Abstract:
A method includes obtaining a photosensor substrate ( 236 ) having two opposing major surfaces. One of the two opposing major surfaces includes at least one photosensor row ( 230 ) of at least one photosensor element ( 232, 234 ), and the obtained photosensor substrate has a thickness equal to or greater than one hundred microns. The method further includes optically coupling a scintillator array ( 310 ) to the photosensor substrate. The scintillator array includes at least one complementary scintillator row ( 224 ) of at least one complementary scintillator element ( 226, 228 ), and the at least one complementary scintillator row is optically coupled to the at least one photosensor row ( 230 ) and the at least one complementary scintillator element is optically coupled to the at least one photosensor element. The method further includes thinning the photosensor substrate optically coupled to the scintillator producing a thinned photosensor substrate that is optically coupled to the scintillator and that has a thickness on the order of less than one hundred microns.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/006,703 filed Sep. 13, 2013, which is a national filing of PCT application Serial No. PCT/IB2012/051300, filed Mar. 19, 2012, published as WO 2012/127403 A2 on Sep. 27, 2012, which claims the benefit of U.S. Provisional application No. 61/467,044 filed Mar. 24, 2011, all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The following generally relates to spectral imaging and more particularly to a spectral imaging detector, and is described in connection with computed tomography (CT). However, it is also amenable to other imaging modalities. 
     BACKGROUND OF THE INVENTION 
     A conventional computed tomography (CT) scanner includes a rotating gantry rotatably mounted to a generally stationary gantry. The rotating gantry supports an x-ray tube and a detector array, which is mounted on the rotatable gantry opposite the x-ray tube, across an examination region. The rotating gantry and hence the x-ray tube and the detector array rotate around the examination region about a longitudinal or z-axis. The x-ray tube is configured to emit radiation that traverses the examination region (and a portion of a subject or object in the examination region) and illuminates the detector array. The detector array detects the radiation and generates electrical signals indicative of the examination region and the subject or object disposed therein. A reconstructor reconstructs the projection data, generating volumetric image data. 
     For spectral CT, the scanner may include an energy-resolving detector array such as a double-decker detector array. An example portion of a double-decker detector array  100  is shown in  FIG. 1 . The detector  100  includes a plurality of detector modules  102  aligned with respect to each other along a substrate  104  in an x-direction  106 . Each module  102  includes first and second scintillator rows  108  and  110  optically coupled to corresponding first and second detection regions  112  and  114  of a photodiode substrate  116 . The first and second scintillator rows  108  and  110  are arranged with respect to each other such that the first scintillator row  108  is above the second scintillator element  110  with respect to the incoming radiation  120 . Generally, lower energy x-rays photons tend to be absorbed in the upper scintillator row  108  and higher energy x-ray photons tend to be absorbed in the lower scintillator row  110 . The first and second scintillator rows  108  and  110  and the detection regions  112  and  114  extend along a z-direction  122 , forming multiple rows of detector elements. 
     With the detector array  100  of  FIG. 1 , the resolution of the detector array  100  in the x-direction  106  generally is limited by a finite thickness  124  of the photodiode substrate  116  of each module  102  in the x-direction  106 , which has been on the order of one hundred (100) microns to four hundred (400) microns. Unfortunately, thinner photodiode substrates are fragile and not well-suited for constructing detector modules such as the detector modules  102  of the detector array  100 . 
     SUMMARY OF THE INVENTION 
     Present aspects of the application provide new and/or improved techniques that address the above-referenced problems and others. 
     In accordance with one aspect, a method includes obtaining a photosensor substrate having two opposing major surfaces. One of the two opposing major surfaces includes at least one photosensor row of at least one photosensor element, and the obtained photosensor substrate has a thickness equal to or greater than one hundred microns. The method further includes optically coupling a scintillator array to the photosensor substrate. The scintillator array includes at least one complementary scintillator row of at least one complementary scintillator element, and the at least one complementary scintillator row is optically coupled to the at least one photosensor row and the at least one complementary scintillator element is optically coupled to the at least one photosensor element. The method further includes thinning the photosensor substrate optically coupled to the scintillator producing a thinned photosensor substrate that is optically coupled to the scintillator and that has a thickness on the order of less than one hundred microns. 
