Medical imaging system

Abstract

A medical imaging system capable of being continuously used without discharging by changing imaging conditions, and capable of urging replacement of a device, the medical imaging system being provided with: a high-voltage generation device provided with a tank in which a high-voltage generation unit is immersed and accommodated with a first insulating oil; an X-ray tube device provided with an outer enclosure for accommodating a cathode and an anode, and a container in which the outer enclosure is immersed and accommodated with a second insulating oil; and a system control device. The system control device calculates a moisture activity value from an in-oil moisture sensor and a temperature sensor attached to at least one of the insulating oils of the high-voltage generation device and the X-ray tube device, indicates a tube voltage in a first range if the moisture activity value is less than a threshold value when imaging is performed without preheating, and indicates a tube voltage in a second range if the moisture activity value exceeds the threshold value, and indicates a tube voltage in a third range if the tube voltage exceeds the threshold value. If so, the tube voltage in the second range is lower than the tube voltage in the first range. When preheating and imaging are performed, a high voltage generation device and / or an X-ray tube device provided with an in-oil moisture sensor and a temperature sensor are preheated.

Description

Technical Field

[0001] The present invention relates to a medical imaging system, and in particular to a medical imaging system comprising a high voltage generating device using insulating oil and an X-ray tube device. Background Art

[0002] One of the medical imaging systems is an X-ray CT device. The X-ray CT device is a device that irradiates a subject with X-rays generated by an X-ray tube device and detects the amount of X-rays that have penetrated the subject to form an image. In order to generate X-rays, a high voltage is applied to the X-ray tube device. Therefore, if a large amount of X-rays are generated for a long time, the heat generated by the high voltage generator and the X-ray tube device increases. In order to ensure insulation and cool the equipment, insulating oil is filled in the X-ray tube device and the high voltage generator.

[0003] Although high voltage generators and X-ray tube devices are oil-tight, moisture may enter the insulating oil due to long-term use. For example, moisture gradually enters through rubber parts such as rubber pads and rubber bellows. The intruded moisture will cause the withstand voltage of the insulating oil to drop, and the required insulation performance cannot be maintained, which may cause the device to discharge and need to be replaced.

[0004] For example, Patent Document 1 discloses an oil-water monitoring device that monitors the water content in the insulating oil filled in the oil tank of an oil-immersed electrical appliance such as an oil-immersed transformer or an oil-immersed converter. The oil-water monitoring device includes an oil-water sensor, and when the water content in the insulating oil exceeds a reference value, it is judged as abnormal and an alarm signal is output.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 4-252945

[0006] In medical imaging systems that generate X-rays, erroneous stoppage during imaging can result in ineffective exposure of the subject, and sudden replacement of the device can also result in loss of the opportunity to image the subject. Therefore, it is desirable to replace the device before a failure occurs, or to change the imaging conditions to prevent discharge and allow continuous use. Summary of the invention

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a medical imaging system that can be used continuously without discharge by changing imaging conditions and can prompt replacement of the device.

[0008] A medical imaging system of a first embodiment includes: a high voltage generating device having a high voltage generating unit and a tank for immersing and accommodating the high voltage generating unit with a first insulating oil; an X-ray tube device having a peripheral device for accommodating a cathode and an anode and a container for immersing and accommodating the peripheral device with a second insulating oil, and irradiating X-rays; an X-ray detector for detecting X-rays that have penetrated a subject; and a system control device, wherein in the medical imaging system, at least one of the first insulating oil of the high voltage generating device or the second insulating oil of the X-ray tube device is provided with an oil moisture sensor and a temperature sensor, The system control device calculates a water activity value based on the amount of water in oil measured by the water-in-oil sensor and the temperature measured by the temperature sensor. When the object is imaged without preheating, if the water activity value is lower than a threshold value, the system control device prompts a tube voltage in a first range. When the water activity value is higher than the threshold value, the system control device prompts a tube voltage in a second range that is lower than the tube voltage in the first range. When the object is imaged with preheating, the high voltage generating device and / or the X-ray tube device equipped with the water-in-oil sensor and the temperature sensor are preheated.

[0009] In the medical imaging system of the second embodiment, in the first embodiment, when the system control device preheats the high voltage generating device and / or the X-ray tube device having the oil moisture sensor and the temperature sensor, the system control device operates the high voltage generating device and / or the X-ray tube device at a voltage lower than that during normal operation, or heats the first insulating oil and / or the second insulating oil with a heater.

[0010] In the medical imaging system of the third mode, when the high voltage generating device or the X-ray tube device is preheated and the subject is imaged, if the water activity value is lower than a threshold value, the system control device prompts the tube voltage in the first range, and if the water activity value is higher than the threshold value, displays a message urging replacement of the first insulating oil and / or the second insulating oil.

[0011] In the medical imaging system of the fourth aspect, in the first to third aspects, when the high voltage generator or the X-ray tube device is preheated, the system control device performs the preheating before the input scheduled imaging time of the subject.

[0012] A medical imaging system according to a fifth aspect is characterized in that, in the first to fourth aspects, the first insulating oil of the high voltage generator and the second insulating oil of the X-ray tube device include an oil moisture sensor and a temperature sensor.

[0013] A sixth aspect of the medical imaging system is a medical imaging system in which, in the first to fifth aspects, the medical imaging system is an X-ray CT apparatus or an X-ray apparatus.

[0014] Effects of the Invention

[0015] According to the present invention, by changing the imaging conditions so as not to discharge, the device can be used continuously and replacement of the device can be urged. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a perspective view illustrating the overall appearance of the X-ray CT apparatus.

