Cooling channel with an in-SITU formed, monolithic heat sink casting for a diagnostic medical imaging apparatus

Abstract

A cooling system for a gantry of a diagnostic medical imaging apparatus incorporates a cooling channel for radiation detectors and electronics packages with an in-situ formed, electrically nonconductive, monolithic heat sink casting that is in direct surface contact and in heat-conductive communication with a cooling conduit and an electronics package having electronic components mounted on a printed circuit board. Electronic components of the electronics package are embedded within the heat sink casting. The cooling channel is typically incorporated within a detector electronics assembly (DEA).

Description

COOLING CHANNEL WITH AN IN-SITU FORMED, MONOLITHIC HEAT SINK CASTING FOR A DIAGNOSTIC MEDICAL IMAGING APPARATUSPRIORITY CLAIM

[0001] This application claims the benefit of priority of United States Provisional Application Number 63 / 721,032, filed November 14, 2024, and entitled “Advanced Cooling of PET Electronics in an MRI”, which is incorporated by reference in its entirety herein.TECHNICAL FIELD

[0002] A cooling system for a gantry of a diagnostic medical imaging apparatus. More particularly, the gantry cooling system incorporates a cooling channel for radiation detectors and electronics packages. The cooling channel incorporates an in-situ formed, monolithic heat sink casting that is in direct surface contact and in heat-conductive communication with a cooling conduit and an electronics package.BACKGROUND

[0003] Diagnostic medical imaging apparatuses include, by way of non-limiting example, computed tomography (CT), two-dimensional digital radiography (DR), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT) modalities. Hybrid modality apparatuses include, by way of non-limiting example, PET / CT, PET / MRI, SPECT / CT and SPECT / MRI, which combine in a single system the local imaging resolution benefits of CT or MRI and the sensitivity for imaging and detecting cellular and metabolic biological processes in a patient. Many of these imaging apparatuses or systems include a toroidal-shaped gantry structure through which is inserted a patient table. The gantry includes one or more electromagnetic radiation detectors, which emit electrons in response to incident photonsof electromagnetic radiation. The output electrons of the detector are processed by detector electronics packages to generate detector output signals, which are subsequently processed by the imaging apparatus to generate or construct patient images. Typical electronics packages utilize printed circuit boards (PCBs) upon which are mounted electronics components. In some imaging systems, detector electronics packages are housed with the detectors within the gantry structure in an integrated detector electronics assembly (DEA).

[0004] Exemplary electromagnetic radiation detectors include photomultiplier tubes (PMTs) and solid-state detectors, such as avalanche photo diodes (APDs) and silicon photomultipliers (SiPMs). Signal gain of solid-state detectors is more temperature dependent than PMTs. The solid-state photon sensors and their detector electronics packages are typically maintained within relatively narrow temperature fluctuation and operational temperature bandwidths to reduce the likelihood of inaccurate detector readings and / or excessive noise generation components in the detector readings that otherwise might lead to inferior quality patient images. The solid-state radiation detectors require external cooling of their DEAs to maintain detector assemblies and their electronics packages within defined temperature fluctuation and bandwidth specifications. In some embodiments, the external cooling system for the medical imaging apparatus incorporates a circulating liquid cooling system that transfers heat generated within the DEAs to a liquid cooling medium.

[0005] In any medical imaging modality, an electronics package with a DEA generates resistive or ohmic heat during operation as current flows through one or more of its PCBs and the mounted electronics components. Some imaging modalities, such as MRI, also generate eddy current heating and frictional heating in the electronics packages during imaging system operation. Eddy currents are generated as the PCB and its electronics components are exposed to changing magnetic fields within the imaging apparatus, which induce current flows within the electronics packages. The induced current flows generate additional resistive heating and kinetic vibrations. The kinetic vibrations generate frictional heating among electronics and other components that rub into contact with each other.Examples of other components within the DEA that are susceptible to eddy current induced heating are cooling tubes, cooling fins and cooling plates incorporated within the DEA’s associated cooling system. Induced eddy currents contribute to MR image distortion, such as artifact ghosting.SUMMARY

[0006] Exemplary embodiments of a cooling system described herein transfer imaging apparatus generated heat, including gantry heat, to fluid-cooled, cooling channels. The cooling channel construction reduces the effects of magnetic and gradient fields, as well as ohmic and eddy current heating that are induced in the gantry during patient scans, all of which otherwise would degrade patient image quality. Exemplary embodiments of a cooling system for a gantry of a diagnostic medical imaging apparatus incorporates a cooling channel for radiation detectors and electronics packages. The cooling channel comprises an in-situ formed, electrically nonconductive, monolithic heat sink casting that is in direct surface contact with one or more electronics packages and in heat-conductive communication with a cooling conduit. In some embodiments, liquid coolant circulates within the cooling conduit. Electronic components of the electronics packages are embedded within and thus in direct surface contact with the heat sink casting. Conductive pathways formed one or more printed circuit boards (PCBs) of the electronics packages are also in direct surface contact with the heat sink casting. The cooling channel transfers heat away from an associated electronic packages by direct heat conductive contact of its embedded electronics components and its PCB with the in-situ formed, electrically nonconductive, monolithic heat sink casting. Heat absorbed from the electronics package by the heat sink casting is in turn transferred to the cooling conduit by the heat sink casting’s direct contact with the cooling conduit. In some embodiments, fins and / or chill plates of the cooling conduit are also embedded within and in direct contact with the in-situ formed heat sink casting. In some embodiments, the cooling channel is incorporated within a detector electronics assembly (DEA) of a medical imaging apparatus.

