JP2013022326A - X-ray ct apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus capable of preventing adverse influence on an X-ray detector by the change of an ambient temperature.SOLUTION: The X-ray CT apparatus includes an X-ray tube 21 for irradiating a subject P with X-rays, an X-ray detection part 22 for detecting the X-rays transmitted through the subject P, and a rotary frame 26 for rotatably holding the X-ray tube 21 and the X-ray detection art 22. The X-ray detection part 22 includes an X-ray detector 70 for detecting the X-rays from the X-ray tube 21, and an enclosure 71 for enclosing the X-ray detector 70. Then, the enclosure 71 includes a first enclosure 72 having an air layer 72a with the X-ray detector 70 and enclosing the X-ray detector 70 so as to transmit the X-rays from the X-ray tube 21, and a second enclosure 73 having a gas layer 73a with the first enclosure 72 and enclosing the first enclosure 72 so as to transmit the X-rays from the X-ray tube 21, and the gas layer 73a is decompressed and exhausted.

Description

  Embodiments described herein relate generally to an X-ray CT apparatus that prevents deterioration of the function of an X-ray detector due to a change in ambient temperature.

  The X-ray CT apparatus includes a gantry unit that performs imaging by irradiating a subject with X-rays, and an image processing unit that reconstructs X-ray projection data generated by the gantry unit by imaging and generates image data. ing. The gantry unit rotates around the subject to irradiate the subject with X-rays, an X-ray detector that detects X-rays transmitted through the subject by irradiating the subject with X-rays, and Each unit includes a data collection unit that collects signals detected by the X-ray detector and generates X-ray projection data.

  By the way, the X-ray CT apparatus is provided with a cooling fan for cooling the inside of the gantry unit in order to prevent the internal temperature from rising due to the heat generated from each unit of the gantry unit and the function of each unit from deteriorating. There is. In this X-ray CT apparatus, calibration for adjusting the sensitivity of the X-ray detector is performed by imaging a calibration phantom. Then, after the calibration is performed, the subject is imaged.

JP 2004-121717 A

  However, after calibration, the temperature of the X-ray detector changes from the time of calibration due to temperature fluctuations around the gantry and heat generated from each unit of the gantry. There is a problem that the image quality of the image data decreases.

  The embodiment has been made to solve the above-described problems, and an object thereof is to provide an X-ray CT apparatus capable of preventing an adverse effect on an X-ray detector due to a change in ambient temperature.

  In order to solve the above problems, an X-ray CT apparatus according to an embodiment detects an X-ray tube that irradiates a subject with X-rays, and X-rays that are irradiated by the X-ray tube and transmitted through the subject. A gas layer is provided between the first enclosure that surrounds and supports the X-ray detector so as to transmit X-rays from the X-ray tube, and the first enclosure. A second enclosure that surrounds and supports the first enclosure so as to be able to transmit X-rays from the X-ray tube; an enclosure having a decompression pump that evacuates the gas in the gas layer; and the X-ray tube; The enclosure includes a rotating frame that rotatably holds the periphery of the subject.

1 is a block diagram showing a configuration of an X-ray CT apparatus according to an embodiment. Sectional drawing which shows the structure of the X-ray detection part which concerns on embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an X-ray CT apparatus according to the embodiment. The X-ray CT apparatus 100 includes a bed unit 10 on which the subject P is movably mounted, a gantry unit 20 that performs imaging by irradiating the subject P mounted on the bed unit 10 with X-rays, And an image processing unit 40 that generates image data based on X-ray projection data generated by imaging in the gantry unit 20. In addition, an operation unit 50 for inputting X-ray irradiation conditions and the like related to the movement of the subject P placed on the bed unit 10 and the imaging of the subject P performed by the platform unit 20, the bed unit 10, and the platform unit 20. And a system control unit 60 that controls the image processing unit 40 in an integrated manner.

  The couch unit 10 is disposed in the vicinity of the front side of the gantry unit 20 and includes a couchtop 11 on which the subject P is placed and a couchtop drive unit 12 that moves the couchtop 11 in the vertical direction and the longitudinal direction. Yes. Then, the top plate drive unit 12 moves the top plate 11 on which the subject P is placed to a position where imaging of the gantry unit 20 is possible.

