Feedback cooling system for an imaging system

Abstract

A cooling system for cooling components of an imaging system located in a scan room. The system includes an inlet passage, an outlet passage, and a return passage. A portion of outlet warm air from a component outlet flows in the return passage to provide recirculated warm air to a mixing zone in the inlet passage. A fan located in the inlet passage draws scan room air into the inlet passage to mix with the recirculated warm air in the mixing zone to form mixed air that flows over the components to cool the components, and wherein the mixed air absorbs heat that warms the mixed air to form the outlet warm air. A valve located in the return passage restricts or allows additional recirculated warm air to flow to the mixing zone to mix with the scan room air to maintain a desired control temperature of the cooling system.

Description

Technical Field

[0001] Aspects of the present invention relate to a cooling system for an imaging system, and more specifically, to a cooling system for cooling at least one component of an imaging system, wherein the cooling system uses a portion of warm air from the outlet of the component, the warm air being recirculated and mixed with scanning chamber air to provide air flowing at a high airflow rate over a narrow temperature range to cool the component. Background Technology

[0002] Many medical imaging systems, such as PET / CT imaging systems, are cooled by a cooling medium such as liquid, air, or a combination of both. For air-cooled imaging systems, it is desirable that the ambient air temperature in the scan room at the customer's site where the imaging system operates is within the range of operating temperatures required for normal system function. The room temperature range required for normal system operation is often too narrow for the needs of the customer's site. Some customer sites have room temperatures below the lower limit required for normal system operation, while others have room temperatures above the upper limit. When the room temperature is outside the imaging system's operating temperature range, the system generates warnings and error indications, which may cause the system to shut down unexpectedly.

[0003] Referring to Figure 1, an exemplary conventional air cooling system 10 for cooling component 12 of an imaging system is shown. The cooling system 10 includes an inlet duct 14 and an outlet duct 16, and a fan 18 located in the inlet duct 14. The cooling system 10 also includes a controller 20 that adjusts the fan speed of the fan 18 in response to ambient temperature of the scanning chamber 22 and component temperature detected by temperature sensors of the scanning chamber 22 and component 24, respectively. In use, cooling air at atmospheric pressure passes through an air filter 26 and is drawn into the inlet duct 14 by the fan 18, flowing through a low-pressure zone 28 located in front of the fan 18. The air then flows over component 12 and dissipates heat from component 12, thereby cooling component 12 and warming the air. The warm air, now at a relatively high pressure, exits from the outlet duct 16.

[0004] Conventional cooling methods drive air in an open loop by controlling the fan speed, which alters the airflow rate through the cooling system 10. In this method, the fan speed decreases when the scanning chamber is relatively cool and increases when the scanning chamber temperature rises. Furthermore, the internal imaging system temperature varies with room temperature. A decrease in fan speed leads to a rise in internal imaging system temperature, and an increase in fan speed leads to a decrease in internal imaging system temperature. The cooling system 10 is driven by the ambient air temperature and the heat load generated by the imaging system, which can expose internal imaging system components to a wide temperature range. For example, the controlled temperature range is typically set within a relatively wide range (e.g., 24°C–38°C or 15°C) because it is a function of the ambient air temperature (e.g., 18°C–30°C) and the heat dissipated in the imaging system. However, when the ambient air temperature exceeds specified limits, the cooling system 10 may fail to maintain the temperature of the components to be cooled within their operating or target range. Furthermore, in components used in PET / CT imaging systems, such as silicon photomultiplier tube (SiPM) detectors, temperature compensation circuits with detector compensation algorithms are used to correct for temperature variations in the detector. However, variations in the target temperature range (i.e., the range of controlled temperatures) can exceed, for example, 15°C. For such ranges, the detector compensation algorithm becomes more difficult to characterize. Summary of the Invention

[0005] A cooling system for cooling at least one component of an imaging system located in a scanning chamber is disclosed. The system includes an inlet channel and an outlet channel in airflow communication with the component, and a return channel in airflow communication with the inlet and outlet channels, wherein a portion of outlet warm air from the component outlet flows in the return channel to provide recirculated warm air to a mixing zone in the inlet channel. The system also includes a fan located in the inlet channel that draws scanning chamber air into the inlet channel, wherein the chamber air is mixed with the recirculated warm air in the mixing zone to form mixed air, the mixed air flowing through the component to cool the component, and wherein the mixed air absorbs heat that warms the mixed air to form outlet warm air. Furthermore, the system includes a valve located in the return channel, wherein the valve restricts or allows additional recirculated warm air to flow through the return channel to the mixing zone to mix with the scanning chamber air to maintain a desired controlled temperature for the cooling system.