[0017] Figure 2 It is a block diagram showing the overall configuration of an X-ray CT apparatus according to the embodiment.

[0018] Figure 3 This is a schematic diagram of the structure of a high voltage generator.

[0019] Figure 4 This is a schematic diagram of the structure of an X-ray tube device.

[0020] Figure 5 This is a graph showing the relationship among time, temperature, and Aw value.

[0021] Figure 6 This is a graph showing the relationship between operating years, time, temperature and Aw value.

[0022] Figure 7 This is a flowchart showing the procedure of processing performed by the X-ray CT apparatus.

[0023] Figure 8 This is a diagram showing an example of a screen for subject registration and normal imaging condition selection for normal imaging.

[0024] Fig. 9 This is a diagram showing an example of a screen for registering a subject for restricted imaging and selecting restricted imaging conditions.

[0025] Fig.10 This is a flowchart showing the procedure of processing performed by the X-ray CT apparatus using the scheduled imaging time.

[0026] Explanation of symbols

[0027] 4-X-ray tube device, 5-detector, 12-high voltage generating device, 36-system control device, 103-insulating oil, 112-temperature sensor, 113-water content sensor in oil, 203-insulating oil, 212-temperature sensor, 213-water content sensor in oil, 215-peripheral device, 301-heater, S-subject. DETAILED DESCRIPTION

[0028] <First embodiment>

[0029] As one embodiment of the medical imaging system of the present invention, an X-ray CT (Computed Tomography) apparatus will be described.

[0030] The overall structure of the X-ray CT apparatus 1 according to the present embodiment will be described. Figure 1 is an external view of the X-ray CT apparatus 1, Figure 2 is a block diagram showing the overall structure. Figure 1 and Figure 2 As shown, the X-ray CT apparatus 1 includes a gantry 20, a bed 3, and an operation unit 30. The gantry 20 has an opening 21 through which the bed 3 can pass. The operation unit 30 includes an input device 31, a display device 32, and a housing 33.

[0031] in addition, Figure 1 and Figure 2 The three-dimensional coordinate system described in the 3D coordinate system is an example of the definition of directions in the X-ray CT apparatus 1. The X-axis, Y-axis, and Z-axis of the three-dimensional coordinate system are examples and are not limited thereto. Here, the Z-axis direction is the body axis direction of the subject S. The Y-axis direction is the up-down direction of the subject S and is parallel to the gravity direction. The X-axis direction is the left-right direction of the subject S and is a horizontal direction orthogonal to the gravity direction.

[0032] like Figure 2 As shown, the frame 20 includes a rotating disk 7 having an opening 21 , a fixed frame (not shown) supporting the rotating disk 7 from the back side via a bearing (not shown), and a stationary side bracket 6 supporting the fixed frame.

[0033] The rotating disk 7 is supported by a fixed frame so as to be rotatable around the rotating shaft. The rotating disk 7 is connected to a large pulley (not shown) via the rotating portion side (inner side) of the bearing. The rotating disk control device 8 is fixed at a position close to the stationary side bracket 6. A driving belt 16 is wound around the outer periphery of the large pulley and the outer periphery of the small pulley (not shown) of the rotating disk control device 8. The small pulley is driven to rotate by the rotating disk control device 8, and the large pulley rotates via the driving belt 16. The rotational force of the large pulley is transmitted to the rotating disk 7 via the inner ring of the bearing, and the rotating disk 7 is driven to rotate around the rotating shaft. The rotating disk control device 8 is a motor.

[0034] The rotating disk 7 carries a plurality of components such as the X-ray tube device 4 , the detector 5 , the X-ray control device 11 , the high voltage generator 12 , the scanner control device 13 , the collimator 14 , and the cooler 15 . These plurality of components rotate together with the rotating disk 7 .

[0035] The X-ray tube device 4 is a device for irradiating an object S placed on the bed 3 with X-rays. The collimator 14 is a device for limiting the radiation range of the X-rays 2 irradiated from the X-ray tube device 4.

[0036] The detector 5 is disposed opposite to the X-ray tube device 4 on the rotating disk 7. The detector 5 is a device that measures the spatial distribution of the transmitted X-rays by detecting the X-rays irradiated from the X-ray tube device 4 and transmitted through the subject S. The detector 5 arranges a plurality of X-ray detection elements along the rotation direction of the rotating disk 7 or two-dimensionally arranges the rotating disk 7 in the rotation direction and the rotation axis direction.

[0037] The X-ray control device 11 is a device for controlling the power input to the X-ray tube device 4. The high voltage generating device 12 applies or supplies the tube voltage and tube current corresponding to the control signal sent from the X-ray control device 11 to the X-ray tube device 4. The X-ray conditions such as the tube voltage and the tube current are selected or input by the operator from the input device 31 and determined by the system control device 36. The scanner control device 13 is a device for controlling the collimator 14 and the detector 5, etc. The cooler 15 is a device for cooling the X-ray tube device 4 to a temperature below a specified temperature. The cooler 15 is composed of, for example, a radiator (heat radiator) and a pump. The DC power supply device 9 generates a DC voltage based on the AC power from a power supply device installed in an inspection room, etc. The DC voltage is transmitted to the rotating disk 7 via the slip ring 10.

[0038] The X-ray tube device 4 is an example of the X-ray tube device of the present invention. The detector 5 is an example of the X-ray detector of the present invention. The high voltage generator 12 is an example of the high voltage generator of the present invention.

