invention, the circuit device provided in the gantry rotating unit that rotates at high speed around the subject is covered with the shield box having a heat dissipation function, so that the heat and radiation noise generated by the circuit device can be stably and effectively. Can be reduced.

(Example)
In an embodiment of the present invention described below, a predetermined thickness is provided on the back surface of a circuit device (hereinafter referred to as a chip device) of a DAS unit provided in a gantry rotating unit of an X-ray CT apparatus that rotates at high speed around a subject. The heat conductor is attached, and the heat conductor is covered with a metal first shield box so as to be fixed to the chip device. Further, the first shield box is covered with a metal second shield box, and a radio wave absorbing sheet is attached to at least one of the inner surface of the second shield box and the outer surface of the first shield box. . The ends of the first shield box and the second shield box are connected to the ground (GND) layer of the circuit board on which the chip device is mounted.

  In the following embodiments, a multi-slice X-ray CT apparatus will be described. However, the present invention is not limited to this, and a helical scan X-ray CT apparatus or a conventional single-slice X-ray CT apparatus may be used. May be.

(Device configuration)
The configuration of the X-ray CT apparatus according to the embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a block diagram showing an overall configuration of an X-ray CT apparatus 100 according to the present embodiment. The X-ray CT apparatus 100 includes an X-ray generation unit 5 that irradiates a subject 30 with X-rays, a subject A projection data collection unit 6 that detects X-rays transmitted through the specimen 30 and collects projection data, and a gantry rotation unit 2 that is equipped with the X-ray generation unit 5 and the projection data collection unit 6 and rotates at high speed around the subject 30. And a bed 1 for placing the subject 30 and inserting it into an opening provided at the center of the gantry rotating unit 2, and a bed and gantry moving mechanism for moving the bed 1 and rotating the gantry rotating unit 2. And a mechanism control unit 4 for controlling the bed / stand moving mechanism unit 3.

  The X-ray CT apparatus 100 also includes an image data generation unit 7 that reconstructs the projection data collected by the projection data collection unit 6 to generate image data, a display unit 9 that displays the generated image data, An input unit 10 for inputting sample information, setting imaging conditions, and the like, and a system control unit 11 for comprehensively controlling each unit described above are provided.

  The couch 1 has a couchtop (not shown) that can be slid in the longitudinal direction by the couch / gantry moving mechanism unit 3 so that the body axis direction of the subject 30 coincides with the longitudinal direction of the couchtop. Placed on. Further, the mechanism control unit 4 controls the moving direction and moving speed of the top plate or the rotating speed of the gantry rotating unit 2 based on the control signal supplied from the system control unit 11.

  On the other hand, the X-ray generator 5 includes an X-ray tube 51 that irradiates the subject 30 with X-rays, and a high-voltage generator 52 that generates a high voltage applied between the anode and the cathode of the X-ray tube 51. , An X-ray diaphragm 53 for collimating X-rays radiated from the X-ray tube 51, and a slip ring 54 for supplying power to the X-ray tube 51 provided in the gantry rotating unit 2.

  The X-ray tube 51 is a vacuum tube that generates X-rays. The X-ray tube 51 accelerates electrons by the high voltage supplied from the high-voltage generator 52, and collides with a tungsten target to emit X-rays. The X-ray diaphragm 53 is located between the X-ray tube 51 and the subject 30 and has a function of narrowing the X-ray beam emitted from the X-ray tube 51 to a predetermined image receiving size. For example, the X-ray beam emitted from the X-ray tube 51 is shaped into a cone beam (quadrangular pyramid) shape or a fan beam shape X-ray beam based on the effective field of view (FOV).

  On the other hand, the projection data collection unit 6 includes an X-ray detector 61 that detects X-rays transmitted through the subject 30, and a switch that bundles a plurality of channels of detection signals output from the X-ray detector 61 into a predetermined number of channels. A group 62, a DAS unit 63 that performs current / voltage conversion and A / D conversion on the output signal of the switch group 62, and an image in which the output of the DAS unit 63 is provided outside the gantry rotating unit 2 in a non-contact manner. A data transmission circuit 64 that supplies the data generation unit 7 is provided.