[0007] In-situ formation of the heat sink casting of the present disclosure, such as by pouring or injecting a flowable composition within a mold cavity containing one or more pre-positioned and oriented electronics packages and one or more cooling conduits and subsequent solidifying of the composition assures direct surface contact between the now solid, monolithic heat sink casting and the various prepositioned components. That direct surface contact facilitates efficient conductive thermal heat transfer from the electronics packages to the cooling conduit within the cooling channel. In some embodiments, the monolithic heat sink casting dampens vibrations induced within the cooling channel.

[0008] The in-situ formed heat sink casting of the present disclosure is inexpensive and easy to manufacture, compared to the cost of a prefabricated casting or a prefabricated machined heat sink that is assembled into a cooling channel by subsequent affixation one or more electronics packages and cooling conduits. In some embodiments, the composition of the heat sink casting material facilitates easy removal of the embedded cooling conduit and the electronics package of the cooling channel for repair or recycling, by re-liquifying of the material or peeling it off of the embedded components. In some embodiments, the flowable composition is selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin. In some embodiments the flowable composition further comprises powdered ceramic filler or other powdered fillers.

[0009] Exemplary embodiments described herein feature a cooling channel for a gantry of a diagnostic medical imaging apparatus. The apparatus comprises a cooling conduit, having a first face that defines an outer surface profile and an electronics package having a first side with electronic components that are mounted to a printed circuit board. The cooling conduit first face and the electronics package first side are in opposed, spaced relationship with each other, and define a gap therebetween. A monolithic, electrically nonconductive, heat sink casting completely fills the defined gap, in direct surface contact and heat-conductive communication with the first face of the cooling conduit and the first side of the electronics package, with the electronic components embedded therein.

[0010] Other exemplary embodiments described herein feature a method for making a cooling channel for a gantry of a diagnostic medical imaging apparatus. A mold is provided with a mold cavity that defines a cavity inner surface. A cooling conduit is oriented in the mold cavity. The cooling conduit has a first face that defines an outer surface profile. An electronics package is oriented in the mold cavity. A first side of the electronics package has electronic components that are mounted to a printed circuit board. The first side of the cooling conduit is oriented in opposed spaced relationship with the first face of the cooling conduit, so that a gap is defined between them. The mold cavity is filled with an electrically nonconductive, flowable composition that completely fills the defined gap between the cooling conduit first face and the electronics package first side, so that the flowable composition is in direct surface contact and heat-conductive communication with the outer surface profile of the cooling channel and encapsulates the electronic components therein. The flowable composition is solidified, thereby forming a monolithic, solid heat sink casting with the electronic components embedded therein.

[0011] The respective features of the exemplary embodiments of the invention that are described herein may be applied jointly or severally in any combination or subcombination.BRIEF DESCRIPTION OF DRAWINGS

[0012] The exemplary embodiments of the invention are further described in the following detailed description in conjunction with the accompanying drawings, in which:

[0013] FIG. 1 is a front elevational view of a gantry of a combination PET / MRI medical imaging scanner for generating PET and / or MRI images of a patient, which incorporatesdetector electronic assemblies (DEAs), respectively including a radiation detector, and a cooling channel that includes a cooling conduit and a detector electronics package;

[0014] FIG. 2 is a cutaway, side elevational view of one of the DEAs of the PET / MRI scanner of FIG. 1;

[0015] FIG. 3 is a top plan view of the DEA of FIG. 2;

[0016] FIGs. 4 and 5 are elevational cross sections of the cooling channel of the DEA of FIG. 3;

[0017] FIG. 6 is a perspective view of an alternative embodiment DEA;

[0018] FIG. 7 is a perspective view of the DEA of FIG. 6 without an external housing cover;

[0019] FIG. 8 is an elevational cross section of the DEA of FIGs. 6 and 7;

[0020] FIG. 9 is a perspective view of the cooling channel of the DEA of FIGs. 6 and 7;

[0021] FIG. 10 is an elevational cross section of the cooling channel of FIG. 9;

[0022] FIG. 11 is an exploded view of the cooling channel of FIGs. 9 and 10;

[0023] FIG. 12 is an elevational cross section of the cooling channel of FIG. 10 after the formation of a monolithic, electrically nonconductive heat sink casting;

[0024] FIG. 13 is a perspective view of an alternative embodiment DEA;

[0025] FIG. 14 is an elevational cross section of the DEA of FIG. 13;

[0026] FIG. 15 is an exploded view of the DEA of FIG. 14, showing components of its cooling channel; and

[0027] FIG. 16 is an elevational cross section of the cooling channel of FIG. 13 after the formation of a monolithic, electrically nonconductive heat sink casting.

[0028] 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.DESCRIPTION OF EMBODIMENTS

[0029] A cooling system for a gantry of a diagnostic medical imaging apparatus incorporates a cooling channel with a cooling conduit and an electronics package. The electronics package includes electronic components that are mounted on a printed circuit board. The cooling channel has an in-situ formed, electrically nonconductive, monolithic heat sink casting that is in direct surface contact and in heat-conductive communication with the cooling conduit and the printed circuit board of the electronics package. The electronic components of the electronics package are embedded or otherwise encapsulated within the monolithic heat sink casting. Embedding the electronic components in the heat sink casting enhances transfer of their internally generated heat to the cooling channel. The cooling channel is typically incorporated within a detector electronics assembly (DEA) that includes radiation detectors.