[0039] The operating unit 30 includes an image computing device 34, a storage device 35, and a system control device 36 in a frame 33. The input device 31 is a device for inputting the name of the subject, the date and time of the examination, the imaging conditions, etc. Specifically, the input device 31 is a keyboard or a pointing device. The image computing device 34 is a device for computing and processing the measurement data detected by the detector 5 to generate a CT image. The display device 32 is a device for displaying the CT image produced by the image computing device 34, such as a liquid crystal display. The storage device 35 is a device for storing the data collected by the detector 5 and the CT image produced by the image computing device 34, such as a HDD (Hard Disk Drive). The system control device 36 is a device for controlling these devices and the scanner control device 13, the X-ray control device 11, and the bed control device (not shown). The system control device 36 is an example of a system control device of the present invention.

[0040] Next, the high voltage generator 12 will be described. Figure 3 1 is a schematic diagram of the high voltage generating device 12. Figure 3As shown, the high voltage generating device 12 includes a tank container 101 and a cover 102 for sealing the tank container 101. The cover 102 is arranged on the upper part of the tank container 101. The high voltage generating device 12 has a structure that is sealed by the cover 102 and the rubber gasket 109 to maintain oil tightness. The high voltage generating device 12 includes a high voltage transformer 104, a high voltage rectifier 105, a smoothing capacitor 106, a high voltage socket 107 and a filament transformer 108 inside the tank container 101. The high voltage transformer 104 boosts the AC voltage input from the AC power supply. The high voltage rectifier 105 rectifies the output of the high voltage transformer 104. The smoothing capacitor 106 smoothes the output of the high voltage rectifier 105. The high voltage socket 107 leads the DC high voltage to the outside of the tank container 101. The filament transformer 108 supplies a DC high voltage to the filament 214 (reference Figure 4 The high voltage transformer 104, the high voltage rectifier 105 and the smoothing capacitor 106 are mounted on the frame 116. The high voltage socket 107 and the filament transformer 108 are mounted on the cover 102.

[0041] The interior of the tank container 101 of the high voltage generator 12 thus configured is filled with insulating oil 103, which is electrically insulating and serves as a cooling medium. That is, the high voltage transformer 104, the high voltage rectifier 105, and the smoothing capacitor 106 are immersed in the insulating oil 103. A rubber bellows 110 that is in communication with the tank container 101 and is expandable and contractible is attached to the side of the tank container 101 so as to be in communication with the tank container 101. The rubber bellows 110 absorbs expansion and contraction caused by the temperature of the insulating oil 103.

[0042] The tank container 101 is an example of the tank of the present invention. The high voltage transformer 104, the high voltage rectifier 105 and the smoothing capacitor 106 are examples of the high voltage generating unit of the present invention. The insulating oil 103 is an example of the first insulating oil of the present invention.

[0043] Next, the X-ray tube device 4 will be described. Figure 4 4 is a schematic structural diagram of the X-ray tube device 4. Figure 4 As shown, the X-ray tube device 4 includes an X-ray tube 202 for generating X-rays and an X-ray tube device housing 201 for housing the X-ray tube 202. The interior of the X-ray tube 202 is kept vacuum by a casing 215. The casing 215 has a glass or metal tube ball called a valve, and is used according to the purpose and installation position.

[0044] A filament 214 and a target 208 disposed opposite to the filament 214 are disposed inside the outer casing 215. The filament 214 emits electrons (electron beam). The target 208 emits X-rays by being injected with the electrons (electron beam) emitted from the filament 214. The cathode of the X-ray tube 202 is composed of the filament 214 as an electron source and a collector 207 that collects the electrons (electron beam) emitted from the filament 214. The anode of the X-ray tube 202 is composed of the target 208 disposed opposite to the filament 214. The anode is configured as a rotating anode. The target 208 is rotatably supported by a rotating body support mechanism 206. The rotor, i.e., the rotating body support mechanism 206 and the target 208 are rotated by the stator coil 205. Two high voltage sockets 209 for applying voltages to the cathode and the anode, respectively, are provided in the X-ray tube device housing 201. The X-ray tube device frame 201 is filled with insulating oil 203, which electrically insulates the X-ray tube 202 and serves as a cooling medium. That is, the outer shell 215 is immersed in the insulating oil 203. A rubber bellows 210 that can be extended and retracted is installed on the side of the X-ray tube device frame 201. The rubber bellows 210 absorbs the expansion and contraction caused by the temperature of the insulating oil 203. The X-ray tube device frame 201 is provided with a radiation window 204 for radiating X-rays 2 to the outside of the X-ray tube device 4. The radiation window 204 is made of a material with a small atomic number such as beryllium that has a high X-ray transmittance.

[0045] The X-ray tube device frame 201 is an example of a container of the present invention. The enclosure 215 is an example of a enclosure of the present invention. The target 208 is an example of an anode of the present invention. The filament 214 and the focusing body 207 are an example of a cathode of the present invention. The insulating oil 203 is an example of a second insulating oil of the present invention. In addition, the insulating oil 203 may be the same as the insulating oil 103 or may be different. In the following description, when there is no need to distinguish between the first insulating oil and the second insulating oil, they are simply described as "insulating oil". There is no limitation on the type of insulating oil, and silicone oil, vegetable oil, etc. can be used.

[0046] Next, the operation of the X-ray CT device 1 is described. Imaging conditions, especially tube voltage and tube current, etc. are input from the input device 31. The rotating disk 7 rotates around the subject S. The power input to the X-ray tube device 4 by the X-ray control device 11 is controlled according to the imaging conditions. The X-ray tube device 4 irradiates the subject S with X-rays corresponding to the imaging conditions. The detector 5 detects the X-rays irradiated from the X-ray tube device 4 and transmitted through the subject S through a plurality of X-ray detection elements. The distribution of the transmitted X-rays is measured based on the detection results. By performing various processes on the detection results, the data of the CT image is generated.

