Patent Publication Number: US-2022229195-A1

Title: Radiation detectors for scanning systems, and related scanning systems

Description:
FIELD 
     Embodiments of the disclosure relate generally to radiation detectors for scanning systems. More particularly, embodiments of the disclosure relate to a radiation detector including an arc portion having a first side configured to carry detector modules for detecting impinging radiation and a second side in thermal communication with one or more heat transfer apparatuses for maintaining a temperature of the detector modules. 
     BACKGROUND 
     Radiation imaging modalities such as computed tomography (CT) systems and single-photon emission computed tomography (SPECT) systems, and/or positron emission tomography (PET), for example, are useful to provide information, or images, of interior aspects of an object under examination. In transmission imaging modalities, such as CT, the object is exposed to radiation comprising photons (e.g., such as x-rays, gamma rays, without limitation), and an image(s) is formed based upon the radiation absorbed and/or attenuated by the interior aspects of the object, or rather a number of radiation photons that are able to pass through the object. Generally, highly dense aspects of the object absorb and/or attenuate more radiation than less dense aspects, and thus an aspect having a higher density, such as a bone or metal, for example, will be apparent when surrounded by less dense aspects, such as muscle or clothing. Emission imaging modalities such as SPECT and PET form image(s) based on the radiation emitted from a radioactive tracer that provides functional information of an object. 
     Radiation photons that pass through an object impinge a surface of one or more detector elements of a detector array (logically referred to as “detector cells”) that typically directly or indirectly generate electrical charge in response to the impinging radiation photons. The detector array typically comprises a plurality of detector cells, respectively configured to convert detected radiation into electrical signals. A magnitude of attenuation by an object in an examination region is inversely related to an amount or rate of electrical charge generated by a detector element. Based upon the number of radiation photons detected by respective detector cells and/or the electrical charge generated by respective detector cells between samplings, images can be reconstructed that are indicative of the density, z-effective (also referred to as the effective atomic number), shape, and/or other properties of the object and/or aspects thereof. 
     The number of detector cells within a detector array may be application specific. For example, in some computed tomography applications, a number of typical detector cells may range from about 16,000 to about 320,000 depending on the desired degree of coverage of the computed tomography system. 
     In use and operation, typical detector cells and the electronic boards associated with such detector cells known to the inventors of this disclosure, generate heat. Detector cells and detector cell arrangements of conventional detector arrays are typically individually cooled by airflow and are susceptible to temperature changes caused by changes in airflow when a radiation scanner changes rotational speed. Inadequate temperature control of detector cells may, for example, contribute to artifact and other noise in images generated by a radiation imaging system. In addition, due to the rotation of the radiation imaging system, conventional detector cells are subject to significant mechanical stresses during use and operation and suffer from bending or other deflection. The bending and deflection of the detector cells may reduce the quality and accuracy of the images created by the radiation imaging system. Other disadvantages of typical detector cells known to the inventors of this disclosure include the difficulty of placement and alignment of detector cells, and access for replacement of detector cells when one or more detector cells fails. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic of a scanning system to perform transmission radiation-based scanning, in accordance with embodiments of the disclosure; 
         FIG. 2A  is a simplified perspective view of a radiation detector, in accordance with embodiments of the disclosure; 
         FIG. 2B  is a simplified front view of the radiation detector of  FIG. 2A ; 
         FIG. 2C  is a simplified top view of the radiation detector of  FIG. 2A ; 
         FIG. 2D  is a simplified cross-sectional view of the radiation detector taken through section line D-D of  FIG. 2B ; 
         FIG. 2E  is a simplified front view of the radiation detector of  FIG. 2A  including a front cover; 
         FIG. 2F  is a simplified perspective view of the radiation detector of  FIG. 2A  including a top cover; 
         FIG. 3  is a simplified perspective view a detector module, in accordance with embodiments of the disclosure; 
         FIG. 4A  and  FIG. 4B  are simplified perspective views of a detector unit, in accordance with embodiments of the disclosure; 
         FIG. 5A  is a simplified cross-sectional view of a radiation detector, in accordance with embodiments of the disclosure; 
         FIG. 5B  is a simplified cross-sectional view of a radiation detector, in accordance with other embodiments of the disclosure; 
         FIG. 5C  is a simplified cross-sectional view of a radiation detector, in accordance with additional embodiments of the disclosure; and 
         FIG. 6  is a schematic of a scanning system to perform emission radiation-based scanning, in accordance with embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrations presented in this disclosure are not meant to be actual views of any particular scanning system for performing radiation-based (e.g., computed tomography (CT)) scanning or component thereof or component thereof, but are merely idealized representations employed to describe illustrative embodiments. Thus, the drawings are not necessarily to scale. 
     The following description provides specific details, such as material types, dimensions, and processing conditions in order to provide a thorough description of embodiments of the disclosure. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without employing these specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional fabrication techniques employed in the industry. In addition, the description provided below does not form a complete apparatus or system for a scanning system including a detector array comprising a cradle. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Also note, any drawings accompanying the present application are for illustrative purposes only, and are thus not drawn to scale. Additionally, elements common between figures may retain the same numerical designation. 
     Disclosed embodiments relate generally to scanning systems configured to inspect translated objects using radiation-based scanning that may reduce artifact and other noise in images generated with the scanning systems. More specifically, disclosed are embodiments of scanning systems configured to control a temperature of detector modules of the radiation detector of the scanning system and provide structural support to the detector modules during use and operation, reducing the artifact in the generated images. In addition, the scanning systems disclosed herein may facilitate placement of the detector modules at precise locations and aligned with respect to other components of the scanning system, and serviceability of the scanning systems (e.g., by facilitate replacement of the detector modules). 
     Terms used in the present disclosure and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including, but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes, but is not limited to,” etc.). As used herein, “each” means some or a totality. As used herein, “each and every” means a totality. 
     Additionally, if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. 
     In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” or “one or more of A, B, and C, etc.” is used, in general such a construction is intended to include A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together, etc. 
     Further, any disjunctive word or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” should be understood to include the possibilities of “A” or “B” or “A and B.” 