[0030] Medical imaging apparatus with cooling systems incorporating cooling channel embodiments described herein, in one or more of their detector packages, e.g., DEAs, transfer heat out of system’s gantry to maintain radiation detector and detector electronics within a designated temperature range, 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), positronemission tomography (PET), and single photon emission computed tomography (SPECT) modalities. Various embodiments of the cooling channels are also suitable for hybrid modality apparatuses that incorporate magnetic resonance imaging (MRI) and another modality, (e.g., PET / MRI or SPECT / MRI) where one or more cooling channels are oriented within the MRI tube scanning field. Efficient cooling attributes of embodiments of these cooling channels are useful for detector assemblies that incorporate solid-state avalanche photo diodes (APDs) and silicon photomultipliers (SiPMs). as these types of solid-state detectors are typically more susceptible to higher temperatures than photo multiplier tubes (PMTs). These cooling channel embodiments described herein achieve high heat-load transfer out of the gantry of the imaging apparatus, while reducing: magnetic field distortions within the MR scanning field, ohmic heating, and eddy current heating, when incorporated in gantries of combination PET / MRI and SPECT / MRI imaging systems.

[0031] In the case of an MRI system, locating an array of radiation imaging detectors inside the patient imaging bore of its gantry, as is done in the imaging tube of combination PET / MRI and SPECT / MRI imaging systems, presents technical challenges. The challenges include, by way of non-limiting example, spatial constraints, distortions in magnetic and gradient fields generated during an MRI scan of a patient, as well as ohmic and eddy current heating. In general, the magnetic field strength and spatial constraints of a combination PET / MRI or SPECT / MRI system generally limit radiation detector sensor selection to solid-state types, such as avalanche photo diodes (APDs) and silicon photo multipliers (SiPMs). Solid-state photon sensors, such as APDs and SiPMs, are relatively small in height (1-2 mm) and are typically unaffected by the magnetic fields of an MRI system, as compared to larger PMTs and the materials of their components, but their gain is more susceptible to fluctuations in temperature. PMTs are evacuated tubes and do not respond to temperature changes as fast as APDs and SiPMs.

[0032] As noted, the cooling channel embodiments herein are capable of transferring heat away from detector electronics packages as well as their APD- and SiPM-type detectors.They incorporate in-situ formed, non-metallic, electrically nonconductive heat sink casting materials that reduce the likelihood of gantry heating attributable to eddy current heating, ohmic heating and frictional heating when the detector assembly is in the electro-magnetic field generated MRI imaging tube, such as by a PET / MRI system. The non-metallic, electrically nonconductive materials in the heat sink casting of the cooling channel embodiments are also relatively more transparent to the electro-magnetic field generated within the MRI imaging tube, which reduces MR image artifacts, including by way of nonlimiting example, artifact ghosting when using the MR system to perform echo planar imaging (EPI), rapid-imaging scans. Thus, the cooling channel embodiments maintain the detector electronics packages and their solid-state detectors within required temperature parameters to reduce temperature-gain distortions to patient PET and SPECT images, while being relatively transparent within MR fields. This reduces eddy current induced heating with the printed circuit boards and their mounted electronic components of the detector electronics package, as well as artifact ghosting and other distortions to MR images.

[0033] Embodiments of the cooling channel efficiently transfer heat from the detector assembly of any modality of medical imaging apparatus by enhancing direct conductive heat transfer from radiation detectors and detector electronics to coolant in the cooling system. More specifically, the in-situ formed heat sink casting transfers heat more efficiently from the printed circuit boards and their mounted electronic components of the electronics package of the detector electronics to the cooling conduits that are also embedded within the cooling channel. The cooling channel can maintain solid-state detectors and the detector electronics within temperature range bandwidths during scanner operation, despite their incorporation of an electrically nonconductive, heat sink casting material that generally has lower thermal conductivity than metal components. In combination MRI / PET or MRI / SPECT scanners, lower metal content in the cooling channel reduces eddy current generation, ohmic heating, and Lorenz force generation (vibrational forces) within the cooling channel, that are induced in the electro-magnetic field of the MRI tube, which would otherwise raise ambient temperature in the detector assembly, cause a spiking artifact, or damage the detector. Lower metal content in thecooling channel embodiments also reduces eddy current-induced artifacts in the MR image. Lowering electro-magnetically conductive material content in the in-situ formed heat sink casting of the detector assemblies beneficially lowers ambient temperature in the gantry and beneficially reduces disruptions of the MR scanning field in the MR imaging tube. The presently disclosed gantry cooling system embodiments can transfer sufficient heat out of the gantry to maintain ambient operational temperature bandwidth and fluctuation specifications of the imaging system, despite use of non-metallic, electrically nonconductive heat sink castings within the cooling channels.

[0034] Cooling system embodiments described herein facilitate direct liquid cooling of the electronics components, using thermal conductivity of the in-situ formed heat sink casting between the components and fluid-cooled conduits. Exemplary coolant fluids include compressible and incompressible fluids such as liquids and gases (e g., room air, nitrogen, water) or phase-change refrigerants. The cooling system embodiments herein, which incorporate the in-situ formed, electrically nonconductive heat sink castings, have overcome several design challenges. First, certain components, such as the SiPM detector elements in the detector assemblies, require lower and tighter temperature tolerances for the detectors to operate quantitatively within their design specifications. Efficient thermal coupling of the heat sink casting to its embedded electronic packages achieves those needed lower and tighter temperature tolerances. Second, electronics boards and other types of other electronic components associated with the electronics packages of the detector assemblies, which also need to be cooled within the gantry, have irregular surface profiles and shapes that complicate capability of their direct contact with their associated, proximate, fluid-cooled conduits.

