Patent Description:
This disclosure relates to cooling systems for medical imaging apparatuses. More particularly, this disclosure relates to modular, scalable fluid-cooling systems and methods for cooling gantries of medical imaging apparatuses, including gantries of long, axial field of view apparatuses.

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 circumferential rows and axially oriented columns of electromagnetic radiation detectors, which form a matrix-like detector array. The respective radiation detectors in the detector array emit electrons in response to incident photons of electromagnetic radiation. In some modalities, the incident photons are transmitted X-rays or ionized radiation emissions at the higher end of the electromagnetic frequency range (e.g., CT, DR, PET, SPECT), while in other modalities (e.g., MRI) the incident photons are within the radio frequency range. The output electrons of the detector elements in the detectors are processed by detector electronics to generate detector output signals, which are subsequently processed by the imaging apparatus to generate or construct patient images. In some imaging systems, detector electronics packages are housed with the detectors within the gantry structure in an integrated detector assembly.

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 are 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 poor quality patient images. The solid-state radiation detectors require external cooling to maintain detector assemblies within defined temperature fluctuation and bandwidth specifications. Typically, radiation detectors and detector assemblies in medical imaging systems are cooled by blowing cooling air over them, or by transferring detector heat to one or more conduits routed about the gantry structure that circulate cooling fluid in proximity to them.

In past cooling system designs for exemplary PET/CT scanning modalities, wherein the imaging apparatus gantry incorporates a PET axial field of view (aFOV) scanning zone that is axially aligned with a CT aFOV scanning zone, the cooling system was specifically sized to transfer heat from only one or two circumferential rows and axial columns of detector assemblies. Blown cooling air systems were satisfactory for such applications. However, recent movement in the field of PET imaging, with aFOV expansion of the patient imaging approaching one to two meters, has made it necessary to revisit the nature of both the design and the fabrication of such cooling systems, including in exemplary PET/CT systems. Often these axially expanded systems require cooling of a plurality of greater than two rows in each column of detector assemblies, further complicating blown cooling air-type cooling system architecture. Past cooling system designs for longer aFOV imaging systems have concatenated two or more existing, shorter aFOV cooling systems within the same gantry. In other words, conventional, known cooling system designs, modified for longer aFOV imaging systems, have utilized multiple water-to-air heat exchangers with fans to blow cooled air within the gantry, to transfer the heat out of the system back to the heat exchanger. This introduces two complexities to the design. The first one is limited space in the system. To remove the heat efficiently, the design might require adding larger and/or more heat exchangers in the gantry of the system. The second is related to noise generated due to the increased number of fans and the air flow required to remove the heat from the gantry of the extended aFOV imaging system. It becomes economically averse to fabricate medical imaging system gantry cooling systems for different combinations and orientations of detector assemblies (e.g., standard FOV systems with one or two /rows of such assemblies in each axially aligned column, versus extended, aFOV systems with more than two rows of detector assemblies per axial column).

Document <CIT> discloses cooling units for imaging systems.

Exemplary cooling system embodiments described herein are modular and scalable to accommodate varying numbers of detector assembly orientations and geometries within gantry architectures of different medical imaging systems. Fluid cooled, modular components of the cooling systems are incorporated within individual detector electronic assemblies (DEAs). Exemplary coolant fluids include compressible and incompressible fluids such as liquids and gases (e.g., room air, nitrogen, water) or phase-change refrigerants. Each DEA includes therein a first chill plate for cooling detector elements and a second chill plate for cooling electronic components, such as printed circuit boards and/or power supplies. In some embodiments, each DEAs' first chill plate is thermally conductively coupled to cooling detector elements therein and the second chill plate is thermally conductively coupled to the other electronic components therein. Coolant flow cascades sequentially through the first chill plate and then through the second chill plate. In some embodiments, plural DEAs are interconnected in cascaded fashion, sharing a common, scalable coolant flow path. In various embodiments, any desired number of rows and columns of DEAs are selectively interconnected within the coolant flow path. In some embodiments, components of the fluid cooling system, such as liquid-liquid heat exchangers, pumps, and flow control valves, are located external the imaging system gantry. External location of such components conserves space within the gantry and reduces likelihood of coolant leak infiltration therein. Beneficially, in some system embodiments, including longer aFOV systems, flexible scaling of higher gantry heat loads is achieved, by increasing or decreasing the heat transfer capability of the external cooling system components in proportion to the number of DEAs within the gantry.

Aspects of this disclosure are directed to a fluid coolant system for a gantry of a medical imaging apparatus where the cooling system cools scalable detector electronic assemblies (DEAs) within the gantry. Each DEA includes within its modular housing a first chill plate thermally conductively coupled to cooling detector elements therein and a separate, second chill plate thermally conductively coupled to other electronic components, such as printed circuit boards and/or power supplies therein. In some embodiments, the first chill plate is oriented between the detector elements and the second chill plate, for thermally isolating the detector elements from other heat dissipating components within the DEA. In some embodiments, one or more of the first or second chill plates are segmented into plural sub segments, sharing a common coolant pipe. In some embodiments, coolant flow cascades sequentially through the first chill plate and then through the second chill plate. In this type of coolant flow path, the detector elements have cooling priority in the DEA over the other cooled components.

