Patent Description:
Temperature control systems are known from documents <CIT>, <CIT>, and <CIT>.

There is a desire, then, to provide a precise temperature control system that is capable of removing heat from a densely packed array of radiation detectors, while maintaining stable temperature for sensor operation.

The present disclosure addresses the aforementioned drawbacks by providing a temperature control assembly that includes a cold plate, a channel formed in the cold plate, an inlet formed in the channel, an outlet formed in the channel, and at least one aperture formed in the cold plate. The cold plate has a first contact surface and a second contact surface opposite the first contact surface, and is composed of a thermally conductive material. The channel formed in the cold plate is enclosed by the cold plate between the first contact surface and the second contact surface of the cold plate. The inlet formed in the channel provides inflow of a liquid to the channel, and the outlet formed in the channel provides for outflow of the liquid from the channel. The at least one aperture formed in the cold plate is sized to receive an electrical connection between a printed circuit board when the printed circuit board is coupled to the first contact surface of the cold plate and a photodetector assembly when the photodetector assembly is coupled to the second contact surface of the cold plate.

It is another aspect of the present disclosure to provide a liquid-cooled radiation detector that includes a first printed circuit board having arranged thereon at least one pre-amplifier, a second printed circuit board electrically connected to a photodetector, and a removable liquid cooling assembly arranged between the first and second printed circuit board. The removable liquid cooling assembly includes a cold plate composed of a thermally conductive material and a channel formed in and enclosed by the cold plate. The channel is formed such that a liquid coolant flowing through the channel removes heat transferred to the cold plate from the first printed circuit board and the second printed circuit board while maintaining a sufficiently low level of humidity external the cold plate such that the first printed circuit board and the second printed circuit board are not damaged by humidity when the liquid coolant is flowing through the channel.

Described here are systems and methods for temperature controlled radiation detectors, such as liquid-cooled positron emission tomography ("PET") detectors. Particularly, temperature control is provided by a temperature control assembly that may include a liquid cooling assembly having a cold plate having formed therein one or more channels through which a liquid coolant is able to flow. The one or more channels are enclosed by the cold plate, such that the liquid coolant does not come into contact with sensitive electronic components used in the radiation detectors. Heating elements are provided to the cold plate of the liquid cooling assembly, which can be controlled to provide an additional level of temperature control. The precision of temperature control provided by the heating elements enables the maintenance of temperature for optimal performance of the radiation detector and associated electronics.

As shown in <FIG>, the temperature control, which may include liquid cooling, is provided by a liquid cooling assembly <NUM> that is designed to be removably positioned between a printed circuit board ("PCB") <NUM> and a photodetector assembly <NUM> of a tileable block detector. An example of tileable block detectors is described in co-pending PCT Application No. <CIT>.

As shown in <FIG>, the liquid cooling assembly <NUM> generally includes a cold plate <NUM> having formed therein one or more channels <NUM> into which one or more tubes <NUM> are arranged. A liquid is provided to circulate through the one or more tubes <NUM> or channels <NUM> to remove heat that is transferred to the cold plate <NUM> from components on the PCB <NUM>, the photodetector assembly <NUM>, or both. In some embodiments, no tubes <NUM> are arranged in the channels <NUM>, and instead the liquid is provided directly to the channels <NUM>. <FIG> shows a cross section of an example cold plate <NUM> in which no tubes <NUM> are arranged in the channels <NUM>, and <FIG> shows an exploded cross section of an example cold plate <NUM> in which tubes <NUM> are arranged in the channels <NUM>.

The cold plate <NUM> has a first contact surface <NUM> that is placed into contact with the PCB <NUM>, and a second contact surface <NUM> that is opposite the first contact surface <NUM> and which is placed into contact with the photodetector assembly <NUM>. In some embodiments, the first contact surface <NUM> may directly contact the PCB <NUM>, but in some other embodiments one or more layers (e.g., insulating or conductive layers) may be provided between the first contact surface <NUM> and the PCB <NUM>.

