Cooling channels with non-metallic heat sink for diagnostic medical imaging devices

Abstract

When included in a magnetic resonance imaging (MRI) system, a cooling channel in a gantry of a medical imaging device transfers heat away from a radiation detector and detector electronics while limiting the impact on a magnetic field generated within the gantry. The cooling channel includes a non-conductive, non-metallic housing in thermally conductive communication with the detector electronics and the radiation detector. A cooling conduit in the housing circulates a coolant fluid. An integral, non-conductive, non-metallic heat sink in the housing is in direct thermally conductive communication with the housing and the cooling conduit. A solid thermally conductive layer is interposed between and secured to opposing, spaced-apart outer surfaces of the conduit and the heat sink.

Description

Technical Field

[0001] A cooling system for a gantry of a diagnostic medical imaging device includes a cooling channel for a radiation detector and detector electronics, the cooling channel having a non-metallic heat sink coupled to a fluid-cooled cooling conduit through a solid thermally conductive layer. Background Art

[0002] As non-limiting examples, diagnostic medical imaging devices include computed tomography (CT), two-dimensional digital radiography (DR), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT) modalities. As non-limiting examples, hybrid modality devices include PET / CT, PET / MRI, SPECT / CT, and SPECT / MRI, which combine the local imaging resolution benefits of CT or MRI with the sensitivity of imaging and detecting cellular and metabolic biological processes in the patient's body in a single system. Many of these imaging devices or systems include an annular gantry structure through which a patient examination table is inserted. The gantry includes one or more electromagnetic radiation detectors that emit electrons in response to incident photons of electromagnetic radiation. In some modalities (e.g., CT, DR, PET, SPECT), the incident photons are transmitted X-rays or ionizing radiation emissions at the higher end of the electromagnetic frequency range, while in other modalities (e.g., MRI), the incident photons are in the radio frequency range. The detector's output electrons are processed by detector electronics to generate a detector output signal, which is then processed by the imaging device to generate or construct an image of the patient. In some imaging systems, the detector electronics package is housed within the gantry structure along with the detector as an integrated detector assembly.

[0003] Exemplary electromagnetic radiation detectors include photomultiplier tubes (PMTs) and solid-state detectors, such as avalanche photodiodes (APDs) and silicon photomultipliers (SiPMs). The signal gain of solid-state detectors is more temperature dependent than that of PMTs. Solid-state photon sensors and their detector electronics packages are typically maintained within a relatively narrow temperature fluctuation and operating temperature bandwidth to reduce the likelihood of inaccurate detector readings and / or excessive noise generation components in the detector readings that could otherwise result in poor quality patient images. Solid-state radiation detectors require external cooling to maintain the detector assembly within defined temperature fluctuation and bandwidth specifications. Typically, the radiation detectors in medical imaging systems are cooled by blowing cooling air over them or by transferring heat from the detector to one or more conduits that circulate a cooling fluid near the detector. Summary of the Invention

[0004] A cooling channel in a gantry of a medical imaging device transfers heat away from a radiation detector and detector electronics. When the cooling channel is contained within the scanning field of an MR gradient tube of a gantry of an MRI system, it may generate eddy currents through electromagnetic fields generated within the gantry. Eddy currents cause MR image distortions, such as ghosting artifacts. An embodiment of the cooling channel includes a non-conductive, non-metallic housing in thermal communication with the detector electronics and the radiation detector. A cooling conduit in the housing circulates a coolant fluid. An integral non-conductive, non-metallic heat sink in the housing is in direct thermal communication with the housing and the cooling conduit. A solid thermally conductive layer is interposed between and secured to opposing spaced-apart outer surfaces of the conduit and the heat sink.

[0005] Exemplary embodiments described herein transfer heat generated by an imaging device, including gantry heat, to a fluid-cooled cooling channel. The cooling channel configuration reduces the effects of magnetic and gradient fields, as well as ohmic and eddy current heating, induced in the gantry during patient scans, all of which would otherwise degrade patient image quality. In some embodiments, the cooling channel is contained within a non-metallic housing interposed between a radiation detector and the detector electronics in a radiation detector assembly. The housing has a flat lower surface for coupling to the radiation detector and a flat upper surface for coupling to the detector electronics. The cooling channel includes a cooling conduit for circulating a fluid coolant through an inlet and an outlet. Heat generated within the detector assembly is transferred to the coolant. In a recirculating coolant system, the coolant in turn transfers its retained heat to a gantry cooling system located within the gantry or another part of the medical imaging system, or to a remotely located cooling system. In some embodiments, the cooling channel comprises an integral non-metallic heat sink that draws heat from the detector and, in many embodiments, the detector electronics. The heat sink has corresponding continuous top and bottom surfaces in direct thermal communication with the corresponding upper and lower surfaces of the housing, and lateral surfaces between the top and bottom surfaces. The lateral surfaces are spaced apart from the outer surface of the conduit. The lateral surfaces of the heat sink and the corresponding outer surfaces of the conduit have contours that conform to each other and are secured to each other by a solid thermally conductive layer.

[0006] The cooling channel configuration transfers heat from the radiation detector and / or detector electronics to the upper and lower surfaces of the housing via direct thermal conduction. The housing, in turn, transfers the heat directly to the heat sink via thermal conduction. In some embodiments, the housing also transfers the heat directly to the conduit via thermal conduction. The heat sink transfers the heat directly to a fixed, solid, thermally conductive layer via thermal conduction; the thermally conductive layer, in turn, transfers the heat directly to the conduit via thermal conduction. Thus, in some embodiments, heat is transferred from the radiation detector and detector electronics to the circulating coolant via a series of conductive heat transfer interfaces within the cooling channel via highly efficient conductive heat transfer.