Exemplary embodiments disclosed herein feature a fluid coolant system for a medical imaging apparatus, having a gantry forming a patient tunnel; 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. The imaging apparatus includes a detector electronic assembly (DEA) within the gantry, coupled to the cooling apparatus, having a housing; detector elements in the housing, for detecting incident photons of electromagnetic radiation originating outside of the housing and other electronic components in the housing. A fluid cooled, first chill plate is thermally conductively coupled to the detector elements, for cooling the detector elements. The first chill plate has a first inlet for receiving the coolant from the coolant supply and a first outlet for discharging the coolant to the coolant return. The DEA also includes a fluid cooled, second chill plate thermally conductively coupled to the other electronic components, for cooling the other electronic components. The second chill plate has a second inlet for receiving the coolant from the coolant supply and a second outlet for discharging the coolant to the coolant return.

Other exemplary embodiments disclosed herein feature a detector electronic assembly (DEA) for a medical imaging apparatus, including a housing; detector elements retained in the housing, for detecting incident photons of electromagnetic radiation originating outside of the housing; and other electronic components in the housing. The DEA includes a fluid cooled, first chill plate thermally conductively coupled to the detector elements, for cooling the detector elements, with the first chill plate having a first inlet for receiving fluid coolant and a first outlet for discharging the coolant. The DEA also includes a fluid cooled, second chill plate thermally conductively coupled to the other electronic components, for cooling the other electronic components, the second chill plate having a second inlet for receiving the coolant and a second outlet for discharging the coolant. The respective first and second inlets and outlets accessible outside the housing.

Additional exemplary embodiments of disclosed herein feature a method for scalable cooling of a gantry of a medical imaging apparatus, including: providing a gantry forming a patient tunnel; providing 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 The method includes providing a selected plurality of detector electronic assemblies (DEAs) for orientation within the gantry, with each respective DEA having a housing; detector elements in the housing, for detecting incident photons of electromagnetic radiation originating outside of the housing; and other electronic components in the housing, including a printed circuit board and a power supply. The provided DEA has a fluid cooled, first chill plate thermally conductively coupled to the detector elements, for cooling the detector elements, which is oriented in the housing intermediate the detector elements and the other electronic components. The first chill plate has a first inlet for receiving the coolant from the coolant supply and a first outlet for discharging the coolant to the coolant return. The provided DEA has a fluid cooled, second chill plate for cooling the other electronic components. The second chill plate has opposed first and second sides, respectively thermally conductively coupled to the printed circuit board on its first side and to the power supply on its second side,. The second chill plate has a second inlet for receiving the coolant from the coolant supply and a second outlet for discharging the coolant to the coolant return. In some embodiments, one or more of the first or second chill plates are segmented into plural sub segments, sharing a common coolant pipe. In this method, the respective first and second inlets and outlets of the first and second chill plates are externally accessible outside of each respective DEA housing. The method includes orienting the plurality of DEAs within the gantry, so that their respective DEA housings are commonly coupled to a housing support of the gantry axially in sequence about an outside of the patient tunnel, parallel to a central axis defined by the patient tunnel; and that their respective detector elements face the patient tunnel, tangential to a circumference thereof, with components of the detector element projecting radially away from the patient tunnel. The method is further practiced by coupling the first inlet of the first chill plate of and the second inlet of the second chill plate of each DEA directly or indirectly to the coolant supply of the cooling apparatus; and coupling the first outlet of the first chill plate and the second outlet of the second chill plate of each DEA directly or indirectly to the coolant return of the cooling apparatus. Cooling capacity of the external cooling apparatus is scaled in proportion to the number of DEAs within the gantry that are cooled thereby. Coolant is circulated between the gantry and the cooling apparatus at a flow rate that maintains a specified stable temperature bandwidth for all detector elements in the each of the respective DEAs.

The respective features of the exemplary embodiments that are described herein may be applied jointly or severally in any combination or sub-combination.

The exemplary embodiments are further described in the following detailed description in conjunction with the accompanying drawings, in which:.

The figures are not drawn to scale.

Medical imaging apparatus with cooling systems incorporating cooling system embodiments described herein, in one or more of their modular, scalable detector electronics assemblies (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 scalable, modular cooling systems are suitable for a broad range of axial field of view (aFOV) architecture applications, including 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 systems and their DEAs are also suitable for hybrid modality apparatuses that incorporate PET and another modality, (e.g., PET/CT or PET/MRI) of any length aFOV architecture.

Efficient cooling attributes of embodiments of these cooling systems are useful for DEAs that incorporate solid-state avalanche photo diodes (APDs) and silicon photomultipliers (SiPMs), as these types of solid-state detectors typically generate more operational heat than photo multiplier tubes (PMTs). Compared to PMTs, APDs and SiPMs are typically more susceptible to output signal distortion unless operated within relatively narrow temperature bandwidths. The scalable, modular cooling system embodiments described herein achieve high heat-load transfer out of the gantry of the imaging apparatus, facilitating operation of APDs and SiPMs within narrow temperature bandwidths, with less noise and construction complexity than known air-cooled systems.

