JP2013056119A - X-ray computerized tomography and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a X-ray computerized tomography capable of cooling a X-ray pipe by using an aqueous cooling liquid and preventing cavitation occurrence in a circulation path of the aqueous cooling liquid, and its control method.SOLUTION: A X-ray computerized tomography includes a X-ray pipe unit 10, an aqueous cooling liquid 9, circulation 11a, 11b, 21a, 21b, 21c, a circulation pump 22, a bellows mechanism mounted on a circulation path 30, a rotary frame, and a X-ray detector. It is characterized by P0-p'>0.5(R0+R1)(R0-R1)ρωand R2>R0.

Description

  Embodiments described herein relate generally to an X-ray computed tomography apparatus and a control method thereof.

  A gantry of an X-ray computed tomography apparatus (hereinafter referred to as an X-ray CT apparatus) includes a fixed frame, a rotating pedestal rotatably supported by the fixed frame, and a housing containing the fixed frame and the rotating pedestal. I have. The gantry also includes an X-ray tube unit, an X-ray detector, a cooling unit, and the like mounted on a rotating mount. The X-ray tube unit and the cooling unit are relatively compact but have a large mass and a high pressure on the installation surface, so that they are firmly attached to the rotating base.

  The X-ray tube unit and the cooling unit are connected via a conduit, and the coolant to which the heat generated by the X-ray tube is transmitted circulates between the X-ray tube unit and the cooling unit. The heat source of the X-ray CT apparatus is an X-ray tube. For this reason, the heat generated by the X-ray tube is transmitted to the cooling liquid, and the high-temperature cooling liquid is sent to the cooling unit. The coolant cooled by the cooling unit is returned to the X-ray tube unit again.

  Generally, a rotary anode type X-ray tube apparatus is known as an X-ray tube unit used in an X-ray CT apparatus. The rotary anode X-ray tube device includes a housing and a rotary anode X-ray tube housed in the housing. The rotary anode type X-ray tube includes a vacuum envelope housed in a housing, an anode target positioned in the vacuum envelope and rotatably provided, and a vacuum envelope located in the vacuum envelope. And a cathode provided stationary with respect to the vessel.

  Among the rotating anode type X-ray tube devices as described above, there are known devices that forcibly cool the vicinity of the target surface of an anode target with a coolant. This makes it possible to transfer the heat generated from the anode target to the coolant during the period in which the electron beam collides with the target surface to emit X-rays. Some coolants use water-based coolants with excellent heat transfer performance.

JP-A-9-56710 JP 2001-137224 A International Publication No. 2008/069195 Pamphlet

  In recent years, in X-ray CT apparatuses, shortening the scan time (imaging time) is a major technical problem. Therefore, in order to shorten the scanning time, the rotating gantry is rotated at a higher speed. The rotation speed of the rotary base is often 1 to 2 rps, and about 3 rps in the highest model. In the future, attempts are being made to achieve 4 rps or higher. In the case of 4 rps compared with the case of 2 rps, the acceleration in the centrifugal direction of the rotating base increases by 300%. In the case of 4 rps compared with the case of 3 rps, the acceleration in the centrifugal direction of the rotating gantry increases by about 78%.

  However, since the water-based coolant has a lower saturated vapor pressure than that of the insulating oil, it is expected that cavitation will occur in the water-based coolant circulation path when the rotational speed of the rotating base is 4 rps or higher. . If cavitation occurs, the flow of the aqueous coolant may be hindered, making it impossible to cool the X-ray tube or causing a problem with the circulation pump. For this reason, the technique which can cool an X-ray tube using a water-system coolant and can prevent generation | occurrence | production of the cavitation in the circulation path of a water-system coolant is calculated | required.

  The present invention has been made in view of the above points, and an object of the present invention is to use an aqueous coolant to cool an X-ray tube and to prevent the occurrence of cavitation in the circulation path of the aqueous coolant. The present invention provides an X-ray computed tomography apparatus and a control method thereof.

An X-ray computed tomography apparatus according to an embodiment includes:
An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit having
An aqueous coolant to which at least part of the heat generated by the X-ray tube is transmitted;
A conduit connected to the housing and through which the aqueous coolant flows;
A circulation pump attached to the conduit for circulating the aqueous coolant and forming a circulation path for circulating the aqueous coolant with the X-ray tube unit and the conduit;
A bellows mechanism attached to the circulation path, having an elastic diaphragm separating the aqueous coolant from a gas space outside the circulation path, and absorbing a volume change of the aqueous coolant;
A rotating gantry that rotates about a rotating shaft and has the X-ray tube unit, conduit, circulation pump, and bellows mechanism attached thereto;
An X-ray detector that is located on the opposite side of the X-ray tube unit with respect to the rotation axis, is attached to the rotary mount, and detects the X-ray;
The average value of the distance from the rotation axis to the elastic diaphragm is R0,
The pressure of the gas space is P0,
P ′ represents a saturated vapor pressure of the aqueous coolant in a state where the maximum temperature of the surface of the housing has been reached.
The minimum value of the distance from the rotation axis to the circulation path including the housing as a part thereof is R1,
The minimum value of the distance from the rotating shaft to the inlet of the aqueous coolant of the circulation pump is R2,
The density of the aqueous coolant is ρ,
When the angular velocity of the rotating mount is ω,
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
It is characterized by being.

In addition, a method for controlling the X-ray computed tomography apparatus according to an embodiment is as follows:
An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit, an aqueous coolant to which at least a part of heat generated by the X-ray tube is transmitted, a conduit connected to the housing and through which the aqueous coolant flows, and the conduit A circulating pump that circulates the aqueous coolant and circulates the aqueous coolant together with the X-ray tube unit and the conduit; and is attached to the circulation path and passes the aqueous coolant to the circulation path A bellows mechanism that has an elastic diaphragm that separates from the gas space separated from the gas space, and absorbs a volume change of the aqueous coolant, and rotates about a rotation axis, and the X-ray tube unit, conduit, and circulation A rotary gantry to which a pump and a bellows mechanism are attached; a drive unit that rotates the rotary gantry; and a rotary shaft that is located on the opposite side of the X-ray tube unit with respect to the rotary shaft, and is attached to the rotary gantry, An X-ray detector that detects the temperature of the water-based coolant flowing in the X-ray tube unit, and an average value of the distance from the rotating shaft to the elastic diaphragm is R0. The pressure of the gas space is P0, the saturated vapor pressure of the water-based coolant in a state where the maximum temperature of the surface of the housing is reached, p ′, and from the rotating shaft to the circulation path including the housing as a part thereof R1 is the minimum distance, R2 is the minimum distance from the rotating shaft to the inlet of the aqueous coolant of the circulation pump, ρ is the density of the aqueous coolant, and ω is the angular velocity of the rotating base. Then
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
In the control method of the X-ray computed tomography apparatus,
The X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant, and performs imaging.
After the imaging, the X-ray emission from the X-ray tube unit is stopped, and the rotating gantry is kept until the temperature of the water-based coolant flowing inside the X-ray tube unit falls below a predetermined allowable upper limit temperature. The cooling is performed while maintaining the rotation of the water-based coolant and the circulation of the aqueous coolant.
It is characterized by that.

In addition, a method for controlling the X-ray computed tomography apparatus according to an embodiment is as follows:
An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit, an aqueous coolant to which at least a part of heat generated by the X-ray tube is transmitted, a conduit connected to the housing and through which the aqueous coolant flows, and the conduit A circulating pump that circulates the aqueous coolant and circulates the aqueous coolant together with the X-ray tube unit and the conduit; and is attached to the circulation path and passes the aqueous coolant to the circulation path A bellows mechanism that has an elastic diaphragm that separates from the gas space separated from the gas space, and absorbs a volume change of the aqueous coolant, and rotates about a rotation axis, and the X-ray tube unit, conduit, and circulation A rotary gantry to which a pump and a bellows mechanism are attached; a drive unit that rotates the rotary gantry; and a rotary shaft that is located on the opposite side of the X-ray tube unit with respect to the rotary shaft, and is attached to the rotary gantry, An X-ray detector for detecting the temperature, a temperature detector for detecting the temperature of the aqueous coolant flowing inside the X-ray tube unit, and a gas pressure communicating with the gas space and capable of adjusting a gas pressure in the gas space And a saturation of the aqueous coolant in a state where the average value of the distance from the rotating shaft to the elastic diaphragm is R0, the pressure of the gas space is P0, and the maximum temperature of the surface of the housing is reached. The vapor pressure is p ′, the minimum value of the distance from the rotation axis to the circulation path including the housing as a part thereof is R1, and the distance from the rotation axis to the inlet of the aqueous coolant of the circulation pump minimum value Is R2, the density of the aqueous coolant is ρ, and the angular velocity of the rotating mount is ω,
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
In the control method of the X-ray computed tomography apparatus,
The X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant, and performs imaging.
After the imaging mode, the emission of X-rays from the X-ray tube unit is stopped, and the gas space is kept until the temperature of the aqueous coolant flowing through the X-ray tube unit falls below a predetermined allowable upper limit temperature. The gas is adjusted to a positive pressure to maintain the circulation of the water-based coolant, and the rotation of the rotating gantry is stopped for cooling.
It is characterized by that.

