English:
[0001] Aspects of the present invention relate to a cooling system for an imaging system, and more particularly, to a cooling system for cooling at least one component of the imaging system wherein the cooling system uses a portion of warm air from an outlet of the component that is then recirculated and mixed with scan room air to provide air within a narrow temperature range that flows at a high air flow rate to cool the component.
[0002] Many medical imaging systems, such as positron emission tomography/computed tomography (PET/CT) imaging systems, are cooled by a cooling media such as liquid, air or a combination of liquid and air. With respect to air cooled imaging systems, it is desirable that the ambient air temperature in a scan room at a customer site wherein the imaging system operates be within a required operating temperature range for proper operation of the imaging system. The room temperature range required for proper operation of the imaging system is frequently too narrow for the needs of the customer site. Some customer sites have a room temperature that is lower than the required lower temperature limit for proper operation of the imaging system whereas other sites have a room temperature that is above the required upper limit for proper operation of the imaging system. When the room temperature is outside of the operating temperature range of the imaging system, warning and error indications are generated by the imaging system which may cause the imaging system to undesirably shut down.
[0003] Referring to Fig. 1, an exemplary conventional air cooling system 10 for cooling a component 12 of an imaging system is shown. The cooling system 10 includes inlet 14 and outlet 16 conduits and a fan 18 located in the inlet conduit 14. The cooling system 10 also includes a controller 20 that regulates a fan speed of the fan 18 in response to scan room ambient and component temperatures detected by scan room 22 and component 24 temperature sensors, respectively. In use, cooling air at atmospheric pressure is drawn through an air filter 26 and into the inlet conduit 14 by the fan 18 and flows through a low pressure zone 28 located before the fan 18. The air then flows over the component 12 and dissipates heat from the component 12 thus cooling the component 12 and warming the air. Warm air at a relatively high pressure then exits from the outlet conduit 16.
[0004] The conventional method to cooling has been to drive air in an open loop by controlling fan speed which changes the air flow rate through the cooling system 10. In this method, fan speed is reduced when the scan room is relatively cold and then increased as the scan room temperature rises. Further, internal imaging system temperatures change with room temperature. When fan speed decreases, the internal imaging system temperature increases and when fan speed increases, the internal imaging system temperatures decrease. The cooling system 10 is driven by the ambient air room temperature and the heat load generated by the imaging system which may result in the exposure of internal imaging system components to a wide range of temperatures. For example, the range of controlled temperatures is normally set at a relatively wide temperature range (24-38°C, or 15°C for example) since this is a function of the ambient air temperature (18-30°C, for example) and the heat being dissipated in the imaging system. However, the cooling system 10 may not be able to maintain the temperature of the components being cooled in their operating or targeted range when the ambient air room temperature goes outside specified limits. Further, in components such as silicon photomultipliers (SiPM) detectors used in PET/CT imaging systems, a temperature compensation circuit having a detector compensation algorithm is utilized to correct for temperature variability in the detector. However, the targeted temperature range (i.e., the range of controlled temperatures) can vary by more than 15°C, for example. With such a range, the detector compensation algorithm becomes more difficult to characterize.
[0005] A cooling system for cooling at least one component of an imaging system located in a scan room is disclosed. The system includes inlet and outlet channels in air flow communication with the component and a return channel in air flow communication with the inlet and outlet channels, wherein a portion of warm outlet air from a component outlet flows in the return channel to provide warm recirculated air to a mixing zone in the inlet channel. The system also includes a fan located in the inlet channel that draws scan room air into the inlet channel wherein the room air is mixed with the warm recirculated air in the mixing zone to form mixed air that flows over the component to cool the component and wherein the mixed air absorbs heat that warms the mixed air to form the warm outlet air. Further the system includes a valve located in the return channel, wherein the valve restricts or allows additional warm recirculated air to flow through the return channel to the mixing zone to mix with the scan room air to maintain a desired control temperature for the cooling system.
[0006] Those skilled in the art may apply the respective features of the present invention jointly or severally in any combination or sub-combination.
[0008] Fig. 1 shows an exemplary conventional air cooling system for cooling a component of an imaging system.
[0009] Fig. 2 is a perspective view of an exemplary medical imaging system that utilizes the invention.
[0010] Fig. 3 depicts a plurality of PET detector rings of a PET portion of the medical imaging system.
