A detector assembly is presented. The detector assembly includes a first detector layer having a top side and a bottom side, where the first detector layer includes a plurality of first coupling gaps. Additionally, the detector assembly includes a first interconnect structure operationally coupled to the first detector layer and configured to facilitate transfer of a first set of image data from the first detector layer to backplane electronics. The detector assembly also includes a second detector layer having a top side and a bottom side and disposed adjacent the bottom side of the first detector layer, where the second detector layer includes a plurality of second coupling gaps configured to facilitate passage of the first interconnect structure from the first detector layer to the backplane electronics. Also, the detector assembly includes a second interconnect structure operationally coupled to the second detector layer and configured to facilitate transfer of a second set of image data from the second detector layer to the backplane electronics.

BACKGROUND

The invention relates generally to radiographic detectors for diagnostic imaging, and more particularly to large area detectors for high flux rate imaging, such as in computed tomography (CT) applications.

Radiographic imaging systems, such as X-ray and computed tomography (CT) have been employed for observing, in real time, interior aspects of an object. Typically, the imaging systems include an X-ray source that is configured to emit X-rays toward an object of interest, such as a patient or a piece of luggage. A detecting device, such as an array of radiation detectors, is positioned on the other side of the object and is configured to detect the X-rays transmitted through the object.

Conventional CT and other radiographic imaging systems utilize detectors that convert radiographic energy into current signals that are integrated over a time period, then measured and ultimately digitized. A drawback of such detectors however is their inability to count at the X-ray photon flux rates typically encountered with conventional CT systems. Additionally, conventional detectors also lack the ability to track the energy of incident x-rays. For example, photon counting direct conversion detectors are known to suffer from decreased detection quantum efficiency (DQE) at high count rates mainly due to detector pile-up. Further, very high X-ray photon flux rate has been known to cause pile-up and polarization that ultimately leads to detector saturation. In other words, these detectors typically saturate at relatively low X-ray flux level thresholds. Above these thresholds, the detector response is not predictable or has degraded dose utilization. That is, once a pixel is saturated (corresponding to a bright spot in the generated signal), additional radiation will not produce useful detail in the image.

Previously conceived solutions to enable photon counting at high X-ray flux rates include employing pixels having a relatively small size to achieve higher spatial resolution and reduce flux rate sensitivity. Unfortunately, this reduction in the pixel size results in increased cost.

Additionally, applications such as medical and industrial imaging, NDE, security, baggage scanning, astrophysics and medicine may entail the use of larger coverage detectors that encompass large areas. In the field of medical diagnostics, such as, but not limited to, computed tomography (CT), ultrasound and mammography, it may be desirable to employ larger detectors to facilitate acquisition of image data from a large portion of the anatomy in a single gantry rotation thereby enhancing image quality.

Previously conceived solutions to obtaining wider coverage involved increasing the number of rows of detector elements. Arrays of detectors have also been utilized to circumvent the problems associated with employing single large area detectors. The X-Y plane may be employed for assembling the detectors arrays to facilitate the construction of large area detectors arrays. However, such arrays can be very dense and necessitate a large quantity of control and amplifier electronics to drive the individual detectors of the array. Presently, the control and amplifier electronics employed to drive the individual detectors are also positioned in the X-Y plane resulting in a large footprint and potentially, gaps in the detector area due to the need to locate electronics in or adjacent to the detector. Furthermore, the density of input/output (I/O) required for coupling the individual detectors with the associated electronics may be very high. Also, the density of I/O may be too large for traditional interconnect strategies to handle. Presently, the interconnect lengths required to couple the detector elements to the electronic device are very long. It would be desirable to minimize interconnect lengths in order to circumvent problems associated with longer interconnect lengths, such as, effects of capacitance, and degraded signal quality.

There is therefore a need for a design of a detector that does not saturate at the X-ray photon flux rates typically found in conventional radiographic systems. In particular, there is a significant need for a design that advantageously enhances the flux rate in detectors that will allow photon counting with energy discrimination in medical and industrial applications that are heretofore unmanageable because either the flux rate or the dynamic range requirements are too high. Additionally, there is a particular need to assemble large area detector arrays in order to circumvent associated problems, such as, complexities and costs associated with manufacturing. Furthermore, it would be desirable to position the associated electronics in close proximity to the individual detector elements of the detector array in order to minimize system size, complexity, interconnect lengths and enhance the performance of the detector arrays.