     As used herein, the terms “substantially” and “about” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially or about a specified value may be at least about 90% the specified value, at least about 95% the specified value, at least about 99% the specified value, or even at least about 99.9% the specified value. 
     As used herein, spatially relative terms, such as “upper,” “lower,” “bottom,” and “top,” are for ease of description in identifying one element&#39;s relationship to another element, as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures. Thus, the term “upper” can encompass elements above, below, to the left of, or to the right of other elements, depending on the orientation of a device. The materials may be otherwise oriented (rotated ninety degrees, inverted, without limitation) and the spatially relative descriptors used herein interpreted accordingly. 
     In this description the term “coupled” and derivatives thereof may be used to indicate that two elements co-operate or interact with each other. When an element is described as being “coupled” to another element, then the elements may be in direct physical or electrical contact or there may be intervening elements or layers present. In contrast, when an element is described as being “directly coupled” to another element, then there are no intervening elements or layers present. The terms “on” and “connected” may be used in this description interchangeably with the term “coupled,” and have the same meaning unless expressly indicated otherwise or the context would indicate otherwise to a person having ordinary skill in the art. 
     As used herein, “arc” means a circular arc, or a portion of a circular arc. 
     According to embodiments described herein, a scanning system (e.g., an imaging system, a radiation imaging system, a radiation scanning system) comprises a gantry including a radiation source and a radiation detector including a detector array configured to observe (e.g., measure, detect, without limitation) radiation photon impingent thereon that passes through an object located in an examination region defined between the radiation source and the radiation detector. A radiation detector comprises a detector array comprising a support structure configured to be operably coupled to the gantry. A support structure may include an arc portion configured to carry a plurality of detector modules. An arc portion may be sized and shaped to span substantially an entire length of a support structure and a detector array carried thereby. The arc portion may include a plurality of facets, each facet including a surface and arranged such that the respective surface is oriented at a substantially perpendicular angle with respect to a radiation path of at least some incident radiation (e.g., an imaginary line between the radiation source and the surface of the facet, without limitation). Each facet may be coupled with a detector module including one or more detector units (e.g., detector tiles, without limitation) at a surface of each respective facet, the surface of each facet facing inward toward the radiation source. In other words, each facet may include a surface that is oriented toward the radiation source to receive radiation from the radiation source at about a 90 degree angle of incidence. The surface of each facet may be configured to receive a detector unit. A detector module may include a base structure on which one or more detector units are supported. A detector module (e.g., a base structure of the detector module) may be substantially completely supported by a facet. Stated another way, substantially all of a surface of a single detector module may contact a surface of a single one of the facets such that substantially no portion of a surface of a detector module in contact with a facet is unsupported by the facet (e.g., the detector module does not include unsupported portions that span between different portions of the facet without contacting the surface of the facet, without limitation). Since substantially all of a disclosed detector module is supported by a facet, during operation of a radiation system (e.g., rotation of the gantry, without limitation), detector modules may be subject to no or inconsequential deflection or bending as in conventional detector modules and radiation systems, improving noise and/or artifact immunity (e.g., limiting noise or artifacts that may be caused by deflection or bending, without limitation) in images generated by a scanning system and improving the quality of the generated images. In addition, the detector modules disclosed herein may be more easily accessed and replaced due to the position of the detector modules on the facets of the arc portion, as compared to replacement of detector modules of conventional scanning systems that may be mounted, for example, to a support structure at an angle, such as at 90°. 
     According to embodiments disclosed herein, detector modules may be in direct thermal contact with the facets. The facets may form a portion of an arc portion and may be located on a first side of the arc portion. The arc portion may define a thermal mass extending substantially an entire length of the support structure carrying the detector modules. One or more heater elements may be in thermal communication with a second side of the arc portion and configured to maintain a temperature of the arc portion at a desired temperature. In addition, a second side of the arc portion may be in thermal communication with one or more heat exchangers for removing heat from the arc portion. In some embodiments, the heat exchanger comprises cooling elements, such as one or more of cooling fins, a water cooler, or a chiller. In operation, a temperature exhibited by the detector modules may be controlled indirectly through the arc portion, such as by contact of second side of the arc portion with heat exchanger. As a non-limiting example, a temperature of detector modules may be controlled through the arc portion, rather than being heated or cooled directed by the respective heater elements or cooling elements. Controlling the temperature of the detector modules through the arc portion may reduce temperature swings in the detector modules and increase a time constant of temperature change of the detector modules relative to conventional scanning systems which are cooled by the passage of air during rotation of the rotor and the detector modules during operation. Stated another way, a rate of temperature change of detector modules coupled to the arc portion during operation of the scanning system may be substantially less than of detector modules of conventional scanning systems. Increased temperature stability of the detector modules of the scanning system may reduce measurement error attributable to temperature changes and improve quality of images generated from the scanning system. 
       FIG. 1  is a schematic of a scanning system  100  to perform transmission radiation-based (e.g., CT) scanning, in accordance with embodiments of the disclosure. Techniques in accordance with this disclosure may find applicability with, for example, CT systems, diffraction systems, and/or other systems comprising a radiation detector system. The scanning system  100  may be configured to examine one or more objects  102  (e.g., a human subject, a series of suitcases at an airport, freight, parcels, without limitation). The scanning system  100  may include, for example, a stator  104  and a rotor  106  rotatable relative to the stator  104 . During examination, the object(s)  102  may be located on a support  108 , such as, for example, a bed, roller conveyor, or conveyor belt, that is selectively positioned in an examination region  110  (e.g., a hollow bore in the rotor  106  in which the object(s)  102  is exposed to radiation  112 ), and the rotor  106  may be rotated about the object(s)  102  by a motivator  115  (e.g., motor, drive shaft, chain, without limitation). 