[0011] Fig. 4 shows an embodiment of a feedback air cooling system for cooling a component of the imaging system.
[0012] Figs. 5A is a schematic representation of a temperature gradient of exemplary PET detectors 1-8 of an imaging system having eight PET detector rings wherein the PET detectors are cooled by air flowing at a low air flow rate.
[0013] Fig. 5B is a schematic representation of a temperature gradient of exemplary PET detectors 1-8 of an imaging system having eight PET detector rings wherein the PET detectors are cooled by air flowing at a higher air flow rate.
[0014] Fig. 6A is a schematic representation of temperature gradients for a PET portion having a short axial field of view (FoV) when using a conventional cooling system (i.e., open loop system) under cold and warm ambient conditions.
[0015] Fig. 6B is a schematic representation of temperature gradients for a PET portion having a short axial FoV when using the cooling system of the invention (i.e., warm air feedback) under cold and warm ambient conditions.
[0016] Although various embodiments that incorporate the teachings of the present disclosure have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The scope of the disclosure is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The disclosure encompasses other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
[0017] Referring to Fig. 2, a perspective view of an exemplary medical imaging system 30 in accordance with an aspect of the invention is shown. The invention may be used in conjunction with a positron emission tomography/computed tomography (PET/CT) imaging system 32 having a CT portion 34 and a PET portion 36 although it is understood that the invention may be used in other types of imaging systems. The CT portion 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 a tomographic image, and the X- ray source 38 emits X-rays 44 during a spiral recording. While an image is being recorded a patient 46 lies on a moveable bed 48 located on a table base 50. The bed 48 is designed to move the patient 46 along a recording direction through an opening or tunnel 52 of a gantry 54 of the imaging system 32. The table 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 that can be executed on the computer 58. The computer 58 is connected to an output unit 60 and an input unit 62. The output unit 60 is, for example, one (or more) liquid crystal display (LCD) or plasma screen(s). An output 64 on the output unit 60 comprises, for example, a graphical user interface for actuating the individual units of the imaging system 32 and the control unit 56. The input unit 62 is for example a keyboard, mouse, touch screen or a microphone for speech input.
[0018] Referring to Fig. 3, the PET portion 36 includes a plurality of PET detector rings 66 arranged about the longitudinal axis 42. For purposes of illustration, exemplary first 68, second 70, third 72 and fourth 74 detector rings are shown. Each detector ring 68, 70, 72, 74 includes a plurality of PET detectors 66 used to scan the patient 46 located in the tunnel 52. During a known operation of the PET portion 36 of imaging system 32, a patient 46 located in the tunnel 52 is injected with a radioisotope. The radioisotope undergoes positron emission decay and emits a positron that encounters and annihilates with an electron to produce a pair of gamma rays moving in approximately opposite directions. The gamma rays are detected by the PET detectors 66 and information from the gamma rays is used to generate PET images. The PET images are then used in conjunction with CT images generated by the CT portion 34 of imaging system 32 to provide images of the patient 46 or part of a patient’s anatomy. Each PET detector 66 generates heat during operation of the PET portion 36.
[0019] Referring to Fig. 4, an embodiment of a feedback air cooling system 80 for cooling at least one component 82 of an imaging system 30 is shown. By way of example, the imaging system 30 may be the PET/CT imaging system 32 and the component 82 may be a PET detector 66 although it is understood that other types of imaging systems and associated components are within the scope of the invention. In accordance with an aspect of the invention, a cooling fluid such as air is used to cool the component although a liquid, or combination of liquid and air, may be used. For purposes of illustration, the invention will be described in connection with a PET/CT imaging system 32 that uses air as a cooling fluid.