[0007] In some embodiments, the housing, cooling conduit, and heat sink are non-metallic and non-conductive. In those exemplary embodiments, the housing and conduit are constructed of a hardened resin or polymer material, and the heat sink is constructed of a ceramic material. In those embodiments, the thermally conductive layer that secures the heat sink to the conduit is a thermally conductive adhesive. In some embodiments, the thermally conductive adhesive contains a conductive (e.g., metal) component to enhance conductive heat transfer from the heat sink to the conduit. The completely non-metallic, non-conductive cooling channel construction greatly reduces the effects of magnetic and gradient fields induced in the gantry during patient scanning, as well as ohmic and eddy current heating, which would otherwise degrade patient image quality.

[0008] In other cooling channel embodiments, such as those requiring higher heat transfer rates than can be achieved with lower metal or non-metallic constructions, the housing is constructed of a hardened resin or polymer material, the heat sink is constructed of a ceramic material, and the conduit is constructed of a metal, such as a metal tube. In these embodiments, the thermally conductive layer securing the outer profile of the metal conduit to the ceramic heat sink is a metal solder bonded to the conduit and to a metal layer deposited on the lateral surface of the heat sink. The deposited metal layer on the ceramic heat sink is bonded to the solder. Thus, the metallic high thermal conductivity layer efficiently transfers heat from the ceramic heat sink to the metal conduit. In some embodiments, the housing is also in direct contact with the metal cooling conduit for direct conductive heat transfer between those components.

[0009] In another exemplary embodiment of the cooling channel, the cooling conduit has a U-shaped flat profile, wherein first and second opposing branches are connected at a proximal end. Those branches respectively define first and second outer surface profiles facing inward relative to each other. The inlet is oriented at the distal end of the first branch, and the outlet is oriented at the distal end of the second branch. The heat sink is oriented between the first and second branches and has first and second opposing lateral surfaces. Each of the corresponding first and second lateral surfaces defines a corresponding first and second outer surface profile, which respectively coincide with the corresponding inward-facing outer profiles of the first and second branches. The corresponding lateral surfaces of the heat sink and the inward-facing outer surface profiles of the branches are in a relatively spaced-apart orientation relative to each other. The corresponding top and bottom surfaces of the heat sink each have a surface area that is sixty percent to eighty-five percent (60%-85%) of the corresponding surface area of ​​the corresponding upper and lower surfaces of the housing. The first and second solid thermally conductive layers are respectively interposed between each of the corresponding first and second outer surface profiles of the heat sink and those outer surface profiles of the first and second branches and secured to each of the corresponding first and second outer surface profiles of the heat sink and those outer surface profiles of the first and second branches.

[0010] Other embodiments feature a medical imaging device, such as a PET / MRI system, comprising: a gantry; a coolant circuit in the gantry for absorbing heat generated within the gantry; and a gantry cooling device coupled to the coolant circuit for receiving the heat generated within the gantry. A coolant fluid circulates within the coolant circuit. The gantry also includes a magnetic resonance imaging tube. The imaging tube includes at least one electromagnetic radiation detector therein and a detector electronics package coupled to the radiation detector for receiving signals generated by the radiation detector. The imaging tube includes a cooling channel therein having a non-metallic housing. The housing has a flat lower surface coupled to the electromagnetic radiation detector and a flat upper surface coupled to the detector electronics package. A cooling conduit in the housing has a contoured outer surface and is respectively coupled to an inlet and an outlet of the coolant circuit for circulating the coolant fluid therethrough. An integral non-metallic heat sink is within the housing. The heat sink has respective continuous top and bottom surfaces in direct thermal communication with the respective upper and lower surfaces of the housing, and lateral surfaces between the top and bottom surfaces. The lateral surface has an outer surface profile that conforms to the outer surface profile of the conduit and is in a relatively spaced orientation relative to the conduit. A solid thermally conductive layer is interposed between and secured to the respective opposing outer surface profiles of the conduit and the heat sink.

[0011] An additional exemplary embodiment features a method for forming a cooling channel for a gantry for diagnostic medical imaging equipment. In the exemplary method, a cooling conduit is formed having an inlet, an outlet, and an outer surface having a surface profile. A unitary non-metallic heat sink is formed having corresponding continuous top and bottom surfaces, and lateral surfaces between the top and bottom surfaces, the lateral surfaces having an outer surface profile that conforms to the outer surface profile of the conduit. Corresponding portions of the outer surface profile of the conduit and the outer surface profile of the heat sink are placed in a relatively spaced-apart orientation, and then the outer surface profile of the conduit and the outer surface profile of the heat sink are rigidly coupled to each other by inserting a solid thermally conductive layer and securing the solid thermally conductive layer to their respective corresponding opposing and spaced-apart outer surfaces. The now coupled conduit and heat sink are enclosed in a non-metallic housing having corresponding flat upper and lower surfaces that are in direct thermal communication with the corresponding top and bottom surfaces of the heat sink. The inlet and outlet of the conduit are accessible from outside the housing.

[0012] In some method embodiments, the heat sink is fabricated as a single piece of ceramic material, and the cooling conduit is constructed of metal, such as a metal tube. In embodiments comprising a metal conduit and a ceramic heat sink, the metal conduit and ceramic heat sink are rigidly coupled by depositing a metal layer on a portion of the outer surface of the ceramic heat sink that couples to the corresponding outer surface contour of the conduit and welding the metal layer previously deposited on the ceramic heat sink to the corresponding outer surface contour of the conduit. In some embodiments, the coupled conduit and heat sink are encapsulated by placing the coupled conduit and heat sink in a mold and encapsulating the coupled conduit and heat sink by filling the mold with a non-solid, non-metallic material, such as liquid polyurethane, and hardening the non-metallic material to form a rigid shell.