     The rotor  106  may surround a portion of the examination region  110  and may be configured as, for example, a gantry supporting at least one radiation source  114  (e.g., an ionizing x-ray source, gamma-ray source, without limitation), the at least one radiation source  114  oriented to emit radiation toward the examination region  110  and at least one radiation detector  116  supported on a substantially diametrically opposite side of the examination region  110  (which may also be a substantially diametrically opposite side of rotor  106 ) relative to the radiation source(s)  114 . During a contemplated examination of object(s)  102  by the scanning system  100 , the radiation source(s)  114  emits fan and/or cone shaped radiation  112  configurations toward the examination region  110 . The radiation  112  may be emitted, for example at least substantially continuously or intermittently (e.g., a pulse of radiation  112  followed by a resting period during which the radiation source(s)  114  is not activated). 
     As the emitted radiation  112  traverses the examination region  110  and the object(s)  102 , the radiation  112  may be attenuated differently by different aspects of the object(s)  102 . Because different aspects attenuate different amounts (e.g., percentages, without limitation) of the radiation  112 , an image or images can be generated based upon the attenuation, or variations in the number of radiation photons that are detected by the radiation detector  116 . As non-limiting examples, more dense aspects of the object(s)  102 , such as an inorganic material, may attenuate more of the radiation  112  (e.g., causing fewer photons to be detected by the radiation detector  116 ) than less dense aspects, such as organic materials. 
     The radiation detector  116  may include, for example, many individual detector elements arranged in a pattern (e.g., a row or an array) on one or more detection assemblies (also referred to as detection modules, detector modules, and/or the like), which are operatively connected to one another to form the radiation detector  116 . In some embodiments, the detector elements may be configured to indirectly convert (e.g., using a scintillator array and photodetectors) detected radiation into analog signals. In other embodiments, the detector elements are configured to directly convert the detected radiation into analog signals. Further, the radiation detector  116 , or detection assemblies thereof, may include electronic circuitry, such as, for example, an analog-to-digital (A/D) converter, configured to filter the analog signals, digitize the analog signals, and/or otherwise process the analog signals and/or digital signals generated thereby. Digital signals output from the electronic circuitry may be conveyed from the radiation detector  116  to digital processing components configured to store data associated with the digital signals and/or further process the digital signals. 
     In some embodiments, the digital signals may be transmitted to an image generator  118  configured to generate image space data, also referred to as images, from the digital signals using a suitable analytical, iterative, and/or other reconstruction technique (e.g., backprojection reconstruction, tomosynthesis reconstruction, iterative reconstruction, without limitation). In this way, the data may be converted from projection space to image space, a domain that may be more understandable by a user  120  viewing the image(s), for example. Such image space data may depict a two dimensional representation of the object(s)  102  and/or a three dimensional representation of the object(s)  102 . In other embodiments, the digital signals may be transmitted to other digital processing components, such as a threat analysis component  121 , for processing. 
     The illustrated scanning system  100  may also include a terminal  122  (e.g., a workstation or other computing device), configured to receive the image(s), which can be displayed on a monitor  124  to the user  120  (e.g., security personnel, medical personnel, without limitation). In this way, the user  120  can inspect the image(s) to identify areas of interest within the object(s)  102 . The terminal  122  may also be configured to receive user input which may direct operations of the scanning system  100  (e.g., a rate at which the support  108  moves, activation of the radiation source(s)  114 , without limitation) and connected to additional terminals  122  through a network (e.g., a local area network or the Internet, without limitation). 
     A control system  126  may be coupled (e.g., operably coupled) to the terminal  122 . The control system  126  may be configured to automatically control at least some operations of the scanning system  100 . For example, the control system  126  may be configured to directly and/or indirectly, automatically, and dynamically control the rate at which the support  108  moves through the examination region  110 , the rate at which the rotor  106  rotates relative to the stator  104 , activation, deactivation, and output level of (e.g., intensity of radiation emitted by) the radiation source(s)  114 , or any combination or subcombination of these and/or other operating parameters. In some embodiments, the control system  126  may also accept manual override instructions from the terminal  122  and to issue instructions to the scanning system  100  to alter the operating parameters of the scanning system  100  based on the manual override instructions. The control system  126  may be located proximate to a remainder of the scanning system  100  (e.g., integrated into the same housing or within the same room as the remaining components) or may be distal from the scanning system  100  (e.g., located in another room, such as, for example, an on-site control room, an off-site server location, a cloud storage system). The control system  126  may be dedicated to control a single scanning system  100 , or may control multiple scanning systems  100  in an operative grouping or subgrouping. 
       FIG. 2A  is a simplified perspective view of a radiation detector  200 , in accordance with embodiments of the disclosure. As a non-limiting example, the radiation detector  200  may form a totality or a portion of the radiation detector  116  of  FIG. 1 .  FIG. 2B  is a simplified front view of the radiation detector  200 ,  FIG. 2C  is a simplified top view of the radiation detector  200 , and  FIG. 2D  is a simplified cross-sectional view of the radiation detector  200  taken through section line D-D of  FIG. 2B .  FIG. 2E  is a simplified front view of the radiation detector  200  with a front cover attached to a support structure thereof, and  FIG. 2F  is a simplified perspective view of the radiation detector  200  with top cover over a detector array thereof, in accordance with embodiments of the disclosure. The radiation detector  200  may also be referred to herein as a “detector measurement system” (DMS). 
     With reference to  FIG. 2A  through  FIG. 2D , the radiation detector  200  may include a support structure  202  (which may also be referred to herein as a “saddle,” a “cradle,” or a “frame”) including a base portion  204 , and an arc portion  206  vertically above the base portion  204  and connected to the base portion  204  by sidewalls  208 . 
     Each of the base portion  204 , the arc portion  206 , and the sidewalls  208  may include a unitary body or element. Stated another way, the base portion  204 , the arc portion  206 , and the sidewalls  208  may form an integral member. In other words, in some such embodiments, the base portion  204 , the arc portion  206 , and the sidewalls  208  form a continuous structure. In some embodiments, the base portion  204 , the arc portion  206 , and the sidewalls  208  are formed of and include the same material composition. In some embodiments, the support structure  202  comprises a metal exhibiting a relatively low density (as compared to other metals), such as, for example, aluminum. However, the disclosure is not so limited and the support structure  202  may include a different material composition than that described above. In addition, non-unitary bodies or elements forming the structure of the support structure  202  do not exceed the scope of this disclosure, such as, as a non-limiting example, portions that are coupled using any suitable technique. In some embodiments, the support structure  202  (e.g., the base portion  204 , the arc portion  206 , and the sidewalls  208 ) comprises a material exhibiting shielding properties with respect to the incident radiation  250 . By way of non-limiting example, in some embodiments, the support structure  202  comprises tungsten. 