  The gantry 20 has a cylindrical opening 20a that passes between the front side and the back side. And the X-ray tube 21 which irradiates X-ray with respect to the subject P sent to the opening part 20a by the movement to the longitudinal direction of the top plate 11 of the bed part 10, and the X-ray tube 21 through the opening part 20a. An X-ray detection unit 22 that detects X-rays that are disposed opposite to each other and transmitted through the subject P, a data collection unit 23 that generates X-ray projection data based on a signal detected by the X-ray detection unit 22, and data A data transmission unit 24 that transmits the X-ray projection data generated by the collection unit 23 to the image processing unit 40 is provided.

  The gantry 20 includes a high voltage generator 25 that supplies a high voltage to the X-ray tube 21, an X-ray tube 21, an X-ray detector 22, a data collector 23, a data transmitter 24, and a high voltage generator. 25, a rotation frame 26 that holds the periphery of the subject P so as to be rotatable, a rotation drive unit 27 that drives the rotation frame 26 to rotate in the direction of the arrow R1, and a frame cover that covers most of the frame unit 20 excluding the opening 20a. 28 and a fan 29 for discharging the heat in the gantry cover 28.

  The X-ray tube 21 generates X-rays by the irradiation drive of the high voltage generator 25. Then, X-rays are irradiated while rotating around the subject P placed on the top 11 at the time of imaging. The X-ray detector 22 detects X-rays irradiated from the X-ray tube 21 and transmitted through the subject P while rotating and converts them into electrical signals, amplifies the converted signals, and sends them to the data collector 23. Output.

  The data collection unit 23 includes an electronic circuit board having an analog / digital conversion circuit and the like, and is arranged on the outer periphery of the X-ray detection unit 22. Then, the signal output from the X-ray detection unit 22 is converted into a digital signal, and the converted digital signal is collected for each predetermined imaging angle rotation of the rotating frame 26 to generate X-ray projection data.

  The data transmission unit 24 includes, for example, a transmission unit and a reception unit for transmitting and receiving by optical communication means, and the transmission unit is disposed in the rotating frame 26, and the X-ray projection data from the data collection unit 23 is converted into an image processing unit. Output to 40.

  The rotating frame 26 holds the X-ray tube 21, the X-ray detection unit 22, the data collection unit 23, the data transmission unit 24, and the high voltage generation unit 25. Then, it rotates in the R1 direction at the time of shooting and stops at times other than shooting.

  The image processing unit 40 generates image data by reconfiguring the storage unit 41 that stores the X-ray projection data output from the data transmission unit 24 of the gantry unit 20 and the X-ray projection data stored in the storage unit 41. And a display unit 43 that displays the image data generated by the reconstruction unit 42.

  The operation unit 50 includes input devices such as a keyboard, a trackball, a joystick, a mouse, and a hand switch. Then, an input for supplying power to the gantry unit 20, an input for stopping the supply of power to the gantry unit 20, an input of X-ray irradiation conditions relating to imaging in the gantry unit 20, and an input for moving the top plate 11 of the bed unit 10 Input of start of shooting, input of end of shooting, and the like are performed.

  The system control unit 60 includes a CPU and a storage circuit, temporarily stores input information input by an operation from the operation unit 50, and then moves the table 11 in the bed unit 10 based on the input information. The entire system is controlled such as X-ray irradiation and stop in the unit 20, rotation and stop of the rotating frame 26, and image data generation and display control in the image processing unit 40.

Next, an example of the configuration of the X-ray detection unit 22 in the gantry unit 20 will be described with reference to FIGS. 1 and 2.
FIG. 2 is a cross-sectional view showing the configuration of the X-ray detection unit 22. The X-ray detector 22 is a cross-sectional view seen from the front side of the gantry 20, and surrounds the X-ray detector 70 that detects X-rays from the X-ray tube 21 and the X-ray detector 70. It is constituted by an enclosure 71 for keeping within a preset allowable range as a temperature range in which image quality deterioration such as artifacts does not occur in image data.

  The X-ray detector 70 includes a scintillator that emits fluorescence when X-rays are incident and a photoelectric conversion element that converts the fluorescence from the scintillator into an electrical signal. Then, the X-ray from the X-ray tube 21 that has passed through the enclosure 71 is detected, and the detection signal is output to the data collection unit 23.

  The enclosure 71 is provided with an air layer 72a between the X-ray detector 70 and a first enclosure 72 that surrounds and supports the X-ray detector 70 so that X-rays from the X-ray tube 21 can be transmitted. A gas layer 73a is provided between the first envelope 72 and the second envelope 73 surrounding and supporting the first envelope 72 so as to transmit X-rays from the X-ray tube 21; The pressure reducing pump 74 is held by the rotary frame 26 that exhausts the air at a reduced pressure, and the temperature sensor 75 detects the temperature of the X-ray detector 70.