[0013] In other method embodiments, a metal cooling conduit is fabricated to have a U-shaped flat profile with first and second opposing branches connected at a proximal end. The branches respectively define first and second outer surface profiles facing inward and laterally spaced relative to each other. The inlet is oriented at the distal end of the first branch, and the outlet is oriented at the distal end of the second branch. A ceramic heat sink is fabricated to have first and second opposing lateral surfaces, wherein each of the respective first and second lateral surfaces defines a respective first and second outer surface profile that coincides with the corresponding inward-facing outer profiles of the first and second branches, respectively. The heat sink is inserted between the first and second branches so that its respective first and second outer surface profiles are in a relatively spaced orientation from the corresponding inward-facing outer profiles of the first and second branches. The first and second branches of the conduit are coupled to each of their respective first and second outer surface profiles of the heat sink by depositing a respective metal layer and welding it to the corresponding outer profiles of the first and second branches.

[0014] The respective features of the exemplary embodiments described herein may be applied collectively or separately in any combination or subcombination. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Exemplary embodiments are further described in the following detailed description in conjunction with the accompanying drawings, in which:

[0016] Figure 1 is a front elevational view of a gantry of a combined PET / MRI medical imaging scanner for generating PET and / or MRI images of a patient, comprising a detector assembly including a radiation detector, detector electronics, and cooling channels, respectively;

[0017] Figure 2 yes Figure 1 A side elevation view of a detector assembly of a PET / MRI scanner;

[0018] Figure 3 yes Figure 2 a cross-sectional plan view of a cooling channel of a detector assembly;

[0019] Figure 4 yes Figure 3 an elevational cross-section of the cooling channel; and

[0020] Figure 5-Figure 8 is an elevational cross-section of an alternative embodiment cooling channel.

[0021] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.The figures are not drawn to scale. DETAILED DESCRIPTION

[0022] A medical imaging device having a cooling system including cooling channel embodiments described herein transfers heat away from the system's gantry in one or more of its detector packages to maintain the radiation detector and detector electronics within a specified temperature range, thereby reducing the likelihood of temperature-related degradation of patient images. Various embodiments of these cooling channels are suitable for computed tomography (CT), two-dimensional digital radiography (DR), positron emission tomography (PET), and single-photon emission computed tomography (SPECT) modalities. Various embodiments of the cooling channels are also suitable for hybrid modality devices (e.g., PET / MRI or SPECT / MRI) that include magnetic resonance imaging (MRI) and another modality, where one or more cooling channels are oriented within the MRI tube scan field. The efficient cooling properties of these cooling channel embodiments are useful for detector assemblies that include solid-state avalanche photodiodes (APDs) and silicon photomultipliers (SiPMs). Because these types of solid-state detectors are generally more susceptible to higher temperatures than photomultipliers (PMTs). When incorporated into a gantry of a combined PET / MRI and SPECT / MRI imaging system, these cooling channel embodiments enable high heat load transfer away from the gantry of the imaging device while reducing ohmic heating, eddy current heating, and magnetic field distortion within an MR scan.

[0023] In the case of MRI systems, positioning the radiation imaging detector array inside the patient imaging bore of its gantry, as is done in the imaging tube of combined PET / MRI and SPECT / MRI imaging systems, presents technical challenges. As non-limiting examples, the challenges include spatial limitations, distortion of the magnetic field and gradient fields generated during the MRI scan of the patient, and ohmic and eddy current heating. In general, the magnetic field strength and spatial limitations of combined PET / MRI or SPECT / MRI systems typically limit the selection of radiation detector sensors to solid-state types, such as avalanche photodiodes (APDs) and silicon photomultipliers (SiPMs). Solid-state photon sensors such as APDs and SiPMs are relatively small in height (1-2 mm) compared to larger PMTs and the materials of their components, and are generally not affected by the magnetic field of the MRI system, but their gain is more susceptible to temperature fluctuations. PMTs are vacuum tubes and do not respond as quickly to temperature changes as APDs and SiPMs.

[0024] As described, the cooling channel embodiments herein are capable of transferring heat away from APD and SiPM type detectors. They comprise a non-metallic, non-conductive material that reduces the likelihood of gantry heating due to eddy current heating, ohmic heating, and friction heating when the detector assembly is within an MRI imaging tube that generates an electromagnetic field (such as that of a PET / MRI system). The non-metallic, non-conductive material of the cooling channel embodiments is also relatively more transparent to the electromagnetic field generated within the MRI imaging tube, which reduces MR image artifacts, including, as non-limiting examples, ghosting when using an MR system to perform echo planar imaging (EPI), rapid imaging scans. Thus, the cooling channel embodiments maintain the solid-state detector within desired temperature parameters to reduce temperature gain distortion in patient PET and SPECT images, while being relatively transparent within the MR field to reduce ghosting and other distortions in the MR images.

[0025] Embodiments of cooling channels efficiently transfer heat from detector assemblies in medical imaging devices of any modality by enhancing direct conductive heat transfer from radiation detectors and detector electronics to the coolant in the cooling system. The cooling channels can maintain the solid-state detectors and detector electronics within a wide temperature range during scanner operation, despite containing non-conductive, non-metallic components that typically have lower thermal conductivity than metal components. In combined MRI / PET or MRI / SPECT scanners, the lower metal content reduces eddy currents and ohmic heating and Lorentz forces (vibrations) induced in the electromagnetic field of the MRI tube in the cooling channels, which would otherwise increase the ambient temperature in the detector assembly, cause spike artifacts, or damage the detector. The lower metal content in cooling channel embodiments also reduces eddy current-induced artifacts in MR images. Reducing the electromagnetically conductive material content in the detector assembly beneficially reduces the ambient temperature in the gantry and reduces interruptions in the MR scan field in the MR imaging tube. Despite the use of non-metallic components within the cooling channels, the presently disclosed gantry cooling system embodiments can transfer sufficient heat out of the gantry to maintain the ambient operating temperature bandwidth and fluctuation specifications of the imaging system.