FIG. 1 is a perspective view showing an appearance of a gantry of the X-ray CT apparatus according to the first embodiment. 2 is a cross-sectional view showing the X-ray CT apparatus taken along line II-II in FIG. FIG. 3 is a front view showing the rotating gantry shown in FIG. 2 and the X-ray tube unit, the cooling unit, and the X-ray detector mounted on the rotating gantry. FIG. 4 is a schematic configuration diagram showing the X-ray tube unit and the cooling unit according to the first embodiment. FIG. 5 is a cross-sectional view showing the X-ray tube unit of Example 1 of the X-ray CT apparatus according to the first embodiment. FIG. 6 is a cross-sectional view showing an X-ray tube unit of Example 2 of the X-ray CT apparatus according to the first embodiment. FIG. 7 is another cross-sectional view showing the X-ray tube unit shown in FIG. FIG. 8 is an enlarged cross-sectional view of a part of the X-ray tube unit shown in FIGS. 6 and 7. FIG. 9 is a table showing data of changes in saturated vapor pressure with respect to the temperature of water 100% and the temperature of PG 50% aqueous solution. FIG. 10 is a graph showing the data shown in FIG. FIG. 11 is a graph showing the relationship between the distance R0 and the distance R1 so that the pressure P0 = atmospheric pressure. FIG. 12 is a graph showing the relationship between the distance R0 and the distance R1 so that the pressure P0 = 0.5 atm. FIG. 13 is a front view showing the rotating gantry of the X-ray CT apparatus according to the second embodiment, and the X-ray tube unit, the cooling unit, and the X-ray detector mounted on the rotating gantry. FIG. 14 is a schematic configuration diagram showing an X-ray tube unit and a cooling unit according to the second embodiment. FIG. 15 is a schematic configuration diagram showing a separated state of the X-ray tube unit shown in FIG. FIG. 16 is a schematic configuration diagram showing a separated state of the cooling unit shown in FIG. FIG. 17 is a front view showing a rotating gantry of an X-ray CT apparatus according to the third embodiment, and an X-ray tube unit, a cooling unit, and an X-ray detector mounted on the rotating gantry. FIG. 18 is a front view showing the rotating gantry of the X-ray CT apparatus according to the fourth embodiment, and the X-ray tube unit, the cooling unit, and the X-ray detector mounted on the rotating gantry. FIG. 19 is a diagram showing a modification of the X-ray CT apparatus, and is a schematic configuration diagram showing an X-ray tube unit and a cooling unit. FIG. 20 is a schematic configuration diagram showing a separated state of the X-ray tube unit shown in FIG. FIG. 21 is a schematic configuration diagram showing a separated state of the cooling unit shown in FIG. FIG. 22 is a schematic cross-sectional view showing a modification of the X-ray tube shown in FIGS. 4, 14, and 19. FIG. 23 is a schematic cross-sectional view showing another modification of the X-ray tube shown in FIGS. 4, 14, and 19. FIG. 24 is a schematic sectional view showing another modification of the X-ray tube shown in FIGS. 4, 14, and 19. FIG. 25 is a diagram showing another modification of the X-ray CT apparatus, and is a schematic configuration diagram showing an air basin, a pressure detector, a pressure control device, and a pressure adjustment mechanism.

  Hereinafter, an X-ray computed tomography apparatus according to the first embodiment and a control method thereof will be described in detail with reference to the drawings. The X-ray computed tomography apparatus is an X-ray CT apparatus (computed tomography system).

  FIG. 1 is a perspective view showing an appearance of a gantry of the X-ray CT apparatus according to the first embodiment. 2 is a cross-sectional view showing the X-ray CT apparatus taken along line II-II in FIG. FIG. 3 is a front view showing the rotating gantry shown in FIG. 2 and the X-ray tube unit, the cooling unit, and the X-ray detector mounted on the rotating gantry.

  As shown in FIGS. 1 to 3, the X-ray CT apparatus 1 includes a housing 2, a base part 4, a fixed base 5, a rotary base 6, a bearing member 8, an X-ray tube unit 10, a cooling unit 20, and an X-ray. A detector 40 is provided.

The housing | casing 2 accommodates many said members. The housing 2 decorates the external appearance of the X-ray CT apparatus 1. The housing 2 includes an exhaust port 2a, an intake port 2b, and an introduction port 2c.
The exhaust port 2 a is formed in the upper part of the housing 2. The exhaust port 2a is closed with a mesh-like cover 3 having excellent air permeability. Although not shown, the X-ray CT apparatus 1 further includes a fan unit provided in the housing 2 and facing the cover 3. Thereby, the air in the housing | casing 2 can be discharged | emitted outside the housing | casing 2 through the exhaust port 2a.

The air inlet 2 b is formed in the lower part of the housing 2. Here, the air inlet 2 b is formed in a gap between the housing 2 and the base portion 4. New air outside the housing 2 can be taken into the housing 2 through the air inlet 2b.
From the above, since the air inside the housing 2 can be replaced, an increase in the temperature of the air inside the housing 2 can be suppressed.
The inlet 2c is for introducing a subject. Although not shown, the X-ray CT apparatus 1 also includes a bed on which a subject is placed.

  The fixed mount 5 is fixed to the base portion 4. A bearing member (rolling bearing, ball / roll bearing, etc.) member 8 that functions as a bearing mechanism is provided between the fixed base 5 and the rotary base 6.

  The rotating gantry 6 is rotatably supported by the fixed gantry 5 via a bearing member 8. The rotating gantry 6 can rotate around the rotation axis a <b> 1 of the rotating gantry 6. The X-ray CT apparatus 1 includes a drive unit (not shown) for rotating the rotary mount 6. In this embodiment, in order to rotate the rotary mount 6 at a high speed, the X-ray CT apparatus employs, for example, a direct drive motor as the drive unit.

  The rotary mount 6 has a ring-shaped frame portion 7 located on the outermost periphery. An opening 7 a is formed in the frame portion 7. Here, the size and the number of the openings 7a correspond to the size and the number of fan units 25 described later.

  The X-ray tube unit 10, the cooling unit 20, and the X-ray detector 40 are attached to the rotating mount 6. The X-ray tube unit 10 and the cooling unit 20 are attached to the inner wall of the frame portion 7. Although not shown, a high voltage generating power source or the like may be attached to the inner wall of the frame portion 7.

  Since the X-ray tube unit 10 and the cooling unit 20 are relatively compact, the mass is large and the pressure on the installation surface is high. By attaching these to the inner wall of the frame portion 7, even when the rotating gantry 6 rotates at a high speed and as a result a great centrifugal force is applied to the X-ray tube unit 10 and the cooling unit 20, these are applied to the frame portion 7. It can maintain strong adhesion.

  The X-ray tube unit 10 emits X-rays. The X-ray detector 40 faces the X-ray tube unit 10 (X-ray tube) across the rotation axis a1. The X-ray detector 40 has a plurality of X-ray detection elements arranged in an arc shape, for example. The X-ray CT apparatus may be provided with a plurality of X-ray detectors 40 and arranged. The X-ray detector 40 detects X-rays emitted from the X-ray tube unit 10 and transmitted through the subject, and converts the detected X-rays into electrical signals.

  Although not shown, the X-ray CT apparatus 1 may further include a data collection device that is attached to the rotary base 6 and that amplifies an electrical signal output from the X-ray detector 40 and performs AD conversion. Further, although not shown, the fixed base 5 may be provided with a device for supplying electric power or a control signal to the X-ray tube unit 10 and the cooling unit 20. The apparatus can supply electric power or a control signal to the X-ray tube unit 10 and the cooling unit 20 attached to the rotary mount 6 via a slip ring.

  FIG. 4 is a schematic configuration diagram showing the X-ray tube unit 10 and the cooling unit 20. In FIG. 4, the connection relationship between the X-ray tube unit 10 and the cooling unit 20 is highlighted, and the relative positional relationship between the X-ray tube unit 10 and the cooling unit 20 is shown in detail as shown in FIG. It is not a thing.

  As shown in FIGS. 3 and 4, the X-ray tube unit 10 includes a housing 12 and an X-ray tube 13 accommodated in the housing 12. The housing 12 (X-ray tube unit 10) is independently and directly attached to and secured to the rotary mount 6. Here, the housing 12 is directly attached to the inner wall of the frame portion 7.

  The X-ray tube 13 includes a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target. Here, the X-ray CT apparatus 1 has an aqueous coolant 9. At least a part of the heat generated by the X-ray tube 13 is transmitted to the aqueous coolant 9.

  The X-ray tube unit 10 has a conduit 11a and a conduit 11b. The conduit 11 a is airtightly attached to the aqueous coolant intake 12 i of the housing 12, one end is airtightly connected to the X-ray tube 13, and the other end is airtightly attached to the socket 72. One end of the conduit 11 b is airtightly attached to the aqueous coolant discharge port 12 o of the housing 12, and the other end is airtightly attached to the plug 82. The conduit 11a, the conduit 11b, the X-ray tube 13 and the housing 12 form a part of a circulation path 30 through which the aqueous coolant 9 circulates.

  In this embodiment, the heat transfer surface 1 s is located inside the X-ray tube 13, and the aqueous coolant 9 is accommodated in the housing 12. The conduit 11a and the X-ray tube 13 may be indirectly connected via a joint. Thereby, the aqueous coolant 9 circulates through the heat transfer surface 1 s inside the X-ray tube 13. Since the heat transfer surface 1s can transfer heat (boiling heat) generated by the collision of electrons to the anode target to the aqueous coolant 9, it suppresses overheating of the X-ray tube 13, particularly the anode target. be able to.

  The X-ray tube unit 10 further includes an air basin 60 as a bellows mechanism. The air basin 60 is attached to the circulation path 30. In this embodiment, the air basin 60 is attached to the outer surface of the housing 12 and is indirectly attached to the rotating mount 6.

  The air basin 60 has a case 61 having an opening 61a. The opening 61a is in airtight communication with the housing 12 through the conduit 12a. The air basin 60 has a bellows 62 as an elastic diaphragm separating the inside of the case 61 into a first space 63 and a second space 64 connected to the opening 61a. The case 61 is formed with a vent hole 65 connected to the second space 64. Since the vent hole 65 allows air to enter and exit, the second space 64 is open to the atmosphere. The bellows 62 is liquid-tightly attached to the case 61. For this reason, the bellows 62 can separate the aqueous coolant 9 from the gas space (second space 64) that is out of the circulation path 30.

  The bellows 62 is telescopic. Here, the bellows 62 is formed of rubber. The bellows 62 is preferably formed of a material that is impermeable to gas. The air basin 60 can absorb the volume change (expansion and contraction of the volume) due to the temperature change of the aqueous coolant 9.

  The X-ray tube unit 10 further includes a first temperature detector 16 and a second temperature detector 17. The first temperature detector 16 detects the temperature of the aqueous coolant 9 upstream of the heat transfer surface 1s. The second temperature detector 17 detects the temperature of the aqueous coolant 9 on the downstream side of the heat transfer surface 1s. In addition, the X-ray tube unit 10 should just be provided with the 2nd temperature detector 17 at least, and can detect the maximum value of the temperature of the water-system coolant 9 by this.