[0020] The cooling system 80 includes inlet 84 and outlet 86 channels that are in air flow communication with the component 82 to be cooled and a return channel 88 that is in air flow communication with the outlet 86 and inlet 84 channels. The cooling system 80 also includes at least one variable speed fan 90 and at least one valve 92 that are each connected to a controller 94 by respective control lines 96. In an embodiment, the fan 90 is located in the inlet channel 84 and the valve 92 is located in the return channel 88. In other embodiments, the fan 90 and valve 92 may be located in other suitable positions in the cooling system 80 in addition to or instead of the inlet 84 and return 88 channels. The cooling system 80 further includes first 98, second 100, third 102 and fourth 104 temperature sensors located in the scan room, the inlet channel 84, on the component 82 and in the return channel 88, respectively, that provide temperature data to the controller via respective signal lines 105 connected between the first 98, second 100, third 102 and fourth 104 temperature sensors and the controller 94. The valve 92 is an electronically actuated valve controlled by the controller 94 to partially open as desired. In an embodiment, the valve 92 may be an electronically actuated butterfly valve. The controller 94 also controls a fan speed of the fan 90 to provide a desired flow of mixed air 106 to the component 82.
[0021] In operation, the fan 90 draws in scan room ambient air 108 at atmospheric pressure through a filter 110 located on an inlet end 112 of the inlet channel 84. The room air 108 then flows through a low pressure zone 114 formed before the fan 90 and subsequently past the fan 90 and the component 82 to dissipate heat from the component 82. This cools the component 82 and forms warm outlet air 116 that exits a component outlet 118 at high pressure 120. When the valve 92 is partially opened, a portion of warm outlet air 116 from the component outlet 118 flows through the return channel 88 to provide warm recirculated air 122 to an air mixing zone 124 in the inlet channel 84. In the mixing zone 124, the warm recirculated air 122 is mixed with the room air 108 by the fan 90 to form mixed air 106 that subsequently flows past the component 82 to cool the component 82 and forms the warm outlet air 116. A remaining portion of the warm outlet air 106 that does not flow into the return channel 88 (i.e., exhaust air 126) exits an outlet end 128 of the outlet channel 86.
[0022] The mixing of warm recirculated air 122 with room air 108 provides mixed air 106 that is warmer than the room air 108. The second temperature sensor 100 is positioned in the inlet channel 84 after the mixing zone 124 to provide mixed air temperature data to the controller 94. The controller 94 may vary a valve opening of the valve 92 to restrict or allow additional warm recirculated air 122 into the return channel 88 and subsequently the mixing zone 124 based on the detected mixed air temperature provided by the second temperature sensor 100 in order to maintain a desired target or control temperature. The controller 94 may also adjust a fan speed of the fan 90 in order to maintain the control temperature and/or provide a desired air flow rate. In accordance with an embodiment of the invention, this provides a range of control temperatures for the mixed air 106 that is sufficient for cooling the component 82 and narrower than in conventional cooling systems. In addition, a control temperature of the cooling system can be set at a higher temperature to enable higher air flow into the cooling system.
[0023] It has been found that when the air speed of scan room air flowing across PET detectors is low, an undesirable temperature gradient develops across the PET detectors in an axial direction substantially parallel to the longitudinal axis 42. Fig. 5A is a schematic representation of a temperature gradient 130 in an axial direction 132 substantially parallel to the longitudinal axis 42 (Fig. 3) for exemplary PET detectors 1-8 (referenced as Det. 1 - Det. 8) in a PET portion 36 (Fig. 2) having eight PET detector rings. Each PET detector 1-8 generates heat during operation of the PET portions 36. An amount of heat Q is transferred from each PET detector 1-8 to cooling air (depicted by arrow 134) flowing at a relatively low air flow rate in the axial direction 132. When using a relatively low air flow rate, the temperature of PET detector 1 is much less than that of PET detector 8, for example, thus forming a relatively large temperature difference between the first PET detector (PET detector 1) and last PET detector (PET detector 8).
[0024] Fig. 5B is a schematic representation of a temperature gradient 136 in the axial direction 132 when the cooling air 138 flows at a higher air flow rate. When this occurs, the amount of heat Q transferred from each PET detector 1-8 to cooling air 138 flowing at a higher air flow rate is greater than that transferred at the lower air flow rate. This results in the temperature of PET detector 1 (the first PET detector) being much closer to that of PET detector 8 (the last PET detector), for example. In accordance with an aspect of the invention, the temperature difference between the PET detector 1 and PET detector 8 in the axial series is minimized by keeping the mixed air temperature 106 in a narrow range and the air flow rate high.