[0047] Next, the mechanism for generating X-rays is described. The input AC voltage on the stationary side is converted into a DC voltage by the DC power supply device 9. The DC voltage is transmitted to the rotating disk 7 via the slip ring 10. The DC voltage is converted into a high-frequency AC voltage by the X-ray control device 11, and converted into a DC high voltage by the high voltage generator 12. A DC high voltage is applied to the X-ray tube device 4 to generate X-rays. The X-ray tube device 4 is cooled by the cooler 15.

[0048] Next, the operation of the high voltage generator 12 will be described. The voltage of the alternating current converted into a high frequency by the X-ray control device 11 is applied to the high voltage transformer 104 and converted into a high frequency alternating current high voltage. This voltage is converted into a direct current high voltage by the high voltage rectifier 105, and further smoothed by the smoothing capacitor 106 and converted into a direct current high voltage with less ripple. This direct current high voltage is output from the high voltage socket 107 and supplies power to the X-ray tube device 4. The filament transformer 108 supplies power to the filament 214 of the X-ray tube device 4.

[0049] Next, the operation of the X-ray tube device 4 will be described. The DC high voltage generated by the high voltage generator 12 supplies power to the X-ray tube device 4 via the high voltage socket 209. In addition, power is also supplied from the filament transformer 108 of the high voltage generator 12 to the filament 214 of the X-ray tube device 4 to generate thermal electrons for generating X-rays 2. The generated thermal electrons are gathered by the collector 207 and accelerated toward the target 208 by the supplied DC high voltage. The X-rays 2 are generated from the target 208 and irradiated to the subject S via the radiation window 204. In order to prevent the thermal electrons from being irradiated at one point of the target 208, the target 208 is rotatably supported by the rotating body support mechanism 206 and rotated by the stator coil 205.

[0050] The high voltage generator 12 may be used for a long time, and water may enter through the rubber bellows 110, rubber pad 109 and other parts, and the insulating performance of the insulating oil 103 may not be maintained. Similarly, the insulating oil in the X-ray tube device 4 may be used for a long time, and water may enter through the rubber bellows 210 and other parts, and the insulating performance of the insulating oil 203 may not be maintained.

[0051] Therefore, in the X-ray CT apparatus 1 of the embodiment, the temperature sensor 112 and the oil moisture sensor 113 are arranged in the insulating oil 103 of the high voltage generator 12. In the X-ray CT apparatus 1, the signals of the temperature sensor 112 and the oil moisture sensor 113 can be taken out from the terminal 111 to the outside to monitor the insulation performance of the insulating oil 103. Similarly, in the X-ray CT apparatus 1 of the embodiment, the temperature sensor 212 and the oil moisture sensor 213 are arranged in the insulating oil 203 of the X-ray tube device 4. In the X-ray CT apparatus 1, the signals of the temperature sensor 212 and the oil moisture sensor 213 can be taken out from the terminal 211 to the outside to monitor the insulating oil 203.

[0052] The temperature sensor 112 is an example of the temperature sensor of the present invention. The moisture in oil sensor 113 is an example of the moisture in oil sensor of the present invention. The temperature sensor 212 is an example of the temperature sensor of the present invention. The moisture in oil sensor 213 is an example of the moisture in oil sensor of the present invention.

[0053] As the oil moisture sensor 113 and the oil moisture sensor 213 , a polymer thin film electrostatic capacitance humidity sensor (HUMICAP: registered trademark) manufactured by Vaisala, a temperature and humidity sensor (MK33-W) manufactured by Innovative Sensor Technology, etc. can be used.

[0054] The temperature sensor 112 and the temperature sensor 212 can be measured using optical fibers, and preferably can be measured directly in the coil.

[0055] Regarding the arrangement positions of the temperature sensor 112 and the water content sensor 113 in the oil, there is a difference in water content and temperature depending on the position of the high voltage generator 12. The high voltage portion is easy to discharge, so the closer to the lower part of the tank container 101, the higher the accuracy, which is preferred. The temperature sensor 112 and the water content sensor 113 in the oil may also be arranged at both the upper and lower parts of the tank container 101.

[0056] Next, the relationship between the Aw value of the insulating oil and the dielectric withstand voltage of the insulating oil is described. In the high voltage generator 12 and the X-ray tube device 4, the insulating oil is filled for the purpose of suppressing discharge and cooling the device. However, it is known that discharge is easy to occur under the condition that the Aw value (water activity value: oil humidity) of the insulating oil is high. For example, if the Aw value becomes 0.4, the dielectric breakdown voltage of the insulating oil drops to about 45% compared to the case where the Aw value is less than 0.2. In addition, the Aw value refers to the ratio of the water content [ppm] in the oil to the maximum water content (saturated water solubility) that can be dissolved in the insulating oil.

[0057] The Aw value and the ppm value have a relationship as shown in the following formula (1). Here, the values ​​of A and B are inherent values ​​of the insulating oil and are different for each insulating oil. A and B are values ​​that can be obtained in advance. T is the temperature of the insulating oil (K).

[0058] [Formula 1]

[0059]

[0060] In the high voltage generator 12 or the X-ray tube device 4, when the device is operated and the temperature rises, the value of the water content [ppm] in the oil increases. In this case, since the saturated water content is also high, the Aw value is suppressed low, making it difficult to discharge.