The presently disclosed gantry cooling system embodiments transfer sufficient heat out of the gantry to maintain ambient operational temperature bandwidth and fluctuation specifications of the imaging system. More specifically, embodiments of the modular, scalable cooling systems disclosed herein efficiently transfer heat from the detector assembly of any modality of medical imaging apparatus by enhancing direct conductive heat transfer from radiation detectors, detector electronics and power supplies to gantry coolant in the cooling system. Cooling system components external the imaging system gantry dissipate heat from the gantry coolant. In this way, for specific aFOV length architectures, varying heat loads generated by varying numbers of DEAs are transferred out of the gantry by scaling the cooling system components located outside the gantry.

Some cooling system embodiments described herein facilitate fan-less direct water cooling of the electronics components, using thermal conductivity between the components and fluid-cooled, chill plate-type heat sinks as a heat transfer mode. 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 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. Second, electronics boards and other types of other electronic components associated with 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 heat sinks. Third, larger other electronic components in the DEA, such as power supplies are very bulky. Fourth, any fluid coolant leak within the gantry may cause electronics and power components therein to malfunction.

In various embodiments, modular, chill plate-type heat sinks are in direct contact with heat generating components. The chill plate has a fluid coolant line or conduit going through it with an inlet and an outlet. The plate material 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 coolant lines. The coolant line takes several turns inside the plate to enhance heat transfer from plate to 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 "chill plate", as used herein is intended to encompass 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 DEA.

In some embodiments, the chill plates have a smooth external surface. In some embodiments, a thermal tape, or foam, or thermally conductive gel, or the like is interposed as a heat transfer median between the chill plate and its associated heat-generating detector elements, electronics board, or power supply. In other embodiments, the outer surface of the chill plate is fabricated to have the opposite, mirror image surface topography of its associated circuit board pattern, where the valleys in the chill plate profile encapsulate integrated circuit (IC) or other components on the circuit board that have high heat dissipation. In such embodiments, a thermally conductive material, such as thermal tape or foam, thermal grease or gel, or the like, is interposed as a thermal median between the plate surface and the associated component to aid the transfer of the heat from the component to the chill plate.

Embodiments of the cooling systems 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, consolidates 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, 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 more chill plates among heat generating components, and minimize the number of coolant line connections between chill plates. In some DEA cooling system embodiments, a first chill plate is thermally coupled to a detector array of detector elements, and a second chill plate is thermally coupled to other electronic components, such as electronics board and a power supply. In some embodiments, the first chill plate is oriented within the DEA housing between the detector array of detector elements and the second chill plate, with the latter's associated other electronic components, such as electronics boards and power supplies.

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 <NUM> with +/- <NUM> to maintain a stable temperature to the SiPMs within the DEAs.

In some embodiments, coolant flowing to the gantry from the cooling apparatus is initially provided to the first chill plate associated with the detectors elements to maintain a tighter, stable temperature bandwidth on the SiPMs in the array. The output of the first chill plate is then plumbed to the second chill plate in the DEA, associated with the electronics and power supply. In some cooling system embodiments, where multiple DEAs are cascaded in the axial direction, the same flow sequence of coolant first flowing to the first chill plate in each DEA, then sequentially each second chill plate is maintained, for all DEAs in the cascade chain. Namely, coolant from the cooling apparatus first flows to the inlet for the first DEA in the cascade, then to the inlet of the second DEA in the cascade, and so on. In the last DEA in the cascade, its outflow from the outlet of its first chill plate is plumbed to its second chill plate. The cascade continues backwards, or upstream back to the return line of the cooling apparatus by routing coolant to and out of each successive second chill plate in the cascade, back to the first DEA in the chain. Thereafter, coolant discharged from the outlet of second chill plate of the first DEA is routed back to the cooling apparatus.

In some embodiments, to ensure all the DEAs in each axially interconnected column in the cooling system about the circumference of the gantry receive the same input coolant temperature, the coolant is branched out from the coolant supply to each DEA column via an annular ring manifold. In another alternative embodiment, coolant is branched out from the coolant supply to each interconnected DEA within an annular row or ring about the gantry circumference.

With reference to the figures, <FIG>, shows a PET/CT imaging apparatus or system <NUM> for generating an overlaid PET and CT image display of a patient P. The apparatus <NUM> includes a gantry <NUM>. A patient tunnel wall <NUM> in the gantry <NUM> defines an axial direction axis Z, extending orthogonally in relation to the plane of the drawing of <FIG>. The patient tunnel wall <NUM> is circumscribed by an acoustic foam liner <NUM>. A plurality of modular, detector electronics assemblies (DEAs) <NUM> are arranged coaxially in a matrix-like axial (Z direction) and circumferential (C directional arrow) array outside the patient tunnel wall <NUM> and the acoustic foam liner <NUM>, equally radially spaced from the axis Z. An image processing system <NUM> is coupled to each DEA <NUM> by a communication and control signals pathway <NUM> and a power conduit <NUM>. A cooling apparatus <NUM>, oriented external the gantry <NUM> circulates fluid coolant through one or more of the DEAs <NUM>, in a closed cooling loop, via coolant supply conduit <NUM> and fluid return conduit <NUM>. Exemplary coolant fluids include compressible and incompressible fluids such as liquids and gases (e.g., room air, nitrogen, water) or phase-change refrigerants.