  Next, the X-ray detector 61 of the projection data collection unit 6 will be described with reference to FIG. FIG. 2 is a development view of the X-ray detector 61 in which the X-ray detection elements 611 are two-dimensionally arranged. Each of the X-ray detection elements 611 includes a scintillator that converts X-rays into light and light. It consists of a photodiode that converts it into an electrical signal.

  The multi-slice X-ray detector 61 includes, for example, 80 elements with respect to the slice direction (Z direction) that is the body axis direction of the subject 30 and the channel direction (X direction) orthogonal to the slice direction. On the other hand, about 900 X-ray detection elements 611 are arranged. However, the X-ray detection elements 611 arranged in the channel direction are actually mounted on the gantry rotating unit 2 along an arc centered on the focal point of the X-ray tube 51. In the central portion of the X-ray detector 61 in the slice direction, 32 X-ray detection elements 611 are arranged at intervals of 0.5 mm, and X-ray detection elements are arranged at both ends of the 32 X-ray detection elements 611. 611 is arranged 24 elements at intervals of 1.0 mm.

  Returning to FIG. 1, the switch group 62 of the projection data collection unit 6 includes, for example, a multiplexer (not shown) and a control circuit that controls the multiplexer, and transfers the projection data supplied from the X-ray detector 61 to the DAS unit 63. At this time, the projection data of a plurality of channels output from the X-ray detection element 611 in the slice direction are “data bundled” to a predetermined number of channels M1 and supplied to the DAS unit 63.

  On the other hand, the DAS unit 63 has an M1 channel receiving unit, which performs current / voltage conversion and A / D conversion on the projection data supplied from the X-ray detector 61.

  FIG. 3 is a block diagram showing the configuration of the DAS unit 63, and the DAS unit 63 is M1 channel projection data for the subject 30 supplied as a current signal from the X-ray detector 61 via the switch group 62. M1 channel current / voltage converter 631 for converting the voltage signal into A / D converter, M1 channel A / D converter 632 for A / D converting the voltage signal, current / voltage converter 631 and A / D converter 632. A DAS control unit 633 for controlling the control.

  A chip device (not shown) provided in the DAS control unit 633 is covered with a shield box provided with a heat dissipation measure, and the chip device transmits a high frequency clock pulse to the A / D converter 632. It has a function of reducing heat and radiation noise generated during supply, the details of which will be described later.

  On the other hand, the data transmission circuit 64 of FIG. 1 supplies the projection data output from the DAS unit 63 to, for example, a projection data storage circuit 71 of the image data generation unit 7 to be described later by optical communication means and stores it. This data transmission method is replaced with another method as long as signal transmission between the projection data collection unit 6 in the gantry rotation unit 2 and the image data generation unit 7 provided outside the gantry rotation unit 2 is possible. For example, a device such as the slip ring described above may be used.

  The X-ray tube 51, the X-ray restrictor 53, the slip ring 54, and the projection data collection unit 6 of the X-ray generation unit 5 are provided in the gantry rotation unit 2 that can rotate at high speed around the subject 30 and control the mechanism. According to the drive control signal supplied from the unit 4, a high-speed rotation of 1 rotation / second to 2 rotations / second is performed about an axis parallel to the body axis direction (Z direction) of the subject 30.

  Next, the details of the “data bundling” in the projection data collection unit 6 will be described with reference to FIG. However, in this figure, in order to simplify the description, a case where 12 X-ray detection elements 611-1 to 611-12 are arranged in the slice direction of one channel in the channel direction will be described.

  That is, in the X-ray detector 61 of FIG. 4, for example, eight X-ray detection elements 611-3 to 611-10 are arranged at 0.5 mm intervals in the center portion in the slice direction, The detection elements 611-1 to 611-2 and the X-ray detection elements 611-11 to 611-12 are arranged at intervals of 1 mm.