  The enclosure 71 also transmits a heating unit 76 for heating the X-ray detector 70, a cooling unit 77 for cooling the X-ray detector 70, and a signal detected by the X-ray detector 70 to the data collection unit 23. A plurality of cables 78, and a gas layer 73a between the first enclosure 72 and the second enclosure 73 are shielded from the inside of the first enclosure 72 and the outside of the second enclosure 73, and the first enclosure 72 and a plurality of first to third pipes 79 to 81 communicating with the outside of the second enclosure 73.

  The first enclosure 72 is formed along the outer surface of the X-ray detector 70. A lightweight and rigid metal member that surrounds the X-ray detector 70 via the air layer 72a and supports a part of the X-ray detector 70 via a support (not shown), and the metal member For example, polyethylene terephthalate resin, acrylic (R) resin, silicone (R resin, Teflon (R) resin, polypropylene resin, etc., which close the opening 721 formed in the region where X-rays transmitted through the second enclosure 73 are incident And an X-ray transmitting member excellent in X-ray transmission.

  The second enclosure 73 is held by the rotating frame 26 and is formed along the outer surface of the first enclosure 72. A lightweight and rigid metal member that surrounds the first enclosure 72 via the gas layer 73a and supports a part of the first enclosure 72 via a support (not shown), An X-ray transmitting member that closes an opening 731 formed in a region where X-rays from the X-ray tube 21 of the metal member enter.

  The decompression pump 74 is a pressure sensor that detects the pressure of the gas layer 73a sealed by the outer surface of the first enclosure 72, the inner surface of the second enclosure 73, and the outer surfaces of the first to third pipes 79 to 81. And is activated and stopped based on the pressure detected by the pressure sensor. Then, when the pressure of the gas layer 73a is equal to or higher than the low pressure upper limit value lower than the atmospheric pressure, the gas layer 73a is exhausted under reduced pressure, for example, air that is the gas of the gas layer 73a. Moreover, it stops when the pressure of the gas layer 73a is not more than the low pressure lower limit value lower than the low pressure upper limit value.

  As described above, the gas layer 73a is provided to surround the X-ray detector 70 sealed by the first envelope 72, the second envelope 73, and the first to third pipes 79 to 81, and the gas layer 73a. By evacuating this gas under reduced pressure, it is possible to cut off heat transfer with the X-ray detector 70 due to temperature fluctuations around the gantry 20 and heat generation of each unit of the gantry 20. Thereby, the temperature influence on the X-ray detector 70 due to ambient temperature fluctuations can be prevented.

  The temperature sensor 75 includes, for example, a thermistor disposed in the vicinity of the X-ray detector 70 in the first enclosure 72. Then, the temperature of the X-ray detector 70 is detected, and information on the detected temperature is output to the heating unit 76 and the cooling unit 77. If the detected temperature is within the allowable range, the temperature information is output to the system control unit 60. The system control unit 60 causes the display unit 43 of the image processing unit 40 to display standby information indicating that photographing is possible based on the temperature information from the temperature sensor 75.

  The heating unit 76 includes a heater disposed close to the outer peripheral side of the X-ray detector 70 in the first enclosure 72, and repeats operation and stop based on the temperature detected by the temperature sensor 75. Then, when the temperature of the X-ray detector 70 is equal to or lower than the allowable lower limit value within the allowable range, the X-ray detector 70 is operated to heat the X-ray detector 70. Moreover, heating is stopped when the temperature of the X-ray detector 70 is equal to or higher than the allowable upper limit value that is higher than the allowable lower limit value within the allowable range.

  The cooling unit 77 includes, for example, a fan disposed outside the second enclosure 73, and repeats operation and stop based on the temperature detected by the temperature sensor 75. Then, when the temperature of the X-ray detector 70 is equal to or higher than the allowable upper limit value, the air outside the second enclosure 73 is transferred from the first pipe 79 to the air layer 72a in the first enclosure 72. The air that has been sucked and the temperature of the air layer 72a has increased is exhausted from the second pipe 80. Further, the exhaust is stopped when the temperature of the X-ray detector 70 is lower than the allowable lower limit value.