A recess <NUM> is formed on the first contact surface <NUM> side of the cold plate <NUM>, such that components on the PCB <NUM> are allowed to extend into the recessed region <NUM> when the PCB <NUM> is coupled to the first contact surface <NUM> of the cold plate <NUM>.

One or more apertures <NUM> are formed in the cold plate <NUM> extending from the second contact surface <NUM> through to the surface in the recessed region <NUM>. The apertures <NUM> allow for electrical connectors to pass between the PCB <NUM> and the photodetector assembly <NUM>. For instance, the photodetector assembly <NUM> can include a circuit board on which sensors or other data acquisition components are located, and electrical connectors can extend through the apertures <NUM> to electrically connect the sensor circuit boards with preamp circuit components located on the PCB <NUM>. This construction allows the overall thickness of the cold plate <NUM> to be reduced. As one example, the thickness of the cold plate <NUM> can be up to <NUM>.

In some embodiments, the cold plate <NUM> includes an upper plate <NUM> and a lower plate <NUM> that is opposite the upper plate <NUM>. As shown in <FIG>, the upper plate <NUM> includes an outward facing surface, which corresponds to the first contact surface <NUM> of the cold plate <NUM>, and an inward facing surface <NUM> that is opposite the first contact surface <NUM>. Likewise, the lower plate <NUM> includes an outward facing surface that corresponds to the second contact surface <NUM> of the cold plate <NUM>, as well as an inward facing surface <NUM> that is opposite the second contact surface <NUM>. In these instances, the inward facing surface <NUM> of the upper plate <NUM> has formed therein upper channel portions <NUM> and the inward facing surface <NUM> of the lower plate <NUM> has matching lower channel portions <NUM> formed therein. When the inward facing surface <NUM> of the upper plate <NUM> is brought into contact with the inward facing surface <NUM> of the lower plate <NUM>, the upper channel portions <NUM> and the lower channel portions <NUM> meet to form the plurality of channels <NUM>. As mentioned above, in some embodiments, one or more tubes <NUM> are arranged in the plurality of channels and thus can be disposed between the upper plate <NUM> and the lower plate <NUM>.

As shown in <FIG>, the outward facing surface of the lower plate <NUM>, which corresponds to the second contact surface <NUM> of the cold plate <NUM>, has coupled thereto a thermally conductive pad <NUM> that can be composed of a compressible material, such that mismatches between the cold plate <NUM> and the faces of the PCB <NUM> and photodetector assembly <NUM> can be taken up, thereby increasing the contact surface of the cold plate <NUM>. Preferably, the thermally conductive pad <NUM> is composed of a material that is electrically insulating (i.e., has a relatively high dielectric constant). As one non-limiting example, the electrically insulating material can be a silicone elastomer. As another non-limiting example, the electrically insulating material can be a polyimide. The thermally conductive pad <NUM> can be coupled to the second contact surface <NUM> using an adhesive, and may have formed therein apertures similar to the apertures <NUM> formed in the cold plate <NUM>.

One or more heating elements <NUM> are coupled to the first contact surface <NUM>, the second contact surface <NUM>, or both. As one example, the heating elements <NUM> can be coupled to the second contact surface <NUM> via coupling to the thermally conductive pad <NUM>. As an example, the one or more heating elements <NUM> can include a thin film heating pad. The thin film heating pad can be constructed as an etched foil, which may be embedded in a substrate material, such as silicon or Kapton wrap, to provide electrical insulation. The one or more heating elements <NUM> can be controlled via a controller in order to precisely control the temperature of the radiation detector assembly or its associated electrical components.

