WO2017220116A1

WO2017220116A1 - Cooling device for ct scanner or radiotherapy devices

Info

Publication number: WO2017220116A1
Application number: PCT/EP2016/064197
Authority: WO
Inventors: Herbert Staffler; Horst Knobl
Original assignee: Schleifring Und Apparatebau Gmbh
Priority date: 2016-06-20
Filing date: 2016-06-20
Publication date: 2017-12-28

Abstract

A cooling device for a CT scanner or RT device comprises a rotating part and a stationary part, the rotating part being freely rotatable relative to the stationary part around an axis of rotation. The rotating part comprises a rotating body with at least one cooling liquid duct. The stationary part comprises a stationary body having at least one wall for containing a transfer liquid. The rotating body is in contact with the transfer liquid for transferring heat between the rotating body and the transfer liquid.

Description

Cooling Device for CT Scanner or Radiotherapy Devices

Field of the invention The invention relates to a device for cooling rotating apparatus. It specifically relates to a device for cooling the rotating gantries of CT scanners (computed tomography scanners) or RT devices (radiotherapy or radiation therapy devices).

Description of the related art In CT scanners, the rotating parts of the gantry, bearing an X-ray tube and a detector, have to be supplied with a large amount of electrical power, and therefore dissipate large amounts of heat. In modern CT scanners, the power supplied to the X-ray tube is in the range of above 10 kW to multiple 100s kW. A significant part of this power is dissipated as heat which must be removed from the rotating part of the gantry. Mainly for safety reasons, the gantry is enclosed by a housing which does not allow for a free air flow to cool the rotating part. Therefore, cooling means which may be integrated into the housing have to be provided.

RT devices are used for generating ionizing radiation, mainly for treating cancer. The radiation source may be rotatable to bring it into a desired position with respect to a patient. In contrast to a CT scanner, which may rotate with high speed, in an RT device positioning is in the foreground. Radiotherapy devices consume and dissipate much more electrical power than CT scanners. Therefore good cooling is even more important. US 2004/0228450 Al discloses a cooled gantry, where the housing forms an air duct, through which air is blown by large fans. The problem is the obstructed air flow, as it passes on one side of the rotating part in rotation direction and at the other side opposite to the rotation direction, causing high friction and low air throughput. At the same time, the high air flow causes significant noise.

US 5,709,156 Bl discloses a cooling unit heat exchangers. The rotating part comprises a plurality of heat exchange elements which are supplied by a cooling liquid and provide a radial flow of hot air, which is further guided through multiple stationary heat exchange elements, which are further cooled by a cooling liquid. The disadvantage is the complex structure and the radial air flow which also requires large air ducts.

DE 199 45 415 Al discloses a ring-shaped heat exchanger. At the rotating part of the gantry, there is a first ring-shaped section which is thermally connected by a cooling liquid to the X-ray tube. This rotating heat exchanger is in close proximity to a stationary heat exchanger which also has a circular shape and is cooled by a cooling liquid. To improve heat exchange, the surface between the rotary and the stationary heat exchanger is increased by a meander shape. As disclosed in this document in col. 5, lines 20 - 21, a thermal power of up to 30 kW can be transferred by this heat exchanger. This is not sufficient for modern CT scanners.

Summary of the invention

The problem to be solved by the invention is to provide a cooling device for rotating apparatus like CT scanners or RT devices which is comparatively compact and does not need large air ducts. It should be useable for large power dissipa- tion in the range of more than 50 kW, and it should avoid the significant noise generated by large fans. Furthermore, manufacturing and maintenance costs should be comparatively low.

Solutions of the problem are described in the independent claims. The dependent claims relate to further improvements of the invention. A first embodiment relates to a cooling device preferably for a CT scanner or RT device which is based on a heat transferring rotary joint. The cooling device has a rotating part and a stationary part which basically are freely rotatable against each other. In the following, the terms "rotating" and "stationary" are used to simplify the explanation. It is obvious, that rotating and stationary parts can easi- ly be exchanged. The rotating part comprises a rotating body having at least one cooling liquid duct or pipe. This cooling liquid duct preferably has a cooling liquid input and a cooling liquid output. By the input, the cooling liquid duct may be supplied with a cooling liquid having a first temperature, preferably a higher temperature, whereas the cooling liquid output is provided for delivery of a sec- ond temperature, preferably of a lower temperature. The cooling liquid input and output may be connected via pipes or tubes or other means to a heat source, like an X-ray tube in a CT scanner, a radiation source in an RT device and/or further components generating heat, like a power supply or others.