     According to another aspect, an imaging detector includes at least one detector tile including a tile substrate and a plurality of detector modules arranged along an x-direction along the tile substrate. A detector module includes a scintillator array having at least one scintillator row of scintillator elements extending along a z-direction coupled to at least one photosensor row of photosensor elements of a photosensor substrate. The photosensor substrate is coupled to the scintillator array and has an initial thickness that is equal to or greater than one hundred microns, and the photosensor substrate of the imaging detector has a thinned thickness of less than one hundred microns. 
     According to another aspect, a method includes assembling an imaging detector module of an imaging system, wherein the imaging detector module includes a scintillator optically coupled to a photosensor substrate, which has a thickness less than one hundred microns. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. 
         FIG. 1  schematically illustrates a perspective view of a prior art double-decker spectral detector array. 
         FIG. 2  schematically illustrates an example imaging system with a spectral detector array including a detector tile with a plurality of detector modules. 
         FIG. 3  schematically illustrates a side view of a detector module from the z-direction. 
         FIGS. 4-12  illustrate a method for assembling the detector module of  FIG. 3 . 
         FIG. 13  illustrates an embodiment in which a support carrier is utilized to facilitate making the individual photo-sensor substrates. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 2  schematically illustrates an imaging system  200  such as a computed tomography (CT) scanner. The imaging system  200  includes a generally stationary gantry portion  202  and a rotating gantry portion  204 . The rotating gantry portion  204  is rotatably supported by the generally stationary gantry portion  202  via a bearing (not shown) or the like. 
     A radiation source  206 , such as an x-ray tube, is supported by the rotating gantry portion  204  and rotates therewith around an examination region  208  about a longitudinal or z-axis  210  in connection with a frame of reference shown at  212 . A source collimator  214  collimates radiation emitted by the radiation source  206 , producing a generally cone, fan, wedge or otherwise-shaped radiation beam that traverse the examination region  208 . 
     An energy-resolving detector array  218  subtends an angular arc opposite the examination region  208  relative to the radiation source  206  and detects radiation that traverses the examination region  208 . The illustrated detector array  218  includes a plurality of tiles  220 . Each tile  220  includes a plurality of detector modules  222   1 , . . . ,  222   N  (wherein N is an integer), arranged on a tile substrate  242 , with respect to each other, along the x-direction. The plurality of detector modules  222   1 , . . . ,  222   N  are also referred to herein as detector modules  222 . 
     Each detector module  222  includes a plurality of rows  224   1 , . . . ,  224   M  (wherein M is an integer equal to or greater than one, and collectively referred to as  224 ) of scintillator elements  226   1 , . . . ,  226   K  and  228   1 , . . . ,  228   K  (wherein K is an integer, and collectively referred to as  226  and  228 ) extending along the z-direction. In the illustrated embodiment, M=2, and the detector module is a spectral detector module. The rows of scintillator elements  226  and  228  are optically coupled to a corresponding plurality of rows  230   1 , . . . ,  230   M  (collectively referred to as  230 ) of photosensor elements  232   1 , . . . , and  234   1 , . . . (collectively referred to as  232  and  234 ) of a photosensor substrate  236  extending along the z-direction. 
     Each detector module  222  also includes electrically conductive pathways or pins  238 . Where the detector module  222  further includes processing electronics  240  incorporated into the photosensor substrate  236  (as shown), the electrically conductive pathways or pins  238  are used to route power and digital signals from the processing electronics  240  to the tile substrate  242 . Where the processing electronics  240  are located external to the photosensor substrate  236 , the electrically conductive pathways or pins  238  are used to route signals from the photosensor elements  232  and  234  to the tile substrate  242   
     As described in greater detail below, the photosensor substrate  236 , in one instance, has an x-axis thickness of less than one hundred (100) microns. With such a photosensor substrate, the detector array  218  can include more detector modules  222  for a given x-axis length relative to a configuration of the detector array with a thicker photosensor substrate (i.e., greater than 100 microns), and hence provide higher resolution in the x-direction. In one instance, such a detector array may include thirty (30) to sixty (60) percent more detector modules  222 . Such a detector array may be considered a high definition detector array. 