[0025] The invention may be used in PET systems having a long axial field of view (FoV), for example, an axial FoV of more than approximately 30cm, wherein a higher air flow across the PET detectors lowers the temperature gradient across the PET detectors in the axial direction 132, as shown in Figure 5B. Additionally, the invention may be used in PET systems having a relatively short axial FoV (for example, a FoV of less than approximately 30cm). In particular, a PET system having a short axial FoV may not provide sufficient heat dissipation to satisfy a lower temperature boundary and a slowest fan speed. The current invention enables additional air flow (i.e., a higher flow rate) in a short axial FoV system when the ambient air room temperature is low by opening the valve 92 to mix additional warm outlet air 116 into the cooling system 80. In accordance with an aspect of the invention, the range of the control temperatures can be set to a narrower range than conventional cooling systems. In an embodiment, the range of control temperatures is approximately 32-36°C.
[0026] Fig. 6A is a schematic representation of temperature gradients for a PET portion 36 having a short axial FoV when using the conventional cooling system 10 (i.e., open loop system) under cold and warm ambient conditions. The PET portion 36 includes exemplary PET detectors 1-3 (referenced as Det. 1 - Det. 3) having three PET detector rings that form a short axial FoV system. A temperature gradient 140 under cold ambient temperature conditions and a low air flow rate indicates that the amount of heat transferred Q from each PET detectors 1-3 is less than the amount of heat transferred Q under warm ambient temperature conditions and a high air flow rate as indicated by temperature gradient 142.
[0027] Fig. 6B is a schematic representation of temperature gradients for a PET portion 36 having a short axial FoV when using the cooling system 80 of the invention (i.e., warm air feedback) under cold and warm ambient conditions. In particular, Fig. 6B shows that a temperature gradient 144 under cold ambient temperature conditions and a low air flow rate is substantially similar to a temperature gradient 146 under warm ambient temperature conditions and a high air flow rate.