  The cooling unit 20 includes a conduit 21 a, a conduit 21 b, a conduit 21 c, a circulation pump 22 and a heat exchanger 23. One end of the conduit 21 a is airtightly attached to the socket 81. One end of the conduit 21c is airtightly attached to the plug 71.

  The circulation pump 22 is independently and directly attached and fixed to the inner wall of the frame portion 7. Here, the circulation pump 22 is directly attached to the inner wall of the frame portion 7. The circulation pump 22 is airtightly attached between the conduit 21a and the conduit 21b. The circulation pump 22 discharges the aqueous coolant 9 to the conduit 21b and takes in the aqueous coolant 9 from the conduit 21a. The circulation pump 22 can circulate the aqueous coolant 9 in the circulation path 30.

The heat exchanger 23 includes a radiator 24, a fan unit 25, and a duct 26.
The radiator 24 includes a conduit 21b and a plurality of heat radiating pipes (not shown) through which the aqueous coolant 9 is connected, and a plurality of heat radiating fins (not shown) attached to the heat radiating pipes. The radiator 24 can release the heat of the aqueous coolant 9 to the outside.

  The fan units 25 are positioned to face the opening 7a and the radiator 24, respectively. The distance from the rotation axis a1 to the fan unit 25 is longer than the distance from the rotation axis a1 to the radiator 24. The fan unit 25 can create an air flow around the radiator 24. The fan unit 25 can discharge the air flowing around the radiator 24 to the outside of the rotary mount 6 (frame portion 7) through the opening 7a.

The conduit 21a, the conduit 21b, the conduit 21c, the circulation pump 22 and the radiator 24 form a part of the circulation path 30.
From the above, the heat exchanger 23 can release the heat of the aqueous coolant 9 to the outside. In addition, since the air flowing around the radiator 24 can be discharged to the outside of the rotating gantry 6, an increase in the temperature of the air inside the rotating gantry 6 can be suppressed.

  The duct 26 is located between the radiator 24 and the fan unit 25. The duct 26 surrounds the peripheral edge of the radiator 24 and the peripheral edge of the fan unit 25. The duct 26 can guide the air flow around the radiator 24 to the fan unit 25. Since the heated air around the radiator 24 can be efficiently guided to the fan unit 25, the temperature of the air inside the rotating mount 6 (the region surrounded by the rotating mount 6 and the housing 2) is further increased. Can be suppressed. Thereby, the cooling performance of the heat exchanger 23 and the stability of the sensitivity of the X-ray detector 40 can be maintained in a high state.

  The cooling unit 20 further includes a housing 50 attached to the rotary mount 6. The housing 50 is attached and fixed to the inner wall of the frame portion 7. The housing 50 is made of sheet metal, for example. The housing 50 is designed to have a mechanical strength that can withstand the centrifugal force applied with the rotation of the rotary mount 6.

  The radiator 24, the fan unit 25, and the duct 26 are housed in a housing 50 and unitized. The housing 50 is formed so as to open so as to expose the radiator 24 and the fan unit 25 to the outside.

  The radiator 24, the fan unit 25, and the duct 26 are directly or indirectly attached to and fixed to the rotary mount 6. Here, the radiator 24, the fan unit 25, and the duct 26 are indirectly attached to the inner wall of the frame portion 7 via the housing 50.

  The plug 71 and the socket 72 form a coupler 70 as a detachable joint, and the socket 81 and the plug 82 form a coupler 80 as a detachable joint. The couplers 70 and 80 can be switched between a connected state (fixed state) in which the plug and the socket are connected and a separated state in which the plug and the socket are separated. The couplers 70 and 80 are connected in an airtight and liquid-tight manner in the connected state. The couplers 70 and 80 are couplers with a shut-off valve. In the separated state of the couplers 70 and 80, the plugs 71 and 82 and the sockets 72 and 81 can prevent leakage of the liquid (water-based coolant 9) to the outside and prevent air from being mixed inside. Has a structure that can. By switching the couplers 70 and 80 to the separated state, the two systems can be separated, and the X-ray tube unit 10 and the cooling unit 20 can be separated.

  Here, as an example of the X-ray tube unit 10 of the X-ray CT apparatus according to the first embodiment, the X-ray tube units of Example 1 and Example 2 will be described. First, the X-ray tube unit 10 of Example 1 will be described. FIG. 5 is a cross-sectional view illustrating the X-ray tube unit 10 according to the first embodiment.

  As shown in FIG. 5, the X-ray tube unit 10 is a rotary anode type X-ray tube unit, and the X-ray tube 13 is a rotary anode type X-ray tube. The X-ray tube unit 10 includes a stator coil 102 as a coil for generating a magnetic field in addition to the X-ray tube 13. Although not shown, the housing 12 (FIG. 4) houses the X-ray tube 13 and the stator coil 102.

  The X-ray tube 13 includes a fixed shaft 110 as a fixed body, a tube portion 130, an anode target 150, a rotating body 160, a liquid metal 170 as a lubricant, a cathode 180, and a vacuum envelope 190. I have. The X-ray tube 13 uses a dynamic pressure slide bearing.

  The fixed shaft 110 extends along the rotation axis a2, is formed in a cylindrical shape with the rotation axis a2 as a central axis, and one end thereof is closed. The fixed shaft 110 has a bearing surface 110 </ b> S on the side surface that is removed from the one end. The fixed shaft 110 is made of a material such as an Fe (iron) alloy or an Mo (molybdenum) alloy. The inside of the fixed shaft 110 is filled with the aqueous coolant 9. The fixed shaft 110 has a flow path through which the aqueous coolant 9 flows. The fixed shaft 110 has a discharge port 110b that discharges the aqueous coolant 9 to the outside on the other end side.

  The pipe part 130 is provided inside the fixed shaft 110 and forms a flow path together with the fixed shaft. One end portion of the tube portion 130 extends to the outside of the fixed shaft 110 through an opening 110 a formed at the other end portion of the fixed shaft 110. The tube part 130 is closely fixed to the opening part 110a.

  The pipe portion 130 has an intake port 130 a for taking in the aqueous coolant 9 therein, and a discharge port 130 b for discharging the aqueous coolant 9 into the fixed shaft 110. The intake 130 a is located outside the fixed shaft 110. The discharge port 130b is located at one end of the fixed shaft 110 with a gap.

  The intake port 130 a is directly connected to the conduit 11 a, and the discharge port 110 b is opened in the housing 12. When the X-ray tube unit 10 is configured as shown in FIG. 5, the intake port 130a may be indirectly connected to the conduit 11a via a joint. Alternatively, the intake port 130a may be opened in the housing 12, and the discharge port 110b may be connected to the conduit 11b directly or indirectly through a joint.

  From the above, the aqueous coolant 9 from the outside of the X-ray tube 13 is taken in from the intake port 130a, discharged through the inside of the tube portion 130 and into the fixed shaft 110, and between the fixed shaft 110 and the tube portion 130. And is discharged from the discharge port 110b to the outside of the X-ray tube 13.

  The anode target 150 includes an anode 151 and a target layer 152 provided on a part of the outer surface of the anode. The anode 151 is formed in a disk shape and is provided coaxially with the fixed shaft 110. The anode 151 is made of a material such as an Mo alloy. The anode 151 has a recess 151a in the direction along the rotation axis a2. The recess 151a is formed in a disc shape. One end of the fixed shaft 110 is fitted in the recess 151a. The recess 151 a is formed with a gap at one end of the fixed shaft 110. The target layer 152 is formed in a ring shape from a material such as a W (tungsten) alloy. The surface of the target layer 152 is an electron collision surface.

  The rotating body 160 is formed in a cylindrical shape having a diameter larger than that of the fixed shaft 110. The rotating body 160 is provided coaxially with the fixed shaft 110 and the anode target 150. The rotating body 160 is formed shorter than the fixed shaft 110.

  The rotating body 160 is made of a material such as Fe or Mo. More specifically, the rotating body 160 is provided at the cylindrical portion 161, an annular portion 162 formed integrally with the cylindrical portion so as to surround a side surface of one end portion of the cylindrical portion 161, and the other end portion of the cylindrical portion 161. A seal portion 163 and a tube portion 164 are provided.

  The cylindrical portion 161 surrounds the side surface of the fixed shaft 110. The cylindrical portion 161 has a bearing surface 160S facing the bearing surface 110S with a gap on the inner surface. One end portion of the rotating body 160, that is, one end portion of the cylindrical portion 161 and the ring portion 162 are joined to the anode target 150. The rotating body 160 is provided so as to be rotatable together with the anode target 150 around the fixed shaft 110.

  The seal portion 163 is located on the opposite side of the ring portion 162 (one end portion) with respect to the bearing surface 160S. The seal portion 163 is joined to the other end portion of the cylindrical portion 161. The seal portion 163 is formed in an annular shape, and is provided with a gap around the entire side surface of the fixed shaft 110. The tube portion 164 is joined to the side surface of the tube portion 161 and is fixed to the tube portion 161. The cylinder part 164 is made of, for example, Cu (copper).

  The liquid metal 170 is filled in a gap between one end of the fixed shaft 110 and the recess 151a, and a gap between the fixed shaft 110 (bearing surface 110S) and the cylindrical portion 161 (bearing surface 160S). These gaps are all connected. In this embodiment, the liquid metal 170 is a gallium / indium / tin alloy (GaInSn).

  In the direction orthogonal to the rotation axis a2, the clearance (clearance) between the seal portion 163 and the fixed shaft 110 is set to a value that can maintain the rotation of the rotating body 160 and suppress the leakage of the liquid metal 170. From the above, the gap is slight and is 500 μm or less. For this reason, the seal part 163 functions as a labyrinth seal ring.

  In addition, the seal portion 163 has a plurality of accommodating portions that are formed with the inner side recessed in a circular frame shape. In the unlikely event that the liquid metal 170 leaks from the gap, the storage portion stores the leaked liquid metal 170.

The cathode 180 is disposed to face the target layer 252 of the anode target 150 with a space therebetween. The cathode 180 has a filament 181 that emits electrons.
The vacuum envelope 190 contains the fixed shaft 110, the tube part 130, the anode target 150, the rotating body 160, the liquid metal 170 and the cathode 180. The vacuum envelope 190 has an X-ray transmission window 190a and an opening 190b. The X-ray transmission window 190a faces the target layer 152 in a direction orthogonal to the rotation axis a2. The other end of the fixed shaft 110 is exposed to the outside of the vacuum envelope 190 through the opening 190b. The opening 190b fixes the fixed shaft 110 closely.
The cathode 180 is attached to the inner wall of the vacuum envelope 190. The vacuum envelope 190 is sealed. The inside of the vacuum envelope 190 is maintained in a vacuum state.