     A reconstructor  246  reconstructs the signals generated by the detector array  218  and generates volumetric image data indicative of the examination region  208 . Generally, the data from the different rows  230  of photosensor elements  232  and  234  can be individually processed for spectral information and/or combined (e.g., by summing the outputs of the different elements in the same ray path) to produce conventional non-spectral CT data. 
     A subject support  248  is configured to position the object or subject in the x, y, and/or z directions with respect to the examination region  208  before, during and/or after scanning the object or the subject. 
     A general purpose computing system serves as an operator console  250 , and includes an output device such as a display, an input device such as a keyboard, mouse, and/or the like, one or more processor and computer readable storage medium (e.g., physical memory). The console  250  allows the operator to control operation of the system  200 , for example, allowing the operator to select a spectral imaging protocol and/or spectral imaging reconstruction algorithm, initiate scanning, etc. 
       FIG. 3  schematically illustrates a side view of a detector module  222  from the z-axis direction. For explanatory purposes, the detector module  222  is shown as having two scintillator rows  224   1  and  224   2  and two corresponding photosensor rows  230   1  and  230   2 . However, as discussed above, the detector module  222  may have one or more of each of the scintillator rows  224  and the photosensor rows  224 . 
     The detector module  222  includes the photosensor substrate  236 . The illustrated photosensor substrate  236  has a thickness  300  on the order of fifty (50) microns (plus or minus a predetermined tolerance), such as a thickness value from a range of ten (10) to ninety (90) microns, twenty-five (25) to seventy-five (75) microns, forty (40) to sixty (60) microns, and/or other thickness value in one or more other ranges. A suitable material of the photosensor substrate  236  includes, but is not limited to silicon. 
     The photosensor substrate  236  includes a first major surface  302 , with a first region  304  and a second region  306 , and a second opposing major surface  308 . The photosensor rows  230   1  and  230   2  are located in the first region  304  of the first major surface  302 . The photosensor row  230   1  is an upper row, which is closer to the radiation source  206  (FIG.  1 ) and hence the incoming radiation, and the photosensor row  230   2  is a lower row, which is farther from the radiation source  206  ( FIG. 1 ) and hence the incoming radiation. 
     The scintillator row  224   1  is an upper scintillator element, which is closer to the radiation source  206  ( FIG. 1 ) and hence the incoming radiation, and the scintillator row  224   2  is a lower row, which is farther from the radiation source  206  ( FIG. 1 ) and hence the incoming radiation. As discussed herein, the upper scintillator row  224   1  is optically coupled to the corresponding upper photosensor row  230   1  and the lower scintillator row  224   2  is optically coupled to the corresponding lower photosensor row  230   2 . 
     In the illustrated embodiment, the upper and lower scintillator row  224   1  and  224   2  are rectangular shaped and are about equal in size. However, it is to be understood that other shapes and different sized scintillator row  224   1  and  224   2  are contemplated herein. Furthermore, spacing between the scintillator row  224   1  and  224   2  can be smaller or larger. Moreover, as the depths (and material) of the scintillator rows  224  can influence energy separation and/or x-ray statistics, the depths, generally, are such that the upper scintillator row  224   1  is primarily responsive to lower energy photons and the lower scintillator row  224   2  is primarily responsive to higher energy photons. 
     The photosensor substrate  236  optionally includes the processing electronics  240  (for processing signals from the photosensor elements  232  and  234 ) that are part of the photosensor substrate  236 . As such, there will be fewer electrical pathways from the photosensor substrate  236  to the tile substrate  242 , and z-axis widths of the photosensor elements  232  and  234  can be narrowed, increasing detector resolution in the z-direction. A non-limiting example of a photosensor substrate with processing electronics incorporated therein is described in patent application PCT/IB2009/054818, filed Oct. 29, 2009, and entitled “Spectral Imaging Detector” (WO/2010/058309), which is incorporated herein by reference in its entirety. 
     In the illustrated embodiment, the sides of the scintillator rows  224  not affixed to the substrate  236  are surrounded by reflective material  312 , which extends over the entire first major surface  302 . The combination of the scintillator rows  224  and the reflective material  312  is referred to herein as scintillator array  310 . In another embodiment, the reflective material  312  can be omitted. In yet another embodiment, the reflective material  312  may only cover the first region  304 . 