  On the other hand, the DAS unit 63 includes M1 (M1 <12) channel current / voltage converters 631-1 to 631-M1 and A / D converters 632-1 to 632-M1 and a DAS control unit (not shown) for controlling them. 633, and the switch group 62 “binds” the 12 columns of received signals detected by the X-ray detection element 611 into the M1 column. This “data bundling” makes it possible to change the slice thickness in the multi-slice.

  For example, by connecting the X-ray detection elements 611-3 to 611-10 to the current / voltage converters 631-1 to 631-M1 of the DAS unit 63 via the switch group 62, data having a slice thickness of 0.5 mm is obtained. M1 slices are obtained. On the other hand, when data with a slice thickness of 1 mm is required, the X-ray detection element 611-1 is the current / voltage converter 631-1, the X-ray detection element 611-2 is the current / voltage converter 631-2, X The line detection elements 611-3 and 611-4 are connected to the current / voltage converter 631-3, the X-ray detection elements 611-5 and 611-6 are connected to the current / voltage converter 631-4, respectively, and further the X-ray detection is performed. Elements 611-7 and 611-8 are current / voltage converters 631-5, X-ray detection elements 611-9 and 611-10 are current / voltage converters 631-6, and X-ray detection elements 611-11 are current / voltages. The converter 631-7 and the X-ray detection element 611-12 are connected to the current / voltage converter 631-M1.

  By performing the above-described “data bundling” on the detection signals obtained from the X-ray detection elements 611 having an interval of 0.5 mm shown in FIG. 4 by the same method, the X-ray detection elements 611 are spaced by 1 mm in the slice direction. Thus, projection data equivalent to the case where 64 elements are arranged is collected. That is, the effective number of elements in the slice direction in this case is 64. By such “data bundling”, it is possible to cope with both a case where a narrow area is imaged with high resolution and a case where a wide area is imaged with high sensitivity.

  The X-ray detector 61 detects a huge amount of two-dimensional projection data during one rotation (0.5 seconds to 1 second), and performs processing and transmission of such a huge amount of projection data in a short time. Therefore, chip devices capable of high-speed processing are used for the switch group 62, the DAS unit 63, and the data transmission circuit 64. For this reason, a large amount of heat and radiation noise are generated from each unit described above.

  In particular, the heat generated by the chip device provided in the DAS control unit 633 of the DAS unit 63 deteriorates its own circuit characteristics, and the radiation noise generated by this chip device affects other units and causes image data. In addition, it makes it difficult to adapt to EMC (electromagnetic compatibility) standards as well as to prevent image quality degradation. For this reason, countermeasures against heat generation and radiation noise with respect to the DAS controller 633 are particularly important.

  Returning to FIG. 1 again, the image data generation unit 7 includes a projection data storage circuit 71, a reconstruction calculation circuit 72, and an image data storage circuit 73.

  The projection data storage circuit 71 is a storage circuit that stores projection data detected by the X-ray detector 61 and sent via the data transmission circuit 64, and collected for a plurality of slice planes of the subject 30. Projection data is saved. Further, the reconstruction calculation circuit 72 generates volume data by reconstructing projection data on a plurality of slice planes stored in the projection data storage circuit 71, and further renders the volume data to perform a three-dimensional image. Generate data. Then, the obtained three-dimensional image data is temporarily stored in the image data storage circuit 73.

  Next, the display unit 9 includes a display data generation circuit 91, a conversion circuit 92, and a monitor 93. The display data generation circuit 91 reads out the 3D image data stored in the image data storage circuit 73, and adds display information such as patient information to the 3D image data to generate display data. Then, the conversion circuit 92 performs D / A conversion and television format conversion on the display data and displays them on the monitor 93.

  On the other hand, the input unit 10 is an interactive interface including input devices such as a display panel, a keyboard, various switches, selection buttons, and a mouse. An operator can use the input unit 10 to collect a subject before collecting projection data. Information input, projection data collection conditions, reconstruction conditions, image display conditions, etc. are set.

  The system control unit 11 includes a CPU and a storage circuit (not shown), and temporarily stores various setting conditions and various command signals sent from the input unit 10 in an internal storage circuit. Then, according to the input information from the input unit 10, the mechanism control unit 4, the X-ray generation unit 5, the projection data processing unit 6, the image data generation unit 7 and the display unit 9 are comprehensively controlled.