     The support structure  202  may exhibit a generally arcuate shape, such as a circular shape. In some embodiments, the arc portion  206  exhibits a substantially circular shape, such as a truncated circular shape. In other words, the arc portion  206  may exhibit a substantially circular shape, but may not define an entire circle. In some embodiments, a center of the circular shape of the support structure  202  (and the arc portion  206 ) may correspond to the focal spot of radiation (e.g., to the radiation source  114  ( FIG. 1 )). Stated another way, the radiation source  114  may be located at the center of a circular shape, a portion of which is defined by the support structure  202  including the arc portion  206 . As will be described herein, in other embodiments, the support structure  202  exhibits a different shape, such as a hexagonal or partial-hexagonal shape; a portion exhibiting a truncated circular shape and other portions comprising a linear shape; or a U-shaped structure. 
     The arc portion  206  may extend substantially along an entire length (e.g., in the X-direction) of the support structure  202 . For example, the arc portion  206  may extend from one sidewall  208  to another sidewall  208  along the length of the support structure  202 . As will be described herein, the arc portion  206  may be configured to carry detector modules  240  of radiation detector  200 . 
     The radiation detector  200  may include a back plate  210  configured to be removably attached to support structure  202 . In the specific non-limiting example depicted by  FIG. 2A , the back plate  210  may include apertures  212  configured to receive one or more fasteners for coupling the back plate  210  of the radiation detector  200  to the rotor  106  ( FIG. 1 ). The fasteners may include, as non-limiting examples, bolts, screws, or other structures configured for attaching (e.g., securing) the back plate  210  to the rotor  106 . Accordingly, in some embodiments, the back plate  210  is an attachment element and configured to interface the support structure  202  of the radiation detector  200  to the rotor  106 . In other words, the back plate  210  may include physical features, such as alignment elements, to facilitate suitable attachment of the radiation detector  200  to the rotor  106 . Alignment elements may include, as non-limiting examples, visual alignment elements to assist a user with appropriate orientation and alignment of the back plate  210 , the support structure  202 , and the rotor  106 , and matingly compatible alignment elements to facilitate an appropriate orientation and alignment. In some embodiments, the back plate  210  further comprises additional apertures  214  configured to facilitate alignment of the back plate  210  to the rotor  106 . 
     In some embodiments, the radiation detector  200  may include a base structure configured to be removably attached to the support structure  202 , such as to the base portion  204 . The base structure may include a surface for receiving one or more electronic boards. As used herein, the term “electronic boards” means electronics, and includes without limitation: integrated circuits (ICs), application specific integrated circuits, digital logic circuits, microcontrollers, microprocessors, and combinations thereof. Electronics of electronic boards may include a number of functional blocks for performing disclosed embodiments or portions thereof coupled by any suitable interconnect, such as a printed circuit board, flexible circuit, a wiring harness, and combinations thereof, without limitation. 
     The arc portion  206  may include facets  230  configured to receive one of the detector modules  240 , as will be described herein. Each facet  230  may be configured to be coupled to a detector module  240 . For clarity and ease of understanding,  FIG. 2A  illustrates only four facets  230  coupled to four respective detector modules  240 . However, it will be understood that a detector module  240  may be coupled to each of the facets  230 . 
     Facets  230  may be located on an upper (e.g., a first) surface of the arc portion  206  and may be separated from each other by spaces  232  ( FIG. 2C ). The upper surface of the arc portion  206  including the facets  230  may be oriented such that the facets  230  face a center of a circle at least partially defined by the support structure  202  including the arc portion  206 . 
     Although  FIG. 2A  through  FIG. 2D  illustrate a particular number (in the specific non-limiting example depicted,  36 ) of facets  230 , additional or fewer facets  230  do not exceed the scope of this disclosure. In some embodiments, the arc portion  206  comprises fewer facets  230  (e.g., fewer than 30 facets  230 , fewer than 26 facets  230 , fewer than 22 facets  230 , fewer than 18 facets  230 , or fewer than 16 facets  230 ). In other embodiments, the support structure  202  comprises a greater number of the facets  230  (e.g., greater than 40 facets  230 , greater than 50 facets  230 , or even greater than 60 facets  230 ). 
     Each facet  230  may individually include apertures  234  ( FIG. 2C ) configured for attachment of a detector module  240  to a respective facet  230 . The facets  230  may each include a surface  236  configured to be coupled to (e.g., receive) a complimentary (e.g., corresponding, without limitation) surface of a corresponding detector module  240 . In one or more embodiments, the surface  236  may be substantially planar, but a non-planar surface  236  does not exceed the scope of this disclosure. In some embodiments, the surface  236  of each facet  230  is oriented such that a center thereof is oriented at substantially a right angle to intended radiation  250  from the radiation source  114  ( FIG. 1 ). In some embodiments, the surfaces  236  may be oriented such that the surfaces  236  are substantially perpendicular to a path of the radiation  250  emitted from the radiation source  114 . In other words, the surfaces  236  may be oriented such that they are substantially perpendicular to a line extending from the respective surface  236  to a center of a circle at least partially defined by the arc portion  206  of the support structure  202 . In some embodiments, the surfaces  236  may be oriented with respect to a radiation source such that an angle of incidence of at least some radiation photons impinging the surface  236  is substantially  90  degrees. In some cases, surfaces of the detector modules  240  mounted to the facets  230  are oriented at a right angle to an imaginary line projected from a radiation source (in some cases using a specific location along a path traveled by radiation emitted from a radiation source during an examination, without limitation) to a facet of interest. 