BRIEF DESCRIPTION

Briefly, in accordance with aspects of the technique, a detector assembly is presented. The detector assembly includes a first detector layer having a top side and a bottom side, where the first detector layer includes a plurality of first coupling gaps. Additionally, the detector assembly includes a first interconnect structure operationally coupled to the first detector layer and configured to facilitate transfer of a first set of image data from the first detector layer to backplane electronics. The detector assembly also includes a second detector layer having a top side and a bottom side and disposed adjacent the bottom side of the first detector layer, where the second detector layer includes a plurality of second coupling gaps configured to facilitate passage of the first interconnect structure from the first detector layer to the backplane electronics. Also, the detector assembly includes a second interconnect structure operationally coupled to the second detector layer and configured to facilitate transfer of a second set of image data from the second detector layer to the backplane electronics.

In accordance with further aspects of the technique, a detector assembly is presented. The detector assembly includes a first detector module, where the first detector module includes a first detector layer having a top side and a bottom side, where the first detector layer includes a plurality of first coupling gaps, a first interconnect structure operationally coupled to the first detector layer and configured to facilitate transfer of a first set of image data from the first detector layer to backplane electronics, and a first set of electronics disposed adjacent the first interconnect structure, where the first set of electronics is in operative association with the first interconnect structure and configured to process the first set of image data. In addition, the detector assembly includes at least a second detector module, where the second detector module includes a second detector layer having a top side and a bottom side, where the second detector layer includes a plurality of second coupling gaps configured to facilitate passage of the first interconnect structure from the first detector layer to the backplane electronics, a second interconnect structure operationally coupled to the second detector layer and configured to facilitate transfer of a second set of image data from the second detector layer to the backplane electronics, and a second set of electronics disposed adjacent the second interconnect structure, where the second set of electronics is in operative association with the second interconnect structure and configured to process the second set of image data.

In accordance with yet another aspect of the technique, a method of imaging is presented. The method includes obtaining a first set of image data from a first detector layer in a detector assembly having a first detector layer and a second detector layer, where the first detector layer includes a plurality of first coupling gaps. Further, the method includes obtaining a second set of image data from a second detector layer, where the second detector layer comprises a plurality of second coupling gaps configured to facilitate passage of a first interconnect structure from the first detector layer to backplane electronics. The method also includes interpolating the second set of image data.

In accordance with further aspects of the technique, an imaging system is presented. The imaging system includes a source of radiation configured to emit a stream of radiation toward a patient to be scanned and a computer configured to generate images with enhanced image quality and to provide tissue composition information. Further, the imaging system also includes a detector assembly configured to detect the stream of radiation and to generate one or more signals responsive to the stream of radiation, where the detector assembly includes a first detector layer having a top side and a bottom side where the first detector layer comprises a plurality of first coupling gaps, a first interconnect structure operationally coupled to the first detector layer and configured to facilitate transfer of a first set of data from the first detector layer to backplane electronics, a second detector layer having a top side and a bottom side and disposed adjacent the bottom side of the first detector layer, where the second detector layer comprises a plurality of second coupling gaps configured to facilitate passage of the first interconnect structure from the first detector layer to the backplane electronics, and a second interconnect structure operationally coupled to the second detector layer and configured to facilitate transfer of a second set of data from the second detector layer to the backplane electronics. Additionally, the imaging system includes a system controller configured to control the rotation of the source of radiation and the detector assembly and to control the acquisition of one or more sets of projection data from the detector assembly via a data acquisition system, and a computer system operationally coupled to the source of radiation and the detector assembly, where the computer system is configured to receive the one or more sets of projection data.

DETAILED DESCRIPTION

FIG. 1is a block diagram showing an imaging system10for acquiring and processing image data in accordance with the present technique. In the illustrated embodiment, the system10is a computed tomography (CT) system designed to acquire X-ray projection data, to reconstruct the projection data into an image, and to process the image data for display and analysis in accordance with the present technique. In the embodiment illustrated inFIG. 1, the imaging system10includes a source of X-ray radiation12. In one exemplary embodiment, the source of X-ray radiation12is an X-ray tube. The source of X-ray radiation12may include one or more thermionic or solid-state electron emitters directed at an anode to generate X-rays or, indeed, any other device capable of generating X-rays having a spectrum and energy useful for imaging a desired object. Examples of suitable electron emitters include tungsten filament, tungsten plate, field emitter, thermal field emitter, dispenser cathode, thermionic cathode, photo-emitter, and ferroelectric cathode.