[0061] However, if the temperature of the insulating oil drops, the saturated water content decreases. On the other hand, since the water content [ppm] in the oil is still high, the Aw value rises sharply. In this state, the withstand voltage of the insulating oil decreases, and it is easy to discharge. In a device used for a long time, it is possible to discharge by emitting X-rays under the maximum tube voltage condition.

[0062] Figure 5 This is a graph showing the relationship between temperature, Aw value and time. The horizontal axis represents time, the left vertical axis represents Aw value, and the right vertical axis represents temperature. The solid line represents Aw value, and the dotted line represents temperature. As shown in the part surrounded by a circle, it can be understood that if the temperature of the insulating oil drops, the Aw value rises sharply. In addition, the following tendency is observed: if the temperature of the insulating oil drops after the Aw value reaches its peak, the Aw value also drops. It is believed that this is because the temperature of the insulating oil drops, and the water content [ppm] in the oil also drops. If the temperature of the insulating oil becomes lower over time, the Aw value also becomes constant.

[0063] Figure 6 This is a graph showing the relationship between temperature, Aw value, time and the operating life of a high voltage generator. The horizontal axis represents time, the left vertical axis represents Aw value, and the right vertical axis represents temperature. In addition, the solid line represents Aw value, and the dotted line represents temperature. As shown in the graph, the following tendency is observed: the Aw value of a high voltage generator with a long operating life becomes higher than that of a high voltage generator with a short operating life. As described above, since the higher the Aw value, the easier it is to discharge, it is preferred to use a high voltage generator with a low Aw value at a low temperature.

[0064] Therefore, the X-ray CT apparatus 1 of the embodiment calculates the Aw value of the insulating oil 103 of the high voltage generator 12 based on the detection results obtained from the temperature sensor 112 and the water content in oil sensor 113. A monitoring threshold value Aw(th) is set in the X-ray CT apparatus 1. The X-ray CT apparatus 1 can monitor the withstand voltage of the insulating oil 103 of the high voltage generator 12 by comparing the calculated Aw value with the threshold value Aw(th).

[0065] The X-ray CT apparatus 1 of the embodiment calculates the Aw value of the insulating oil 203 of the X-ray tube assembly 4 based on the detection results obtained from the temperature sensor 212 and the water content in oil sensor 213. A monitoring threshold value Aw(th) is set in the X-ray CT apparatus 1. The X-ray CT apparatus 1 can compare the Aw value with the threshold value Aw(th) to monitor the withstand voltage of the insulating oil 203 of the X-ray tube assembly 4.

[0066] The Aw value calculated based on the detection results of the temperature sensor 112 and the water content in oil sensor 113 is an example of the first water activity value of the present invention. The Aw value calculated based on the detection results of the temperature sensor 212 and the water content in oil sensor 213 is an example of the second water activity value of the present invention.

[0067] Next, the procedure of processing performed by the X-ray CT apparatus 1 will be described. Figure 7 It is a flowchart which shows the process procedure.

[0068] like Figure 7 As shown, the operator selects a subject registration button on the screen (step S1). Specifically, the operator operates the input device 31 to display the registration button on the display device 32. The operator selects the subject registration button on the screen from the input device 31.

[0069] Next, it is determined whether the Aw value is less than or equal to the threshold value Aw(th) (step S2). Specifically, the system control device 36 reads the signals of the temperature sensor 112 and the water content sensor 113 from the terminal 111. The system control device 36 calculates the Aw value of the insulating oil 103 based on the temperature T(K) of the temperature sensor 112, the water content [ppm] of the oil content sensor 113, and the formula (1). A and B of the insulating oil 103 are obtained in advance.

[0070] The system control device 36 reads the signals of the temperature sensor 212 and the water content sensor 213 from the terminal 211. The system control device 36 calculates the Aw value of the insulating oil 203 based on the temperature T (K) of the temperature sensor 212, the water content [ppm] of the oil content sensor 213, and the formula (1). A and B of the insulating oil 203 are obtained in advance.

[0071] The system control device 36 compares the calculated Aw value with the threshold value Aw(th). The system control device 36 determines whether the Aw value is less than the threshold value Aw(th). As a result of this determination, if the Aw value is less than the threshold value Aw(th) (step S2: "Yes"), the process proceeds to step S3.

[0072] In addition, the same threshold value Aw(th) may be set for the insulating oil 103 and the insulating oil 203, or different threshold values ​​Aw(th) may be set. When the Aw value of the insulating oil 103 is less than the threshold value Aw(th) and the Aw value of the insulating oil 203 is less than the threshold value Aw(th), it can be determined that the Aw value is less than the threshold value Aw(th). That is, both the Aw value of the insulating oil 103 and the Aw value of the insulating oil 203 are less than the threshold value Aw(th). Since the Aw value is less than the threshold value Aw(th), it can be determined that the insulating oil 103 and the insulating oil 203 have high dielectric strength voltage.

[0073] Next, the operator registers the subject (step S3 ). Figure 8 This is a diagram showing an example of a screen for subject registration and imaging condition selection. Figure 8 8-1 is an example of the subject registration screen. Figure 8 8-2 is an example of an imaging condition selection screen. In step S3, when the operator registers a subject, the subject registration screen 40 is displayed on the display device 32. The operator inputs the subject ID, subject name, date of birth, and gender to the subject registration screen 40 from the input device 31.