[0035] In various embodiments of the cooling channels described herein, the in-situ formed heat sink castings assure that cooling conduits with or without chill plates and / or cooling fins are in efficient thermally conductive, direct contact with heat generating components of their associated electronics packages. In some embodiments, the cooling conduit has an inlet and an outlet for passage of flowing coolant Material forming thecooling conduit and its related chill plates and / or fins is selected for its thermal conductivity properties and may include one or more metals and / or thermally conductive ceramic compositions. Aluminum and copper are typically used for the cooling conduit. In many embodiments, the cooling conduit takes several turns inside the cooling channel to enhance heat transfer from the conduit to the flowing coolant. In some embodiments, the chill plate is designed as top and bottom plates with a groove for receiving the coolant line. Both plates are pressed against each other, sandwiching the coolant line therebetween, to enhance conductivity between the respective plate and its line. The term “cooling conduit”, as used herein is intended to encompass multiple component fabrications including tubes within which flow the liquid coolant, and any associated solo, monolithic plates, as well as composite structures incorporating multiple subplates joined together to function as a unitary heat transfer medium, for absorbing heat generated or dissipated by an electronic component or other device within the associated electronics package of a DEA or other devices within the medical imaging apparatus that requires external cooling.

[0036] Embodiments of the cooling systems herein have scalable architecture, with one or more modular detector electronics assemblies (DEAs), allowing for axial FoV scalability of various imaging system configurations. Furthermore, having a DEA as a self-sufficient design in a housing with integrated input / output (I / O) communication of control / data information capability, electric power supply, chill plates with fluid coolant inlets and outlets, consolidate detector elements of detectors, electronics, and power supplies into one cohesive package. These DEA embodiments package the main heat generators / dissipators in the gantry of the imaging system, such as the detector electronics, other electronic component boards or printed circuit boards and power supplies into one package with its own dedicated cooling system components. In some embodiments a DEA’s power supply is thermally coupled to a chill plate associated with a cooling channel, to remove the heat from the former. By packaging other electronic components, such as the power supply, electronic boards, and printed circuit boards in the same housing as the detector elements, the integrated DEA is more compact, can share one or cooling channels among heatgenerating components in the DEA housing, and minimize the number of coolant line connections between cooling channels.

[0037] In some embodiments the scalable cooling system is a closed loop system. This design has great advantages such as having a finite amount of coolant, such as water, that does not flood the system and facility if and where there is a leak, as compared to an open loop system with a relatively infinite coolant flow capability. This also allows the cooling system to provide stable coolant temperature to the chill plates within the DEAs, as ADP or SiPM components in their detector arrays require relatively narrow temperature bandwidth to operate quantitatively. In some imaging system embodiments, the specified coolant temperature bandwidth is 23 °C with + / - 2°C to maintain a stable temperature to the SiPMs within the DEAs.

[0038] With reference to the figures, FIGs. 1 and 2 show a PET / MR imaging apparatus or system 10 for generating an overlaid PET and MR image display of a patient P. The apparatus 10 includes a gantry 12. A patient tunnel wall 14 in the gantry 12 defines an axial direction axis Z, extending orthogonally in relation to the plane of the drawing of FIG. 1. The patient tunnel wall 14 is circumscribed by an acoustic foam liner 16. A plurality of modular detector electronics assemblies (DEAs) 18 are arranged circumferentially (C directional arrow) and coaxially (Z direction) in an array outside the patient tunnel wall 14 and the acoustic foam liner 16, equally radially spaced from the axis Z. An image processing system 22 is coupled to each DEA 18 by a communication and control signals pathway 24 and a power conduit 26. A cooling apparatus 30, oriented externally of the gantry 12 circulates fluid coolant through one or more of the DEAs 18, in a closed cooling loop, via coolant supply conduit 32 and fluid return conduit 34. Exemplary coolant fluids include compressible and incompressible fluids such as liquids and gases (e.g., room air, nitrogen, water) or phase-change refrigerants.

[0039] Referring to FIGs. 1-5, exemplary DEAs 18 comprise a DEA housing 40, coupled to the gantry 12 by a housing support (not shown). The housing 40 has an outer, radiallyfacing side 42, an inner, radially facing side 44 and an internal barrier 46. A housing cavity 47 is defined in the housing 40 between the outer, radially facing side 42 and the barrier 46 Detector elements 48 are retained in the housing 40 between the inner, radially facing side 44 and the internal barrier 46.

[0040] A cooling channel 49 is retained within the housing cavity 47 to transfer heat generated within the cavity to the cooling apparatus 30 by flow of coolant therethrough from the coolant supply conduit 32 to the fluid return conduit 34. The cooling channel 49 comprises a closed-loop cooling conduit 50, having a first face 52 that is defined by its outer surface profile. In some embodiments the cooling conduit 50 incorporates a chill plate and / or segmented fins, such as shown in United States Patent No. 8,590,331.