     The surfaces  236  may be sized and shaped to receive and contact substantially all of or a portion of a surface of a corresponding detector module  240  to provide structural support to the detector modules  240  during use and operation of the scanning system  100  ( FIG. 1 ) (e.g., rotation of the rotor  106  ( FIG. 1 )). When coupled to the surfaces  236 , the detector modules  240  may be oriented to face a direction of the radiation  250  from the radiation source  114  ( FIG. 1 ). The surfaces  236  of the facets  230  may facilitate improved accuracy of desired placement of the detector modules  230  compared to conventional detector arrays that do not include the facets  230  or the arc portion  206 . By way of non-limiting example, conventional detector arrays known to inventors of this disclosure may include detector modules that are mounted to a detector array support structure (e.g., cradle) with mounting brackets or blocks including a major surface that mounts to the detector array support structure oriented at an angle (e.g., a right angle) with respect to a surface of the mounting bracket that is configured to receive the detector module. Such a configuration typically requires fabrication of accurate surfaces that are oriented at right angles to each other and which increases the likelihood of misalignment of a detector module to a detector array support structure and the cost of fabrication/assembly. In addition, as will be described herein, the apertures  234  of the facets  230  facilitates serviceability of the radiation detector  200 , such as installation and removal of the detector modules  240  from the surfaces  236  of the facets  230  compared to installation and replacement of detector modules of conventional scanning systems. 
     The detector modules  240  may be configured to generate imaging signals indicative of attenuation of the radiation  250  that impinges the detector module  240 . More specifically, the detector modules  240  may be configured to indirectly convert (or directly convert detected radiation  250  into analog or digital imaging signals. For example, the detector modules  240  configured to indirectly convert radiation (e.g., the radiation  250 , without limitation) to imaging signals may include a scintillator sub-assembly and a detector sub-assembly, as will be described herein. As a non-limiting example, the detector modules  240  configured to directly convert radiation (e.g., the radiation  250 , without limitation), may include a material and/or circuitry adapted to generate an electrical charge or a representation thereof in response to radiation and analog or digital signals indicative of the radiation. In some such embodiments, the detector modules  240  may include a detector sub-assembly comprising, for example, cadmium zinc telluride (CZT) or another direct conversion material, without limitation. 
     The sidewalls  208  and the arc portion  206  of the support structure  202  may define a cavity  255  configured to at least partially receive one or more heat exchangers  245  (e.g., cooling structures) configured to thermally couple to the arc portion  206  to provide cooling of the detector modules  240  through the arc portion  206 . In some embodiments, the heat exchangers comprise fins  252  (e.g., cooling fins) configured to exchange thermal energy with an ambient environment by passing fluid (e.g., air) across (e.g., adjacent to) the fins  252 . Stated another way, and as will be described herein, the cavity  255  may be configured to be fluidly coupled to a fluid for exchanging heat with the fins  252 . The cavity  255  may be at least partially defined by a lower surface (e.g., a second surface) of the arc portion  206 . In some embodiments, the cavity  255  is sized and shaped to facilitate flow of air through the cavity  255  and the fins  252  to transfer heat from the arc portion  206  through the fins  252 . The cavity  255  may be in operable communication with fans  290  ( FIG. 2D ,  FIG. 2E ,  FIG. 2F ) configured to provide air to the cavity  255  to facilitate heat transfer from the fins  252 . 
     The fins  252  may include a metal, such as, for example, copper, aluminum, or another material. In some embodiments, the fins  252  comprise the same material composition as the support structure  202 . In some embodiments, the fins  252  comprise aluminum (e.g., an aluminum-containing material). In some embodiments, the fins  252  comprise a different material composition than the support structure  202 . In some embodiments, the fins  252  are integral with the support structure  202  and extend from, for example, surfaces of the base portion  204  to a lower surface of the arc portion  206 . In other embodiments, the fins  252  are configured to be removably coupled to the support structure  202 . For example, fins  252  may be detachable from within the cavity  255  and removed from the support structure  202 . 
     The fins  252  may be in direct thermal and physical contact with at least a portion of the arc portion  206 . In some embodiments, the fins  252  directly contact the lower surface of the arc portion  206 . As described above, the arc portion  206  may be configured to facilitate thermal transfer (e.g., heat transfer) between the detector modules  240  and an external environment (e.g., air circulated through the fins  252 ). The fins  252  may be sized, shaped, and spaced to facilitate a desired amount of thermal transfer (e.g., heat transfer) from the arc portion  206  to the external environment. 
     With reference to  FIG. 2A  and  FIG. 2D , the radiation detector  200  may further include one or more heater elements configured to provide heat to the arc portion  206 . For example, a front of the radiation detector  200  may include a heater element  260   a  ( FIG. 2A ,  FIG. 2D ) and a back of the radiation detector  200  may include a heater element  260   b  ( FIG. 2D ), collectively referred to herein as heater elements  260 . The heater element  260   a  in  FIG. 2A  is illustrated in broken lines to indicate that the heater element is located under the arc portion  206  (e.g., between the arc portion  206  and the fins  252 ). In some embodiments, heat from the heater elements  260  is transferred to the detector modules  240  through the arc portion  206  through the respective facets  230 . In some embodiments, the heater elements  260  may be configured to maintain the temperature of the arc portion  206  at a substantially uniform temperature. In some embodiments, the heater elements  260  are configured to maintain a temperature of the facets  230  and the detector modules  240  at a temperature above room temperature (e.g., above about 20° C., above about 25° C.). 
     The heater elements  260  may be located, for example, in front of and behind (e.g., in the Z-direction) facets  230 . For example, the heater element  260   a  may be located in front of the facets  230  and the heater element  260   b  may be located behind the facets  230 . In some embodiments, the heater elements  260  may extend along a substantial entire length (e.g., in the X-direction) of the arc portion  206 . 
     The heater elements  260  may each comprise, for example, a resistive heater. For example, the heater elements  260  may each comprise a strip heater, a ribbon heater, a cartridge heater, a tubular heater, a band heater, a wire element heater, an open coil heater, a flexible heater, or another type of heating element. The heater elements  260  may include, for example, a nickel alloy (e.g., NiCr, FeCrAl, CuNi), a molybdenum alloy, a stainless steel alloy, a tungsten alloy, a ceramic material (e.g., MoSi 2 , SiC, graphite), or another material, without limitation. 