  The stator coil 102 is provided so as to surround the outer side of the vacuum envelope 190 so as to face the side surface of the rotating body 160, more specifically, the side surface of the cylindrical portion 164. The shape of the stator coil 102 is annular.

Here, operation states of the X-ray tube 13 and the stator coil 102 will be described.
Since the stator coil 102 generates a magnetic field applied to the rotating body 160 (particularly the cylindrical portion 164), the rotating body rotates. Thereby, the anode target 150 also rotates. Further, a negative voltage (high voltage) is applied to the cathode 180, and the anode target 150 is set to the ground potential.

As a result, a potential difference is generated between the cathode 180 and the anode target 150. Therefore, when the cathode 180 emits electrons, the electrons are accelerated and collide with the target layer 152. That is, the cathode 180 irradiates the target layer 152 with an electron beam. Thereby, the target layer 152 emits X-rays when colliding with electrons, and the emitted X-rays are emitted to the outside of the vacuum envelope 190 and the X-ray emission port 12w of the housing 12 through the X-ray transmission window 190a. As a result, it is discharged outside the housing 12.
As described above, the X-ray tube unit 10 of the first embodiment is formed.

  Next, the X-ray tube unit 10 of Example 2 will be described. FIG. 6 is a cross-sectional view illustrating the X-ray tube unit according to the second embodiment. FIG. 7 is another cross-sectional view showing the X-ray tube unit shown in FIG. FIG. 8 is an enlarged cross-sectional view of a part of the X-ray tube unit shown in FIGS. 6 and 7.

  As shown in FIGS. 6 to 8, the X-ray tube unit 10 is a fixed anode type X-ray tube unit, and the X-ray tube 13 is a fixed anode type X-ray tube. The X-ray tube 13 includes a vacuum envelope 231. The vacuum envelope 231 includes a vacuum container 232 and an insulating member 250. In this embodiment, the insulating member 250 functions as a high voltage insulating member. A cathode 236 is attached to the insulating member 250, and the insulating member 250 forms a part of the vacuum envelope 231.

  The anode target 235 forms a part of the vacuum envelope 231. The anode target 235 is formed in a bowl shape that opens small outside the vacuum envelope 231 and swells in the vicinity of the target surface 235b. The anode target 235, the cathode 236, the focusing electrode 209, and the acceleration electrode 208 are accommodated in the vacuum envelope 231. A voltage supply wiring is connected to the anode target 235. The anode target 235 and the acceleration electrode 208 are set to the ground potential. The vacuum vessel 232 at a location facing the cathode 236 and the focusing electrode 209 is formed in a cylindrical shape. A negative high voltage is applied to the cathode 236. The adjusted negative high voltage is supplied to the focusing electrode 209. The inside of the vacuum envelope 231 is in a vacuum state. The metal surface portion 234 is provided inside the vacuum vessel 232 including the surface on the vacuum side of the X-ray transmission window 231w, and is set to the ground potential.

  The X-ray tube 13 includes a tube portion 241 and a ring portion 242. The pipe part 241 is made of metal. One end of the tube part 241 is inserted into the anode target 235. The ring portion 242 is provided in the anode target 235. The ring portion 242 is formed integrally with the tube portion 241 so as to surround the side surface of one end portion of the tube portion 241. The ring portion 242 is provided with a gap in the anode target 235. The other end of the pipe part 241 forms an aqueous coolant intake and is connected to the conduit 11a. An opening of the anode target 235 forms an aqueous coolant discharge port between the tube portion 241 and the opening. For this reason, the inside of the housing 12 is filled with the aqueous coolant 9. The housing 12 has an X-ray emission port 12w facing the X-ray transmission window 231w.

A deflection unit 270 is accommodated in the housing 12. The deflection unit 270 is a magnetic deflection unit, and is provided outside the vacuum vessel 232 at a position surrounding the electron beam trajectory. The deflecting unit 270 deflects the electron beam emitted from the cathode 236 and moves the focal position on the target surface 235b.
As described above, the X-ray tube unit of the second embodiment is formed.

  Next, the results of the investigation by the inventors of the present application on the change in the saturated vapor pressure with respect to the temperature of the aqueous coolant 9 will be described. As the aqueous coolant 9, generally known aqueous coolants such as pure water and those containing an antifreeze such as glycol water can be used.

  Here, a description will be given of the results of investigations on the case where a 100% water coolant is used as the aqueous coolant and the case where a PG 50% aqueous solution (propylene glycol 50%, water 50%) is used. The results of the investigation are shown in FIGS. Note that 100 kPa is approximately 1 atm (atmospheric pressure), 50 kPa is approximately 0.5 atm, and 200 kPa is approximately 2 atm.

  As shown in FIGS. 9 and 10, the saturated vapor pressure was 1.9192 kPa when the temperature of 100% water was 17 ° C. and the temperature of the PG 50% aqueous solution was 25 ° C. In other words, in an environment of 1.9192 kPa, it can be seen that 100% water reaches the boiling point at 17 ° C. and PG 50% aqueous solution reaches 25 ° C., respectively.

  The saturation vapor pressure was 6.2282 kPa when the temperature of 100% water was 37 ° C. and the temperature of the PG 50% aqueous solution was 45 ° C. The saturated vapor pressure was 17.202 kPa when the temperature of 100% water was 57 ° C and the temperature of the 50% aqueous PG solution was 65 ° C. The saturated vapor pressure was 41.647 kPa when the temperature of 100% water was 77 ° C and the temperature of the 50% aqueous PG solution was 85 ° C. The saturated vapor pressure was 62.139 kPa when the temperature of 100% water was 97 ° C and the temperature of the 50% aqueous PG solution was 105 ° C. The saturated vapor pressure was 128.74 kPa when the temperature of water 100% was 107 ° C. and the temperature of the PG 50% aqueous solution was 115 ° C. When the temperature of water 100% was 117 ° C. and the temperature of the PG 50% aqueous solution was 125 ° C., the saturated vapor pressure was 179.48 kPa.

  From the above, it can be seen that in an environment of 100 kPa, 100% water reaches a boiling point at 100 ° C., and an aqueous PG 50% solution reaches 108 ° C. In an environment of 200 kPa, it can be seen that 100% water reaches the boiling point at 120 ° C. and PG 50% aqueous solution reaches 128 ° C. It can be seen that in an environment of 50 kPa, 100% water reaches a boiling point at 82 ° C., and PG 50% aqueous solution reaches 90 ° C.

  Next, the configuration of the X-ray CT apparatus 1 for preventing the occurrence of cavitation (Trichelli's vacuum) in the circulation path 30 through which the aqueous coolant 9 flows will be described. In order to increase the cooling efficiency of the X-ray tube 13, the water-based coolant 9 is used instead of the insulating oil, and the rotation speed of the rotating mount 6 is set to 3 rps or more in order to shorten the scanning time (imaging time), the circulation path Cavitation is likely to occur within 30. However, as a result of investigations by the inventors of the present application, the rotation speed of the rotary mount 6 is set to 3 rps or more by using the water-based coolant 9 by specifying the positions of the circulation pump 22 and the air basin 60 as described below. Even in this case, the X-ray CT apparatus 1 capable of preventing the occurrence of the cavitation is obtained.

  As shown in FIGS. 3 and 4, here, the average value of the distance from the rotation axis a1 to the bellows 62 is R0. The pressure in the second space 64 (gas space) is P0. In this embodiment, since the second space 64 is open to the atmosphere, P0 = 1 atm.

  From the viewpoint of ensuring the safety (burn prevention) of the examinee, the examiner, or the service person, the surface temperature of the housing 12 must be 85 ° C. or less in the JIS standard and international standards. For this reason, it is necessary to limit the temperature so that the allowable maximum temperature on the surface of the housing 12 is 85 ° C. or less.

  Let p ′ be the saturated vapor pressure of the aqueous coolant 9 when the maximum temperature of the surface of the housing 12 has been reached. In this embodiment, the maximum allowable temperature of the surface of the housing 12 is set to a temperature between 85 ° C. and 75 ° C. (for example, 80 ° C.).

  The minimum value of the distance from the rotation axis a1 to the circulation path 30 excluding the air basin 60 including the housing 12 is defined as R1. Since the region corresponding to the minimum value R1 includes the housing 12, the temperature of the aqueous coolant 9 in this region is a value that is substantially close to the temperature on the surface side of the housing 12. In this embodiment, the region corresponding to the minimum value R1 is a region in the vicinity of the inner wall of the housing 12 located on the rotation axis a1 side.

The minimum value of the distance from the rotating shaft a1 to the inlet of the aqueous coolant 9 of the circulation pump 22 is R2. Let ρ be the density of the aqueous coolant 9. The angular velocity of the rotating gantry 6 is assumed to be ω. The minimum value of the distance from the rotation axis a1 to the heat transfer surface 1s is R3.

  The internal pressure component p due to the centrifugal force difference applied to the position of the bellows 62 (distance R0) is expressed by the following equation.

p = 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ²
(1) First, an area where cavitation is most likely to occur in the circulation path 30 (excluding the air basin 60) including the housing 12 as a part thereof is an area located closest to the rotation axis a1. For this reason, the pressure P0 (total internal pressure applied to the position of the bellows 62 (distance R0)), the internal pressure component p, and the saturated vapor pressure p ′ satisfy the following relationship, so that the bellows 62 of the air basin 60 is pushed out to the atmosphere side. (The bellows 62 can be prevented from expanding toward the second space 64), and the generation of a vacuum portion in the region in the circulation path 30 located closest to the rotation axis a1 can be prevented. It can be prevented.

P0> p + p ′
That is,
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ²
It is.

In this embodiment, since the region located closest to the rotation axis a1 includes the region near the X-ray transmission window 231w in the housing 12, the following effects can also be obtained.

-The possibility that the cooling of the X-ray transmission window 231w is impaired is avoided.
-X-ray intensity distribution can always emit uniform X-rays.