As an example, under high load of radiation, more heat will be generated by preamplifiers, therefore resulting in more powerful cooling. In these instances, the temperature of the sensors in the radiation detector assembly may change significantly, which is undesirable because such sensors are often highly sensitive to changes in temperature. The one or more heating elements <NUM> can then be operated to increase the temperature of the radiation detector assembly, or its associated electrical components, to avoid overcooling and to maintain the radiation detector assembly operating within a temperature range in which the sensors have optimal or otherwise satisfactory performance. A temperature sensor is provided and coupled to the liquid cooling assembly <NUM> in order to monitor temperature. Feedback from the temperature sensor can then be used to control the operation of the heating elements <NUM> to precisely adjust the temperature of the radiation detector assembly in those instances where the radiation detector assembly may be overcooled by the liquid cooling assembly. For instance, power to the heating elements <NUM> can be controlled such that the heating elements <NUM> start heating only when the temperature of the sensors in the radiation detector assembly is changing.

The upper plate <NUM> and the lower plate <NUM> can be composed of the same material, or in some instances can be composed of different materials. As one example, the upper plate <NUM> and the lower plate <NUM> can both be composed of copper or other thermally conductive metals, metal alloys, plastics, carbon fiber, carbon fiber epoxies, or other materials.

In some embodiments, the cold plate <NUM> includes a single piece in which the one or more channels <NUM> are machined or otherwise formed, as shown in <FIG>. In these instances, the cold plate <NUM> has a first contact surface <NUM> that is placed into contact with the PCB <NUM>, and a second contact surface <NUM> opposite the first contact surface <NUM>, which is placed into contact with the photodetector assembly <NUM>. A thermally conductive pad <NUM> may also be coupled to the second contact surface <NUM>, as noted above.

The cold plate <NUM> can be dimensioned to provide thermal control (e.g., cooling, heating, or both) to a single tileable radiation detector, a large area monolithic radiation detector, or multiple tileable radiation detectors that are arranged in an array. For instance, the cold plate <NUM> can be dimensioned to provide cooling to an M × N array of tileable radiation detectors. In other instances, the cold plate <NUM> can be dimensioned to provide cooling to an M × <NUM> or <NUM> × N array of tileable radiation detectors. In these latter configurations, multiple cold plates <NUM> can be arrayed to provide cooling to larger array of tileable radiation detectors. These configurations have an advantage that if there is a failure in one of the cold plates <NUM> that particular cold pate <NUM> can be removed from the liquid cooling assembly <NUM> and replaced with a properly functioning cold plate <NUM> without having to replace the entire liquid cooling assembly.

As shown in <FIG>, in some embodiments, each tube <NUM> has an inlet <NUM> and an outlet <NUM>. In other embodiments, each channel <NUM> may have more than one inlet, more than one outlet, or combinations thereof. In those embodiments where a tube <NUM> is not arranged in the channel <NUM>, then the inlet <NUM> and outlet <NUM> are formed in the channel <NUM> instead of the tube <NUM>.

In some embodiments, the channels <NUM>, tube <NUM>, or both, are constructed to form separate loops to maximize temperature uniformity, as shown in <FIG>. In such instances, each channel <NUM>, tube <NUM>, or both can be U-shaped, or can have other shapes and configurations. For ease of use, the inlet <NUM> and outlet <NUM> can be arranged on the same side of the cold plate <NUM>, but in other configurations the inlet <NUM> and outlet <NUM> can be arranged on different sides of the cold plate <NUM>.

A separate line can be provided to each inlet <NUM> to provide inflow of a liquid into the channels <NUM>, and a separate line can be provided to each outlet <NUM> to provide outflow of the liquid from the channels <NUM>. In some embodiments, a manifold can be provided to connect each inlet <NUM> together to a common inflow line and to connect each outlet <NUM> together to a common outflow line. The manifold can include a single structure that keeps the inlet <NUM> lines and outlet <NUM> lines separate, or can include two separate structures, one for the inlet <NUM> lines and one for the outlet <NUM> lines.