     The radiation detector  200  may include one or more temperature sensors  262  for providing an indication of a temperature of one or more portions of radiation detector  200 . The temperature sensors  262  may be arranged to measure the temperature of one or more portions of the radiation detector  200 , such as the temperature of the facets  230  or temperatures in proximity thereto. In some embodiments, the temperature sensors  262  are located within cavities formed within the facets  230  or within the arc portion  206 . 
     The detector modules  240  in direct physical and thermal contact with the facets  230  may be heated and cooled by the facets  230  which are, in turn, in thermal contact with the heating elements  260  and the heat exchanger  245  (e.g., the fins  252 ). Accordingly, the temperature of the arc portion  206  may be controlled with the heater elements  260  and the fins  252 . In some embodiments, the temperature of the detector modules  240  is indirectly controlled by thermal transfer between the detector modules  240  and the facets  230 . Accordingly, the arc portion  206  including the facets  230  to which the detector modules  240  are directly coupled, facilitates improved temperature control of the detector modules  240  and the radiation detector  200 . 
     The temperature of the radiation detector  200  (e.g., one or more of the detector modules  240 , the support structure  202 , the facets  230 , and the arc portion  206 ) may be controlled with a temperature control system. For example, one or more of the temperature sensors  262  may be electrically coupled to a controller. The controller may be operably coupled to one or more fans  290  for directing air through the volume and across the fins  252  and may also be operably coupled to one or more of the heater elements  260 . The fans  290  and the heater elements  260  may be in electrical communication with the controller through one or more electronic boards. The controller may be configured to control the temperature of the detector modules  240  by adjusting one or both of the flow of air through the fins  252  and the power to the resistive heater  260  via one or more control signals (not shown). In one or more embodiments, temperature may be controlled in response to a control loop of controller executing a control algorithm or control law known to a person having ordinary skill in the art. 
     With reference to  FIG. 2A  and  FIG. 2E , in use and operation, the radiation detector  200  may include a cover  292  configured to be coupled to the support structure  202 . The cover  292  may be configured to enclose the cavity  255  such that during use and operation, the flow of air through the cavity  255  and across the fins  252  is independent of the rotation speed of the radiation detector  200 . In some embodiments, the fans  290  are coupled to the cover  292 . In some embodiments, the support structure  202  includes apertures  294  for receiving fasteners for coupling the cover  292  to the support structure  202 . 
     With reference to  FIG. 2F , in some embodiments, the radiation detector  200  includes a top cover  295  configured to be operably coupled to the support structure  202 . The top cover  295  may be transparent to the radiation  250 . With reference to  FIG. 2A , in some embodiments, the radiation detector  200  includes shielding materials  296  configured to shield the radiation  250  from undesired portions of the radiation detector  200 . In some embodiments, the shielding material  296  comprise tungsten. In some embodiments, a shielding material  270  may be located within the spaces  232  between neighboring facets  230 . In some embodiments, the shielding material  270  comprises tungsten. 
     As described above, the radiation detector  200  may include one or more electronic boards to facilitate operation of the detector modules  240  and the scanning system  100  ( FIG. 1 ) and more specifically, to facilitate electrical communication between the detector modules  240  and the radiation detector  200 . Electronics of the electronic boards may be configured to control the radiation detector  200  and the rotor  106  ( FIG. 1 ). In some embodiments, the electronic boards may be configured to distribute power throughout the scanning system  100  ( FIG. 1 ) and signals to and from, for example, the rotor  106  and other components of scanning the system  100  and the radiation detector  200 . 
     Although the radiation detector  200  has been described and illustrated as including a heat exchanger  245  including the fans  290  and the fins  252 , the disclosure is not so limited. In other embodiments, the heat exchanger  245  configured for cooling the temperature of the arc portion  206  and the detector modules  240  may include other structures. For example, the heat exchanger  245  may include a cooling structure including a chiller or a water cooler. In some such embodiments, the cavity  255  may not include the fins  252  and may include a chiller including, for example, pipes through which cooling water flows to control a temperature of the arc portion  206  with water cooling. In some embodiments, the arc portion  206  is in thermal communication with a structure including pipes or channels through which water may be flowed to control a temperature thereof. By way of non-limiting example, the cavity  255  may not include the fins  252  but may include a structure interfacing with a lower portion of the arc portion  206  and including channels configured to flow water therethrough. A temperature of the structure and the temperature of the arc portion  206  may be controlled based on one or both of the temperature of a fluid (e.g., water) flowing through the channel, a flow rate of the fluid, a surface area of the channel, and a volume of the channel. In some embodiments, the cavity  255  is replaced with a solid material including one or more channels therein. In other embodiments, at least a portion of the arc portion  206  may include pipes through which water may be flowed to control a temperature of the arc portion  206 . 
       FIG. 3  is a simplified perspective view of a detector module  300 , in accordance with embodiments of the disclosure. The detector module  300  may include the detector module  240  of  FIG. 2A . The detector module  300  may include a base structure  310  including a first surface  312  and a second surface  314  opposite the first surface  312 , one or more detector units  320  overlying the base structure  310 , and an anti-scatter module (ASM)  330  overlying the detector units  320 . The detector module  300  may further include a handle  340  operably coupled to the base structure  310 . Each detector unit  320  may be referred to herein as a “detector tile” or simply as a “tile.” The anti-scatter module may absorb undesired radiation that has been scattered by the object (e.g., object  102  ( FIG. 1 )) being scanned. 
     The detector module  300  may include one or more connectors for electrically connecting the detector module  300  to the radiation detector  200  (e.g., such as to an electronic board of the radiation detector  200 ). 