The stationary part preferably comprises a stationary body which preferably is enclosed by a stationary wall, forming a container for a transfer liquid. The primary body is held rotatably within/relative to the stationary body. The stationary body is at least partially filled with a transfer liquid, such that the transfer liquid is in contact with the rotating body to perform a heat exchange. The rotating body can freely rotate, while being in continuous contact with the transfer liquid. Therefore, it can continuously couple heat to the stationary body via the transfer liquid. To increase the heat transfer, it is preferred, if the rotating body has a surface structure for increasing the thermal transfer surface which may comprise fins or grooves to increase the surface, and therefore to increase thermal coupling. Preferably, the rotating body has a constant cross-section, most preferably including the surface structure to provide a low flow resistance through the transfer liquid. There may be minor discontinuities, edges or fins to cause addi- tional turbulence in the transfer liquid to further increase heat exchange. The stationary body preferably is connected to input and output pipes, by which the transfer liquid may be exchanged or at least forwarded to a cooler, which may be cooling device, a heat exchanger, or any other means for reducing the temperature of the transfer liquid. The cooler preferably removes warm or hot transfer liquid, preferably supported by a pump, from the stationary body and delivers cooled transfer liquid back to the stationary body.

There may be further means, like pumps at the rotating and/or stationary side to increase pressure and/or throughput of liquids through the primary body and/or secondary body. Furthermore, there may be devices for maintaining a certain pressure and/or liquid level, either at the primary and/or the secondary side. Such devices may be liquid reservoirs coupled to valves and/or pumps, which further may be coupled to an electronic and/or mechanic control system for maintaining a constant pressure and/or liquid level.

The secondary body forms at least a container for the transfer liquid which may be open at one side, preferably the top side. It may also completely enclose the primary body to avoid any leakage and spillage of the transfer liquid, even at high rotational speeds.

Generally, it is preferred, if the transfer liquid at the stationary part is continuously exchanged to keep a low transfer liquid temperature. In an alternate em- bodiment, there may be a heat exchanger or cooler at the stationary body to cool the transfer liquid. There may also be at least one pipe or duct guided through the transfer liquid or a heat exchanger in contact with or within the transfer liquid for cooling the transfer liquid.

Preferably, any of the liquids mentioned herein, like cooling liquids or transfer liquids, may comprise water, alcohol, oil, or any combination thereof. They may further comprise any other medium, which has a liquid-like characteristic and is suitable for transferring heat. Such a medium may be a gas, a liquid gas, or even a liquid metal. It is obvious that the solution explained herein, based on a preferred embodiment which relates to a CT scanner or RT device, is not limited to such CT scanners or RT devices. The general inventive concept is applicable to a large variety of rotating devices and apparatus which require heating and/or cooling. The invention is also not limited to cooling as described above, but it may also be used for heating a rotating device. Furthermore, it may be used for combined heating and cooling. For example before startup, the rotating part may be heated to a minimum operational temperature, whereas it will later be cooled to prevent overheating.

The embodiments described herein have a significantly smaller size compared to the prior art. No air ducts are required. Due to the liquid heat transfer medium between the rotating and the stationary part, a very low thermal resistance can be realized which allows to reduce the coupling surface and therefore the overall size of the device significantly, compared to the prior art as known for example from the DE 199 45 415 Al. Furthermore, the embodiments disclosed herein cause significantly less noise than the air cooling devices known from the prior art, as the high volume air stream through the prior art devices always generates noise from air flow and noise from the fans generating the air flow, which are no more required in the embodiments disclosed herein. Finally, the embodiments require less and simpler mechanical parts. For example, fans known from the prior art having a rotation axis radial to the main rotation axis of the CT scanner gantry have only a short life time due to the tilting forces on the bearings due to gyro effect.

Description of Drawings

In the following the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

Figure 1 shows a first embodiment in a front view and a sectional side view. Figure 2 shows a second embodiment.

Figure 3 shows another embodiment with a transfer liquid cooling pipe. Figure 4 shows a block diagram of a preferred embodiment. Figure 5 shows a CT scanner gantry.