Referring to <FIG> and <FIG>, exemplary DEAs <NUM> comprise a modular DEA housing <NUM>, coupled to the gantry <NUM> by a housing support <NUM>. An exemplary DEA modular housing and housing support comprises a detector head, pivotable detector bearing and mounting rail as shown and described in co-pending <CIT>. In jurisdictions permitting incorporation of patent documents by reference, the entire contents of Application No. <CIT>. The DEA housing <NUM> includes a plurality of radiation detector elements <NUM>, clustered in a two-dimensional array facing the patient P. Exemplary radiation detector elements <NUM> include avalanche photo diodes (APDs) or silicon photomultipliers (SiPMs). A detector data acquisition (DDA) package <NUM>, for example incorporated on a printed circuit board, receives signals from the individual radiation detector elements <NUM> that are indicative of photons sensed by their detector crystals. The received detector crystal signals are routed from the DDA package <NUM>, via a detector data-signal pathway <NUM> (e.g., a plug-in terminal-type, electrical connector), to a DEA electronic circuit board <NUM> for further signal processing. Some electronic circuit boards in the DEA incorporate printed circuit boards.

The DEA electronic circuit board <NUM> generates respective detector output signals, which are routed to the image processing unit <NUM>, via a communications port <NUM> on the DEA housing <NUM> that interconnects an internal logic signals pathway <NUM> to the communication and control signals path <NUM>. The detector output signals are subsequently processed by the image processing unit <NUM> to generate or construct patient images. In some embodiments, DDA package functionality is incorporated within the DEA circuit board rather than as a separate component. The DEA <NUM> also incorporates an internal DEA power supply <NUM>. A power inlet <NUM> on the DEA housing <NUM> interconnects a power cable <NUM> of the power supply <NUM> to the external power conduit <NUM>. Each DEA <NUM> is a self-contained modular unit, incorporating radiation detector elements <NUM>, the electronics DDA <NUM>, and related other electronics, (including by way of example the DEA electronics board or circuit board <NUM> to acquire and process signals indicative of incident photons sensed by the detectors, and routing output signals to the image processing unit <NUM>, and the internal DEA power supply <NUM>). Accordingly, any desired number of the individual, modular DEAs <NUM> are readily combined, by coupling each of its respective power inlet <NUM> and communications port <NUM> on the housing <NUM> into its respective complementary power conduit <NUM> and communication and control signals path <NUM> within the gantry <NUM>, to create scalable two-dimensional matrices of detector elements <NUM> for any diameter and axial length patient tunnel wall dimensions within the gantry; including those of extended aFOV imaging apparatuses.

The modular DEA <NUM> also incorporates scalable cooling system architecture, complementary to the previously described scalable detector element <NUM> architecture. Varying heat transfer loads for different arrays of modular DEAs <NUM> are accommodated by altering the heat transfer capacity of the external cooling apparatus <NUM>, rather than by altering internal structure of each DEA. The internal cooling system components in the DEA housing <NUM> comprise a fluid-cooled, first chill plate <NUM>, oriented proximate the heat-generating radiation detector elements <NUM> and/or the DDA package <NUM>, and a second chill plate, oriented proximate the heat-generating "other electronic components" (e.g., the DEA circuit board <NUM> and power supply <NUM>).

In the embodiment of <FIG>, the first chill plate <NUM> is oriented generally parallel to the detector elements <NUM> and interposed between them and the relatively higher heat-generating "other electronic components" DEA circuit board <NUM> and power supply <NUM>. This first chill plate <NUM> orientation provides additional heat shielding for the relatively more temperature sensitive detector elements <NUM>. The second chill plate <NUM> is oriented generally perpendicular to and radially inwardly from the first chill plate <NUM>, spanning almost the entire width and height of the DEA housing <NUM>. This orientation of the second chill plate <NUM> provides a relatively large surface area and thermal mass for enhancing heat transfer from any other electronic components in the DEA, including by way of example the circuit board <NUM> and power supply <NUM>. While the first <NUM> and second <NUM> chill plates shown in <FIG> are generally planar, in other embodiments one or more of the chill plates, or sub-plate components thereof that are joined into a unitary, composite chill plate have non-planar profiles. Non-planar profile chill plate embodiments are suitable for wrapping around multiple surfaces of a heat generating/dissipating electronic component or other component.

To enhance direct, conductive heat transfer within the DEA <NUM>, in some embodiments one or both of the first <NUM> and second <NUM> chill plates are at least partially in direct abutting, thermally conductive contact with their proximate heat-generating components. In other embodiments, one or both of the first <NUM> and second <NUM> chill plates are oriented in opposed, mutually spaced relationship with their proximate heat-generating components. To enhance conductive heat transfer across mutually spaced, opposed components, selectively, all or portions of the gaps therebetween are filled with a thermally conductive material median, such as thermally conductive sheet foam, tape, gel or grease.