Here, FIG. 11 shows the results calculated by the inventors of the present invention regarding the relationship between the distance R0 and the distance R1 when the pressure of the air basin 60 is matched with the atmospheric pressure.
As shown in FIG. 11, cavitation does not occur if it is below the line graph. For example, when the distance R1 is 0.625 m, it can be seen that the distance R0 may be set to 0.748 m or less.

  Focusing on a specific example of the X-ray CT apparatus 1, the distance R1 is in the range of 0.55 m to 0.70 m. When the rotational speed of the rotating gantry 6 is 4 rps, if the height difference (R0-R1) is larger than about 12 cm, a vacuum portion is generated in the circulation path 30 (housing 12) at the position of the distance R1. When the rotational speed of the rotating gantry 6 becomes faster, the temperature of the aqueous coolant 9 becomes higher, or when the second space 64 is depressurized as described later, the above-mentioned height difference becomes smaller. For example, when the rotation speed of the rotating gantry 6 is 4 rps and the second space 64 is set to a negative pressure (depressurized to 0.5 atm), as shown in FIG. 1 cm or less. For this reason, special attention should be paid to the occurrence of cavitation when the second space 64 is decompressed.

  (2) Next, the region where cavitation is likely to occur is the inlet side of the aqueous coolant 9 of the circulation pump 22. In this region, the pressure decreases, and a negative pressure (negative pressure from atmospheric pressure) is likely to occur, so that cavitation is likely to occur. If cavitation occurs, the circulation pump 22 does not operate normally, and there is a risk that the flow rate will decrease or parts of the circulation pump 22 may be damaged. In order to prevent the occurrence of cavitation, it is effective to apply a pressure by the action of centrifugal force caused by the rotation of the rotating gantry 6.

  That is, satisfying the following relationship is a necessary condition for preventing the occurrence of cavitation in the circulation path 30 in a region where negative pressure (negative pressure than atmospheric pressure) is likely to occur.

R2> R0
(3) Further, a region where cavitation is likely to occur is a boiling heat transfer region. Since the temperature of the aqueous coolant 9 flowing in this region is high, cavitation is likely to occur. When cavitation occurs, the flow of the water-based coolant 9 is lowered, resulting in insufficient cooling, and the X-ray tube 13 may be damaged. In order to prevent the occurrence of cavitation, it is effective to apply a pressure by the action of centrifugal force caused by the rotation of the rotating gantry 6.

  That is, satisfying the following relationship is a necessary condition for preventing the generation of a vacuum portion in the region where the aqueous coolant 9 is likely to become high temperature in the circulation path 30.

R3> R0
Next, as a control method of the X-ray CT apparatus 1 configured as described above, an operation in the imaging mode and an operation in the cooling mode by the X-ray CT apparatus 1 will be described.
The X-ray CT apparatus 1 further includes a control unit (not shown). The control unit controls the drive unit, the circulation pump 22, the X-ray tube unit 10, and the X-ray detector 40, and the water-system cooling detected by the temperature detector (the first temperature detector 16 and the second temperature detector 17). Information on the temperature of the liquid 9 can be acquired. The control unit can be switched between a photographing mode and a cooling mode.

  When the control unit is switched to the imaging mode, the X-ray detector 40 can detect and capture the X-rays emitted from the X-ray tube 13 while rotating the rotating base 6 and circulating the aqueous coolant 9. .

  Specifically, when the photographing mode is entered (when the control unit switches to the photographing mode), the rotating gantry 6 rotates about the rotation axis a1. At this time, the X-ray tube unit 10, the cooling unit 20, the X-ray detector 40, and the like rotate integrally around the subject. The circulation pump 22 circulates the aqueous coolant 9 in the circulation path 30, and the X-ray tube unit 10 emits X-rays.

  X-rays pass through the subject and enter the X-ray detector 40, and the X-ray detector 40 detects the intensity of the X-rays. The detection signal detected by the X-ray detector 40 is amplified by the data acquisition device described above, converted into a digital detection signal by A / D conversion, and supplied to a computer (not shown).

  The computer calculates the X-ray absorption rate in the region of interest of the subject based on the digital detection signal, and constructs image data for generating a tomographic image of the subject from the calculation result. The image data is sent to a display device (not shown) and displayed as a tomographic image on the screen.

  As described above, in the X-ray CT apparatus 1, the X-ray tube unit 10 and the X-ray detector 40 rotate with the subject interposed therebetween, and so-called projections of X-ray intensity transmitted through all points in the examination section of the subject. Data is acquired from various angles, for example from a range of 360 °. Based on this projection data, a tomographic image is generated by a data reconstruction program programmed in advance.

  When the control unit switches to the cooling mode after the imaging mode, the control unit pauses the emission of X-rays from the X-ray tube unit 10 and the temperature of the aqueous coolant 9 flowing inside the X-ray tube unit 10 is a predetermined allowable upper limit. Cooling can be performed by maintaining the rotation of the rotating gantry 6 and the circulation of the aqueous coolant 9 until the temperature is lower than the temperature (for example, lower than the boiling point in the case of atmospheric pressure).

  That is, in the cooling mode, the point is that pressure is applied by the action of the centrifugal force due to the rotation of the rotating gantry 6, and the temperature of the aqueous coolant 9 after the X-ray exposure by the X-ray tube 13 is completed. As long as it is high, it is preferable to continue the rotation without stopping the rotation of the rotating gantry 6, thereby preventing the occurrence of cavitation.

  According to the X-ray CT apparatus 1 and the control method thereof according to the first embodiment configured as described above, the X-ray CT apparatus 1 includes an X-ray tube unit 10, an aqueous coolant 9, a conduit 11a, 11b, 21a, 21b, 21c, the circulation pump 22, the air basin 60 attached to the circulation path 30, the rotary mount 6, and the X-ray detector 40.

Since the water-based coolant 9 can be used for cooling the X-ray tube 13 instead of the insulating oil, the cooling efficiency of the X-ray tube 13 can be increased.
X-ray CT apparatus 1, because they meet the P0-p'> 0.5 · (R0 + R1) · (R0-R1) · ρ · ω 2 relationship circulation path 30 located closest to the rotation axis a1 Occurrence of cavitation in the inner region can be prevented.

Since the X-ray CT apparatus 1 satisfies the relationship of R2> R0, it is possible to prevent the occurrence of cavitation in a region where the negative pressure is likely to occur in the circulation path 30.
Since the X-ray CT apparatus 1 satisfies the relationship of R3> R0, it is possible to prevent the occurrence of cavitation in a region where the aqueous coolant 9 is likely to become high temperature.

  The control unit can switch from the photographing mode to the cooling mode. For this reason, even if the temperature of the aqueous coolant 9 is high after the end of the X-ray exposure by the X-ray tube 13, the occurrence of cavitation can be prevented.

  From the above, the X-ray CT apparatus 1 capable of cooling the X-ray tube 13 using the aqueous coolant 9 and preventing the occurrence of cavitation in the circulation path 30 of the aqueous coolant 9 and its A control method can be obtained.

  Further, the distance from the rotation axis a1 to the fan unit 25 is longer than the distance from the rotation axis a1 to the radiator 24. The fan unit 25 discharges the air flowing around the radiator 24 to the outside of the rotating mount 6 through the opening 7a.

  The radiator 24 is not attached in close contact with the frame portion 7. The size of the opening 7 a need not be substantially the same as the size of the radiator 24, and can be made smaller than the size of the radiator 24. For this reason, the fall of the mechanical strength of the frame part 7 can be suppressed. Since there is no need for reinforcement such as making the frame portion 7 wide or thick, the apparatus can be reduced in size and weight.

  As the usage time of the X-ray CT apparatus 1 elapses, dust accumulates in the gaps between the heat radiation pipes and the heat radiation fins of the radiator 24, so that air gradually becomes difficult to pass through the radiator 24, and the cooling performance of the heat exchanger 23 is improved. And the cooling rate of the X-ray tube also decreases.

  However, the radiator 24 is exposed in the space on the inner wall side of the frame portion 7. For this reason, the radiator 24 can be cleaned from the space on the inner wall side of the frame portion 7 only by removing a part of the housing 2, and dust accumulated on the radiator 24 can be removed. Since the radiator 24 can be cleaned without removing the cooling unit 20 from the rotating mount 6 and further removing the X-ray tube unit 10 connected to the cooling unit 20, it takes a cleaning (maintenance work). Time can be shortened.

By maintaining so that the function of the heat exchanger 23 does not deteriorate, overheating generated in the X-ray tube 13 can be reduced, so that the occurrence of frequent discharge in the X-ray tube 13 can be reduced. The shortening of the lifetime can be reduced.
From the above, it is possible to obtain the X-ray CT apparatus 1 that can prevent the mechanical strength from being lowered and can be cleaned without removing the radiator 24 from the rotary mount 6.

  Next, an X-ray CT apparatus according to the second embodiment will be described. In this embodiment, other configurations are the same as those of the first embodiment described above, and the same parts are denoted by the same reference numerals and detailed description thereof is omitted. FIG. 13 is a front view showing the rotating gantry 6 of the X-ray CT apparatus 1 according to the second embodiment, and the X-ray tube unit 10, the cooling unit 20 and the X-ray detector 40 mounted on the rotating gantry 6. .

  FIG. 14 is a schematic configuration diagram showing the X-ray tube unit 10 and the cooling unit 20. In FIG. 14, the connection relationship between the X-ray tube unit 10 and the cooling unit 20 is shown in an emphasized manner, and the relative positional relationship between the X-ray tube unit 10 and the cooling unit 20 is shown in detail as shown in FIG. It is not a thing.

  As shown in FIGS. 13 and 14, the cooling unit 20 does not include the casing 50. The cooling unit 20 includes a mount 27 and a mount 28. The mount 27 and the mount 28 are each formed in a rectangular frame shape. One end of the mount 27 is attached to the inner wall of the frame portion 7. The mount 27 surrounds the opening 7a. One side edge of the mount 28 is attached to the inner wall of the frame portion 7.

The circulation pump 22 is located in the mount 28, is attached to the mount 28, and is indirectly attached and fixed to the inner wall of the frame portion 7.
The air basin 60 is located between the mount 28 and the rotation axis a1, is mounted on the mount 28, and is indirectly attached and fixed to the inner wall of the frame portion 7.