In Figure 1, a first embodiment of a cooling device is shown in a front view (left image) and a side view (right image). The cooling device comprises a rotating part 100 and a stationary part 200. The rotating part preferably has an axis of rotation 310 around which it rotates freely within/relative to the stationary part. The rotating part 100 comprises a rotating body 110, having at least one cooling liquid duct 120, which may also be a larger cooling liquid duct. This cooling liquid duct may be connected via a first rotating pipe connector 131 and a second rotating pipe connector 132 to a first rotating pipe 141 and a second rotating pipe 142, for exchanging liquid within the cooling liquid duct. Accordingly, for example a hot cooling liquid may be fed via first rotating pipe connector 131 and first rotating pipe 141 into the cooling liquid duct 120 of the rotating body, and it may exit the cooling liquid duct 120 via second rotating pipe connector 132 and a second rotating pipe 142. The stationary part 200 comprises a stationary body 210 having at least one wall 211. Preferably, the wall comprises a liquid guide 212, which allows spillage of the liquid. The stationary body 210 encloses a transfer liquid 220, which is in contact with the rotating body 110 to provide heat exchange. Such a heat exchange may be improved by an increased surface of the rotating body 110, which for example may have a surface structure 121 for increasing the thermal transfer surface. The stationary body preferably has at least one first stationary pipe connector 231 which may be connected to a first stationary pipe 241, and at least one secondary stationary pipe connector 232 which may be connector to a sec- ondary stationary pipe 242. By this means, the liquid may be exchanged, or there may be at least a liquid flow through the stationary body to remove hot liquid and to feed cold liquid. Obviously, the stationary part may have any other means for exchanging the transfer liquid 220 therein.

In Figure 2, a second embodiment is shown. This is basically similar to the first embodiment. Here, the stationary body 210 does not fully enclose the primary body 110, as shown in Figure 1. Instead, it only provides a section which is sufficient to hold the transfer liquid. As the transfer liquid preferably flows to the bottom side of the stationary part due to gravity, it is only necessary to provide a section at the bottom side. The top side may be left open. This embodiment is at least useable for low rotational speeds. At higher rotational speeds, the liquid may be accelerated within the stationary body by the rotating body. Therefore, a full cover as shown in Figure 1 is appreciated for higher rotational speeds, whereas for lower rotational speeds, the second embodiment provides cost and weight benefits due to the use of less material. In Figure 3, a further embodiment is shown. In this embodiment, there is a transfer liquid cooling pipe or duct (250) within the transfer liquid, such that the transfer liquid may be cooled without exchanging the transfer liquid itself by means of a further cooling liquid which may be fed or guided through the transfer liquid cooling duct.

In Figure 4, a block diagram of a preferred embodiment is shown. On top of the Figure is the rotating component 591, whereas at the bottom, there is the sta- tionary component 592. Between the rotating and the stationary component, there is the cooling device having a rotating part 100 and a stationary part 200. The rotating part 100 is preferably connected via first rotating pipe 141 and second rotating pipe 142 to a heat source, like an X-ray tube 510. The X-ray tube 510 may be directly connected to the rotating part 100, although it is preferred to have a heat exchanger in-between. It is further preferred, if there is at least one pump for ensuring a liquid flow through the X-ray tube and the heat exchanger. There may be a further pump between the heat exchanger and the rotating part, which is not shown in-here. The X-ray tube 510 may have a cooling liquid output 511 which is connected to a heat exchanger primary input 531. Fur- thermore, the heat exchanger primary output 532 may be connected via a pump 520 to cooling liquid input 512 of X-ray tube 510, thus providing a closed system. The heat exchanger 530 couples heat from its primary side from primary input 531 and primary output 532 to its secondary side, connected to secondary output 534 and secondary input 533. A hot cooling liquid from the heat exchanger is input to rotating body via first rotating pipe 141, whereas the cooled liquid is fed back from the rotating part 100 via the second rotating pipe 142 to the secondary input 533 of heat exchanger 530, therefore providing a second closed liquid cooling circuit. At the stationary side, the stationary part of the cooling system preferably provides a liquid output to a first stationary pipe 241, which may be fed to a cooler 550 via cooler input 551. The cooler provides a cooled liquid output at its cooler output 552, which may be fed via second stationary pipe 242 back into the stationary part 200. It is preferred, if there is a pump 540 between the cooler 550 and the stationary part 200, preferably between the cooler output 552 and second stationary pipe 242 of stationary part 200. As the liquid level in the stationary part may change dependent of the rotating speed, it is preferred to have means for controlling or at least limiting the transfer liquid level to a certain amount or within certain limits. This may be done by having a reservoir 570, which may be connected via a control valve and/or pump 560 to the liquid circuit of the stationary part 200 where it may be connected to the first stationary pipe 241 or the second stationary pipe 242. There may be a further control circuit which may collect information via an electrical, electronic or mechanical level or pressure sensor for keeping the level constant.