  In addition, since it can prevent that the heat | fever by the temperature fluctuation of the base part 20 periphery and the heat_generation | fever of each unit of the base part 20 move to the X-ray detector 70, the X-ray detector 70 is in the temperature more than an allowable upper limit. If the thermal stability is excellent and the image quality of the image data is not deteriorated, the cooling unit 77 may be removed from the enclosure 71.

  The cable 78 has one end connected to the X-ray detector 70 and the other end connected to the data processing unit 23. Then, the signal that is disposed through the third pipe 81 and detected by the X-ray detector 70 is transmitted to the data collection unit 23.

  The first pipe 79 includes a first opening formed in the vicinity of one end portion on the outer peripheral side of the first enclosure 72 and a second opening formed in the vicinity of one end portion on the inner peripheral side of the second enclosure 73. Arranged between. A passage through which air outside the second enclosure 73 flows into the second enclosure 73 is formed by the operation of the cooling unit 77.

  The second pipe 80 has a third opening formed in the vicinity of the other end portion on the inner peripheral side of the first enclosure 72 and a fourth opening formed in the vicinity of the other end portion on the inner periphery side of the second enclosure 73. Between the openings. A passage through which the air in the first enclosure 72 flows out of the second enclosure 73 is formed by the operation of the cooling unit 77.

  The third pipe 81 includes a plurality of fifth openings formed between the first opening on the outer periphery side of the first enclosure 72 and the third opening, and the second periphery on the inner periphery side of the second enclosure 73. And the same number of sixth openings as the fifth openings formed between the two openings and the fourth openings. A passage through which the cable 78 is disposed is formed.

  In this way, by surrounding the X-ray detector 70 with the gas layer 73a having a low thermal conductivity and reduced pressure, the temperature fluctuation around the gantry 20 and the heat generated by each unit of the gantry 20 can generate the X-ray detector. Therefore, the heating unit 76 and the cooling unit 77 can be simply configured, and the temperature of the X-ray detector 70 can be accurately controlled.

Hereinafter, an example of the operation of the X-ray CT apparatus 100 will be described with reference to FIGS. 1 and 2.
When an input for supplying electric power from the operation unit 50 to the gantry unit 20 is performed, the X-ray CT apparatus 100 starts operation. Then, the fan 29 of the gantry 20 exhausts the air in the gantry cover 28. The enclosure 71 in the X-ray detection unit 22 performs an operation for keeping the temperature of the X-ray detector 70 within an allowable range.

  Here, the temperature sensor 75 of the enclosure 71 detects the temperature of the X-ray detector 70 and outputs it to the heating unit 76 and the cooling unit 77. The heating unit 76 heats the X-ray detector 70 until the temperature detected by the temperature sensor 75 reaches the allowable upper limit value, and stops heating when the temperature exceeds the allowable upper limit value. The cooling unit 77 evacuates the first enclosure 72 to cool the X-ray detector 70 when the temperature detected by the temperature sensor 75 reaches the allowable upper limit value, and stops when the temperature falls below the allowable lower limit value. To do. The decompression pump 74 decompresses and exhausts the gas layer 73a until the pressure of the gas layer 73a reaches the low pressure lower limit value, and stops the decompression exhaust when it falls below the low pressure upper limit value.

  When the temperature of the X-ray detector 70 falls within the allowable range, the temperature sensor 75 outputs the temperature information to the system control unit 60. The system control unit 60 displays standby information on the display unit 43 of the image processing unit 40 based on the temperature information from the temperature sensor 75.

  After the standby information is displayed on the display unit 43, the rotation frame 26 is rotated by an input for executing calibration, for example, from the operation unit 50, and the calibration phantom placed on the top 11 is photographed. Then, calibration including adjustment of the sensitivity of the X-ray detector 70 is performed. When the calibration is performed, the enclosure 71 continues to perform an operation for keeping the X-ray detector 70 within the allowable temperature. After the calibration is completed, when the subject P placed on the top plate 11 is imaged by rotating the rotating frame 26 by inputting imaging start, the enclosure 71 continues to move the X-ray detector 70. Perform the operation to keep within the allowable temperature. During the standby after the rotation frame 26 is stopped by the end of imaging and the imaging is completed, the enclosure 71 continues to operate to keep the X-ray detector 70 within the allowable temperature.

  When an input for stopping the power supply from the operation unit 50 to the gantry unit 20 is performed, the enclosure 71 stops the operation for keeping the X-ray detector 70 within the allowable temperature, and the X-ray CT apparatus 100. Ends the operation.