[0026] Figure 1 A PET / MRI imaging apparatus or system 10 is shown for generating overlapping MRI and PET image displays. The apparatus 10 includes a gantry 12. An MRI gradient tube 14 in the gantry 12 defines a longitudinal axis Z that is oriented relative to the longitudinal axis Z. Figure 1. A plurality of PET detector assemblies 16 (hereinafter, detector assemblies) are coaxially arranged within the MRI tube 14 in opposing pairs radially spaced apart from the longitudinal axis Z. Each detector assembly 16 includes a radiation detector 18 facing the patient P. Exemplary radiation detectors include avalanche photodiodes (APDs) or silicon photomultipliers (SiPMs). A detector electronics package 20 (hereinafter, detector electronics) receives signals from the radiation detectors 18 via a signal path, such as a plug-in terminal-type electrical connector 21, the signals being indicative of photons sensed by the array of detector crystals in the detector. Each detector electronics 20 generates a corresponding detector output signal, which is subsequently processed by an image processing unit 22 to generate or construct an image of the patient. The plurality of detector assemblies 16 define a cylindrical PET image field along the longitudinal direction Z, wherein the image is generated by the image processing unit 22. Along its coaxial longitudinal direction Z, the MRI tube 14 defines a cylindrical MR image field, wherein the image is also generated by the image processing unit 22. This is achieved by corresponding adaptation of the arrangement density of the PET detector assembly 16 along the longitudinal direction Z to provide simultaneous imaging of both modalities. In operation, the PET and RM image fields are substantially matched to each other and both image scans are performed in tandem.

[0027] Each detector assembly 16 includes cooling channels 24 for transferring heat generated within the detector assembly to a gantry cooling system 26 by circulating a fluid coolant in a cooling loop 28. In a recirculating coolant system, the coolant in turn transfers its retained heat to a gantry cooling system typically located in the gantry or another part of the medical imaging system, or to a cooling system such as a gantry. Figure 1 In some modality embodiments that include MR scanning capabilities, supply coolant within cooling circuit 28 is first directed to detector assembly 16 and then return coolant is directed through the gradient coils of the MR system before returning to the coolers of cooling system 26.

[0028] exist Figure 1-Figure 4In some embodiments, a cooling channel 24 is interposed between each radiation detector 18 and its detector electronics 20. The cooling channel 24 includes a non-metallic housing 30 having a flat lower surface 32 for abutting coupling to a corresponding flat surface of the radiation detector 18 and a flat upper surface 34 for abutting coupling to a corresponding flat surface of the detector electronics 20. Fasteners (not shown) couple the radiation detectors 18 and the detector electronics 20 to the housing 30. In other embodiments, the corresponding abutting surfaces of the detectors 18, the detector electronics 20, and the housing define other mutually consistent shapes. In some embodiments, the male terminal-type electrical connector 21 is oriented in the through-channel of the housing 30. The cooling channel 24 includes a cooling conduit 36 ​​in the housing 30 for circulating a fluid coolant within the cooling circuit 28 of the gantry cooling system 26 via an inlet 38 and an outlet 40. The cooling conduit 36 ​​is a metal tube, but in other embodiments, the conduit is constructed of a non-metallic material such as a polymer. Typically, metallic cooling conduits are used to achieve higher heat transfer rates to the coolant in the cooling circuit 28 than would be possible with non-metallic conduits, as long as the metallic structures do not cause unacceptable distortion of patient images, particularly MR images in combined MRI / PET or MRI / SPECT systems.

[0029] The cooling conduit 36 ​​has a U-shaped flat profile with opposing first and second branches 42, 44 coupled at proximal ends. The distal end of the first branch 42 includes the inlet 38, while the distal end of the second branch 44 includes the outlet 40. The cooling conduit 36 ​​has a flat oval cross-section with flat lower and upper surfaces 46, 48, which are in direct thermal contact with the lower and upper planar surfaces 32, 34, respectively, of the housing 30. The opposing first and second branches 42, 44 define first and second outer surface profiles 50, 52, respectively, that face inward relative to each other.

[0030] The cooling passage 24 includes a non-metallic, non-conductive heat sink 54 within the housing having respective continuous top and bottom surfaces 56, 58 in direct thermal communication with the respective upper and lower surfaces 34, 32 of the housing 30. In some embodiments, the respective top and bottom surfaces 56, 58 of the heat sink 54 each have a surface area that is between sixty percent and eighty-five percent (60%-85%) of the respective surface area of ​​their respective upper and lower surfaces 34, 32 of the housing 30. In some embodiments, the heat sink 54 is formed from a single piece of ceramic material or by casting and curing a ceramic slurry. In other embodiments, the heat sink 54 is a single structural fabrication of fixed ceramic subcomponents. Various embodiments of the heat sink 54 are constructed from one or more of the following ceramic materials: silicon nitride, boron carbide, aluminum nitride, aluminum oxide, and silicon carbide.

[0031] The heat sink 54 is oriented between the first and second branches 42, 44 of the conduit 36 ​​and has opposing first and second lateral surfaces 60, 62. The outer surface profile of each of the respective first and second lateral surfaces 60, 62 conforms to the respective first and second inwardly facing outer surface profiles 50, 52 of the first and second branches 42, 44 of the conduit 36. The respective pairs of surfaces 50 and 42, 52 and 44 are in relatively spaced-apart orientations relative to each other.