     The detector module  300  may include apertures  360  or cutout portions that correspond to the spacing and location of the apertures  234  ( FIG. 2C ) of the facets  230  ( FIG. 2C ). In some embodiments, the detector module  300  may be attached to the surface  236  of the facet  230  by aligning the apertures  360  with the apertures  234  of a corresponding facet  230  and securing the detector module  300  to the corresponding facet  230  with fastening means (e.g., bolts, screws, other structures). 
     Surfaces of the detector units  320  may directly contact the second surface  314  of the base structure  310 . The detector units  320  may be in direct thermal contact with the second surface  314  of the base structure  310 . In some embodiments, the first surface  312  may be substantially planar and may contact the surface  236  of a corresponding facet  230  and the second surface  314  may be substantially planar and parallel to the first surface  312  and may be configured to receive one or more detector units  320 . 
       FIG. 4A  is a simplified perspective view of a detector unit  400  (e.g., an indirect conversion detector unit, a direct conversion detector unit), in accordance with embodiments of the disclosure. The detector unit  400  may include, for example, one of detector units  320  ( FIG. 3 ) of the detector module  300  ( FIG. 3 ).  FIG. 4B  is a simplified perspective view of a detector unit  400 ′ that may correspond to, for example, one of the detector units  320  ( FIG. 3 ), in accordance with embodiments of the disclosure. 
     The detector units  400 ,  400 ′ may comprise a detector tile configured to be coupled to the detector module  300  ( FIG. 3 ). With reference to  FIG. 4B , in some embodiments, the detector unit  400 ′ includes a connector  402  for electrically coupling the detector unit  400 ′ to the radiation detector  200  ( FIG. 2 ), such as to an electronic board of the radiation detector  200 . 
     The detector units  400 ,  400 ′ may comprise an indirect conversion detector unit, or a direct conversion detector unit. For example, in some embodiments, the detector units  400 ,  400 ′ include a photodetector array coupled to a scintillator array, as known in the art. In another embodiment, the detector units  400 ,  400 ′ include a direct conversion detector such as CzZnTe, as known in the art. In addition, in some embodiments the detector units  400 ,  400 ′ may include radiation shielding materials formulated and configured to inhibit or attenuate at least some of the radiation photons (e.g., x-ray and/or gamma-ray photons) impingent thereon. By way of non-limiting example, the radiation shielding materials may include one or more of tungsten, lead, tantalum, leaded glass, and heavy metal powder composites (e.g., tungsten powder in a polymer binder). In some embodiments, radiation shielding material comprises tungsten. 
     In use and operation of the scanning system  100 , the detector units  320  (e.g., detector units  400 ,  400 ′) of the detector module  300  generate heat. As the size of the scanning system  100  (and the corresponding size of the radiation detector  116 ) increases, the size of the detector modules  240 ,  300  and/or number of the detector units  320  may exhibit a corresponding increase. The heat generated by the detector units  320  may be removed from the radiation detector  116  by means of the support structure  202  including the arc portion  206 . For example, heat from the detector units  320  may be transferred from the detector units  320  to the first surface  312  of the base structure  310  and from the base structure  310  directly to the facets  230  of the arc portion  206 . Heat may be transferred through the arc portion  206  and may be removed from the system through the fins  252 , such as by flowing air through the fins  252  or through a cooling medium (e.g., cooling water), as described above. 
     The radiation detector  200  according to embodiments of the disclosure may facilitate improved accuracy of images generated with the scanning system  100  ( FIG. 1 ). For example, the facets  230  may substantially completely support the detector modules  240 ,  300 , reducing or substantially preventing deflection of the detector modules  240  and the associated detector units (e.g., the detector units  320 ). Stated another way, the base structure  310  of the detector modules  240 ,  300  may be fully supported on the surface  236  of the facets  230  and the detector units  320  may be fully supported on the second surface  314  of the base structure  310 . Accordingly, during rotation of the rotor  106  ( FIG. 1 ) and accompanying the radiation detector  116  ( FIG. 1 ), the G-forces exerted on the detector modules  240 ,  300  may not substantially deflect the detector module  240 ,  300  including the detector units  320  since the base structure  310  is supported by the facets  230 . By way of comparison, detector units of conventional scanning systems are not fully supported by a facet or other supporting structure. For example, detector units of so-called “spine” type cradles include a mounting bracket comprising a first surface that is mounted to the cradle that is rotated and a second surface to which the detector units are mounted. The second surface is oriented at a right angle with respect to the first surface. Accordingly, as the rotor rotates, the G-forces on the detector module cause the detector units to bend, reducing the accuracy of measurements made with the detector units. Other types of conventional scanning system include so-called “polygon” type cradles wherein support structures for the detector units are spanned across different portions of the cradle. However, as the rotor rotates, the support structures bend, causing a corresponding bend in the detector units and a reduction in accuracy of the measurements made with the detector units. 
     In addition, the radiation detector  200  including the including the arc portion  206  according to embodiments of the disclosure may facilitate improved temperature control of the detector modules  240 ,  300  and the detector units  320  (e.g., the detector units  400 ,  500 ) compared to conventional scanning systems. For example, the arc portion  206  facilitates indirect thermal transfer between the detector modules  240  and a surrounding environment through the arc portion  206 . The temperature of the arc portion  206  may be controlled by removing heat from the arc portion  206  by means of the fins  252  and the passage of air, and by controlling the power of the heater elements  260 . By way of comparison, the temperature of detector modules of conventional scanning systems may be directly controlled by passage of air as the rotor rotates and air is passed across the detector modules. However, such methods may result in inadequate temperature control of the detector module. For example, the rate of heat transfer from the detector modules may be dependent upon the rotation speed of the rotor. Removing heat from the radiation detector  200  through the arc portion  206 , as described herein, may facilitate a more uniform temperature control of the radiation detector  200  compared to conventional scanning systems. For example, due to the relatively large thermal mass of the arc portion  206 , the rate of temperature change of the arc portion  206  and coupled detector arrays  200  is substantially slower (e.g., the time constant of temperature change is greater) compared to conventional scanning systems. Accordingly, the scanning systems including the detector array according to embodiments described herein may not be as susceptible to changes in air flow or rotation speed of the rotor compared to conventional scanning systems. 