  As described above, the enclosure 71 operates when waiting after the power is supplied to the gantry 20, when calibration is being performed, and when the subject P is being imaged. The temperature of the X-ray detector 70 can be kept within an allowable range. Thereby, it is possible to prevent an adverse effect on the X-ray detector 70 due to a change in ambient temperature, and it is possible to prevent a deterioration in image quality of image data generated by imaging the subject P.

  According to the embodiment described above, the gas layer 73a surrounding the X-ray detector 70 sealed by the first enclosure 72, the second enclosure 73, and the first to third pipes 79 to 81 is provided. By providing and exhausting the gas layer 73a under reduced pressure, it becomes possible to block temperature fluctuations around the gantry 20 and heat transfer with the X-ray detector 70 due to heat generated by each unit of the gantry 20, and ambient temperature fluctuations The influence of the temperature of the X-ray detector 70 due to the above can be prevented. Then, the X-ray detector 70 surrounded by the gas layer 73a having a low thermal conductivity is heated and cooled based on the temperature detected by the temperature sensor 75, whereby the X-ray detector 70 The temperature can be controlled with high accuracy.

  Thereby, it is possible to prevent an adverse effect on the X-ray detector 70 due to a change in ambient temperature, and it is possible to prevent a deterioration in image quality of the image data.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

21 X-ray tube 22 X-ray detection unit 23 Data collection unit 70 X-ray detector 71 Enclosure 72 First enclosure 72a Air layer 73 Second enclosure 73a Gas layer 74 Depressurization pump 75 Temperature sensor 76 Heating unit 77 Cooling Portion 78 Cable 79 First pipe 80 Second pipe 81 Third pipe 82 Gas layers 721, 731 Opening

Claims (6)

An X-ray tube that irradiates the subject with X-rays;
An X-ray detector for detecting X-rays irradiated by the X-ray tube and transmitted through the subject;
A first envelope that surrounds and supports the X-ray detector so that X-rays from the X-ray tube can be transmitted, and a gas layer is provided between the first envelope and the X-ray from the X-ray tube. A second enclosure that surrounds and supports the first enclosure so as to be permeable, and an enclosure having a decompression pump that evacuates the gas in the gas layer;
An X-ray CT apparatus comprising: a rotating frame that rotatably holds the X-ray tube and the surrounding body around the subject.   The X-ray CT apparatus according to claim 1, wherein the decompression pump decompresses and exhausts the gas in the gas layer while the rotary frame is rotating.   The X-ray CT apparatus according to claim 1, wherein the decompression pump decompresses and exhausts the gas in the gas layer while the rotating frame is stopped. A temperature sensor disposed within the first enclosure for detecting the temperature of the X-ray detector;
A heater disposed in the first enclosure for heating the X-ray detector based on the temperature detected by the temperature sensor;
The gas layer is disposed between the first opening formed in the first enclosure and the second opening formed in the second enclosure, and the gas layer is disposed in the first enclosure and the second enclosure. A first pipe that cuts off the outside of the enclosure and communicates between the air layer provided between the X-ray detector in the first enclosure and the outside of the second enclosure;
The gas layer is disposed between a third opening formed in the first enclosure and a fourth opening formed in the second enclosure, and the gas layer is disposed in the first enclosure and the second enclosure. A second pipe that shuts off from the outside of the enclosure and communicates between the air layer and the outside of the second enclosure,
Based on the temperature detected by the temperature sensor, the air outside the second enclosure is sucked into the air layer through the first pipe, and the air in the air layer is sucked through the second pipe. The X-ray CT apparatus according to any one of claims 1 to 3, further comprising a fan that exhausts air to the outside of the second enclosure. A data collection unit that generates X-ray projection data based on a detection signal detected by the X-ray detector;
The gas layer is disposed between a fifth opening formed in the first enclosure and a sixth opening formed in the second enclosure, and the gas layer is disposed in the first enclosure and the second enclosure. A third pipe that shuts off the outside of the enclosure and communicates between the first enclosure and the outside of the second enclosure;
A cable disposed through the third pipe and having one end connected to the X-ray detector and the other end connected to the data collection unit. The X-ray CT apparatus according to claim 4.   In the second enclosure, an area where X-rays from the X-ray tube are incident is configured by an X-ray transmitting material that transmits X-rays, and the first enclosure transmits the second enclosure. 6. The X-ray CT apparatus according to claim 1, wherein a region where X-rays are incident is configured by the X-ray transmitting material.

Images