[0028] In addition to the advantages described above, the invention enables the use of a simplified detector compensation algorithms for the SiPM detectors used in PET/CT imaging systems. Further, the invention avoids the use of inline heaters to warm inlet air flow which would increase cost and power usage and undesirably increase the carbon footprint of an imaging system.
[0029] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.

中文:
[0001]本发明的各方面涉及一种用于成像系统的冷却系统,并且更具体地,涉及一种用于冷却成像系统的至少一个组件的冷却系统,其中所述冷却系统使用来自所述组件的出口的一部分暖空气,所述暖空气然后被再循环并与扫描室空气混合,以提供在窄温度范围内以高空气流率流动的空气来冷却所述组件。
[0002]许多医疗成像系统(诸如正电子发射断层扫描/计算机断层扫描(PET/CT)成像系统)都是通过诸如液体、空气或者液体和空气的组合的冷却介质来冷却的。就空气冷却的成像系统而言,期望的情况是成像系统运行于其中的客户现场处的扫描室内的环境空气温度在成像系统正常运行所需的运行温度范围内。成像系统正常运行所需的室温范围对于客户现场的需要来说时常太窄。一些客户现场的室温低于成像系统正常运行所需的温度下限,而其他现场的室温高于成像系统正常运行所需的上限。当室温在成像系统的运行温度范围之外时,成像系统会生成警告和错误指示,这可能会导致成像系统不合期望地关闭。
[0003]参考图1,示出了用于冷却成像系统的组件12的示例性传统空气冷却系统10。冷却系统10包括入口导管14和出口导管16以及位于入口导管14中的风扇18。冷却系统10还包括控制器20,其响应于由扫描室22和组件24的温度传感器分别检测到的扫描室环境温度和组件温度来调节风扇18的风扇转速。在使用中,处于大气压下的冷却空气穿过空气过滤器26并被风扇18吸进入口导管14,并且流经位于风扇18前面的低压区28。空气然后流过组件12并消散来自组件12的热量,从而使组件12冷却并使空气变暖。接下来,处于相对高压下的暖空气从出口导管16离开。
[0004]用来进行冷却的传统方法通过控制改变经过冷却系统10的空气流率的风扇转速来在开放环路中驱动空气。在该方法中,当扫描室相对冷时,风扇转速会降低,并且当扫描室温度上升时,风扇转速则会升高。此外,内部成像系统温度会随室温而变化。当风扇转速降低时,内部成像系统温度升高,并且当风扇转速升高时,内部成像系统温度降低。冷却系统10受环境空气室温和成像系统所产生的热负荷的驱动,这可能导致内部成像系统组件暴露在宽的温度范围。例如,受控温度的范围通常被设置在相对宽的温度范围内(例如24°C-38°C或15°C),因为这是环境空气温度(例如18°C-30°C)和成像系统中被消散的热量的函数。然而,当环境空气室温超出指定的限制时,冷却系统10可能无法将要被冷却的组件的温度保持在其运行或目标范围内。此外,在PET/CT成像系统中使用的诸如硅光电倍增管(SiPM)探测器的组件中,利用具有探测器补偿算法的温度补偿电路来校正探测器中的温度变率。然而,目标温度范围(即受控温度的范围)的变化可以超过例如15°C。对于这样的范围,探测器补偿算法变得更加难以表征。
[0005]公开了一种用于冷却位于扫描室中的成像系统的至少一个组件的冷却系统。所述系统包括与所述组件气流相通(air flow communication)的入口通道和出口通道、以及与所述入口通道和所述出口通道气流相通的返回通道,其中来自组件出口的一部分出口暖空气在所述返回通道中流动,以向所述入口通道中的混合区提供再循环暖空气。所述系统还包括位于所述入口通道中的风扇,其将扫描室空气吸入所述入口通道中,其中所述室空气与所述混合区中的再循环暖空气混合以形成混合空气,所述混合空气流过所述组件从而使所述组件冷却,并且其中所述混合空气吸收使所述混合空气变暖的热量来形成出口暖空气。此外,所述系统还包括位于所述返回通道中的阀,其中所述阀限制或允许附加的再循环暖空气经过所述返回通道流到所述混合区来与所述扫描室空气混合,以保持所述冷却系统所期望的控制温度。
[0006]本领域技术人员可以以任何组合或子组合联合地或分别地应用本发明的各个特征。
[0008]图1示出用于冷却成像系统的组件的示例性传统空气冷却系统。
[0009]图2是利用本发明的示例性医疗成像系统的透视图。
[0010]图3描绘医疗成像系统的PET部分的多个PET探测器环。
[0011]图4示出用于冷却成像系统的组件的反馈空气冷却系统的实施例。