[0074] Next, the operator selects normal imaging conditions (step S4). Specifically, if the operator registers the subject, Figure 8 As shown in 8-2, the normal imaging condition selection screen 42 is displayed on the display device 32. The operator selects the imaging condition from the input device 31. The normal imaging condition selection screen 42 displays kV (tube voltage) and parameters 1 to 3. In step S2, the Aw value is determined to be below the threshold value Aw (th), so the operator can select any imaging condition from 80kV to 140kV. Parameters 1 to 3 include other imaging conditions such as tube current, imaging site and time. 80kV to 140kV that the operator can select is an example of the first range of tube voltages of the present invention.

[0075] Next, normal imaging is performed (step S5). Specifically, as described above with respect to the operation of the X-ray CT apparatus 1, in the X-ray CT apparatus 1, the X-ray tube device 4 irradiates the subject S with X-rays corresponding to normal imaging conditions (tube voltage and tube current, etc.), and generates image data based on the detection results of the X-rays that have penetrated the subject S. When the normal imaging (step S5) is terminated, the imaging by the X-ray CT apparatus 1 is completed.

[0076] Next, in step S2 , when the Aw value is larger than the threshold value Aw(th) (step S2 : No), the process proceeds to step S6 .

[0077] Next, it is determined whether or not to start imaging without performing warm-up (step S6 ). Fig. 9 FIG. 4 is a diagram showing an example of a screen for restricting the registration of subjects to be photographed and the selection of photographing conditions. Fig. 9 As shown in 9-1 of FIG. 1 , a message “Do you want to start imaging without preheating?” is displayed on the display device 32. The operator determines whether to start imaging without preheating. When the operator determines to start imaging without preheating (step S6: “Yes”), the process proceeds to step S7. When making the determination, the operator may consider, for example, whether to urgently perform the examination of the subject using the X-ray CT apparatus 1.

[0078] Next, the operator registers the subject (step S7). Fig. 9 As shown in 9-2, similarly to step S3, the operator inputs the subject ID, subject name, date of birth, and gender into the subject registration screen 40 from the input device 31.

[0079] Next, the operator selects the restricted imaging conditions (step S8). Specifically, if the operator registers the subject, Fig. 9 As shown in FIG9-3, the restricted imaging condition selection screen 44 is displayed on the display device 32. In the restricted imaging condition selection screen 44, the imaging condition with a high tube voltage (140 kV) is highlighted in a warning color such as red. Fig. 9 In 9-3, it is displayed with a dot pattern. The 80kV to 120kV selectable by the operator is an example of the second range of tube voltages of the present invention. If the maximum selectable tube voltages of the first range of tube voltages (80kV to 140kV) and the second range of tube voltages (80kV to 120kV) are compared, the tube voltages of the second range are lower than the tube voltages of the first range.

[0080] When the operator selects a limited imaging condition, it is determined in step S2 that the Aw value is greater than the threshold value Aw(th). That is, the dielectric withstand voltage of the insulating oil 103 or the insulating oil 203 decreases, and there is a possibility that discharge may occur.

[0081] Therefore, in order to suppress discharge, highlighting or warning display is performed in the restricted imaging condition selection screen 44 to prevent the operator from selecting an imaging condition with a high tube voltage. The display device 32 can display a message such as "may cause device failure" as a warning display.

[0082] Next, the restricted imaging is performed (step S9). Specifically, in the X-ray CT apparatus 1, the X-ray tube device 4 irradiates the subject S with X-rays corresponding to the restricted imaging conditions (tube voltage and tube current, etc.), and generates image data based on the detection results of the X-rays that have penetrated the subject S. When the restricted imaging (step S9) is terminated, the imaging by the X-ray CT apparatus 1 is completed.

[0083] Next, in step S6 , when the operator determines to perform warm-up and start imaging (step S6 : No), the process proceeds to step S10 .

[0084] Next, it is determined whether the preheating is the first time (step S10). Specifically, the system control device 36 counts the number of preheating times and can determine whether the preheating is the first time based on whether the number of preheating times is 0 or 1 or more. If the system control device 36 determines that the preheating is the first time, the process proceeds to step S11.

[0085] Next, preheating is performed (step S11 ). Preheating is an operation for increasing the temperature of the insulating oil 103 filled in the high voltage generator 12 and / or the insulating oil 203 filled in the X-ray tube device 4 .

[0086] Specifically, preheating is performed by operating the high voltage generator 12 and / or the X-ray tube device 4, for example, at a low tube voltage (kV) by the system control device 36. For example, in preheating, the normal operation is set to 100%, and the operation is performed at 15% to 30%. Since the high voltage generator 12 and / or the X-ray tube device 4 is operated, the temperature of the insulating oil 103 and / or the insulating oil 203 can be increased. Since the operation is performed at a low tube voltage (kV), there is no need to re-prepare the equipment.

[0087] As another preheating, the heater 301 (see Figure 3 ) to heat the insulating oil 103 to increase the temperature. In addition, the heater 301 (see Figure 4 ) Heat the insulating oil 203 to increase the temperature.

[0088] When the heater 301 is used, the insulating oil 103 and / or the insulating oil 203 can be heated without emitting X-rays, and the operator can enter the device room. For example, the heater can be turned on when preparing to photograph a subject, and the device can be heated while preparing for photography. The heater 301 consumes a large amount of power, but can quickly increase the temperature of the insulating oil 103 and / or the insulating oil 203. The heater 301 can be an IH (Induction Heating) type heater.

[0089] This preheating can increase the temperature of the insulating oil 103 filled in the high voltage generator 12 and / or the insulating oil 203 filled in the X-ray tube device 4. If the temperature of the insulating oil 103 and / or the insulating oil 203 rises, as described above (refer to Figure 5 ), the Aw value of the insulating oil 103 and / or the insulating oil 203 decreases. By reducing the Aw value of the insulating oil 103 and / or the insulating oil 203, discharge can be suppressed.