[0041] The cooling channel 49 further comprises an electronics package 60 whose first side 62 includes a printed circuit board (PCB) 64 with mounted electronic components 66. Exemplary electronic components include integrated circuits, capacitors, resistors, inductors that generate internal heat and that potentially generate eddy currents during operation of the imaging apparatus 10. The electronics package 60 generates respective detector elements 48 output signals, which are routed to the image processing unit 22, via a communications and power port 68 on the DEA housing 40. The power port 68 interconnects to the communication and control signals path 24 of the imaging processing system 22 of the imaging apparatus 10. The detector elements 48 output signals are subsequently processed by the image processing unit 22 to generate or construct patient images. The communications and power port 68 also supplies electric power to the electronic package 60 via the power conduit 26.

[0042] Within the cooling channel 49, the first face 52 of the cooling conduit 50 and the first side 62 of the electronics package 60 (including the exposed face of the PCB 64 and its mounted electronic components 66) are in opposed, spaced relationship with each other, and define a gap therebetween. The cooling channel 49 further comprises a monolithic, electrically nonconductive, heat sink casting 70 that completely fills the defined gapbetween the cooling conduit 50 and the electronics package 60. The heat sink casting 70 is in direct surface contact and heat-conductive communication with the first face 52 of the cooling conduit 50 and the first side 62 of the electronics package 60. The exposed face of the PCB 64 directly contacts the heat sink casting 70 and the electronic components 66 are embedded or otherwise encapsulated within the heat sink casting. In this way the heat sink casting 70 facilitates direct conductive heat transfer of heat generated by the electronic components 66, as well as heat generated by any eddy currents generated within conductive pathways of the PCB 64 and / or directly between the electronic components to the cooling conduit 50.

[0043] The material comprising the heat sink casting 70 is an electrically nonconductive, initially flowable composition selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin. After the flowable composition completely fills the gap defined between the cooling conduit 50 and the electronics package 60 it is solidified to form the monolithic heat sink casting structure 70. In some embodiments, the composition includes powdered ceramic to enhance heat transfer. Powdered ceramic filled, room temperature vulcanized silicone typically has a thermal conductivity of 1-6 W / mk. In some embodiments, its thermal conductivity is 3 W / mk.

[0044] Thermal simulations indicate that the introduction of a monolithic heat sink casting 70 comprising powdered ceramic filled, room temperature vulcanized silicone, having thermal conductivity of 3 W / mk, within the cooling channel 49 to fill the gap between the first face 52 of the cooling conduit 50 and the first side 62 of the electronics package 60 reduces operating temperature by 72 percent, compared to prior designs having limited surface area contact with only the top surfaces of some heat generating components

[0045] FIGs. 6-12 depict another exemplary DEA 80 embodiment. FIG. 6 shows an assembled DEA 80, having a housing 82 with a detector window 84 covering a pluralityof detector elements 86. A communications and power port 88 on the DEA housing 82 that interconnects to the communication and control signals path 24 of the imaging processing system 22 of the imaging apparatus 10. As with the DEA 18 embodiment of FIGS. 1-5, detector elements 86 output signals are subsequently processed by the image processing unit 22 to generate or construct patient images. The communications and power port 68 also supplies electric power to the electronic package 60 via the power conduit 26.

[0046] A cooling channel 90 is retained within the housing 82 to transfer heat generated therein to the cooling apparatus 30 by flow of coolant therethrough from the coolant supply conduit 32 to the fluid return conduit 34. The cooling channel 90 comprises a closed-loop cooling conduit 92, having a coolant tube 94 with a plurality of fingered fins 95. An inlet 96 of the coolant tube 94 is coupled to and in fluid communication with the coolant supply 32 of the cooling apparatus 30. An outlet 98 of the coolant tube 94 is coupled to and in fluid communication with the coolant return 34 of the cooling apparatus 30. The cooling conduit 92 has a first face 100 that is defined by its outer surface profile. In some embodiments the cooling conduit 50 incorporates a chill plate and / or segmented fins, such as shown in United States Patent No. 8,590,331.

[0047] The cooling channel 90 further comprises an electronics package 102 whose first side 104 includes a printed circuit board (PCB) 106 with mounted electronic components 108. Exemplary electronic components include integrated circuits, capacitors, resistors, inductors that generate internal heat and that potentially generate eddy currents during operation of the imaging apparatus 10. The PCB 106 includes electrical connectors 110 for connection to corresponding, mating electrical connectors that are coupled to the detector elements 86. The electronics package 102 generates respective detector element 86 output signals, which are routed to the image processing unit 22, via the communications and power port 88, which in turn interconnects to the communication and control signals path 24 of the imaging processing system 22 of the imaging apparatus 10. The detector elements 88 output signals are subsequently processed by the image processing unit 22 to generateor construct patient images. The communications and power port 88 also supplies electric power to the electronics package 102 via the power conduit 26.

[0048] A cover 112, also referred to as a forming cap, covers the cooling conduit 92 and a portion of the PCB 106 and mounted electronic components 108 of the electronics package 102. The cover 112 includes a filling port 114 that is circumscribed by a sealing grommet 116 and an inside surface 118. In some embodiments, the cover is selectively removable from the PCB 106. A cavity 120 is defined by a cavity surface that is formed between the inside surface 118 of the cover 112 and the PCB 106. The PCB 106 also forms the first side 104 of the electronics package 102. Therefore, the cavity 120 envelops and encapsulates a portion of the cooling conduit 92, as well as the portion of the PCB 106 and its mounted electronic components 108 that are positioned under the cover 112.