[0006] Those skilled in the art can apply the various features of the present invention in any combination or sub-combination, either jointly or separately. Attached Figure Description

[0007] Exemplary embodiments of the present invention will be further described in the following detailed description in conjunction with the accompanying drawings, wherein:

[0008] Figure 1 illustrates an exemplary conventional air cooling system for cooling components of an imaging system.

[0009] Figure 2 This is a perspective view of an exemplary medical imaging system utilizing the present invention.

[0010] Figure 3 Depicting multiple PET detector rings in the PET section of a medical imaging system.

[0011] Figure 4 An embodiment of a feedback air cooling system for cooling components of an imaging system is shown.

[0012] Figure 5A This is a schematic representation of the temperature gradient of exemplary PET detectors 1-8 in an imaging system with eight PET detector rings, wherein the PET detectors are cooled by air flowing at a low airflow rate.

[0013] Figure 5B This is a schematic representation of the temperature gradient of exemplary PET detectors 1-8 in an imaging system with eight PET detector rings, wherein the PET detectors are cooled by air flowing at a higher airflow rate.

[0014] Figure 6A This is a schematic representation of the temperature gradient of a PET section with a short axial field of view (FoV) when using a conventional cooling system (i.e., an open loop system) under cold and warm environmental conditions.

[0015] Figure 6B This is a schematic representation of the temperature gradient for a PET portion having a short axial FoV when using the cooling system of the present invention (i.e., warm air feedback) under cold and warm environmental conditions. Detailed Implementation

[0016] Although various embodiments incorporating the teachings of this disclosure have been shown and described in detail herein, those skilled in the art can readily devise many other diverse embodiments that still incorporate these teachings. The scope of this disclosure is not to limit its application to the exemplary embodiment details of the construction and arrangement of components set forth in the description or illustrated in the figures. This disclosure includes other embodiments and is practiced or performed in various ways. Furthermore, it should be understood that the terms and terminology used herein are for descriptive purposes and should not be considered limiting. The terms “comprising,” “including,” or “having,” and variations thereof, as used herein, are intended to include the items listed below and their equivalents, as well as additional items. Unless otherwise specified or limited, the terms “mounted,” “connected,” “supported,” and “coupled,” and variations thereof, are used broadly and include direct and indirect mounting, connection, support, and coupling. Furthermore, “connected” and “coupled” are not limited to physical or mechanical connections or couplings.

[0017] refer to Figure 2 The diagram shows a perspective view of an exemplary medical imaging system 30 according to one aspect of the invention. The invention can be used in conjunction with a positron emission tomography / computed tomography (PET / CT) imaging system 32 having a CT section 34 and a PET section 36, but it is understood that the invention can also be used in other types of imaging systems. The CT section 34 includes a recording unit comprising an X-ray source 38 and an X-ray detector 40. The recording unit rotates about a longitudinal axis 42 during the recording of tomographic images, and the X-ray source 38 emits X-rays 44 during helical recording. While the images are being recorded, a patient 46 lies on a movable bed 48 located on a worktable base 50. The bed 48 is designed to allow the patient 46 to move along the recording direction through an opening or tunnel 52 in the gantry 54 of the imaging system 32. The worktable base 50 includes a control unit 56 connected to a computer 58 to exchange data. The computer 58 includes a determination unit 55 in the form of a computer program executable on the computer 58. The computer 58 is connected to an output unit 60 and an input unit 62. For example, output unit 60 is one or more liquid crystal displays (LCDs) or one or more plasma screens. Output 64 on output unit 60 includes, for example, graphical user interfaces for the various units of actuating imaging system 32 and control unit 56. Input unit 62 is, for example, a keyboard, mouse, touchscreen, or microphone for voice input.