[0090] Next, the number of preheating times is counted (step S12). The system control device 36 counts the number of preheating times and stores the number of preheating times in the storage device 35. Next, the process proceeds to step S2. In step S2, it is determined whether the Aw value of the preheated insulating oil 103 and / or insulating oil 203 is less than the threshold value Aw(th). If the Aw value is less than the threshold value Aw(th), steps S3, S4, and S5 are executed.

[0091] In step S10 , when the preheating is not the first time (step S10 : No), the process proceeds to step S13 .

[0092] Next, a message urging replacement of the device is displayed (step S13 ). Specifically, if the system control device 36 determines that the warm-up is not the first time, a message such as “Device replacement is required” is displayed on the display device 32 .

[0093] If preheating is not the first time (step S10: No), even if preheating is performed, the Aw value of the insulating oil 103 and / or the insulating oil 203 is greater than the threshold value Aw(th). It can be inferred that the high voltage generator 12 and / or the X-ray tube device 4 have been in operation for a long time. Therefore, by displaying a message to replace the device, the operator can be notified that discharge may occur.

[0094] Next, it is determined whether to enter the imaging (step S14). The operator determines whether to enter the imaging. If it is determined not to enter the imaging (step S14: "No"), the imaging is terminated and the high voltage generator 12 and / or the X-ray tube device 4 are replaced. By replacing the device, discharge can be suppressed.

[0095] If it is determined that imaging is to be performed (step S14: "Yes"), the process proceeds to step S7. The operator registers the subject (step S7), then selects the restricted imaging condition (step S8), and performs restricted imaging (step S9). In the restricted imaging condition selection (step S8), when preheating is not the first time, for example, tube voltage 140 kV and tube voltage 120 kV can be highlighted. Even after preheating, the Aw value is greater than the threshold value Aw (th), so there is a possibility of discharge. Therefore, in order to avoid the occurrence of discharge after preheating, it can be made different from the imaging condition when preheating is the first time, and a lower range of tube voltage (imaging condition) can be selected.

[0096] When the limited imaging is completed (step S9 ), the imaging by the X-ray CT apparatus 1 is completed.

[0097] Next, the procedure of the warm-up process performed by the X-ray CT apparatus 1 using the scheduled imaging time will be described. Fig.10 It is a flowchart which shows the process procedure.

[0098] like Fig.10 As shown, it is determined whether it is the scheduled time for photography of the subject (step S21). Specifically, the system control device 36 compares the scheduled time for photography stored in the storage device 35 with the current time. The system control device 36 calculates the time difference. If the current time is, for example, before the scheduled time for photography, the system control device 36 determines that it is not the scheduled time for photography of the subject (step S21: "No"), and proceeds to step S22. For example, the scheduled time for photography can be set to 10 minutes before the actual scheduled time for photography. The time of 10 minutes can be set in advance.

[0099] Next, preheating is performed (step S22). Preheating is performed in the same steps as step S11. The operator can set the time to perform preheating. For example, the operator can set it to 5 minutes before the actual scheduled shooting time. When preheating is completed, the process proceeds to step S21.

[0100] In step S21 , when the time difference between the current time and the scheduled imaging time is shorter than the set time, it is determined to be the scheduled imaging time of the subject (step S21 : Yes), and the process proceeds to step S23 .

[0101] Next, it is determined whether the Aw value is less than or equal to the threshold value Aw(th) (step S23). The determination of step S23 is performed in the same steps as step S2. As a result of this determination, if the Aw value is less than or equal to the threshold value Aw(th) (step S23: "Yes"), the process proceeds to step S24.

[0102] Next, the operator registers the subject (step S24), selects normal imaging conditions (step S25), and performs normal imaging (step S26). When normal imaging is completed (step S26), imaging by the X-ray CT apparatus 1 is completed. Steps S24, S25, and S26 are performed in the same manner as steps S3, S4, and S5.

[0103] Next, in the determination of step S23 , when the Aw value is larger than the threshold value Aw(th) (step S23 : No), the process proceeds to step S27 .

[0104] Next, a message urging replacement of the device is displayed (step S27). Step S27 is performed in the same steps as step S13. In this flow, preheating is performed before the start of the shooting time, so if the answer is "No" in step S23, the same processing is performed as when preheating is not the first time, and the message urging replacement of the device is displayed (step S27).

[0105] Next, it is determined whether to enter the imaging (step S28). The operator determines whether to enter the imaging. If it is determined not to enter the imaging (step S28: "No"), the imaging is terminated and the high voltage generator 12 and / or the X-ray tube device 4 are replaced. By replacing the device, discharge can be suppressed.

[0106] If it is determined that imaging is to be performed (step S28: Yes), the process proceeds to step S29. The operator registers the subject (step S29), then selects the restricted imaging condition (step S30), and executes the restricted imaging (step S31). If the restricted imaging is terminated (step S31), the imaging by the X-ray CT apparatus 1 is completed. In addition, even if preheating is performed before the scheduled imaging time, if the time difference between the actual imaging time and the preheating execution time is large, the effect of preheating is reduced. In this case, the same process as the case where preheating is not performed before the scheduled imaging time can be performed. Figure 7 The process of performing the processing steps of the X-ray CT device 1.

[0107] As described above, according to the X-ray CT apparatus 1 of the first embodiment, by changing the imaging conditions so as not to discharge, the apparatus can be continuously used and replacement of the apparatus can be urged.