[0049] Within the cavity 120, under the cover 112 within the cooling channel 90, the first face 100 of the cooling conduit 92 and the first side 104 of the electronics package 102 (including the exposed face of the PCB 106 and its mounted electronic components 108) are in opposed, spaced relationship with each other, and define a gap therebetween.

[0050] The cooling channel 90 further comprises a monolithic, electrically nonconductive, heat sink casting 122 that completely fills the cavity 120 within the cover 112 and the defined gap, between the portions of the cooling conduit 92 and the electronics package 102 that are within the cavity. Therefore, within the cavity 120 the heat sink casting 122 is in direct surface contact and heat-conductive communication with the first face 100 of the cooling conduit 92 and the first side 104 of the electronics package 102. The exposed face of the PCB 106 directly contacts the heat sink casting 122 and the electronic components 108 are embedded or otherwise encapsulated within the heat sink casting. In this way the heat sink casting 122 facilitates direct conductive heat transfer of heat generated by the electronic components 108, as well as any heat generated by eddy currents generated within conductive pathways of the PCB 106 to the cooling conduit 92.

[0051] As in the previously described cooling embodiments of FIGs. 1-5, the material comprising the heat sink casting 122 is an electrically nonconductive, initially flowable composition selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin that is poured, injected or otherwise introduced into the cavity 120 via the filling port 114. In some embodiments, the composition includes powdered ceramic to enhance heat transfer. After the flowable composition completely fills the gap defined between the cooling conduit 92 and the electronics package 102, it is solidified to form the monolithic heat sink casting structure 122. In some embodiments, the cover 112 is removed after solidification of the heat sink casting structure 122.

[0052] FIGs. 13-16 depict another exemplary DEA 130 embodiment. FIG. 13 shows an assembled DEA 130, having a housing 132. A cooling channel 133 is retained within the housing 132 to transfer heat generated therein to the cooling apparatus 30 (see FIG. 1) by flow of coolant therethrough from the coolant supply conduit 32 to the coolant return conduit 34. The cooling channel 133 comprises a chill plate 134 that also functions as a lid for the housing 132, with a first face 135 on its underside and a thermal mat 136 that is interposed between the outwardly facing, top side of the chill plate 134 and a closed-loop coolant tube 138 that is shown in phantom. The coolant tube 138 receives coolant from the coolant supply conduit 32 and returns warmer coolant back to the cooling apparatus 30 via the coolant return conduit 34. The conductive thermal path established by the cooling channel 133 transfers heat from the first face 135 of the chill plate through the thermal mat 136 and in turn to the coolant tube 138. In some embodiments the coolant tube 138 incorporates a chill plate and / or segmented fins, such as shown in United States Patent No.8,590,331.

[0053] The cooling channel 133 further comprises an electronics package 140 whose first side 142 includes a printed circuit board (PCB) 144 with mounted electronic components 146. Exemplary electronic components include integrated circuits, capacitors, resistors,inductors that generate internal heat and that potentially generate eddy currents during operation of the imaging apparatus 10. The peripheral walls of the housing 132 and the underside first face 135 of the chill plate / lid 134 define an internal cavity 148, which retains the electronics package 140 and detector elements 150. Within the internal cavity 148, the first face 135 of the chill plate / lid 134 and the first side 142 of the electronics package 140 (including the exposed face of the PCB 144 and its mounted electronic components 146) are in opposed, spaced relationship with each other, and define a gap therebetween.

[0054] The cooling channel 133 further comprises a monolithic, electrically nonconductive, heat sink casting 151 that completely fills the defined gap within the internal cavity 148. Therefore, within the internal cavity 148 the heat sink casting 151 is in direct surface contact and heat-conductive communication with the first face 135 of the chill plate / lid 134 and the first side 142 of the electronics package 140. The exposed face of the PCB 144 directly contacts the heat sink casting 151 and the electronic components 146 are embedded within the heat sink casting. In this way the heat sink casting 151 facilitates direct conductive heat transfer of heat generated by the electronic components 146, as well as heat generated by any eddy currents generated within conductive pathways of the PCB 144 and / or directly between the electronic components to the chill plate / lid 134.

[0055] As in the previously described cooling embodiments of FIGs. 1-12, the material comprising the heat sink casting 151 an electrically nonconductive, initially flowable composition selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin that is poured, injected or otherwise introduced into the cavity 148 via one or both of the filling ports 152 formed in the chill plate / lid 134. The chill plate / lid 134 is retained on the housing 132 by lid clips 154. In some embodiments, the flowable composition includes powdered ceramic to enhance heat transfer. After filling the cavity 148 with the flowable composition, it is then solidified to form the monolithic heat sink casting structure 151.

[0056] As was described with respect to the embodiments of FIGs. 1-12, the electronics package 142 generates respective detector elements 150 output signals that are routed to the image processing unit 22, via an electrical connector 156. The electrical connector 156 in turn interconnects to the communication and control signals path 24 of the imaging processing system 22 of the imaging apparatus 10. The detector elements 150 output signals are subsequently processed by the image processing unit 22 to generate or construct patient images. The electrical connector 156 also supplies electric power to the electronics package 102 via the power conduit 26. An electromagnetic interference (EMI) gasket 158 circumscribes the electrical connector 156 to prevent electromagnetic interference, including radio frequency interference from entering the cavity 148.