[0012]图5A是具有八个PET探测器环的成像系统的示例性PET探测器1-8的温度梯度的示意性表示,其中PET探测器是由以低空气流率流动的空气来冷却的。
[0013]图5B是具有八个PET探测器环的成像系统的示例性PET探测器1-8的温度梯度的示意性表示,其中PET探测器是由以较高空气流率流动的空气来冷却的。
[0014]图6A是在冷和暖环境条件下使用传统冷却系统(即开放环路系统)时对于具有短轴向视场(FoV)的PET部分的温度梯度的示意性表示。
[0015]图6B是在冷和暖环境条件下使用本发明的冷却系统(即暖空气反馈)时对于具有短轴向FoV的PET部分的温度梯度的示意性表示。
[0016]尽管本文中已经详细示出和描述了包含本公开的教导的各种实施例,但本领域技术人员可以容易地设计出仍然包含这些教导的许多其他各种各样的实施例。本公开的范围不会将其应用限于描述中所阐述的或图中所图示的组件的构造和布置的示例性实施例细节。本公开包括其他实施例,并且以各种方式被实行或执行。此外,应当理解的是,本文中所使用的用语和术语用于描述的目的,并且不应该被视为限制性的。本文中使用的“包括”、“包含”或“具有”及其变体旨在包括下文列出的条目及其等同物以及附加条目。除非另外指定或限制,术语“安装”、“连接”、“支撑”和“耦接”及其变体被广泛地使用,并且包括直接和间接安装、连接、支撑和耦接。此外,“连接”和“耦接”不限于物理或机械连接或耦接。
[0017]参考图2,示出了根据本发明的一个方面的示例性医疗成像系统30的透视图。本发明可以与具有CT部分34和PET部分36的正电子发射断层扫描/计算机断层扫描(PET/CT)成像系统32结合使用,但可以理解的是,本发明也可以用在其他类型的成像系统中。CT部分34包括记录单元,其包括X射线源38和X射线探测器40。记录单元在断层扫描图像的记录期间绕纵向轴线42旋转,且X射线源38在螺旋记录期间发射X射线44。在图像被记录的同时,患者46躺在位于工作台底座50上的可移动床48上。床48被设计为使患者46沿记录方向移动通过成像系统32的门架54的开口或隧道52。工作台底座50包括与计算机58连接以交换数据的控制单元56。计算机58包括处于可在计算机58上执行的计算机程序的形式的确定单元55。计算机58与输出单元60和输入单元62连接。例如,输出单元60是一个(或多个)液晶显示器(LCD)或(一个或多个)等离子屏幕。输出单元60上的输出64包括例如用于致动成像系统32和控制单元56的各个单元的图形用户接口。输入单元62例如是键盘、鼠标、触摸屏或用于语音输入的麦克风。
[0018]参考图3,PET部分36包括绕纵向轴线42布置的多个PET探测器环66。为了便于说明,示出了示例性的第一探测器环68、第二探测器环70、第三探测器环72和第四探测器环74。每个探测器环68、70、72和74都包括用来扫描位于隧道52中的患者46的多个PET探测器66。在成像系统32的PET部分36的已知运行期间,位于隧道52中的患者46被注入放射性同位素。放射性同位素经历正电子发射衰变并发射正电子,该正电子与一个电子相遇并湮灭以产生沿大致相反方向移动的一对伽马射线。该伽马射线被PET探测器66探测到,并且来自伽马射线的信息被用来生成PET图像。然后,结合成像系统32的CT部分34所生成的CT图像来使用PET图像,以提供患者46或患者的部分解剖结构的图像。每个PET探测器66都会在PET部分36的运行期间产生热量。
[0019]参考图4,示出了用于冷却成像系统30的至少一个组件82的反馈空气冷却系统80的一个实施例。举例来说,成像系统30可以是PET/CT成像系统32,且组件82可以是PET探测器66,但可以理解的是,其他类型的成像系统和相关组件也在本发明的范围之内。根据本发明的一个方面,诸如空气的冷却流体被用来冷却组件,但也可以使用液体或液体与空气的组合。为了便于说明,将结合使用空气作为冷却流体的PET/CT成像系统32来描述本发明。
[0020]冷却系统80包括与待冷却的组件82气流相通的入口通道84和出口通道86、以及与出口通道86和入口通道84气流相通的返回通道88。冷却系统80还包括至少一个变速风扇90和至少一个阀92,它们中的每个都通过相应控制线96连接到控制器94。在一个实施例中,风扇90位于入口通道84中,并且阀92位于返回通道88中。在其他实施例中,风扇90和阀92可以位于冷却系统80中除入口通道84和返回通道88之外或取代入口通道84和返回通道88的其他适当位置。冷却系统80还包括分别位于扫描室中、入口通道84中、组件82上以及返回通道88中的第一温度传感器98、第二温度传感器100、第三温度传感器102和第四温度传感器104,它们经由连接在第一温度传感器98、第二温度传感器100、第三温度传感器102和第四温度传感器104与控制器94之间的相应信号线105向控制器提供温度数据。阀92是由控制器94控制的电致动阀,以便根据需要而部分地打开。在一个实施例中,阀92可以是电驱动蝶阀。控制器94还控制风扇90的风扇转速,以向组件82提供期望的混合空气流106。