Referring to <FIG>, the first <NUM> and second <NUM> chill plates transfer heat absorbed from their respective, proximate radiation detectors <NUM>, DDA package <NUM>, other electronic components, including the DEA circuit board <NUM>, or power supply <NUM> to fluid coolant that is circulating within a closed loop between the gantry <NUM> and the external cooling apparatus <NUM>. Within each DEA <NUM>, the first chill plate <NUM> receives circulating fluid coolant entering through a first coolant inlet <NUM>. Coolant flows through an internal conduit formed within the first chill plate <NUM>, absorbing heat from the plate material by conductive and convective heat transfer modes and is discharged out of a first cooling outlet <NUM>. Similarly, within each DEA <NUM>, the second chill plate <NUM> receives circulating fluid coolant entering through a second coolant inlet <NUM>. Coolant flows through an internal conduit formed within the second chill plate <NUM>, absorbing heat from the plate material by conductive and convective heat transfer modes and is discharged out of a second cooling outlet <NUM>.

In some cooling system embodiments, respective inlets <NUM>, <NUM> and outlets <NUM>, <NUM> of the first <NUM> and second <NUM> chill plates communicate directly and independently with the cooling loop in the gantry <NUM>, with parallel respective coolant flow paths for each DEA <NUM>. In some medical imaging applications, it is desirable to minimize the number of coolant conduits in the gantry <NUM>, to reduce likelihood of coolant leak damage to equipment. In some cooling system embodiments, providing cascading, serial coolant flow from the coolant supply conduit <NUM> of the cooling system <NUM>, through the first chill plate <NUM>, then the second chill plate <NUM> and back to the coolant return conduit <NUM> simplifies the cooling path and reduces the quantity of conduits, compared to cooling systems relying on independent, parallel coolant flow to each DEA. In other embodiments, the scalable, modular DEA <NUM> is used in a single component application (e.g., as a detector for a digital radiography imaging device). Referring to the DEA <NUM> shown in <FIG> and <FIG>, and the fluid flow path of DEA <NUM> of <FIG>, in such single-component DEA applications, coolant from the coolant supply <NUM> of the cooling apparatus <NUM> enters the first coolant inlet <NUM> of the first chill plate <NUM>, exits its first coolant outlet <NUM>, enters the second coolant inlet <NUM> of the second chill plate <NUM> and exits its second coolant outlet <NUM>, for discharge into the coolant return <NUM> of the cooling apparatus.

In the cooling system embodiment of <FIG>, four DEAs, designated <NUM>, <NUM>, <NUM> and <NUM> are sequentially cooled in a cascading flow path, wherein DEA <NUM> is the first, most upstream DEA relative to the cooling apparatus <NUM> and DEA <NUM> is the last, most downstream DEA in the flow path. Components in each of the DEAs and coolant flow paths are shown schematically. All four of the respective first chill plates <NUM> receive coolant sequentially in a cascading fashion, in the direction of the flow arrows shown in the figure. The first DEA <NUM> in the cascading flow sequence receives flowing coolant from the coolant supply conduit <NUM> via the first inlet <NUM> of its first chill plate <NUM>, which then exhausts the coolant via the first outlet <NUM>. The coolant exhausted from the first outlet <NUM> of the first chill plate <NUM> of DEA <NUM> then enters DEA <NUM> via the first inlet <NUM> of its first chill plate <NUM>, exhausting out of the latter's respective first outlet <NUM>. Sequentially, coolant exhausting DEA <NUM> enters into and exhausts out of DEA <NUM>, via the latter's first inlet <NUM> and first outlet <NUM> of its respective first chill plate <NUM>. After exiting DEA <NUM>, the coolant enters into the last, furthest downstream DEA <NUM> in the cascading fluid flow path, via the latter's first inlet <NUM> its respective first chill plate <NUM>. By now, the first chill plate <NUM> in each and all of the respective DEAs <NUM>-<NUM> have been cooled.

Coolant returns to the cooling apparatus <NUM> by cascading flow through the second chill plates <NUM> of each of the respective DEAs in reverse order, from DEA <NUM> back to DEA <NUM> and the coolant return conduit <NUM>, completing the coolant loop. Focusing now on the last downstream DEA <NUM> in the coolant flow path, coolant exhausted from the first outlet <NUM> of its first chill plate <NUM> flows into the second coolant inlet <NUM> of its second chill plate <NUM> and exhausts from the second coolant outlet <NUM>. Thereafter, the coolant exiting DEA <NUM> flows back upstream toward the coolant return conduit <NUM> of the cooling apparatus <NUM>, in cascading fashion, by entering the second coolant inlet <NUM> and exiting the second coolant outlet <NUM> of the second chill plate <NUM> of upstream DEA <NUM>. Thereafter, in sequence, the coolant enters the second coolant inlet <NUM> and exits the second coolant outlet <NUM> of the second chill plate <NUM> of the next upstream DEA <NUM>. Finally, the coolant enters the second coolant inlet <NUM> and exits the second coolant outlet <NUM> of the second chill plate <NUM> of the first upstream DEA <NUM>, whereupon the now heated coolant returns and recirculates back to the cooling apparatus <NUM>, via the coolant return conduit <NUM>.