[0057] Cooling channels disclosed herein, with in situ formed heat sink castings, are simpler and less expensive to manufacture and provide more efficient conductive heat transfer than cooling channels that utilize assembled, machined, composite components. Typically, those assembled cooling channel components have gaps separating them, in which case heat needs to be conducted in air through the gap. In some instances, thermally conductive but electrically nonconductive material (e.g., caulk, gel, foam or tape) is used to fill the gaps to enhance conductive heat transfer across the gaps. The complex surface profile and topology of electronic components mounted on a printed circuit board makes it difficult to fill gaps between them and their associated chill plates and / or coolant pipes. Gap filling with subsequently applied material adds production steps and complexity to the manufacturing processes, which are avoided by manufacture of the in-situ formed heat sink castings of the present disclosure.

[0058] The methods for manufacturing cooling channels herein are described with reference to the embodiments of the cooling channels of FIGs. 1-16. Reference numbers of structural elements shown in the respective figures follow the element name. The cooling channels 49, 90, 133 that are disclosed herein, with their respective in situ-formed heat sink castings 70, 122, 151 are made by providing a mold with a cavity 47, 120, 148 that defines a cavity inner surface. A cooling conduit 50, 92, 134 having a first face 52,100, 135 that defines an outer surface profile is oriented in the mold cavity. An electronics package 60, 102, 140 is also oriented in the mold cavity. The electronics package has a first side 62, 104, 142 with electronic components 66, 108, 146 that are mounted to a printed circuit board 64, 106, 144. The first side 62, 104, 142 of the electronics package is oriented in opposed spaced relationship with the first face 52, 100, 135 of the cooling conduit, so that a gap is defined therebetween.

[0059] After relative orientation and definition of the gap between the cooling conduit 50, 92, 134 and the electronics package 60, 102, 140, the mold cavity is filled with an electrically nonconductive, flowable composition (ultimately solidified to form the heat sink casting 70, 122, 151), which completely fills the defined gap between the cooling conduit first face 52, 100, 135 and the electronics package first side 62, 104, 142. Thus, the flowable composition is in direct surface contact and heat-conductive communication with the outer surface profile of the cooling conduit 50, 92, 134 and encapsulates the electronic components 66, 108, 146 as well as the first side of the PCBs 64, 106, 144 therein. By filling the defined gap with the filler composition and solidifying it to form the heat sink castings 70, 122, 151, facilitate direct, conductive heat transfer from the electronics package 60, 102, 140 to the cooling conduit 50, 92, 134. In various embodiments, the flowable composition filling is performed by pressurized injection or by gravity pour.

[0060] After filling the defined gap, the flowable composition is solidified and forms the monolithic, solid heat sink casting 70, 122, 151 with the electronic components embedded therein. In various embodiments, the flowable composition is selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin. In various embodiments, powdered ceramic is added to the flowable composition.

[0061] In some embodiments, the flowable composition that forms the solid, monolithic heat sink casting 70, 122, 151 is selected for easier separation of the cooling conduit 50,92, 134 and the electronics package 60, 102, from the assembled cooling channel 49, 90, 133, for repair or recycling of the now disassembled components. For example, room temperature vulcanized silicone, with or without powdered ceramic filler, once hardened is peelable from its embedded cooling conduit 50, 92, 134 and / or its embedded electronics package 60, 102. After separation from the heat sink casting the used electronics package and / or the cooling conduit is repairable or replaceable. Easy formation of a new heat sink casting returns the refurbished cooling channel into service. The replaced components are more easily recyclable than if the entire, assembled cooling channel were scrapped.

[0062] In some embodiments, the cooling conduit comprises a cooling tube having an inlet and an outlet accessible outside the mold cavity for circulation of fluid coolant therethrough. In such embodiments, the cooling conduit is oriented in the mold cavity with the inlet and outlet positioned outside the mold cavity.

[0063] In some embodiments, the cooling channel is fabricated in a mold and is removed from the mold after solidifying the monolithic, solid heat sink casting, rather than being formed in situ within the housing of a DEA. In such embodiments, the cooling channel is a modular component that can be inserted into a housing cavity of a DEA.

[0064] In some embodiments, at least part of the cavity inner surface is defined by the first face of the cooling conduit and / or the first side of the electronics package. In some embodiments, at least part of the cavity is defined by a cavity cover. In some embodiments, the cavity cover defines a filler port for filling the cavity with the flowable liquid composition that forms the heat sink casting.

[0065] As described, cooling channel embodiments, which incorporate in-situ formed heat sink castings are easier and cheaper to manufacture than cooling channels comprising separately manufactured heat sink castings that are thereafter joined to cooling conduits and electronics packages. Inevitably, the now joined heat sink castings, cooling conduits and electronic packages have assembly gaps between them. Those assembly andfabrication gaps reduce heat transfer. While filling fabrication gaps with grease or foam pads or the like does improve heat transfer, it is not as efficient as embedding components within an in-situ formed heat sink casting as described in this disclosure.

[0066] Advantageously, some embodiments of the cooling channels with the in-situ formed, solidified heat sink casting facilitate easier repair and recycling of those cooling channels. For example, embodiments of heat sink casting compositions with low melting points below the maximum permissible working temperature range of their embedded electronics packages are melted to separate the PCBs and the cooling conduits from the cooling channel. Some composition embodiments are dissolved and removed with a chemical solvent. Some soft, solidified heat sink casting composition embodiments are gently pulverized or chipped away from their embedded components. Some heat sink casting compositions comprising room-temperature vulcanized silicone can be peeled away from their embedded components for repair or recycling of their associated cooling channels.