[0021]在运行中,风扇90通过位于入口通道84的入口端112上的过滤器110吸入处于大气压下的扫描室环境空气108。然后,室空气108流经形成于风扇90前面的低压区114,且随后流过风扇90和组件82,以消散来自组件82的热量。这样就使组件82冷却并形成在高压120下离开组件出口118的出口暖空气116。当阀92被部分打开时,来自组件出口118的一部分出口暖空气116流经返回通道88,以便向入口通道84中的空气混合区124提供再循环暖空气122。在混合区124中,再循环暖空气122通过风扇90与室空气108混合,以形成混合空气106,该混合空气106随后流过组件82以便使组件82冷却并形成出口暖空气116。未流入返回通道88中的出口暖空气106的剩余部分(即排出空气126)离开出口通道86的出口端128。
[0022]再循环暖空气122与室空气108的混合提供了比室空气108更暖的混合空气106。第二温度传感器100被定位于入口通道84中混合区124的后面,以便向控制器94提供混合空气温度数据。控制器94可以基于由第二温度传感器100提供的所检测的混合空气温度来改变阀92的阀开度,以限制或允许附加的再循环暖空气122进入返回通道88中且随后进入混合区124中,以便保持期望的目标温度或控制温度。控制器94还可以调节风扇90的风扇转速,以便保持控制温度和/或提供期望的空气流率。根据本发明的一个实施例,这为混合空气106提供了足以使组件82冷却并且比传统冷却系统中的更窄的控制温度范围。此外,还可以将冷却系统的控制温度设置在较高的温度,以使得较高的空气流能够进入冷却系统中。
[0023]已经发现,当流经PET探测器的扫描室空气的空气速度为低时,沿基本平行于纵向轴线42的轴向方向的PET探测器上会出现不期望的温度梯度。图5A是对于具有八个PET探测器环的PET部分36(图2)中的示例性PET探测器1-8(被称为探测器1-探测器8)的沿基本平行于纵向轴线42(图3)的轴向方向132的温度梯度130的示意性表示。在PET部分36的运行期间,每个PET探测器1-8都产生热量。一定量的热量Q被从每个PET探测器1-8传递到以相对低的空气流率沿轴向方向132流动的冷却空气(箭头134所描绘的)中。当使用相对低的空气流率时,例如PET探测器1的温度远低于PET探测器8的温度,从而在第一个PET探测器(PET探测器1)和最后一个PET探测器(PET探测器8)之间形成相对大的温度差。
[0024]图5B是当冷却空气138以较高的空气流率流动时沿轴向方向132的温度梯度136的示意性表示。当出现这种情况时,从每个PET探测器1-8传递到以较高空气流率流动的冷却空气138的一定量的热量Q要大于以较低空气流率流动时所传递的热量。例如,这导致PET探测器1(第一个PET探测器)的温度更接近于PET探测器8(最后一个PET探测器)的温度。根据本发明的一个方面,通过将混合气体温度106保持在窄的范围内并且保持高的空气流率,可以使轴向系列的PET探测器1和PET探测器8之间的温度差最小化。
[0025]本发明可以用于具有长轴向视场(FoV)(例如大于约30厘米的轴向FoV)的PET系统,其中流过PET探测器的较高的空气流降低了PET探测器上的沿轴向方向132的温度梯度,如图5B所示。此外,本发明可以用于具有相对短轴向FoV(例如小于约30厘米的FoV)的PET系统。特别地,具有短轴向FoV的PET系统可能无法提供足够的热耗散来满足较低的温度边界和最慢的风扇转速。当前发明在环境空气室温为低时通过打开阀92将附加的出口暖空气116混合到冷却系统80中,使得附加的空气能够流入(即以较高的流率)短轴向FoV系统中。根据本发明的一个方面,控制温度的范围可以被设置为比传统冷却系统更窄的范围。在一个实施例中,控制温度的范围约为32°C-36°C。
[0026]图6A是在冷和暖环境条件下使用传统冷却系统10(即开放环路系统)时对于具有短轴向FoV的PET部分36的温度梯度的示意性表示。PET部分36包括示例性PET探测器1-3(被称为探测器1-探测器3),其具有形成短轴向FoV系统的三个PET探测器环。在冷环境温度条件和低空气流率下的温度梯度140表明,从每个PET探测器1-3传递的一定量的热量Q小于在暖环境温度条件和高空气流率下传递的一定量的热量Q,如温度梯度142所指示的。
[0027]图6B是在冷和暖环境条件下使用本发明的冷却系统80(即暖空气反馈)时对于具有短轴向FoV的PET部分36的温度梯度的示意性表示。特别地,图6B示出在冷环境温度条件和低空气流率下的温度梯度144与在暖环境温度条件和高空气流率下的温度梯度146基本相似。
[0028]除了上述优点之外,本发明还实现了对PET/CT成像系统中使用的SiPM探测器使用简化的探测器补偿算法。此外,本发明避免了使用管线上加热器(inline heater)来加热入口空气流,使用管线上加热器来加热入口空气流将会增加成本和用电量,并不合期望地增加成像系统的碳足迹。
[0029]虽然已经说明并描述了本公开的特定实施例,但对于本领域的技术人员来说,显而易见的是,在不脱离本公开的精神和范围的情况下,还可以进行各种其他更改和修改。因此,意图在所附的权利要求书中覆盖在本公开的范围内的所有此类更改和修改。