[0032] A first solid thermally conductive layer 64 is interposed between and secured to each of the corresponding first outer surface profiles 60 and 50 of the lateral surface of the heat sink 54 and the lateral surface of the first branch 42 of the conduit 36. Similarly, a second thermally conductive layer 66 is interposed between and secured to each of the corresponding second outer surface profiles 62 and 52 of the lateral surface of the heat sink 54 and the lateral surface of the second branch 44 of the conduit 36. A solid thermally conductive layer directly adhered to the opposing surfaces of the heat sink 54 and the conduit 36 ​​has a higher overall thermal conductivity than a layer with no contact gap, or with only surface contact, or with the application of a non-solid thermally conductive grease between these components. Solid thermally conductive layers 64 and 66 facilitate direct conductive heat transfer from the lateral surfaces of heat sink 54 to cooling conduits 36 .

[0033] The secure attachment of the conduit 36 ​​and the heat sink 54 to each other enhances the overall structural integrity of the cooling channel 24 and inhibits relative displacement of the metal cooling conduit 36 ​​caused by the induced Lorentz force when the cooling channel is exposed to the electromagnetic field within the MR tube 14. This prevents relative displacement of the metal conduit 36 ​​from generating noise in the electromagnetic field generated within the MR tube 14 or damaging the PET detector. The former helps maintain the integrity of the radiation detector 18, thereby preventing distortion of CT, PET, or SPECT images. The latter helps reduce the likelihood of image artifacts and spikes in MR images.

[0034] Each of the first and second thermally conductive layers 64, 66 comprises a metal layer 68 deposited on its corresponding outer lateral surface 60 or 62 of the non-metallic heat sink 54. Preferably, the deposition area of ​​the metal layer 68 is limited to a zone of the lateral surfaces 60 and 62 that is opposite the corresponding outer surfaces 50 and 52 of the conduits to minimize the total metal content within the cooling channel 24. A solder layer 70 is secured to its corresponding metal layer 68 and to its corresponding outer surface profile 50 or 52 of its corresponding conduit branch 42 or 44, thereby completing the securing of these components to one another. The hardened solid solder layer 70 is relatively soft and flexible, which is beneficial for accommodating the different thermal expansion rates of the different materials in the cooling conduit 36 ​​and the heat sink 54. The thermal conductivity of commercially available solder ranges from approximately 50 to 80 W / mK.

[0035] In other cooling channel embodiments, thermally conductive layers 64 and / or 66 include a solid thermally conductive adhesive having a higher thermal conductivity than a non-thermally conductive adhesive. The thermally conductive adhesive adheres to the cooling conduit 36 ​​and heat sink 54 and rigidly secures the cooling conduit 36 ​​and heat sink 54 to each other. Thermally conductive adhesives are used to bond non-metallic cooling conduits and heat sinks to each other when securing them with deposited metal coatings and solder is not feasible, for example, when the cooling conduits are constructed of polymeric materials. Commercially available thermally conductive adhesives have a thermal conductivity of approximately 1 W / mK.

[0036] exist Figure 2-Figure 4 In embodiments of the cooling passage 24, female thread fasteners 72 are embedded in or otherwise secured to the side of the housing 30 between the lower surface 32 and the upper surface 34 of the housing 30 for selectively coupling the cooling passage directly or indirectly to the gantry 12. In some embodiments, the fasteners 72 are constructed of a non-metallic, non-conductive material to minimize the metal content of the detector assembly 16.

[0037] exist Figure 1-Figure 4In the embodiment of the cooling channels 24, heat generated by the radiation detector 18 and detector electronics 20 within the detector assembly 16 is ultimately transferred through the cooling channels 24 to the coolant circulating in the coolant loop 28 at a series of direct thermally conductive junctions. Specifically, the cooling conduits 36 and the heat sink 54 are embedded in the material forming the housing 30 and in direct thermally conductive contact therewith. Heat generated by the radiation detector 18 and detector electronics 20 within the detector assembly 16 is initially transferred to the cooling channels 24 via the corresponding lower and upper surfaces 32, 34 of the housing 30. The upper and lower surfaces 34, 32 of the housing 30 are in direct contact and thermally conductive communication with their respective upper and lower surfaces 48, 46 of the cooling conduits 36. The heat thus absorbed by the conduits 36 is in turn transferred to the circulating coolant in the coolant loop 28. Similarly, the upper and lower surfaces 34, 32 of the housing 30 are in direct contact and thermally conductive communication with their respective top and bottom surfaces 56, 58 of the heat sink 54. Heat absorbed by the top and bottom surfaces 56 , 58 of the heat sink 54 is transferred to the cooling conduit 36 ​​in thermally conductive communication via its first and second lateral surfaces 60 , 62 and respective first and second thermally conductive layers 64 , 66 .

[0038] Figure 5-Figure 8 is an alternative embodiment of a cooling channel that includes different flow paths for its cooling conduits and different placement of the heat sink. Figure 5-Figure 8 Each of the embodiments described in the previous paragraph Figure 1-Figure 4 The embodiments of the cooling channels 24 of FIG. 1 are similar. Heat generated by the radiation detector and the detector electronics is ultimately transferred through each of the alternative cooling channel embodiments to the coolant circulating in the coolant circuit in a series of direct thermally conductive junctions.

[0039] exist Figure 5 In the embodiment shown, cooling channel 80 includes a housing 82 in which is embedded a three-circuit serpentine cooling conduit 84 having an inlet 86 and an outlet 88 for coolant circulation. Three heat sinks 90, 92, and 94 are interposed between the serpentine coils of conduit 84. A thermally conductive layer 96 secures the conduit 84 and the corresponding outer surfaces of the heat sinks 90, 92, and 94.