<FIG> show an example in which a liquid cooling assembly <NUM> is arranged between an array of PCBs <NUM> and photodetector assemblies <NUM> corresponding to an array of tileable radiation detectors. In this example, liquid coolant is provided to the liquid cooling assembly via an inflow line <NUM>. As the liquid coolant passes through the tubes <NUM> in the liquid cooling assembly <NUM> it removes heat from the PCBs <NUM> and photodetector assemblies <NUM>. The liquid coolant then leaves the liquid cooling assembly via an outflow line <NUM>, after which the liquid coolant can be cooled again for later use, recycled, or otherwise stored.

Preferably, the inflow line <NUM> and the outflow line <NUM> are composed of a flexible material, such as a flexible PVC. In these instances, the radiation detector (e.g., a tileable block detector composed of PCBs <NUM> and photodetector assemblies <NUM>) can be moved without needing to disconnect the cold plate <NUM>. Such functionality is advantageous for medical procedures, such as those where it may be desired to perform a biopsy during which the radiation detector assembly needs to be moved to provide access to the patient. Such functionality can also be advantageous for multimodality imaging applications where it may be necessary to move the radiation detector assembly to provide access for other imaging modalities, such as x-ray or ultrasound imaging. As shown, light-tight flexible shrouds <NUM> can be coupled to the inflow line <NUM> and the outflow line <NUM> in order to enable flexible tubing connection while maintaining light tightness for detector operation. As one example, the light-tight flexible shrouds <NUM> can be composed of silicone.

As seen in <FIG>, the photodetector assemblies <NUM> include an electrical connector <NUM> that extends through the apertures <NUM> formed in the cold plate <NUM> in order to engage and electrically connect to the PCBs <NUM>, as mentioned above.

In this example, the cold plate <NUM> does not have a recess <NUM> formed in the first contact surface <NUM> side. In some embodiments, it will be appreciated that the apertures <NUM> can be sized and arranged such that some or all of the components on the PCBs <NUM> facing the first contact surface <NUM> extend into the apertures <NUM> when the PCBs <NUM> are coupled to the cold plate <NUM>.

As seen in <FIG> and <FIG>, an electrically insulating layer <NUM> can be coupled to the first contact surface <NUM> of the cold plate <NUM>. As one example, the electrically insulating later <NUM> can be composed of a continuous-woven glass fabric laminate with an epoxy resin, such as FR4 Garolite® (McMaster-Carr), or other epoxy sheets or plastic sheets or laminates or carbon fiber compositions. The electrically insulating layer <NUM> can also reduce the thermal conductivity
<FIG> illustrates another example of a liquid cooling assembly <NUM> in which the cold plate <NUM> is composed of a bonded aluminum assembly, lid, and main body. The cold plate <NUM> has an anodized finish, with contact face machined to expose metal. A compressible thermal pad can be coupled to the contact face. The liquid cooling assembly <NUM> shown in <FIG> is sized to fit between a preamp PCBs and a sensor PCBs of photodetector assemblies. The liquid cooling assembly <NUM> shown in <FIG> provides single path cooling with one port in and one port out.

Claim 1:
A temperature control assembly, comprising:
a cold plate having a first contact surface and a second contact surface opposite the first contact surface, wherein the cold plate is composed of a thermally conductive material;
a channel formed in the cold plate and enclosed by the cold plate between the first contact surface and the second contact surface of the cold plate;
an inlet formed in the channel for providing inflow of a liquid to the channel;
an outlet formed in the channel for providing outflow of the liquid from the channel;
at least one aperture formed in the cold plate, wherein the aperture is sized to receive an electrical connection between a printed circuit board when the printed circuit board is coupled to the first contact surface of the cold plate and a photodetector assembly when the photodetector assembly is coupled to the second contact surface of the cold plate; and
characterized in that the temperature control assembly further comprises:
a thermally conductive pad coupled to the second contact surface;
a heating element coupled to the thermally conductive pad; and
a temperature sensor that measures a temperature of electrical components mounted to a printed circuit board when the printed circuit board is coupled to one of the first contact surface or the second contact surface, and wherein the temperature sensor provides the measured temperature to a controller in order to control a power supplied to the heating element.