[0067] Although various embodiments that incorporate the invention have been shown and described in detail herein, others can readily devise many other varied embodiments that still incorporate the claimed invention. The invention 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 invention is capable of other embodiments and of being practiced or of being conducted in many 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 or electrical connections or couplings.

Claims

CLAIMSWhat is claimed is:

1. A cooling channel for a gantry of a diagnostic medical imaging apparatus, comprising:a cooling conduit, having a first face that defines an outer surface profile; an electronics package having a first side with electronic components that are mounted to a printed circuit board;the cooling conduit first face and the electronics package first side in opposed, spaced relationship with each other, defining a gap therebetween; anda monolithic, electrically nonconductive, heat sink casting completely filling the defined gap, in direct surface contact and heat-conductive communication with the first face of the cooling conduit and the first side of the electronics package, with the electronic components embedded therein.

2. The cooling channel of claim 1. the cooling conduit further comprising a cooling tube having an inlet and an outlet accessible outside the heat sink casting for circulation of fluid coolant therethrough.

3. The cooling channel of claim 1, the first face of the cooling conduit comprising a chill plate.

4. The cooling channel of claim 1, the heat sink casting formed by the process of filling the defined gap between the cooling conduit first face and the electronics package first side with a flowable composition selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin; and thereafter solidifying the composition to form the monolithic heat sink casting structure.

5. A detector electronic assembly (DEA) of a medical imaging apparatus, which retains the cooling channel of claim 1 within a cavity of a housing thereof, the DEA housing incorporating a plurality of detector elements therein, wherein the heat sink casting completely fills the cavity and embeds both the cooling conduit and the first side of the electronics package therein.

6. The DEA of claim 5, wherein at least part of a cavity’ surface that defines the cavity is defined by the first face of the cooling conduit and / or the first side of the electronics package.

7. The cooling channel of claim 5, wherein at least part of the cavity surface that defines the cavity is defined by a cavity cover.

8. The DEA of claim 7, the cavity cover defining a filler port for filling the cavity with the flowable liquid composition that forms the heat sink casting.

9. The DEA of claim 5, the cooling conduit further comprising a cooling tube having an inlet and an outlet accessible outside the heat sink casting for circulation of fluid coolant therethrough.

10. The DEA of claim 9, the first face of the cooling conduit further comprising a chill plate.

11. A medical imaging system incorporating a plurality of the DEAs of claim 9, further comprising:a cooling apparatus, coupled to and external the gantry, having a coolant supply for supplying fluid coolant to the gantry, and a coolant return for returning the coolant to the cooling apparatus; andthe plurality of DEAs each coupled to the cooling apparatus by its respective inlet and outlet, which are respectively accessible external its DEA housing.

12. A method for making a cooling channel for a gantry of a diagnostic medical imaging apparatus, comprising:providing a mold with a cavity that defines a cavity inner surface; orienting a cooling conduit in the mold cavity, the cooling conduit having a first face that defines an outer surface profile;orienting an electronics package in the mold cavity, a first side of the electronics package having electronic components that are mounted to a printed circuit board, wherein the first side is oriented in opposed spaced relationship with the first face of the cooling conduit, defining a gap therebetween;filling the mold cavity with an electrically nonconductive, flowable composition that completely fills the defined gap between the cooling conduit first face and the electronics package first side, so that the flowable composition is in direct surface contact and heat-conductive communication with the outer surface profile of the cooling channel and encapsulates the electronic components therein; and solidifying the flowable composition, thereby forming a monolithic, solid heat sink casting with the electronic components embedded therein.

13. The method for making the cooling channel of claim 12, the cooling conduit further comprising a cooling tube having an inlet and an outlet accessible outside the mold cavity for circulation of fluid coolant therethrough.

14. The method for making the cooling channel of claim 12, wherein the flowable composition is selected from the group comprising room temperature vulcanized silicone, and / or vulcanized rubber, and / or ceramic slurry, and / or polymer liquid, and / or polymer powder, and / or thermosetting resin, and / or thermoplastic resin.

15. The method for making the cooling channel of claim 12, further comprising removing the cooling channel from the mold after solidifying the monolithic, solid heat sink casting.

16. The method for making the cooling channel of claim 12, wherein the mold cavity is a cavity formed within a housing of a detector electronic assembly (DEA) of a medical imaging apparatus, the DEA housing incorporating a plurality of detector elements therein, and wherein the flowable composition completely fills the cavity and embeds both the cooling conduit and the first side of the electronics package therein.

17. The method for making the cooling channel of claim 16, wherein at least part of the cavity inner surface is defined by the first face of the cooling conduit and / or the first side of the electronics package.

18. The method for making the cooling channel of claim 16, wherein at least part of the cavity inner surface is defined by a cavity cover.

19. The method for making the cooling channel of claim 18, the cavity cover defining a filler port for filling the cavity’ with the flowable liquid composition that forms the heat sink casting.

20. The method for making the cooling channel of claim 16, the cooling conduit having a cooling tube including an inlet and an outlet accessible outside the mold cavity for circulation of fluid coolant therethrough, further comprising orienting both the inlet and the outlet outside the mold cavity.

21. The method for making the cooling channel of claim 16, the first face of the cooling conduit further comprising a chill plate.

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