[0108] <Second embodiment>

[0109] In the first embodiment, the high voltage generator 12 includes the temperature sensor 112 and the oil moisture sensor 113 in the insulating oil 103 , and the X-ray tube assembly 4 includes the temperature sensor 212 and the oil moisture sensor 213 in the insulating oil 203 .

[0110] However, this is not limiting, and only the high voltage generator 12 may include the temperature sensor 112 and the oil moisture sensor 113 in the insulating oil 103 , or only the X-ray tube device 4 may include the temperature sensor 212 and the oil moisture sensor 213 in the insulating oil 203 .

[0111] In the case where only the high voltage generator 12 is provided with the temperature sensor 112 and the water content sensor 113 in the insulating oil 103, Figure 7 In step S2 of the process, the system control device 36 calculates the Aw value of the insulating oil 103 based on the temperature T (K) of the temperature sensor 112, the amount of water in the oil [ppm] of the water in the oil sensor 113, and the formula (1), and compares the calculated Aw value with the threshold value Aw (th). In step S11, only the high voltage generator 12 is preheated. And, Fig.10 In step S23 , the Aw value of the insulating oil 103 is also compared with the threshold value Aw(th).

[0112] Next, when only the X-ray tube device 4 is provided with the temperature sensor 212 and the water content sensor 213 in the insulating oil 203, Figure 7 In step S2 of the process, the system control device 36 calculates the Aw value of the insulating oil 203 based on the temperature T (K) of the temperature sensor 212, the amount of water in the oil [ppm] of the water in the oil sensor 213, and the formula (1), and compares the calculated Aw value with the threshold value Aw (th). In step S11, only the X-ray tube device 4 is preheated. Fig.10 In step S23 , the Aw value of the insulating oil 203 is also compared with the threshold value Aw(th).

[0113] Therefore, in the second embodiment, similarly to the first embodiment, by changing the imaging conditions so as not to discharge the device, the device can be continuously used and replacement of the device can be urged.

[0114] <Other>

[0115] The functions of the system control device 36 are implemented by various processors. The various processors include general-purpose processors that execute programs and function as various processing units, namely CPUs and / or GPUs (Graphic Processing Units), FPGAs (Field Programmable Gate Arrays), and other processors whose circuit structures can be changed after manufacturing, such as Programmable Logic Devices (PLDs), ASICs (Application Specific Integrated Circuits), and other processors with circuit structures specially designed to perform specific processing, namely dedicated circuits. Programs and software have the same meaning.

[0116] One processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same type or different types. For example, one processing unit may be composed of multiple FPGAs, or a combination of a CPU and an FPGA. In addition, multiple processing units may be composed of one processor. As an example of multiple processing units composed of one processor, first, there is a method in which a processor is composed of a combination of one or more CPUs and software, as represented by computers used in clients, servers, etc., and the processor functions as multiple processing units. Secondly, there is a method in which a processor that implements the functions of the entire system including multiple processing units is used by one IC (Integrated Circuit) chip, as represented by a system on chip (SoC). In this way, as a hardware structure, various processing units are composed of more than one of the above-mentioned various processors.

[0117] The present invention is not limited to the above-described embodiment, and various modifications are possible. The medical imaging system can be applied to an X-ray device in addition to an X-ray CT device.

Claims

1. A medical imaging system, comprising: A high voltage generating device comprising a high voltage generating unit and a tank for accommodating the high voltage generating unit by impregnating the high voltage generating unit with a first insulating oil; An X-ray tube device includes an outer casing for accommodating a cathode and an anode and a container for accommodating the outer casing by impregnating the outer casing with a second insulating oil, and irradiates X-rays; An X-ray detector that detects X-rays that have passed through the subject; and System control device, In the medical image photography system, At least one of the first insulating oil of the high voltage generator or the second insulating oil of the X-ray tube device includes an oil moisture sensor and a temperature sensor. The system control device calculates a water activity value based on the amount of water in the oil measured by the water in oil sensor and the temperature measured by the temperature sensor, When the subject is imaged without preheating, When the water activity value is lower than a threshold value, the system control device prompts a tube voltage within a first range. When the water activity value is higher than a threshold value, a tube voltage in a second range lower than the tube voltage in the first range is presented. When the subject is imaged while being preheated, the high voltage generator and / or the X-ray tube device including the oil moisture sensor and the temperature sensor is preheated.

2. The medical imaging system according to claim 1, wherein: When preheating the high voltage generator and / or the X-ray tube device having the oil moisture sensor and the temperature sensor, the system control device operates the high voltage generator and / or the X-ray tube device at a voltage lower than that during normal operation, or heats the first insulating oil and / or the second insulating oil with a heater.

3. The medical imaging system according to claim 1 or 2, wherein: When the high voltage generator or the X-ray tube device is preheated and the subject is imaged, When the water activity value is lower than a threshold value, the system control device prompts the tube voltage in the first range. When the water activity value is higher than a threshold value, a message urging replacement of the first insulating oil and / or the second insulating oil is displayed.

4. The medical imaging system according to claim 3, wherein: When the high voltage generator or the X-ray tube device is preheated, The system control device performs the operation before the input scheduled imaging time of the subject.

5. The medical imaging system according to claim 1 or 2, wherein: The first insulating oil of the high voltage generator and the second insulating oil of the X-ray tube device include the oil moisture sensor and the temperature sensor.

6. The medical imaging system according to claim 1 or 2, wherein: The medical imaging system is an X-ray CT device or an X-ray device.

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