(Measures against heat generation and radiation noise in the DAS unit)
Next, a chip device shielding method for the purpose of countermeasures against heat generation and radiation noise in the DAS unit 63 will be described with reference to FIG.

  In FIG. 5, for example, a signal terminal of the chip device 83 in the DAS control unit 633 of the DAS unit 63 is connected to a signal line (not shown) of the circuit board 81 via a BGA (ball grid array) 82. A heat conductor 84 having a predetermined thickness is attached to the back surface. Further, a first shield box 85 is attached so as to cover the chip device 83 and the heat conductor 84, and an end portion thereof is connected to the GND layer 89 of the circuit board 81 through an on-board clip 88. At this time, the heat conductor 84 is fixed by the first shield box 85 so as not to peel from the back surface of the chip device 83 even when the gantry rotating unit 2 rotates at a high speed.

  Next, a second shield box 86 is attached so as to further cover the first shield box 85 covering the chip device 83 and the heat conductor 84, and the end thereof is turned on in the same manner as the first shield box 85. The board clip 88 is connected to the GND layer 89 of the circuit board 81. Then, a radio wave absorbing sheet 87 is attached to at least one of the inner surface of the second shield box 86 and the outer surface of the first shield box 85.

  The radio wave absorbing sheet 87 is preferably affixed to the inner surface of the second shield box 86 so as not to peel off at the high speed rotation of the gantry rotating unit 2, but is not particularly limited. You may affix on the outer surface of the 1st shield box 85. FIG.

  Note that the first shield box 85 and the second shield box 86 described above can be formed using copper, aluminum, or the like, both of which have high electrical conductivity and thermal conductivity. It can be formed by dispersing particles such as silver or alumina having good thermal conductivity in a silicon-based material such as silicon rubber or silicon gel pad. The radio wave absorbing sheet 87 is obtained, for example, by molding a paste obtained by uniformly mixing an elastic binder and anisotropic graphite into a sheet shape.

  A mechanism of heat generation reduction and radiation noise reduction by the first shield box 85 and the second shield box 86 to which the above-described heat conductor 84 and radio wave absorbing sheet 87 are added will be described with reference to FIGS.

  FIG. 6 is a diagram for explaining a mechanism of heat generation reduction by the first shield box 85, and an arrow in the figure indicates a heat transfer direction. That is, the heat generated from the chip device 83 in operation is transmitted to the first shield box 85 via the heat conductor 84, and this heat fixes the end of the first shield box 85. It is transmitted to the GND layer 89 of the circuit board 81 via the on-board clip 88 and is radiated to the outside of the DAS control unit 633.

  On the other hand, FIG. 7 is a diagram for explaining a mechanism of radiation noise reduction by the first shield box 85 and the second shield box 86, and arrows in the figure indicate radiation noise radiation paths. That is, the radiation noise radiated from the chip device 83 in operation is shielded by the first shield box 85 that is directly or high-frequency grounded via the on-board clip 88.

  On the other hand, the radiated noise transmitted through the first shield box 85 is shielded by the second shield box 86 grounded via the on-board clip 88 in the same manner as the first shield box 85, and is electromagnetically trapped inside. Most of the energy is absorbed by the radio wave absorbing sheet 87.

  That is, due to the shielding effect by the first shield box 85 and the second shield box 86 and the electromagnetic wave absorption effect by the radio wave absorbing sheet 87, the radiation noise generated from the chip device 83 of the DAS control unit 633 is greatly radiated to the outside. Can be suppressed.

(Modification 1)
Next, a first modification of the above embodiment will be described with reference to FIG. In the above-described embodiment, the case where one chip device 83 mounted on the circuit board 81 is covered with the first shield box 85 and the second shield box 86 has been described. In this first modification, a plurality of chip devices 83 are covered. Each chip device is covered with a first shield box, and a plurality of chip devices covered with the first shield box are collectively covered with a second shield box.