[0040] exist Figure 6 In the embodiment of the present invention, the cooling channel 100 has a housing 102 in which a dual-circuit serpentine cooling conduit 104 is embedded, having an inlet 106 and an outlet 108 for coolant circulation. A pair of heat sinks 110 and 112 are interposed between the serpentine coils of the conduit 104. A thermally conductive layer 114 secures the conduit 104 and the heat sinks 110 and 112 to the opposing outer surfaces.

[0041] exist Figure 7In the embodiment of the present invention, the cooling channel 120 has a housing 122 in which a single-circuit cooling conduit 124 is embedded, having an inlet 126 and an outlet 128 for circulating coolant. A pair of heat sinks 130 and 132 are located on either side of the conduit 124. A thermally conductive layer 134 is fixed to the opposing outer surfaces of the conduit 124 and the heat sinks 130 and 132.

[0042] exist Figure 8 In the embodiment shown, cooling channel 140 includes a housing 142, within which is embedded a multi-tube parallel-flow cooling conduit 144 having an inlet 146 and an outlet 148 for coolant circulation. In this embodiment, cooling conduit 144 includes four parallel branch conduits 150, 152, 154, and 156. Three heat sinks 158, 160, and 162 are interposed between opposing pairs of branch conduits. A thermally conductive layer 164 secures the opposing outer surfaces of branch conduits 150, 152, 154 and corresponding heat sinks 158, 160, and 162.

[0043] An exemplary method for making any of the cooling channels 24, 80, 100, 120, and 140 is now described. For the sake of brevity, this description focuses on the method for making the cooling channel 24. The cooling conduit 36 ​​and the heat sink 54 are made. In some embodiments, the cooling conduit 36 ​​is formed by forming a metal tube to have a Figure 3 and Figure 4 . Similarly, the heat sink 54 is fabricated to have first and second lateral edges 60, 62 that match the respective profiles of their corresponding first and second outer surface profiles 50, 52 of the first and second branches 42, 44 of the cooling conduit.

[0044] The first and second lateral edges 60, 62 of the heat sink 54 are metallized by depositing a metal layer 68 on the first and second lateral edges 60, 62. In some embodiments, the metal layer is deposited on the lateral surfaces 60 and / or 62 by coating the lateral surfaces 60 and / or 62 with a metal coating that promotes electroplating (e.g., a palladium or platinum coating), or the metal can be deposited by electron beam deposition, sputter coating, or vapor deposition. The first and second branches 42, 44 of the cooling conduit 36 ​​are then advanced over the corresponding first and second now metallized lateral edges 60, 62 of the heat sink 54. Thereafter, the corresponding first and second heat conductive layers 64, 66 are completed by welding the corresponding metallized lateral edges 60 and 62 of the heat sink 54 to their corresponding first and second outer surface profiles 50, 52 of the cooling conduit, thereby forming a solidified weld joint 70 having relatively high thermal conductivity. In other embodiments, the lateral edges 60 and 62 of the heat sink are not metallized, and the first and second thermally conductive layers 64 and 66 comprise a thermally conductive adhesive that, once cured, bonds or otherwise secures the cooling conduit 36 ​​and the heat sink 54 to each other. In cooling channel embodiments utilizing non-metallic cooling conduits, the thermally conductive layers 64 and / or 66 are formed using a thermally conductive adhesive.

[0045] Regardless of whether the thermally conductive layer 64 or 66 is formed with a metal layer and solder or an adhesive layer, the now fixed cooling conduits 36 and radiator 54 are encapsulated or otherwise encapsulated in the non-metallic housing 30 along with any desired fasteners 72. The inlet 38 and outlet 40 of the cooling conduits and the engaging surfaces of any fasteners 72 remain exposed outside the housing 30. In some embodiments, the housing is formed by placing the fixed cooling conduits 36 and radiator 54 components and any fasteners 72 in a mold (not shown). The mold is filled with a non-solid non-metallic material such as polyurethane or other thermoplastic or thermosetting resin. Thereafter, the material is hardened to form the now rigid housing 30. All cooling conduits 36 and radiator 54 components encapsulated within the housing 30 are now rigidly positioned and are in direct thermal communication with each other. In some embodiments, the mold is removed after the housing material solidifies and hardens. In other embodiments, the mold remains in place as an outer shell of the housing 30.

[0046] The completed cooling channel 24 is prepared for inclusion in the detector assembly 16 by forming a through-passage in the housing 30 between the respective upper and lower surfaces 34, 32 of the housing 30 for receiving an electrical connector 21, such as a plug-in terminal block. In some embodiments, the through-passage is formed in the mold before the filler material is poured by placing a mold insert that is removed after the filler material has at least partially hardened. In other embodiments, the through-passage is formed after the filler material has hardened by removing the hardened material with a drill or other cutting tool. The terminal block or other electrical connector 21 is then inserted into the through-passage of the housing 30. The electromagnetic radiation detector 18 is coupled to the electrical connector 21 and is securely coupled in abutting contact with the lower surface 32 of the housing 30 by means of fasteners for direct thermal communication therebetween. Similarly, the detector electronics package 20 is coupled to the electrical connector 21 so that it can receive signals generated by the radiation detector 18 through the signal path established by the electrical connector. The detector electronics package 20 is securely coupled in abutting contact with the upper surface 34 of the housing 30 by means of fasteners for direct conductive thermal communication therebetween. The completed detector assembly 16 is now ready for installation into the gantry 12 of the medical imaging apparatus 10.