[0018] refer to Figure 3The PET section 36 includes a plurality of PET detector rings 66 arranged about a longitudinal axis 42. For ease of illustration, exemplary first detector ring 68, second detector ring 70, third detector ring 72, and fourth detector ring 74 are shown. Each detector ring 68, 70, 72, and 74 includes a plurality of PET detectors 66 for scanning a patient 46 located in tunnel 52. During known operation of the PET section 36 of the imaging system 32, a radioactive isotope is injected into the patient 46 located in tunnel 52. The radioactive isotope undergoes positron emission decay and emits a positron, which encounters an electron and annihilates to produce a pair of gamma rays traveling in generally opposite directions. These gamma rays are detected by the PET detectors 66, and information from the gamma rays is used to generate a PET image. The PET image is then used in conjunction with a CT image generated by the CT section 34 of the imaging system 32 to provide an image of the patient 46 or parts of the patient's anatomy. Each PET detector 66 generates heat during operation of the PET section 36.

[0019] refer to Figure 4 An embodiment of a feedback air cooling system 80 for cooling at least one component 82 of an imaging system 30 is shown. For example, the imaging system 30 may be a PET / CT imaging system 32, and the component 82 may be a PET detector 66, but it is understood that other types of imaging systems and related components are also within the scope of this invention. According to one aspect of the invention, a cooling fluid such as air is used to cool the component, but liquids or a combination of liquid and air may also be used. For ease of illustration, the invention will be described in conjunction with a PET / CT imaging system 32 using air as the cooling fluid.

[0020] The cooling system 80 includes an inlet passage 84 and an outlet passage 86 in airflow communication with the component 82 to be cooled, and a return passage 88 in airflow communication with the outlet passage 86 and the inlet passage 84. The cooling system 80 also includes at least one variable-speed fan 90 and at least one valve 92, each of which is connected to a controller 94 via a corresponding control line 96. In one embodiment, the fan 90 is located in the inlet passage 84, and the valve 92 is located in the return passage 88. In other embodiments, the fan 90 and the valve 92 may be located in other suitable locations within the cooling system 80 besides or replacing the inlet passage 84 and the return passage 88. The cooling system 80 also includes a first temperature sensor 98, a second temperature sensor 100, a third temperature sensor 102, and a fourth temperature sensor 104, respectively located in the scanning chamber, the inlet channel 84, the assembly 82, and the return channel 88. These sensors provide temperature data to the controller 94 via corresponding signal lines 105 connecting the first temperature sensor 98, the second temperature sensor 100, the third temperature sensor 102, and the fourth temperature sensor 104 to the controller 94. Valve 92 is an electrically actuated valve controlled by the controller 94 to be partially opened as needed. In one embodiment, valve 92 may be an electrically driven butterfly valve. The controller 94 also controls the fan speed of fan 90 to provide a desired mixed airflow 106 to assembly 82.

[0021] During operation, fan 90 draws in ambient air 108 of the scanning chamber at atmospheric pressure through filter 110 located at inlet end 112 of inlet passage 84. The chamber air 108 then flows through a low-pressure zone 114 formed in front of fan 90, and subsequently through fan 90 and assembly 82 to dissipate heat from assembly 82. This cools assembly 82 and forms outlet warm air 116 exiting assembly outlet 118 at high pressure 120. When valve 92 is partially opened, a portion of the outlet warm air 116 from assembly outlet 118 flows through return passage 88 to provide recirculated warm air 122 to air mixing zone 124 in inlet passage 84. In mixing zone 124, the recirculated warm air 122 is mixed with chamber air 108 by fan 90 to form mixed air 106, which then flows through assembly 82 to cool assembly 82 and form outlet warm air 116. The remaining portion of the outlet warm air 106 that does not flow into the return channel 88 (i.e., exhaust air 126) leaves the outlet end 128 of the outlet channel 86.

[0022] The mixing of recirculated warm air 122 with room air 108 provides mixed air 106 that is warmer than room air 108. A second temperature sensor 100 is positioned downstream of the mixing zone 124 in the inlet channel 84 to provide mixed air temperature data to the controller 94. The controller 94 can adjust the valve opening of valve 92 based on the detected mixed air temperature provided by the second temperature sensor 100 to limit or allow additional recirculated warm air 122 to enter the return channel 88 and subsequently the mixing zone 124, in order to maintain a desired target or control temperature. The controller 94 can also adjust the fan speed of fan 90 to maintain the control temperature and / or provide a desired airflow rate. According to one embodiment of the invention, this provides the mixed air 106 with a control temperature range sufficient to cool component 82 and narrower than that in conventional cooling systems. Furthermore, the control temperature of the cooling system can be set at a higher temperature to allow a higher airflow into the cooling system.