  That is, the signal terminals of a plurality of (two in FIG. 8) chip devices 83a and 83b in the present modification shown in FIG. 8 are connected to signal lines (not shown) of the circuit board 81 via BGAs 82a and 82b. Thermal conductors 84a and 84b are mounted on the back surfaces of the chip devices 83a and 83b. Further, a first shield box 85a covering the chip device 83a and the heat conductor 84a and a first shield box 85b covering the chip device 83b and the heat conductor 84b are attached, and both the first shield boxes 85a and 85b are attached. A covering second shield box 86 is attached.

  The end portions of the first shield boxes 85a and 85b and the second shield box 86 are connected to the GND layer 89 of the circuit board 81 via the on-board clip 88, and the inner surface of the second shield box 86 or the second shield box 86 A radio wave absorbing sheet 87 is attached to at least one of the outer surfaces of the one shield box 85a and 85b.

(Modification 2)
Next, a second modification of the above embodiment will be described with reference to FIG. In the above-described embodiment, the case where one chip device 83 mounted on the circuit board 81 is covered with the first shield box and the second shield box has been described. In this second modification, a plurality of chip devices are used. Is covered with a first shield box, and a plurality of chip devices covered with the first shield box are covered with a second shield box.

  That is, the signal terminals of a plurality (two in FIG. 9) of chip devices 83a and 83b in the present modification shown in FIG. 9 are connected to signal lines (not shown) of the circuit board 81 via BGAs 82a and 82b. Thermal conductors 84a and 84b are attached to the back surfaces of the chip devices 83a and 83b. Further, a first shield box 85 that covers both the chip device 83a to which the heat conductor 84a is attached and the chip device 83b to which the heat conductor 84b is attached is attached, and a second shield that covers the first shield box 85 is attached. The shield box 86 is attached.

  The end portions of the first shield box 85 and the second shield box 86 are connected to the GND layer 89 of the circuit board 81 via the on-board clip 88, and the inner surface of the second shield box 86 or the first shield box 86 A radio wave absorbing sheet 87 is attached to at least one of the outer surfaces of the shield box 85.

  According to the above-described embodiment and its modification, the heat generated by the chip device can be obtained by covering the chip device of the gantry rotating unit with a two-layer shield box having a radio wave absorbing sheet and a heat conductor. Radiation noise can be reduced simultaneously.

  In addition, since the shield structure using the first shield box, the second shield box, the radio wave absorbing sheet, and the heat conductor can be realized in a small size and light weight, damage due to centrifugal force when the gantry rotating part rotates at high speed is prevented. be able to. In particular, since the heat conductor mounted on the back surface of the chip device is fixed by the first shield box, there is no fear of peeling off due to the high-speed rotation described above.

  Furthermore, according to the first modification or the second modification described above, when a plurality of chip devices are mounted adjacent to the circuit board, the weight can be further reduced by simplifying the shield structure. It becomes possible, and the reliability with respect to the rotation of the gantry rotating part is improved.

  In other words, since the heat and radiation noise generated by the chip device provided in the gantry rotating part that rotates at high speed can be stably and effectively reduced, the deterioration of the circuit characteristics due to heat generation of the chip device and the image data due to the radiation noise can be reduced. It is possible to prevent image quality deterioration and to easily conform to the EMC standard.

  As mentioned above, although the Example of this invention has been described, this invention is not limited to the above-mentioned Example, You may deform | transform and implement. For example, in the above-described embodiment, the case where the heat and radiation noise generated by the chip device 83 provided in the DAS control unit 633 of the DAS unit 63 is reduced has been described. However, chips included in other units in the gantry rotating unit 2 are described. It may be a device. For example, it may be a chip device of the current / voltage converter 631 of the DAS unit 63 or the A / D converter 632, or a chip device provided in the multiplexer of the switch group 62 and its control circuit.

  The first shield box 85 and the second shield box 86 are connected to the GND layer 89 of the circuit board 81 via the on-board clip 88. However, the first shield box 85 and the second shield box 86 are directly connected to the GND layer 89 by soldering or the like. May be.