Figure 5 shows schematically a CT (Computed Tomography) scanner gantry. The stationary part is suspended within a massive frame 810. The rotating part 809 of the gantry is rotatably mounted with respect to the stationary part and rotates along the rotation direction 808. It supports an X - ray tube 801 for generating an X-ray beam 802 that radiates through a patient 804 lying on a table 807 and which is intercepted by a detector 803. Electrical power from power supply unit 811 may be transmitted by a slipring (not shown) to the rotating part. The imaging data obtained by the detector 803 are transmitted via contactless rotary joint 800 to an evaluation unit 806 by means of a data bus or network 805.

List of reference numerals

100 rotating part

110 rotating body

120 cooling liquid duct

121 surface structure

131 first rotating pipe connector

132 second rotating pipe connector

141 first rotating pipe

142 second rotating pipe

200 stationary part

210 stationary body

211 wall

212 liquid guide

220 transfer liquid

231 first stationary pipe connector

232 second stationary pipe connector

241 first stationary pipe

242 second stationary pipe

250 transfer liquid cooling duct

310 axis of rotation

510 X-ray tube

511 cooling liquid output

512 cooling liquid input

520 pump

530 heat exchanger

531 heat exchanger input primary

532 heat exchanger output primary heat exchanger input secondary heat exchanger output secondary pump

cooler

cooler input

cooler output

control valve

reservoir

rotating component

stationary component contactless rotary joint x-ray tube

x-ray beam

x-ray detector

patient

network

evaluation unit

patient table

rotation direction

rotating part

frame

power supply unit

Claims

1. Cooling device (100, 200) for a rotating device like a CT scanner or RT device, comprising a rotating part (100) and a stationary part (200), the rotating part (100) being freely rotatable relative to the stationary part (200) around an axis of rotation (310),

the rotating part (100) comprising a rotating body (110) having at least one cooling liquid duct (120),

the stationary part (200) comprising a stationary body (210) having at least one wall (211) for containing a transfer liquid (220),

wherein the rotating body (110) is in contact with the transfer liquid (220) for transferring heat between the rotating body and the transfer liquid.

2. Cooling device according to claim 1,

characterized in that

a cooler (550) is connected to the stationary body (210) for removing warm or hot transfer liquid (220) from the stationary body (210), cooling the transfer liquid (220) and delivering cooled transfer liquid (220) to the stationary body (210).

3. Cooling device according to any of the preceding claims,

characterized in that

at least one transfer liquid cooling duct (250) or heat exchanger is provided at least partially within the transfer liquid for cooling the transfer liquid (220).

4. Cooling device according to any of the preceding claims,

characterized in that

the rotating body (110) has a circular outer contour.

5. Cooling device according to any of the preceding claims,

characterized in that

the rotating body (110) has a surface structure (121) for increasing the thermal transfer surface.

6. Cooling device according to any of the preceding claims,

characterized in that

the rotating body (110) has fins and/or discontinuities for generating turbulences in the transfer liquid (220).

7. Cooling device according to any of the preceding claims,

characterized in that

the stationary body (210) has a circular shape and encloses the rotating body (110).

8. Cooling device according to any of the preceding claims 1 to 6

characterized in that

the stationary body (210) comprises a circular section at the bottom of the device for holding the transfer liquid (220).

9. Cooling device according to any of the preceding claims,

characterized in that

the transfer liquid (220) comprises water, alcohol, oil, or any combination thereof.

10. Computer tomography scanner comprising a cooling device according to any of the previous claims,

wherein the cooling liquid duct (120) is connected to an X-ray tube and/or any other heat generating device.

11. Computer tomography scanner comprising a cooling device according to claim 10,

wherein at least one cooling liquid pump (520, 540) is connected to the rotating body (110) and/or the stationary body (210) for increasing liquid flow there-through.

12. Computer tomography scanner comprising a cooling device according to any of claims 10 to 11,

wherein at least one reservoir (570) and an optional control valve/pump (560) are coupled to the stationary part for maintaining a predetermined level of transfer liquid.