[0023] It has been found that when the air velocity of the air flowing through the scanning chamber of the PET detector is low, an undesirable temperature gradient appears on the PET detector in an axial direction that is substantially parallel to the longitudinal axis 42. Figure 5A This is for PET section 36 with eight PET detector rings. Figure 2 The exemplary PET detectors 1-8 (referred to as detectors 1-8) in the example are arranged along a line substantially parallel to the longitudinal axis 42. Figure 3 A schematic representation of the temperature gradient 130 along the axial direction 132. During operation of the PET section 36, each PET detector 1-8 generates heat. A certain amount of heat Q is transferred from each PET detector 1-8 to cooling air (depicted by arrow 134) flowing along the axial direction 132 at a relatively low airflow rate. When a relatively low airflow rate is used, for example, the temperature of PET detector 1 is much lower than the temperature of PET detector 8, thus creating a relatively large temperature difference between the first PET detector (PET detector 1) and the last PET detector (PET detector 8).

[0024] Figure 5BThis is a schematic representation of the temperature gradient 136 along the axial direction 132 when the cooling air 138 flows at a higher airflow rate. When this occurs, a certain amount of heat Q is transferred from each PET detector 1-8 to the cooling air 138 flowing at a higher airflow rate than the heat transferred when flowing at a lower airflow rate. For example, this causes the temperature of PET detector 1 (the first PET detector) to be closer to the temperature of PET detector 8 (the last PET detector). According to one aspect of the invention, by maintaining the mixed gas temperature 106 within a narrow range and maintaining a high airflow rate, the temperature difference between the axially sequenced PET detectors 1 and PET detector 8 can be minimized.

[0025] This invention can be used in PET systems with a long axial field of view (FoV) (e.g., an axial FoV greater than about 30 cm), wherein a higher airflow through the PET detector reduces the temperature gradient along the axial direction 132 on the PET detector, such as... Figure 5B As shown. Furthermore, the present invention can be used in PET systems with a relatively short axial FoV (e.g., less than about 30 cm FoV). In particular, PET systems with a short axial FoV may not provide sufficient heat dissipation to meet lower temperature boundaries and the slowest fan speeds. The present invention mixes additional outlet warm air 116 into the cooling system 80 by opening valve 92 when the ambient air temperature is low, allowing additional air to flow into (i.e., at a higher flow rate) the short axial FoV system. According to one aspect of the invention, the range of controlled temperature can be set to a narrower range than that of conventional cooling systems. In one embodiment, the range of controlled temperature is approximately 32°C–36°C.

[0026] Figure 6A This is a schematic representation of the temperature gradient for a PET section 36 with a short-axial FoV when using a conventional cooling system 10 (i.e., an open-loop system) under cold and warm environmental conditions. The PET section 36 includes exemplary PET detectors 1-3 (referred to as detectors 1-3) having three PET detector rings forming the short-axial FoV system. Temperature gradient 140 under cold environmental temperature conditions and low airflow rates indicates that a certain amount of heat Q transferred from each PET detector 1-3 is less than a certain amount of heat Q transferred under warm environmental temperature conditions and high airflow rates, as indicated by temperature gradient 142.

[0027] Figure 6B This is a schematic representation of the temperature gradient for the PET portion 36 with a short axial FoV when using the cooling system 80 (i.e., warm air feedback) of the present invention under cold and warm environmental conditions. Specifically, Figure 6BThe temperature gradient 144 under cold ambient temperature conditions and low air flow rate is shown to be substantially similar to the temperature gradient 146 under warm ambient temperature conditions and high air flow rate.

[0028] In addition to the advantages mentioned above, this invention also implements a simplified detector compensation algorithm for the SiPM detector used in PET / CT imaging systems. Furthermore, this invention avoids the use of an inline heater to heat the inlet airflow, which would increase cost and power consumption and undesirably increase the carbon footprint of the imaging system.

[0029] While specific embodiments of this disclosure have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of this disclosure. Therefore, it is intended that all such changes and modifications be covered within the scope of this disclosure in the appended claims.

Claims

1. A cooling system for cooling at least one component of an imaging system located in a scanning chamber, comprising: An inlet channel and an outlet channel that communicate with the airflow of the component; A return channel communicating with the airflow of the inlet channel and the outlet channel, wherein a portion of the outlet warm air from the component outlet flows in the return channel to provide recirculated warm air to the mixing zone in the inlet channel; and A fan located in the inlet channel, wherein the fan draws scanning chamber air into the inlet channel, and wherein the scanning chamber air is mixed with recirculated warm air in the mixing zone to form mixed air, wherein the mixed air flows through the component to cool the component, and wherein the mixed air absorbs heat that warms the mixed air to form the outlet warm air.