The described cascading, cooling flow path of <FIG> is scalable to accommodate any desired number of rows or columns of DEAs in the gantry <NUM>. While four cascading DEAs <NUM>, <NUM>, <NUM> and <NUM>, are shown in <FIG>, other embodiments of cooling systems that incorporate the described cascading cooling flow path have fewer or greater numbers of DEAs. In some cooling system embodiments, the cascading cooling flow sequence of DEAs and their associated cooling system coolant conduits are selectively aligned in one or more columns, axially along the Z axis of the gantry <NUM>, as shown in <FIG>. The designated position of each DEA <NUM> in the matrix of detectors is DEA Δ. Θ, where Δ is the circumferential row in the directional axis C and Θ is the axial column in the directional axis Z. The bold line, coolant supply conduit <NUM> branches off, via an annular supply manifold <NUM> in parallel to each of the columns, designated DEA Δ. <NUM> to Δ. <NUM>, feeding coolant, in cascading fashion, to each respective downstream, first chill plate in the associated column. Coolant exiting the first outlet of each respective, first chill plate of the last downstream DEA <NUM> to <NUM> in turn is routed to the second inlet of its corresponding respective second chill plate, and sequentially back upstream, from its respective second outlet to the outlet of the next upstream corresponding DEA <NUM> to <NUM>, thereafter upstream to corresponding DEA <NUM> to <NUM>, and lastly to the first upstream corresponding DEA <NUM> to <NUM>. Coolant exiting the corresponding second outlet of the second chill plate in DEAs <NUM> to <NUM> flows in parallel, via annular return manifold <NUM> back to the coolant return <NUM> of the coolant system <NUM>. In other cooling system embodiments, the cascading coolant flow path from the coolant supply <NUM> to the coolant return <NUM> of the cooling system <NUM> is parallel among the circumferential rows or rings of DEAs <NUM>. Θ to <NUM>. Θ (not shown in the figures).

<FIG> show another exemplary embodiment of a first chill plate <NUM>, wherein a thermally conductive foam layer <NUM> fills gaps or voids between that chill plate and its corresponding, opposing detector element components of the detector elements <NUM> and DDA <NUM>. In other embodiments, other thermally conductive material, such as thermally conductive tape, thermal gel and/or thermal grease substitutes for or is used in conjunction with the thermal foam layer <NUM>. The first chill plate <NUM> is a split-construction, joined composite of a top plate <NUM> and a bottom plate <NUM>. A coolant pipe <NUM> forms the first coolant inlet <NUM> and the first coolant outlet <NUM>; it is in thermally conductive communication with and sandwiched between the thermally conductive top <NUM> and bottom <NUM> plates. Inwardly facing, opposing surfaces of the top <NUM> and bottom <NUM> plates conform to the outer surface profile of the corresponding coolant pipe <NUM>, for direct contact therebetween, or with any gaps or voids filled with thermally conductive material. In various embodiments, the conforming profiles of inwardly facing, opposing surfaces of the top <NUM> and bottom <NUM> plates are formed by known casting, molding, <NUM>-D printing and/or machining manufacturing process. In some embodiments, the first chill plate <NUM> is cast or molded in place about the coolant pipe <NUM>, without the need for a sandwiched construction with joined separate top <NUM> and bottom <NUM> plates. In plan form, such as the serpentine-axial profile shown in <FIG>, the coolant pipe <NUM> is formed in any desired axial profile that enhances conductive heat transfer from the top <NUM> and bottom <NUM> plates to coolant flowing through the pipe. The chill plate <NUM>, including its top <NUM> and bottom <NUM> plates and its coolant pipe <NUM> are constructed of thermally conductive material. In some embodiments, the chill plate is constructed as shown and described as a cooling channel and heat sink in co-pending International Application No. <CIT>.

<FIG> is another embodiment of a chill plate <NUM> for absorbing heat generated by a proximate circuit board <NUM>. The chill plate <NUM> has a sandwiched construction like that of the first chill plate <NUM> of <FIG>. The opposing joined second top plate <NUM> and second bottom plate <NUM> capture a second coolant pipe <NUM> therebetween. To enhance conductive heat transfer from the opposing circuit board <NUM>, one or more regions of the bottom face <NUM> of the second bottom plate <NUM> have formed elevational surface profiles that are mirror images of the elevational surface profile of a corresponding region of the circuit board. In some regions, the bottom face <NUM> forms a post or island <NUM> projecting outwardly therefrom, towards the circuit board <NUM>. In other regions the bottom face <NUM> forms a well or cavity <NUM> that receives a component, such as the integrated circuit packages IC-<NUM> and IC-<NUM> projecting from the circuit board <NUM>. At the region <NUM> of the bottom face <NUM>, the integrated circuit package IC-<NUM> is in direct abutting contact with the chill plate <NUM>. At the region <NUM>, the integrated circuit package IC-<NUM> is spaced away from the opposing bottom face <NUM>; the gap therebetween is filled with thermally conductive grease or gel, or any other desired thermally conductive filler material.