  The radiator 24 has a peripheral edge attached to the other end of the mount 27 and is indirectly attached and fixed to the inner wall of the frame portion 7. Needless to say, the radiator 24 is exposed in the space on the inner wall side of the frame portion 7.

The fan unit 25 is directly attached to the frame portion 7. Here, the fan unit 25 is directly attached and fixed to the opening 7 a of the frame portion 7.
For this reason, the mount 27 is located between the radiator 24 and the fan unit 25, and also functions as a duct that guides the air flow around the radiator 24 to the fan unit 25.

The cooling unit 20 further includes a conduit 21d. One end of the conduit 21d is airtightly attached to the conduit 21a.
The air basin 60 is provided in the cooling unit 20. The opening 61a of the air basin 60 is in airtight communication with the conduit 21d.

  Also in this embodiment, the X-ray CT apparatus 1 satisfies the following relationship.

P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ²
R2> R0
R3> R0
The air basin 60, the housing 12, the radiator 24 and the circulation pump 22 connected so as to form the circulation path 30 can be separated into two systems by two detachable joints. For this reason, in the maintenance method of the X-ray CT apparatus 1, as shown below, after separating into the above two systems, another air basin is attached to the system not including the air basin 60 via a detachable joint. May be.

  That is, the X-ray tube unit 10 in the separated state is configured to hardly absorb the volume change of the aqueous coolant 9. Therefore, by forming the conduits 11a and 11b with rubber hoses, the conduits 11a and 11b can have a function of absorbing the volume change of the aqueous coolant 9. However, there are cases where the volume changes of the aqueous coolant 9 cannot be sufficiently absorbed by the conduits 11a and 11b alone. In this case, it is preferable to attach an air tray to the X-ray tube unit 10 in the separated state.

FIG. 15 is a schematic configuration diagram showing a separated state of the X-ray tube unit 10 shown in FIGS. 13 and 14.
As shown in FIG. 15, an air tray 90 as a bellows mechanism is attached to the X-ray tube unit 10. The air basin 90 is attached to the X-ray tube unit 10 through a socket 83 and a conduit 84 that are airtightly and liquidtightly connected to each other. The socket 83 and the plug 82 form a coupler as a detachable joint and are connected in an airtight and liquid-tight manner in the connected state.

  The air basin 90 has a case 91 having an opening 91a. The opening 91 a is in airtight communication with the conduit 84. The air basin 90 has a bellows 92 as an elastic diaphragm that divides the inside of the case 91 into a first region 93 and a second region 94 connected to the opening 91a. The case 91 has a vent hole 95 connected to the second region 94. Since the ventilation hole 95 allows air to enter and exit, the second region 94 is open to the atmosphere. In addition, the ventilation hole 95 does not need to be formed in the case 91. In this case, the second region 94 is a sealed space.

The bellows 92 is attached to the case 91 in a liquid-tight manner. The bellows 92 is telescopic. Here, the bellows 92 is made of rubber. The bellows 92 can absorb a volume change (expansion and contraction of the volume) due to a temperature change of the aqueous coolant 9. The bellows 92 is preferably formed of a material that is impermeable to gas.
Thereby, in the X-ray tube unit 10 in the separated state (after separation), leakage of the liquid (aqueous cooling liquid 9) to the outside can be prevented, and mixing of air into the inside can be prevented.

FIG. 16 is a schematic configuration diagram illustrating a separated state of the cooling unit 20 illustrated in FIGS. 13 and 14.
On the other hand, as shown in FIG. 16, the separated cooling unit 20 includes an air basin 60. For this reason, without adding to the cooling unit 20, leakage of the liquid (aqueous cooling liquid 9) to the outside in the separated cooling unit 20 can be prevented, and mixing of air into the inside can be prevented. .

  According to the X-ray CT apparatus 1 and the control method thereof according to the second embodiment configured as described above, the X-ray CT apparatus 1 and the control method thereof have the same effects as those of the first embodiment. be able to.

The X-ray CT apparatus 1 includes a mount 27. For this reason, the X-ray CT apparatus 1 can be formed without the housing 50 of the first embodiment, which is difficult to design mechanical strength.
The X-ray CT apparatus 1 includes a mount 28. Since the air basin 60 can be mounted on the mount 28, the cooling unit 20 can be designed compactly.
From the above, the X-ray CT apparatus 1 capable of cooling the X-ray tube 13 using the aqueous coolant 9 and preventing the occurrence of cavitation in the circulation path 30 of the aqueous coolant 9 and its A control method can be obtained.

  Next, an X-ray CT apparatus according to the third embodiment will be described. In this embodiment, other configurations are the same as those of the second embodiment described above, and the same parts are denoted by the same reference numerals and detailed description thereof is omitted. FIG. 17 is a front view showing the rotary base 6 of the X-ray CT apparatus 1 according to the third embodiment, and the X-ray tube unit 10, the cooling unit 20, and the X-ray detector 40 mounted on the rotary base 6. .

As shown in FIG. 17, the cooling unit 20 does not include the mounts 27 and 28. The cooling unit 20 includes a mount 29. The mount 29 is formed integrally with a rectangular frame-shaped peripheral wall portion, a plate-shaped ceiling wall portion, and a pair of plate-shaped side wall portions located between the peripheral wall portion and the ceiling wall portion. The peripheral wall portion of the mount 29 is attached to the inner wall of the frame portion 7. The peripheral wall of the mount 29 surrounds the opening 7a.
The circulation pump 22 and the air basin 60 are located between the mount 29 and the rotation axis a1, are placed on the ceiling wall portion of the mount 29, and are indirectly attached and fixed to the inner wall of the frame portion 7.

  The radiator 24 is attached to the peripheral wall portion of the mount 29 at the periphery, and is indirectly attached and fixed to the inner wall of the frame portion 7. In the space on the inner wall side of the frame portion 7, the pair of side wall portions of the mount 29 have a predetermined height so that the radiator 24 is exposed. In other words, the pair of side walls of the mount 29 has a predetermined height so that the radiator 24 can be cleaned from the space between the ceiling wall of the mount 29 and the radiator 24. In addition, since air is allowed to enter and leave in the space between the ceiling wall portion of the mount 29 and the radiator 24, the air passing through the space between the ceiling wall portion of the mount 29 and the radiator 24 passes through the radiator 24.

The fan unit 25 is directly attached to the frame portion 7. Here, the fan unit 25 is directly attached and fixed to the opening 7 a of the frame portion 7.
For this reason, the peripheral wall portion of the mount 29 is located between the radiator 24 and the fan unit 25, and also functions as a duct for guiding the air flow around the radiator 24 to the fan unit 25.

  According to the X-ray CT apparatus 1 and the control method thereof according to the third embodiment configured as described above, the X-ray CT apparatus 1 and the control method thereof have the same effects as those of the second embodiment. be able to.

The X-ray CT apparatus 1 includes a mount 29. For this reason, the X-ray CT apparatus 1 can be formed without the housing 50 of the first embodiment, which is difficult to design mechanical strength.
Since the circulation pump 22 and the air basin 60 can be mounted on the ceiling wall part of the mount 29, the cooling unit 20 can be designed compactly.

  Since the pair of side wall portions of the mount 29 have a predetermined height, the radiator 24 is exposed in the space on the inner wall side of the frame portion 7. The radiator 24 can be accessed from the space between the ceiling wall of the mount 29 and the radiator 24. For this reason, the radiator 24 can be cleaned from the space on the inner wall side of the frame portion 7 only by removing a part of the housing 2, and dust accumulated on the radiator 24 can be removed. Since the radiator 24 can be cleaned without removing the cooling unit 20 from the rotating mount 6 and further removing the X-ray tube unit 10 connected to the cooling unit 20, it takes a cleaning (maintenance work). Time can be shortened.

  From the above, the X-ray CT apparatus 1 capable of cooling the X-ray tube 13 using the aqueous coolant 9 and preventing the occurrence of cavitation in the circulation path 30 of the aqueous coolant 9 and its A control method can be obtained.

  Next, an X-ray CT apparatus according to the fourth embodiment will be described. In this embodiment, other configurations are the same as those of the second embodiment described above, and the same parts are denoted by the same reference numerals and detailed description thereof is omitted. FIG. 18 is a front view showing the rotary base 6 of the X-ray CT apparatus 1 according to the fourth embodiment, and the X-ray tube unit 10, the cooling unit 20, and the X-ray detector 40 mounted on the rotary base 6. .

As shown in FIG. 18, the cooling unit 20 does not include the mount 27. The cooling unit 20 further includes a mount 29.
The circulation pump 22 is located in the mount 28, is attached to the mount 28, and is indirectly attached and fixed to the inner wall of the frame portion 7.
The air basin 60 is located between the mount 28 and the rotation axis a1, is mounted on the mount 28, and is indirectly attached and fixed to the inner wall of the frame portion 7.

  The mount 29 is formed integrally with a rectangular frame-shaped peripheral wall portion, a plate-shaped ceiling wall portion, and a pair of plate-shaped side wall portions located between the peripheral wall portion and the ceiling wall portion. The peripheral wall portion of the mount 29 is attached to the inner wall of the frame portion 7. The peripheral wall of the mount 29 surrounds the opening 7a.

  The X-ray tube unit 10 (housing 12) is located between the mount 29 and the rotation axis a1, is placed on the ceiling wall portion of the mount 29, and is indirectly attached and fixed to the inner wall of the frame portion 7. .

  The radiator 24 is attached to the peripheral wall portion of the mount 29 at the periphery, and is indirectly attached and fixed to the inner wall of the frame portion 7. In the space on the inner wall side of the frame portion 7, the pair of side wall portions of the mount 29 have a predetermined height so that the radiator 24 is exposed. In other words, the pair of side walls of the mount 29 has a predetermined height so that the radiator 24 can be cleaned from the space between the ceiling wall of the mount 29 and the radiator 24. In addition, since air is allowed to enter and leave in the space between the ceiling wall portion of the mount 29 and the radiator 24, the air passing through the space between the ceiling wall portion of the mount 29 and the radiator 24 passes through the radiator 24.

The fan unit 25 is directly attached to the frame portion 7. Here, the fan unit 25 is directly attached and fixed to the opening 7 a of the frame portion 7.
For this reason, the peripheral wall portion of the mount 29 is located between the radiator 24 and the fan unit 25, and also functions as a duct for guiding the air flow around the radiator 24 to the fan unit 25.