       FIGS. 4-12  describe an approach for assembling the detector array  218 . 
     At  402 , a photosensor substrate having a thickness of greater than one hundred (100) microns is obtained. For example, in one instance, the photosensor substrate  236  is obtained. An example of the substrate  236  is schematically illustrated in  FIG. 5  and includes the two photosensor rows  232  and  234 , a region  502  for the processing electronics  240 , electrically conductive pads  504  for electrical components, and electrically conductive pads  506  for the electrically conductive pins  238 . 
     Note that in  FIG. 5  the photosensor rows  232  and  234 , the region  502  and the pads  504  and the pads  506  are on a same surface plane  508  of the first major surface  302  of the photosensor substrate  236 .  FIG. 6  schematically shows an embodiment in which the scintillator array  310  to be affixed to the photosensor substrate  236  includes a first surface  602  with a recess  604  and a second surface  606  in the recess  604  for the processing electronics  240 , the electrical components, and the electrically conductive pins  238 . 
     At  404 , various electronics are mounted to the photosensor substrate. For example, and as schematically shown in  FIG. 7 , an integrated chip  702  (including the processing electronics  240  and/or other components) is mounted to the region  502 , electrical components  704  (e.g., passive components) are mounted to the electrically conductive pads  504 , and the electrically conductive pins  238  connected to a lead frame  708  are mounted to the electrically conductive pads  506 . 
     At  406 , a scintillator is affixed to the photosensor substrate with the installed electronics, forming a scintillator-photosensor assembly. For example,  FIG. 8  schematically shows the photosensor substrate  236  with the scintillator array  310  affixed thereto via an optical adhesive, forming a scintillator-photosensor assembly  804 . Note that there are cavities  806  between the electrically conductive pins  238 . 
     At  408 , electrical pins mounted in act  404  above are secured in the scintillator—photosensor substrate assembly. For example,  FIG. 9  schematically shows the scintillator—photosensor assembly  804  with adhesive  902  in cavities  806  between the electrically conductive pins  238 . Note that the lead frame  708  has been removed from the scintillator—photosensor assembly  804 . 
     At  410 , the photosensor substrate is thinned to a thickness of fifty (50) microns or less. For example,  FIG. 10  schematically shows the scintillator—photosensor assembly  804  with a thinned photosensor substrate  236  having a thickness of fifty (50) microns or less. In one instance, the photosensor substrate  236  can be thinned via grinding. Other thinner techniques are also contemplated herein. 
     At  412 , a detector tile is created from a plurality of the scintillator—photosensor assemblies  804 . For example,  FIGS. 11 and 12  respectively show bottom and top perspective views in which a plurality of the scintillator—photosensor assemblies  804  are physically and electrically connected to the tile substrate  242  via the pins  238  forming the tile  220 . Note the tile substrate  242  also includes electrically conductive pins  1102  for the physically and electrically connecting the tile  220  to the detector array  218 . 
     It is to be appreciated that the ordering of the above acts is not limiting. As such, other orderings are contemplated herein. In addition, one or more acts may be omitted and/or one or more additional acts may be included, and/or one or more acts may occur concurrently. 
       FIG. 13  illustrates an embodiment in which a support carrier  1302  is utilized to facilitate making the individual substrates  236 . In one instance, a sheet  1304  of material including a plurality of substrates  236  is processed and thinned, for example, to a thickness of less than one hundred microns. The sheet  1304  is then transferred to the support carrier  1302 . The processing electronics  240  are mounted to the plurality of substrates  236 . The individual substrates  236  are then cut from the sheet using a laser, mechanical saw, etc. and left on the carrier  1302 . A vacuum chuck feature of the carrier is activated after the individual substrates  236  are cut. The scintillator array  310  is then optically coupled to the bonded to the individual substrates  236  and cured. The resulting assemblies can then be further processed as described herein. 
     Variations are contemplated. 
     In another embodiment, the processing electronics  240  are located external to the photosensor substrate  236 . 
     In another embodiment, the module  222  includes a single scintillator row optically couple to a single photosensor row. 
     Additionally or alternatively, in yet another instance, each scintillator row and each photosensor row respectively includes a single scintillator element and a single photosensor element. 
     The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.