[0047] Although various embodiments have been shown and described in detail herein, others can readily devise embodiments that still incorporate many other variations of the claimed invention. The present invention is not limited in its application to the exemplary embodiment construction details and component arrangements set forth in the specification or illustrated in the accompanying drawings. The present invention is capable of other embodiments and can be practiced or performed in various ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be considered restrictive. The use of "comprising," "including," or "having," and variations thereof herein, is intended to encompass the items listed thereafter and their equivalents, as well as additional items. Unless otherwise specified or limited, the terms "mounted," "connected," "supported," and "coupled," and variations thereof, are to be interpreted broadly; they encompass direct and indirect mounting, connection, support, and coupling.

Claims

1. A cooling channel for a gantry of a diagnostic medical imaging device, comprising: a non-metallic housing having a lower surface for abutting contact and coupling to the electromagnetic radiation detector and an upper surface for abutting contact and coupling to the detector electronics package; a cooling conduit in the housing for circulating a coolant fluid therethrough, the cooling conduit having an inlet and an outlet, each accessible from an exterior of the housing, and an exterior surface profile; An integral non-metallic heat sink in the housing, the integral non-metallic heat sink having: Respective continuous top and bottom surfaces in direct thermal communication with respective upper and lower surfaces of the housing, and a lateral surface between the top surface and the bottom surface, the lateral surface having an outer surface profile that conforms to the outer surface profile of the cooling conduit and being oriented relatively spaced from the cooling conduit; as well as A solid heat-conducting layer is interposed between and secured to the respective opposing outer surface contours of the cooling conduit and the heat sink.

2. The cooling channel of claim 1, wherein the heat sink comprises a single piece of ceramic material.

3. The cooling channel according to claim 2, further comprising: The cooling duct is constructed of metal; as well as The solid heat conductive layer has a metal layer deposited on the outer surface contour of the heat sink; and a solder layer secured to the metal layer and to the outer surface profile of the cooling conduit. The cooling channel of claim 1 , wherein the solid thermally conductive layer comprises a thermally conductive adhesive.

5. The cooling channel according to claim 1, further comprising: The cooling duct is constructed of metal; as well as The solid heat conductive layer has a metal layer deposited on the outer surface contour of the heat sink; and a solder layer secured to the metal layer and to the outer surface profile of the cooling conduit.

6. The cooling passage of claim 1, the inlet and outlet being oriented on opposite ends of the housing. 7 . The cooling channel of claim 6 , further comprising the cooling conduit having a serpentine flat profile.

8. The cooling channel of claim 1 , contained within a detector assembly, further comprising: an electromagnetic radiation detector coupled to the lower surface of the housing; a detector electronics package coupled to the upper surface of the housing; as well as An electrical connector passes through the upper and lower planar surfaces of the housing for transmitting signals generated by the electromagnetic radiation detector to the detector electronics package.

9. The cooling channel according to claim 1, further comprising: the cooling conduit having a u-shaped flat profile with opposing first and second branches joined at proximal ends thereof, the first and second branches respectively defining first and second outer surface profiles facing inwardly relative to each other; the inlet being oriented on a distal end of the first branch; the outlet being oriented on a distal end of the second branch; the heat sink being oriented between the first and second branches, the heat sink having first and second opposing lateral surfaces, each of the respective first and second lateral surfaces defining respective first and second outer surface profiles that coincide with, in an opposing, spaced-apart orientation, corresponding inwardly facing outer profiles of the first and second branches, respectively; The respective top and bottom surfaces of the heat sink each have a surface area between sixty percent and eighty-five percent of the respective surface area of ​​its corresponding respective upper and lower surfaces of the housing; as well as a first solid thermally conductive layer and a second solid thermally conductive layer, the first solid thermally conductive layer and the second solid thermally conductive layer being interposed between and fixed to each of the respective corresponding first and second outer surface contours of the heat sink and those outer surface contours of the first and second branches, respectively.

10. The cooling channel of claim 9, contained within a detector assembly, further comprising: an electromagnetic radiation detector coupled to the lower surface of the housing; a detector electronics package coupled to the upper surface of the housing; as well as An electrical connector passes through the upper and lower surfaces of the housing for transmitting signals generated by the electromagnetic radiation detector to the detector electronics package.

11. The cooling channel according to claim 9, further comprising: A monolithic heat sink constructed of ceramic material; The cooling duct is constructed of metal; each of the first solid thermally conductive layer and the second solid thermally conductive layer comprises a metal layer deposited on its corresponding outer surface contour of the heat sink, and a solder layer fixed to its corresponding metal layer and to its corresponding outer surface contour of the conduit branch; and The housing includes a non-metallic molding that encapsulates the cooling duct and the heat sink therein.

12. The cooling channel of claim 11 , contained within a detector assembly, further comprising: an electromagnetic radiation detector coupled to the lower surface of the housing; a detector electronics package coupled to the upper surface of the housing; as well as An electrical connector passes through the upper and lower surfaces of the housing for transmitting signals generated by the electromagnetic radiation detector to the detector electronics package.

13. A medical imaging device comprising: Stand; a coolant circuit in the gantry for absorbing heat generated within the gantry; a gantry cooling device coupled to the coolant loop for receiving heat generated within the gantry; a coolant fluid circulating within the coolant circuit; The magnetic resonance imaging tube in the gantry has: at least one electromagnetic radiation detector and a detector electronics package coupled to the electromagnetic radiation detector for receiving a signal generated by the electromagnetic radiation detector, and; A cooling channel in the gantry, the cooling channel having: a non-metallic housing having a planar lower surface coupled to the electromagnetic radiation detector and a planar upper surface coupled to the detector electronics package; a cooling conduit in the housing, the cooling conduit having an outer surface profile, an inlet and an outlet respectively coupled to the coolant circuit for circulating the coolant fluid therethrough; an integral non-metallic heat sink in the housing, the integral non-metallic heat sink having respective continuous top and bottom surfaces in direct thermally conductive communication with respective upper and lower surfaces of the housing, and lateral surfaces therebetween, the lateral surfaces having an outer surface contour conforming to an outer surface contour of the cooling conduit, in an opposed, spaced orientation relative to the cooling conduit; as well as A solid heat-conductive layer is interposed between and secured to the respective opposing outer surface contours of the cooling conduit and the heat sink.