2. The cooling system according to claim 1, further comprising a valve located in the return channel, wherein, The valve restricts or allows additional recirculated warm air to flow through the return channel to the mixing zone to mix with the scanning chamber air.

3. The cooling system according to claim 2, wherein, The valve is a butterfly valve.

4. The cooling system according to claim 3 further includes a temperature sensor coupled to the controller, wherein, The temperature sensor is located in the inlet channel to detect the temperature of the mixed air, wherein the controller controls the valve to limit or allow additional recirculated warm air based on the mixed air temperature to maintain the desired control temperature.

5. The cooling system according to claim 4, wherein, The recirculated warm air, mixed with the air in the scanning chamber, achieves a high controlled temperature so that the warmer air can flow into the cooling system.

6. The cooling system according to claim 4, wherein, Limit or allow additional recirculated warm air to form a narrow controlled temperature range.

7. The cooling system according to claim 1, wherein, The mixed air used to cool the components flows at a high airflow rate in order to minimize the temperature difference between components oriented along the axis of the imaging system.

8. The cooling system according to claim 7, wherein, The imaging system has a short axial field of view and maintains a high airflow rate when the temperature of the air in the scanning chamber is low.

9. A cooling system for cooling at least one component of an imaging system located in a scanning chamber, comprising: An inlet channel and an outlet channel that communicate with the airflow of the component; A return channel communicating with the airflow of the inlet channel and the outlet channel, wherein a portion of the outlet warm air from the component outlet flows in the return channel to provide recirculated warm air to the mixing zone in the inlet channel; A fan located in the inlet channel, wherein the fan draws scanning chamber air into the inlet channel, and wherein the scanning chamber air is mixed with recirculated warm air in the mixing zone to form mixed air, wherein the mixed air flows through the assembly to cool the assembly, and wherein the mixed air absorbs heat that warms the mixed air to form the outlet warm air; and A valve located in the return channel, wherein the valve restricts or allows additional recirculated warm air to flow through the return channel to the mixing zone to mix with the scanning chamber air in order to maintain the desired control temperature of the cooling system.

10. The cooling system according to claim 9, wherein, The valve is a butterfly valve.

11. The cooling system of claim 9, further comprising a temperature sensor coupled to the controller, wherein, The temperature sensor is located in the inlet channel to detect the temperature of the mixed air, wherein the controller controls the valve to limit or allow additional recirculated air based on the mixed air temperature to maintain the control temperature.

12. The cooling system according to claim 9, wherein, The recirculated warm air, mixed with the air in the scanning chamber, achieves a high controlled temperature so that the warmer air can flow into the cooling system.

13. The cooling system according to claim 9, wherein, Limit or allow additional recirculated warm air to form a narrow controlled temperature range.

14. The cooling system according to claim 9, wherein, The outlet warm air used to cool the components flows at a high airflow rate in order to minimize the temperature difference between components oriented along the axis of the imaging system.

15. The cooling system according to claim 14, wherein, The imaging system has a short axial field of view and maintains a high airflow rate when the temperature of the air in the scanning chamber is low.

16. The cooling system according to claim 9, wherein, The imaging system is a positron emission tomography / computed tomography (PET / CT) imaging system.

17. The cooling system according to claim 16, wherein, The at least one component is a PET detector.

18. A method for cooling at least one component of an imaging system located in a scanning chamber, comprising: Provide inlet and outlet air passages to allow air to flow into and out of the component; An air return path is provided so that a portion of the outlet warm air from the component can flow in the air return path to provide recirculated warm air to the mixing zone in the inlet air path; Air from the scanning chamber is drawn into the inlet air passage; The scanning chamber air is mixed with recirculated warm air in the mixing zone to form a mixed gas, wherein the mixed gas flows through the component to cool the component, and wherein the mixed gas absorbs heat that warms the mixed gas to form the outlet warm air.

19. The cooling method of claim 18, further comprising restricting or allowing additional recirculated warm air to flow through the air return passage to the mixing zone to mix with the scanning chamber air.

20. The cooling method of claim 19, further comprising detecting the temperature of the mixed air, wherein, The controller controls the valve to limit or allow additional recirculated warm air based on the temperature of the mixed air to maintain the desired control temperature.

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