<FIG> is a schematic of an exemplary embodiment of a cooling apparatus <NUM> of the extended aFOV, PET/CT modality, medical imaging apparatus <NUM>, comprising a fluid, continuous flow, closed coolant loop, circulating a liquid coolant such as water or a compressed, gaseous coolant, such as nitrogen or compressed air. In other embodiments, the coolant is a mixed phase, liquid/gas refrigerant, in which case the cooling apparatus incorporates a refrigeration system with an expansion valve, compressor, condenser and the like (not shown). In general, flowing coolant in the coolant loop absorbs heat generated by various components within the gantry <NUM>, such as the exemplary DEA <NUM>, and transfers the absorbed heat to a heat sink.

Here, the heat sink is a facility water system <NUM>, which provides a flowing, cool water supply <NUM> into an intake loop of a liquid-liquid heat exchanger <NUM>; thereafter, warmer return water <NUM> exits the heat exchanger. The previously circulated, heated coolant from the gantry <NUM> flows through a corresponding outlet loop of the heat exchanger <NUM>, transferring heat to return water <NUM>. In some embodiments, coolant exiting the heat exchanger <NUM> passes through an optional CT cooling unit <NUM> before entering a tee-type mixing valve <NUM>.

The mixing valve <NUM> selectively mixes proportionally cooled coolant that has passed through the heat exchanger <NUM> and relatively hotter coolant from the coolant return conduit <NUM> to achieve a desired coolant temperature. Coolant of the desired coolant temperature exits the mixing valve <NUM> into the coolant supply conduit <NUM>, where it enters the gantry <NUM>, absorbs heat from the DEAs <NUM> and any other, if any, cooled components in the gantry. More specifically, the coolant in the coolant supply conduit <NUM> passes through the previously described first and second chill plates of one or more of the DEAs <NUM>, where it absorbs heat generated by various internal detector elements, circuit electronic boards and power supplies, etc. The now heated coolant returns to the cooling apparatus <NUM> via the coolant return conduit <NUM>. The heated coolant received from the coolant return conduit <NUM> is stored in an expansion tank <NUM>. Circulating pump <NUM> pumps the still heated coolant through the coolant loop through bypass tee <NUM>, where a portion of the heated coolant flows to the heat exchanger <NUM>, for subsequent refresh cooling and the remaining portion of the heated coolant is routed to the mixing valve <NUM>. The mixing valve <NUM> and the pump <NUM> adjust flow rate and mixing proportions of the recirculating coolant to achieve desired heat absorption from the gantry. One specific coolant temperature control parameter of interest is maintaining a stable temperature bandwidth of the detector elements in each DEA within specification parameters, to avoid detector distortion. In some imaging system embodiments, where its DEAs incorporate SiPM detector elements, the coolant temperature bandwidth is <NUM> within +/- <NUM>. The mixing valve <NUM> and the pump <NUM> circulate the coolant between the gantry <NUM> and the cooling apparatus <NUM> at a flow rate that maintains a specified stable temperature bandwidth for all detector elements in the each of the respective DEAs <NUM> in the gantry.

Heat absorption and transfer capacity of the external cooling apparatus <NUM> is proportionately scaled to the number of modular DEAs <NUM> in the gantry <NUM>. As each modular DEA <NUM> incorporates its own dedicated internal cooling components (e.g., its first and second chill plates and their related coolant inlets and outlets), there is no need to add additional configurations of auxiliary cooling devices, such as cooling fans, to the gantry <NUM>, when changing the number of DEAs in the gantry for different imaging scanning field dimensions.

<FIG> are embodiments of segmented chill plates that incorporate plate sub-segments with commonly shared inlets and outlets. Each sub-segment functions as an independent chill plate. Segmented chill plates are useful for packaging and distributing heat absorption and heat isolation capacities into smaller, confined zones within a DEA that cannot physically accommodate a single, larger chill plate having the same heat absorption capacity. They are also useful for conforming to multiple faces of an electronic component, such as a base and one or more lateral sides of a power supply. In other applications, segmented chill plates provide selective heat isolation between components within a DEA housing.

The segmented chill plate <NUM> incorporates cascading, sequential coolant flow from coolant supply <NUM> to coolant return <NUM>, via a continuous coolant pipe <NUM>, to each of the respective first <NUM>, second <NUM> and third <NUM> chill plate sub-segments. The coolant pipe <NUM> captured within the chill plate sub-segments has a serpentine profile, similar to the coolant pipe <NUM> of <FIG>. In this embodiment of <FIG>, each of those sub-segments124, <NUM>, <NUM> have differing surface area profiles. The coolant inlet side <NUM> of the coolant pipe <NUM> is in direct or indirect communication with the coolant supply <NUM> and the coolant outlet side <NUM> thereof is in direct or indirect communication with the coolant return <NUM>. Conceptually in some embodiments, the segmented chill plate <NUM> is readily substituted for any one of the first <NUM> or second <NUM> chill plates shown in any of the DEAs of <FIG> or <FIG>. For example, if the segmented chill plate <NUM> is substituted for any one of the second chill plates <NUM> of <FIG>, its coolant inlet <NUM> substitutes for the second coolant inlet <NUM> and its coolant outlet <NUM> substitutes for the second coolant outlet <NUM>.