  According to the X-ray CT apparatus 1 and the control method thereof according to the fourth embodiment configured as described above, the X-ray CT apparatus 1 and the control method thereof have the same effects as those of the second embodiment. be able to.

The upper X-ray CT apparatus 1 includes a mount 29. For this reason, the X-ray CT apparatus 1 can be formed without the housing 50 of the first embodiment, which is difficult to design mechanical strength.
Since the air basin 60 can be placed on the mount 28 and the X-ray tube unit 10 (housing 12) can be placed on the ceiling wall of the mount 29, the cooling unit 20 can be designed to be compact. Can do.

  From the above, the X-ray CT apparatus 1 capable of cooling the X-ray tube 13 using the aqueous coolant 9 and preventing the occurrence of cavitation in the circulation path 30 of the aqueous coolant 9 and its A control method can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

For example, the air basin 60 only needs to be attached to the circulation path 30, and may be provided separately from the cooling unit 20 as in the first embodiment.
As shown in FIG. 19, the air basin 60 may be provided in the X-ray tube unit 10.

The housing 61 and the opening 61a of the air basin 60 are in airtight communication with each other via a conduit 12a.

FIG. 20 is a schematic configuration diagram showing a separated state of the X-ray tube unit 10 shown in FIG.
As shown in FIG. 20, the X-ray tube unit 10 in the separated state includes an air basin 60. For this reason, without adding to the X-ray tube unit 10, leakage of the liquid (aqueous coolant 9) to the outside in the X-ray tube unit 10 in the separated state can be prevented, and mixing of air into the inside can be prevented. can do.

  The cooling unit 20 in the separated state is configured to hardly absorb the volume change of the aqueous coolant 9. Therefore, by forming the conduits 21a, 21b, and 21c with hoses, the conduits 21a, 21b, and 21c can have a function of absorbing the volume change of the aqueous coolant 9. However, there are cases where the volume changes of the aqueous coolant 9 cannot be sufficiently absorbed by the conduits 21a, 21b, and 21c alone. In this case, it is preferable to attach an air tray to the cooling unit 20 in the separated state.

FIG. 21 is a schematic configuration diagram showing a separated state of the cooling unit 20 shown in FIG.
As shown in FIG. 21, an air tray 90 as a bellows mechanism is attached to the cooling unit 20. The air basin 90 is attached to the cooling unit 20 via a plug 85 and a conduit 86 that are connected to each other in an airtight and liquid-tight manner. The socket 81 and the plug 85 form a coupler as a detachable joint, and are connected in an airtight and liquid-tight manner in the connected state. The opening 91 a is in airtight communication with the conduit 86.
As a result, leakage of the liquid (aqueous coolant 9) to the outside in the separated cooling unit 20 can be prevented, and air can be prevented from being mixed inside.

  As shown in FIG. 22, when the heat transfer surface 1 s is located inside the X-ray tube 13, the aqueous coolant 9 is accommodated in the housing 12. The conduit 11b and the X-ray tube 13 may be connected directly or indirectly through a joint. One end of the conduit 11 a is airtightly attached to the aqueous coolant intake 12 i of the housing 12.

  As shown in FIG. 23, when the heat transfer surface 1 s is located inside the X-ray tube 13, the aqueous coolant 9 is accommodated in the housing 12. And both the conduit | pipe 11a and the conduit | pipe 11b may be connected with the X-ray tube 13 directly or indirectly through the coupling. In this case, the aqueous coolant may be accommodated in the housing 12 or may not be accommodated conversely. The inside of the X-ray tube 13 forms a part of the circulation path 30 together with the conduit 11a and the conduit 11b. Thus, the aqueous coolant 9 circulates through the heat transfer surface 1s inside the X-ray tube 13, whereby the X-ray tube 13, particularly the anode target, can be cooled.

  As shown in FIG. 24, when the heat transfer surface 1 s is the outer surface of the X-ray tube 13, the aqueous coolant 9 is accommodated in the housing 12. The housing 12 forms a part of the circulation path 30 together with the conduit 11a and the conduit 11b. And the water-system coolant 9 circulates through the heat transfer surface 1s of the X-ray tube 13, whereby the X-ray tube 13, particularly an anode target described later, can be cooled.

  As shown in FIG. 25, the X-ray CT apparatus 1 may further include a pressure detector 301, a pressure control device 302 that is a part of the above-described control unit, a pressure adjustment mechanism 303, and a conduit 304. The pressure detector 301 (pressure sensor) is airtightly attached to the case 61. The pressure detector 301 detects the pressure (gas pressure) in the second space 64. The pressure detector 301 transmits information on the detected pressure to the pressure control device 302. The pressure control device 302 controls the driving of the pressure adjustment mechanism 303 based on the pressure information.

  The pressure adjustment mechanism 303 is in airtight communication with the vent hole 65 via a conduit 304. In this example, it goes without saying that the second space 64 is not opened to the atmosphere. The pressure adjustment mechanism 303 can adjust the gas pressure in the second space 64.

  When the pressure adjusting mechanism 303 functions as a pressurizing mechanism, the gas pressure in the second space 64 can be adjusted to a positive pressure that is higher than the atmospheric pressure. When the pressure adjustment mechanism 303 functions as a pressure reduction mechanism, the gas pressure in the second space 64 can be adjusted to a negative pressure.

  Next, as a method for controlling the X-ray CT apparatus 1 configured as shown in FIG. 25, the operation in the cooling mode by the X-ray CT apparatus 1 will be described. The control unit (pressure control device 302) further controls the pressure adjustment mechanism 303.

  When the control unit switches to the cooling mode after the imaging mode, the control unit stops the emission of X-rays from the X-ray tube unit 10 and the temperature of the aqueous coolant 9 is equal to or lower than a predetermined allowable upper limit temperature (for example, in the case of atmospheric pressure). The pressure of the gas in the second space 64 is adjusted to a positive pressure and the rotation of the rotating gantry 6 can be stopped and cooled while the circulation of the aqueous coolant 9 is maintained until the boiling point is below the boiling point).

  That is, in the cooling mode, after the X-ray exposure by the X-ray tube 13 is finished, the gas pressure in the second space 64 is adjusted to a positive pressure while the temperature of the aqueous coolant 9 is high, so Even without maintaining the rotation, it is possible to avoid the occurrence of burnout in a region near the heat transfer surface 1s.

  In addition, in a state where the temperature of the aqueous coolant 9 is sufficiently low, such as an initial state immediately after the operation of the X-ray tube unit 10 is started, the pressure adjusting mechanism 303 increases the pressure of the second space 64 in order to increase the heat flow rate. Is adjusted to a negative pressure to lower the boiling point of the aqueous coolant 9. Since boiling heat transfer is possible even when the temperature of the aqueous coolant 9 is low, it is possible to increase the heat transfer amount while keeping the temperature of the heat generating part of the X-ray tube 13 low.

  When the operation of the X-ray tube unit 10 continues and the temperature of the heat transfer surface of the X-ray tube 13 rises, the temperature of the aqueous coolant 9 also rises. Therefore, as the temperature of the aqueous coolant 9 increases, the pressure adjustment mechanism 303 adjusts the pressure of the second space 64 to atmospheric pressure, increases the boiling point of the aqueous coolant 9, and further increases the pressure of the second space 64. Is adjusted to a positive pressure to further increase the boiling point of the aqueous coolant 9. Thereby, the boiling heat released from the heat transfer surface 1 s of the X-ray tube 13 can be transmitted to the aqueous coolant 9. Since a sufficient heat flow rate can be obtained while avoiding the occurrence of burnout, continuous input with a constant X-ray tube input power can be made possible.

  The aqueous coolant 9 is preferably degassed in advance. Otherwise, the dissolved gas is generated as bubbles as the temperature of the aqueous coolant 9 rises during use, or cavitation is likely to occur.

The air basin 60 may be directly or indirectly attached to the rotating mount 6 independently of the housing 12 and the circulation pump 22.
The housing 12, the circulation pump 22, and the air basin 60 may be independently and directly or indirectly attached to the rotating mount 6.
The circulation pump 22, the radiator 24, and the fan unit 25 may be housed in a housing and unitized.

  The X-ray tube unit 10 (housing 12), the circulation pump 22, the radiator 24, the fan unit 25, and the air basin 60 may be directly or indirectly attached to the rotating mount 6 independently of each other.

  The radiator 24 has a flat plate shape and is disposed substantially parallel to the inner wall of the frame portion 7, but can be variously modified. The radiator 24 may have an arbitrary shape, may be stacked, and may be disposed to be inclined with respect to the inner wall of the frame portion 7.

  When the rotational speed of the rotating gantry 6 exceeds 3 rps, the fan unit 25 is directly attached to the opening 7a of the rotating gantry 6 as shown in the second to fourth embodiments to secure mechanical strength. It is preferable that the radiator 24, the air basin 60, and the circulation pump 22 are also attached to dedicated mounts fixed to the rotary mount 6. As a modification of the second to fourth embodiments, at least one of the circulation pump 22 and the duct 26 is housed in a single casing together with the radiator 24, and the casing is mounted on the rotary base 6 and the fan unit. It can also be mounted so that it is located directly above.

  It should be noted that a mesh-like cover or filter (hereinafter referred to as a filter) that has good air permeability to the extent that the cooling performance of the radiator 24 is not adversely affected is detachably installed on the exposed surface of the radiator 24 on the rotating shaft side. Thus, large dust can be removed. Cleaning or replacement of these filters and the like can be performed in a shorter time than cleaning of the radiator 24. By frequently performing cleaning or replacement of the filter or the like, it is possible to reduce the frequency of cleaning of the radiator 24.

The pressure adjustment mechanism 303 may be formed so that the pressure of the gas in the second space 64 can be adjusted to atmospheric pressure or positive pressure. The pressure adjustment mechanism 303 may be formed so that the gas pressure in the second space 64 can be adjusted to atmospheric pressure or negative pressure.
As the circulation pump 22, a centrifugal pump or a gear pump can be used.

  The present invention is not limited to the X-ray CT apparatus described above, and can be applied to various X-ray CT apparatuses.