14. The medical imaging apparatus according to claim 13, wherein the cooling channel further comprises: the cooling conduit having a u-shaped flat profile with opposing first and second branches joined at proximal ends thereof, the first and second branches respectively defining first and second outer surface profiles facing inwardly relative to each other; the inlet being oriented on a distal end of the first branch; the outlet being oriented on a distal end of the second branch; The inlet and outlet are respectively accessible from the outside of the housing; the heat sink being oriented between the first and second branches, the heat sink having first and second opposing lateral surfaces, each of the respective first and second lateral surfaces defining respective first and second outer surface profiles that conform to, and are in a relatively spaced-apart orientation to, corresponding inwardly facing outer profiles of the first and second branches, respectively; The respective top and bottom surfaces of the heat sink each have a surface area between sixty percent and eighty-five percent of the respective surface area of ​​its corresponding respective upper and lower surfaces of the housing; as well as a first solid thermally conductive layer and a second solid thermally conductive layer, the first solid thermally conductive layer and the second solid thermally conductive layer being interposed between and fixed to each of the respective corresponding first and second outer surface contours of the heat sink and those outer surface contours of the first and second branches, respectively.

15. The medical imaging apparatus according to claim 14, wherein the cooling channel further comprises: A monolithic heat sink constructed of ceramic material; The cooling duct is constructed of metal; Each of the first solid thermally conductive layer and the second solid thermally conductive layer comprises a metal layer deposited on its corresponding outer surface contour of the heat sink, and a solder layer fixed to its corresponding metal layer and to its corresponding outer surface contour of the conduit branch; a molded housing enclosing the cooling duct and the radiator therein; as well as An electrical connector passes through the upper and lower planar surfaces of the housing for transmitting signals generated by the electromagnetic radiation detector to the detector electronics package.

16. The medical imaging apparatus of claim 15, further comprising a fastener accessible from an exterior of the housing, the fastener embedded in a molding between the upper and lower planar surfaces of the housing for coupling the housing to the gantry.

17. A method for making a cooling channel for a gantry of a diagnostic medical imaging device, comprising: fabricating a cooling conduit for circulating a coolant fluid therethrough, the cooling conduit having an inlet, an outlet, and an outer surface having a surface contour; A unitary non-metallic heat sink is fabricated, wherein the unitary non-metallic heat sink comprises: a respective continuous top and bottom surface, and a lateral surface between the top and bottom surfaces, the lateral surface having an outer surface profile that conforms to the outer surface profile of the cooling conduit; orienting the outer surface profile of the cooling conduit and corresponding portions of the outer surface profile of the heat sink in a relatively spaced orientation therebetween; rigidly coupling the cooling conduit and the heat sink to one another by interposing and securing a solid thermally conductive layer to respective opposing and spaced-apart outer surfaces of the cooling conduit and the heat sink; as well as The coupled cooling conduit and heat sink are enclosed within a non-metallic housing having respective upper and lower surfaces in direct thermal communication with respective top and bottom surfaces of the heat sink, wherein an inlet and an outlet of the cooling conduit are accessible from outside the housing.

18. The method of claim 17, further comprising: Making the heat sink into a single piece of ceramic material; constructing the cooling conduit from metal; rigidly coupling the cooling conduit and the heat sink by depositing a metal layer on a portion of the outer surface of the ceramic heat sink coupled to a corresponding outer surface contour of the cooling conduit and welding the metal layer previously deposited on the ceramic heat sink to the corresponding outer surface contour of the cooling conduit; as well as The coupled cooling conduits and heat sink are encapsulated by placing the coupled cooling conduits and heat sink in a mold and encapsulating the coupled cooling conduits and heat sink by filling the mold with a non-solid, non-metallic material and hardening the non-metallic material to form a rigid shell.

19. The method of claim 18, further comprising: fabricating the cooling conduit to have a u-shaped flat profile with opposing first and second branches joined at proximal ends thereof, the first and second branches respectively defining first and second outer surface profiles facing inwardly and laterally spaced relative to each other; orienting the inlet at a distal end of the first branch; orienting the outlet at a distal end of the second branch; fabricating the ceramic heat sink to have first and second opposing lateral surfaces, each of the respective first and second lateral surfaces defining respective first and second outer surface profiles that conform to corresponding inwardly facing outer profiles of the first and second branches, respectively; inserting the heat sink between the first and second branches so that its respective first and second outer surface contours are in an opposing, spaced-apart orientation with respect to the respective corresponding inwardly facing outer contours of the first and second branches; as well as The first and second branches are rigidly coupled to each of their respective first and second outer surface contours of the heat sink by depositing and soldering respective metal layers to the corresponding outer contours of the first and second branches.

20. A method for making a detector assembly for a gantry of a diagnostic medical imaging device, the detector assembly comprising a cooling channel made by the method of claim 19, the method comprising: forming a through passage in the housing between the respective upper and lower planar surfaces thereof, either before or after hardening the polymer material; inserting an electrical connector into the through passage, coupling an electromagnetic radiation detector to the electrical connector and to the hardened lower surface of the housing; as well as A detector electronics package is coupled to the electrical connector and to the upper surface of the housing such that the detector electronics package can receive signals generated by the electromagnetic radiation detector.

Images