  Furthermore, the second shield box 86 may be grounded at a high frequency, and instead of being connected to the GND layer 89, it may be connected to a power supply layer (not shown) of the circuit board 81 via a capacitor or the like.

  The number of shield boxes covering the chip device 83 is not limited to two. For example, the second shield box 86 may be further covered with one or a plurality of shield boxes.

  On the other hand, although the multi-slice type X-ray CT apparatus 100 has been described in the above-described embodiment, a helical-scan type X-ray CT apparatus or a conventional single-slice type X-ray CT apparatus may be used. Although the case where the three-dimensional image data is generated based on the projection data has been described, the present invention is not limited to this.

  Furthermore, the above-described heat conductor 84 may be a thin sheet, or may be constituted by an adhesive having a high heat conductivity.

1 is a block diagram showing the overall configuration of an X-ray CT apparatus according to an embodiment of the present invention. The figure which shows the structure of the X-ray detector in the Example. The figure which shows the structure of the DAS unit in the Example. The figure which shows the structure of the projection data collection part in the Example. The figure for demonstrating the shield structure of the chip device in the DAS unit of the Example. The figure which shows the mechanism of the heat_generation | fever reduction by the shield box of the Example. The figure which shows the mechanism of radiation noise reduction by the shield box of the Example. The figure which shows the shield structure of the chip device in the 1st modification of the Example. The figure which shows the shield structure of the chip device in the 2nd modification of the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bed 2 ... Base rotation part 3 ... Bed / base movement mechanism part 4 ... Mechanism control part 5 ... X-ray generation part 51 ... X-ray tube 52 ... High voltage generator 53 ... X-ray restrictor 54 ... Slip ring 6 ... Projection data collection unit 61 ... X-ray detector 611 ... X-ray detection element 62 ... switch group 63 ... DAS unit 631 ... current / voltage converter 632 ... A / D converter 633 ... DAS control unit 64 ... data transmission circuit 7 ... Image data generation unit 71 ... projection data storage circuit 72 ... reconstruction operation circuit 73 ... image data storage circuit 81 ... circuit board 82 ... BGA
83 ... Chip device 84 ... Thermal conductor 85, 86 ... Shield box 87 ... Radio wave absorbing sheet 88 ... On-board clip 89 ... GND layer 9 ... Display unit 91 ... Display data generation circuit 92 ... Conversion circuit 93 ... Monitor 10 ... Input unit 11 ... System control unit 100 ... X-ray CT apparatus

Claims (7)

X-ray generation means for generating X-rays on the subject, projection data collection means having a plurality of chip devices that detect X-rays transmitted through the subject and collect projection data, and the X-ray generation means And an X-ray CT apparatus comprising: a rotation unit that rotates the projection data collection unit at high speed around the body axis of the subject; and an image data generation unit that reconstructs the projection data to generate image data. ,
The projection data acquisition unit includes a heat conductor mounted on the back for each respective chip devices mounted on its own circuit board, and the heat conductor in a state in which the thermal conductor was fixed to the tip device wherein the first shielding box covering the chip device, this first X-ray CT apparatus characterized by comprising a shielding means having a second shielding box which covers apart the shield box. Said shield means, said first shielding box X-ray CT apparatus according to claim 1, wherein the attaching a wave absorbing sheet to at least one of the outer surface or inner surface of the second shielding box of . It said shield means, X-rays CT apparatus according to claim 1, wherein grounding the ends of the first shielding box and the second shielding box high frequency. It said shield means, X-rays CT apparatus according to claim 1, characterized in that for connecting the ends of the first shielding box directly or via on-board clip to the ground layer of the circuit board. It said shield means, X-rays CT apparatus according to claim 1, wherein the connecting directly or through a on-board clip an end portion of the second shielding box to the ground or power source layer of the circuit board.   The projection data collecting means includes the shield means for a chip device mounted on at least one of a circuit board of a switch group or a DAS unit provided in the projection data collecting means. The X-ray CT apparatus according to 1.   2. The X-ray CT apparatus according to claim 1, wherein the projection data collecting means includes the shield means for a chip device mounted on a DAS control board of a DAS unit.

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