  DESCRIPTION OF SYMBOLS 1 ... X-ray CT apparatus, 1s ... Heat transfer surface, 2 ... Housing, 5 ... Fixed mount, 6 ... Rotating mount, 9 ... Coolant, 10 ... X-ray tube unit, 11a, 11b, 12a, 21a, 21b, 21c, 21d ... conduit, 12 ... housing, 12w ... X-ray emission port, 13 ... X-ray tube, 16 ... first temperature detector, 17 ... second temperature detector, 20 ... cooling unit, 22 ... circulation pump, 23 ... heat exchanger, 24 ... radiator, 25 ... fan unit, 26 ... duct, 27, 28, 29 ... mount, 30 ... circulation path, 40 ... X-ray detector, 50 ... housing, 60, 90 ... air tray, 150, 235 ... anode target, 180, 236 ... cathode, 190, 231 ... vacuum envelope, 301 ... pressure detector, 302 ... pressure control device, 303 ... pressure adjusting mechanism, a1, a2 ... rotating shaft, R0, R1 , R2, R3 ... Distance from the rotation axis , [Rho ... density of the cooling liquid, omega ... angular velocity, p ... pressure component, P0 ... pressure, p'... saturated vapor pressure.

Claims (16)

An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit having
An aqueous coolant to which at least part of the heat generated by the X-ray tube is transmitted;
A conduit connected to the housing and through which the aqueous coolant flows;
A circulation pump attached to the conduit for circulating the aqueous coolant and forming a circulation path for circulating the aqueous coolant with the X-ray tube unit and the conduit;
A bellows mechanism attached to the circulation path, having an elastic diaphragm separating the aqueous coolant from a gas space outside the circulation path, and absorbing a volume change of the aqueous coolant;
A rotating gantry that rotates about a rotating shaft and has the X-ray tube unit, conduit, circulation pump, and bellows mechanism attached thereto;
An X-ray detector that is located on the opposite side of the X-ray tube unit with respect to the rotation axis, is attached to the rotary mount, and detects the X-ray;
The average value of the distance from the rotation axis to the elastic diaphragm is R0,
The pressure of the gas space is P0,
P ′ represents a saturated vapor pressure of the aqueous coolant in a state where the maximum temperature of the surface of the housing has been reached.
The minimum value of the distance from the rotating shaft to the circulation path including the housing as a part thereof is R1,
The minimum value of the distance from the rotating shaft to the inlet of the aqueous coolant of the circulation pump is R2,
The density of the aqueous coolant is ρ,
When the angular velocity of the rotating mount is ω,
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
An X-ray computed tomography apparatus characterized by The X-ray tube unit further has a heat transfer surface that transfers heat generated by collision of electrons to the anode target to the water-based cooling liquid,
When the minimum value of the distance from the rotating shaft to the heat transfer surface is R3,
R3> R0
The X-ray computed tomography apparatus according to claim 1, wherein: The gas space is open to the atmosphere;
3. The X-ray computed tomography apparatus according to claim 1, wherein P0 = 1 atm. A radiator attached to the rotating mount, attached to the conduit to form a part of the circulation path, and releasing heat of the aqueous coolant to the outside;
4. The X-ray computed tomography apparatus according to claim 1, further comprising: a fan unit that is attached to the rotating mount and creates a flow of air around the radiator. 5. .   5. The X-ray computer according to claim 1, wherein the bellows mechanism is directly or indirectly attached to the rotating mount independently of the housing and the circulation pump. Tomography apparatus.   The X-ray computed tomography apparatus according to claim 5, wherein the housing, the circulation pump, and the bellows mechanism are independently or directly attached to the rotating mount.   The X-ray computed tomography apparatus according to any one of claims 1 to 4, wherein the bellows mechanism is attached to an outer surface of the housing. Further comprising a housing attached to the rotating mount,
The X-ray computed tomography apparatus according to claim 4, wherein the circulation pump, the radiator, and the fan unit are housed in the casing and unitized.   The X-ray computed tomography apparatus according to any one of claims 1 to 8, further comprising a temperature detector that detects a temperature of the water-based coolant flowing inside the X-ray tube unit.   The X-ray computed tomography apparatus according to claim 1, wherein the aqueous coolant is deaerated in advance. A drive unit for rotating the rotary mount;
A controller that controls the drive unit, the circulation pump, the X-ray tube unit, and the X-ray detector, and acquires information on the temperature of the aqueous coolant detected by the temperature detector;
The controller is
An imaging mode in which the X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant.
After the imaging mode, the emission of X-rays from the X-ray tube unit is suspended, and the rotation of the rotating gantry is continued until the temperature of the aqueous coolant flowing through the X-ray tube unit falls below a predetermined allowable upper limit temperature. A cooling mode for maintaining rotation and circulation of the aqueous coolant;
The X-ray computed tomography apparatus according to claim 9, wherein the X-ray computed tomography apparatus can be switched to A drive unit for rotating the rotary mount;
A pressure adjusting mechanism communicated with the gas space and capable of adjusting a gas pressure in the gas space;
A controller that controls the drive unit, the circulation pump, the X-ray tube unit, the X-ray detector, and the pressure adjustment mechanism, and acquires information on the temperature of the aqueous coolant detected by the temperature detector;
The controller is
An imaging mode in which the X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant.
After the imaging mode, the emission of X-rays from the X-ray tube unit is stopped, and the gas space is kept until the temperature of the aqueous coolant flowing through the X-ray tube unit falls below a predetermined allowable upper limit temperature. A cooling mode in which the rotation of the rotating gantry is stopped in a state where the pressure of the gas is adjusted to a positive pressure and the circulation of the aqueous coolant is maintained.
The X-ray computed tomography apparatus according to claim 9, wherein the X-ray computed tomography apparatus can be switched to   The X-ray computed tomography apparatus according to claim 11 or 12, wherein the predetermined allowable upper limit temperature is a boiling point of the aqueous coolant at atmospheric pressure. An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit, an aqueous coolant to which at least a part of heat generated by the X-ray tube is transmitted, a conduit connected to the housing and through which the aqueous coolant flows, and the conduit A circulating pump that circulates the aqueous coolant and circulates the aqueous coolant together with the X-ray tube unit and the conduit; and is attached to the circulation path and passes the aqueous coolant to the circulation path A bellows mechanism that has an elastic diaphragm that separates from the gas space separated from the gas space, and absorbs a volume change of the aqueous coolant, and rotates about a rotation axis, and the X-ray tube unit, conduit, and circulation A rotary gantry to which a pump and a bellows mechanism are attached; a drive unit that rotates the rotary gantry; and a rotary shaft that is located on the opposite side of the X-ray tube unit with respect to the rotary shaft, and is attached to the rotary gantry, An X-ray detector that detects the temperature of the water-based coolant flowing in the X-ray tube unit, and an average value of the distance from the rotating shaft to the elastic diaphragm is R0. The pressure of the gas space is P0, the saturated vapor pressure of the water-based coolant in a state where the maximum temperature of the surface of the housing is reached, p ′, and from the rotating shaft to the circulation path including the housing as a part thereof R1 is the minimum distance, R2 is the minimum distance from the rotating shaft to the inlet of the aqueous coolant of the circulation pump, ρ is the density of the aqueous coolant, and ω is the angular velocity of the rotating base. Then
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
In the control method of the X-ray computed tomography apparatus,
The X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant, and performs imaging.
After the imaging, the X-ray emission from the X-ray tube unit is stopped, and the rotating gantry is kept until the temperature of the water-based coolant flowing inside the X-ray tube unit falls below a predetermined allowable upper limit temperature. The cooling is performed while maintaining the rotation of the water-based coolant and the circulation of the aqueous coolant.
A control method for an X-ray computed tomography apparatus. An X-ray tube housed in the housing, comprising a housing, a cathode that emits electrons, an anode target that emits X-rays when the electrons collide, and a vacuum envelope that houses the cathode and anode target And an X-ray tube unit, an aqueous coolant to which at least a part of heat generated by the X-ray tube is transmitted, a conduit connected to the housing and through which the aqueous coolant flows, and the conduit A circulating pump that circulates the aqueous coolant and circulates the aqueous coolant together with the X-ray tube unit and the conduit; and is attached to the circulation path and passes the aqueous coolant to the circulation path A bellows mechanism that has an elastic diaphragm that separates from the gas space separated from the gas space, and absorbs a volume change of the aqueous coolant, and rotates about a rotation axis, and the X-ray tube unit, conduit, and circulation A rotary gantry to which a pump and a bellows mechanism are attached; a drive unit that rotates the rotary gantry; and a rotary shaft that is located on the opposite side of the X-ray tube unit with respect to the rotary shaft, and is attached to the rotary gantry, An X-ray detector for detecting the temperature, a temperature detector for detecting the temperature of the aqueous coolant flowing inside the X-ray tube unit, and a gas pressure communicating with the gas space and capable of adjusting a gas pressure in the gas space And a saturation of the aqueous coolant in a state where the average value of the distance from the rotating shaft to the elastic diaphragm is R0, the pressure of the gas space is P0, and the maximum temperature of the surface of the housing is reached. The vapor pressure is p ′, the minimum value of the distance from the rotation axis to the circulation path including the housing as a part thereof is R1, and the distance from the rotation axis to the inlet of the aqueous coolant of the circulation pump minimum value Is R2, the density of the aqueous coolant is ρ, and the angular velocity of the rotating mount is ω,
P0−p ′> 0.5 · (R0 + R1) · (R0−R1) · ρ · ω ² , and R2> R0
In the control method of the X-ray computed tomography apparatus,
The X-ray detector detects the X-rays emitted from the X-ray tube unit while rotating the rotating mount and circulating the aqueous coolant, and performs imaging.
After the imaging mode, the emission of X-rays from the X-ray tube unit is stopped, and the gas space is kept until the temperature of the aqueous coolant flowing through the X-ray tube unit falls below a predetermined allowable upper limit temperature. The gas is adjusted to a positive pressure to maintain the circulation of the water-based coolant, and the rotation of the rotating gantry is stopped for cooling.
A control method for an X-ray computed tomography apparatus.   The method of controlling an X-ray computed tomography apparatus according to claim 14 or 15, wherein the predetermined allowable upper limit temperature is a boiling point of the aqueous coolant at atmospheric pressure.

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