The curved, segmented chill plate <NUM> of <FIG> incorporates parallel coolant flow architecture, with plate coolant-supply manifold <NUM>, whose inlet <NUM> is in direct or indirect communication with the coolant supply <NUM>, and plate coolant-return manifold <NUM>, whose outlet <NUM> is in direct or indirect communication with the coolant return <NUM>. In this exemplary coolant flow architecture, a first chill plate sub-segment <NUM> incorporates a first coolant pipe <NUM>, a second chill plate sub-segment <NUM> incorporates a second coolant pipe <NUM> and a third chill plate sub-segment <NUM> incorporates a third coolant pipe <NUM>. The opposite ends of the first <NUM>, second <NUM> and third <NUM> coolant pipes are respectively in fluid communication with the coolant- supply manifold <NUM> and the coolant-return manifold <NUM>. Each chill plate sub-segment has a different planform profile for conductive heat absorption from a corresponding heat dissipating component within a DEA. The third chill plate sub-segment <NUM> has a curved planform profile.

The modular, scalable, fluid cooling systems described herein operate within imaging system gantries at lower noise levels than existing forced air, with air-liquid heat exchanger-type cooling systems. In an exemplary modular, fluid cooling system embodiment, designed for incorporation within a long aFOV PET system, such as shown in <FIG> and <FIG>, operating noise within the patient tunnel was measured to be less than fifty-five decibels (<NUM> dB). As shown in <FIG>, coolant pumps and other noise generating components are in the external cooling apparatus <NUM> outside the gantry <NUM>. The fluid cooling system embodiments described herein do not need or utilize noisy cooling fans within the gantry <NUM>. Additionally, the acoustic foam liner <NUM> circumscribing the patient tunnel wall <NUM> further suppresses noise within the patient tunnel. In contrast, in a comparable long aFOV PET system, employing a forced air-cooling system, the measured noise level in its patient tunnel was on the order greater than ten decibels (> 10dB) higher than that of the exemplary PET system with the modular, fluid cooling system.

Scalable cooling system embodiments disclosed herein maintain thermal operating stability of detector elements, such as SiPMs, no matter how many modular DEAs are ganged together. For example, in a long aFOV PET/CT system, four gantries incorporating the disclosed DEAs are ganged together axially, with the previously described cascading coolant flow between the first chill plates in each DEA, followed by cascading flow through the second chill plates. The cascading cooling flow interconnection reduces the number of coolant fittings and coolant lines within the gantry or gantries. All the interconnected DEAs are desirably serviced by a single coolant pump of the cooling apparatus. The modular DEAs are compact, reducing needed gantry internal volume, despite increasing axial lengths of long aFOV imaging systems.

Claim 1:
A fluid coolant system for of a medical imaging apparatus (<NUM>), comprising:
a gantry (<NUM>) forming a patient tunnel;
a cooling apparatus (<NUM>), coupled to and external the gantry (<NUM>), having a coolant supply for supplying fluid coolant to the gantry (<NUM>), and a coolant return for returning the coolant to the cooling apparatus (<NUM>);
a detector electronic assembly (DEA) (<NUM>) within the gantry (<NUM>), coupled to the cooling apparatus (<NUM>), having:
a housing (<NUM>);
detector elements (<NUM>) in the housing (<NUM>), for detecting incident photons of electromagnetic radiation originating outside of the housing (<NUM>);
other electronic components (<NUM>, <NUM>) in the housing (<NUM>);
a fluid cooled, first chill plate (<NUM>, <NUM>) thermally conductively coupled to the detector elements (<NUM>), for cooling the detector elements (<NUM>), the first chill plate (<NUM>, <NUM>) having a first inlet (<NUM>) for receiving the coolant from the coolant supply and a first outlet (<NUM>) for discharging the coolant to the coolant return; and
a fluid cooled, second chill plate (<NUM>) thermally conductively coupled to the other electronic components (<NUM>, <NUM>) for cooling the other electronic components (<NUM>, <NUM>), the second chill plate (<NUM>) having a second inlet (<NUM>) for receiving the coolant from the coolant supply and a second outlet (<NUM>) for discharging the coolant to the coolant return;
the fluid coolant system, further comprising:
the detector elements (<NUM>) having detector element components projecting away therefrom, defining a first surface profile;
the first chill plate (<NUM>, <NUM>) in thermally conductive, direct contact with at least a portion of the first surface profile of the detector element components;
at least one of the other electronic components (<NUM>, <NUM>) defining a second surface profile; and
the second chill plate (<NUM>) in thermally conductive, direct contact with at least a portion of the second surface profile of the at least one of the other electronic components (<NUM>, <NUM>).