     In addition, the second surface  314  of the detector module  300  that contacts the corresponding substantially planar surface  236  of the facet  230  facilitates direct coupling and alignment of the detector module  300  to the facets  230  of the radiation detector  200 . In addition, the apertures  360  of the detector module  300  facilitate alignment of the detector module  300  to the flat substantially planar surface  236  of the facets  230 . The apertures  360  and the handle  340  of the detector module  300  allow for improved servicing of the radiation detector  200  compared to conventional scanning systems. 
     Although  FIG. 2A  through  FIG. 2E  have been described and illustrated as including the radiation detector  200  comprising the support structure  202  including the arc portion  206  having a particular shape, the disclosure is not so limited.  FIG. 5A  is a simplified cross-sectional view of a radiation detector  500 , in accordance with embodiments of the disclosure. The radiation detector  500  may be substantially similar to the radiation detector  200  of  FIG. 2A  through  FIG. 2F , except that the radiation detector  500  may include a support structure  502  exhibiting a different shape than the support structure  202  of the radiation detector  200 . The support structure  502  may exhibit a truncated hexagonal shape. The support structure  502  may be located opposite a radiation source  514  configured to emit radiation  550  toward facets  530  of the support structure  502 . 
     The support structure  502  may define a cavity  555  configured to receive a heat exchanger  545 , as described above with reference to the cavity  255  of the support structure  202 . In some embodiments, the heat exchanger  545  may comprise fins  552 , as described above with reference to the heat exchanger  245 . Fans may be coupled to the support structure  502  and configured to provide air through the fins  552 , as described above with reference to the fans  290 . Accordingly, the support structure  502  may exhibit a truncated hexagonal shape. 
       FIG. 5B  is a simplified cross-sectional view of a radiation detector  500 ′, in accordance with embodiments of the disclosure. The radiation detector  500 ′ may be substantially similar to the radiation detector  500 , except that the radiation detector  500 ′ may exhibit a different cross-sectional shape. For example, the radiation detector  500 ′ may include a support structure  502 ′ including a first portion  590  exhibiting a circular shape and second portions  592  coupled to the first portion  590  and exhibiting a substantially linear shape. The support structure  502 ′ may include facets (not shown) as described above with reference to the radiation detector  500  and the radiation detector  200 . 
       FIG. 5C  is a simplified cross-sectional view of a radiation detector  500 ″, in accordance with embodiments of the disclosure. The radiation detector  500 ″ may be used in an emission system (e.g., a SPECT system, a PET system). The radiation detector  500 ″ may be substantially similar to the radiation detector  500 ′, except that the radiation detector  500 ″ may exhibit a different cross-sectional shape. For example, the radiation detector  500 ″ may include a support structure  502 ″ exhibiting a U-shape. The support structure may include a first portion  590  exhibiting a circular shape and second portions  592 ′ coupled to the first portion  590 ′ and exhibiting a substantially linear shape. An angle between the first portion  590 ′ and the second portions  592 ′ may be different than the angle between the first portion  590  and the second portions  592  of the support structure  502 ′ of  FIG. 5B . In some embodiments, the second portions  592 ′ are oriented substantially parallel to one another. The support structure  502 ″ may include facets (not shown) as described above with reference to the radiation detector  500  and the radiation detector  200 . 
     Although  FIG. 1  and  FIG. 2A  through  FIG. 2E  have been described and illustrated as comprising a scanning system  100  including a particular type of radiation detector  116 ,  200 , the disclosure is not so limited. In other embodiments, radiation detector  200  may include a so-called position emission tomography (PET) system wherein the radiation detector is in the form of a ring.  FIG. 6  is a simplified schematic of a scanning system comprising, for example, a position emission tomography (PET) scanning system  600 . PET scanning system  600  may be substantially similar to the scanning system  100  of  FIG. 1 , except that PET scanning system  600  may include a different radiation detector. The PET scanning system  600  may include a detector array  616  arranged in a ring shape. The detector array  616  may be substantially similar to the radiation detector  116 ,  200  ( FIG. 1 .  FIG. 2A  through  FIG. 2F ), except that the radiation detector  616  may include detectors arranged around a circumference of substantially all of a circle. In some embodiments, the radiation detector  616  may be formed from segments, such as from one or more radiation detectors  200 ,  500 ,  500 ′,  500 ″ arranged to form a circular shape. Accordingly, the radiation detector  616  may include a support structure (e.g., the support structure  202 ) including an arc portion (e.g., the arc portion  206 ) arranged around substantially all of a circle. Alternatively, the PET scanning system  600  may include a detector array  616  arranged in a combination of circular and linear sections, such as shown and described with reference to  FIG. 5B . In addition, the PET scanning system  600  may not include a radiation source (e.g., the radiation source  114  ( FIG. 1 )). In some such embodiments, a patient  602  may include (e.g., be injected with) a radioactive tracer material. 
     Accordingly, radiation detectors according to embodiments described herein may include a support structure including an arc portion configured to be in physical and thermal contact with detector modules placed on facets of the arc portion. The facets and the detector modules may be enclosed within the support structure and may not be in direct fluid communication with an external environment. The arc portion may exhibit a thermal mass relatively larger than a thermal mass of the individual detector modules. The arc portion may be in thermal communication with one or more heater elements and one or more cooling elements (e.g., the fins  252  ( FIG. 2A ,  FIG. 2B )). A temperature of the detector modules may be controlled indirectly through controlling the temperature of the arc portion of the support structure, which may be controlled by operation of the heater elements and the cooling elements. The relatively large thermal mass of the arc portion and the isolation of the detector modules from the external environment may facilitate improved temperature control of the detector modules compared to conventional scanning systems. In addition, the facets may facilitate improved physical support of the detector modules during use and operation, reducing physical deflection and bending of the detector modules compared to conventional scanning system. 
     While embodiments of the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the disclosure is not limited to the particular forms disclosed. Rather, the disclosure encompasses all modifications, variations, combinations, and alternatives falling within the scope of the disclosure as defined by the following appended claims and their legal equivalents.