The source of radiation12may be positioned near a collimator14, which may be configured to shape a stream of radiation16that is emitted by the source of radiation12. The stream of radiation16passes into the imaging volume containing the subject to be imaged, such as a human patient18. The stream of radiation16may be generally fan-shaped or cone-shaped, depending on the configuration of the detector array, discussed below, as well as the desired method of data acquisition. A portion20of radiation passes through or around the subject and impacts a detector array, represented generally at reference numeral22. Detector elements of the array produce electrical signals that represent the intensity of the incident X-ray beam. These signals are acquired and processed to reconstruct an image of the features within the subject.

The radiation source12is controlled by a system controller24, which furnishes both power, and control signals for CT examination sequences. Moreover, the detector22is coupled to the system controller24, which commands acquisition of the signals generated in the detector22. The system controller24may also execute various signal processing and filtration functions, such as for initial adjustment of dynamic ranges, interleaving of digital image data, and so forth. In general, system controller24commands operation of the imaging system to execute examination protocols and to process acquired data. In the present context, system controller24also includes signal processing circuitry, typically based upon a general purpose or application-specific digital computer, associated memory circuitry for storing programs and routines executed by the computer, as well as configuration parameters and image data, interface circuits, and so forth.

In the embodiment illustrated inFIG. 1, the system controller24is coupled via a motor controller32to a rotational subsystem26and a linear positioning subsystem28. In one embodiment, the rotational subsystem26enables the X-ray source12, the collimator14and the detector22to be rotated one or multiple turns around the patient18. In other embodiments, the rotational subsystem26may rotate only one of the source12or the detector22while the system controller24may differentially activate various stationary electron emitters to generate X-ray radiation if the detector22is rotated and/or detector elements arranged in a ring about the imaging volume if the source12is rotated. In yet another embodiment both the source12and the detector22may remain stationary. In embodiments in which the source12and/or detector22are rotated, the rotational subsystem26may include a gantry. Thus, the system controller24It may be utilized to operate the gantry. The linear positioning subsystem28enables the patient18, or more specifically a patient table, to be displaced linearly. Thus, the patient table may be linearly moved within the gantry to generate images of particular areas of the patient18.

Additionally, as will be appreciated by those skilled in the art, the source of radiation12may be controlled by an X-ray controller30disposed within the system controller24. Particularly, the X-ray controller30is configured to provide power and timing signals to the X-ray source12.

Further, the system controller24is also illustrated comprising a data acquisition system34. In this exemplary embodiment, the detector22is coupled to the system controller24, and more particularly to the data acquisition system34. The data acquisition system34receives data collected by readout electronics of the detector22. The data acquisition system34typically receives sampled analog signals from the detector22and converts the data to digital signals for subsequent processing by a computer36.

The computer36typically is coupled to or incorporates the system controller24. The data collected by the data acquisition system34may be transmitted to the computer36for subsequent processing and reconstruction, or stored directly to memory38. The computer36may comprise or communicate with a memory38that can store data processed by the computer36or data to be processed by the computer36. It should be understood that any type of memory configured to store a large amount of data might be utilized by such an exemplary system10. Moreover, the memory38may be located at the acquisition system or may include remote components, such as network accessible memory media, for storing data, processing parameters, and/or routines for implementing the techniques described below.

The computer36may also be adapted to control features such as scanning operations and data acquisition that may be enabled by the system controller24. Furthermore, the computer36may be configured to receive commands and scanning parameters from an operator via an operator workstation40, which is typically equipped with a keyboard and other input devices (not shown). An operator may thereby control the system10via the input devices. Thus, the operator may observe the reconstructed image and other data relevant to the system from computer36, initiate imaging, and so forth.

A display42coupled to the operator workstation40may be utilized to observe the reconstructed images. Additionally, the scanned image may also be printed by a printer44, which may be coupled to the operator workstation40. The display42and printer44may also be connected to the computer36, either directly or via the operator workstation40. The operator workstation40may also be coupled to a picture archiving and communications system (PACS)46. It should be noted that PACS46might be coupled to a remote system48, such as radiology department information system (RIS), hospital information system (HIS) or to an internal or external network, so that others at different locations may gain access to the image data.

It should be further noted that the computer36and operator workstation40may be coupled to other output devices, which may include standard or special purpose computers and associated processing circuitry. One or more operator workstations40may be further linked in the system for outputting system parameters, requesting examinations, viewing images, and so forth. In general, displays, printers, workstations, and similar devices supplied within the system may be local to the data acquisition components, or may be remote from these components, such as elsewhere within an institution or hospital, or in an entirely different location, linked to the image acquisition system via one or more configurable networks, such as the Internet, a virtual private network or the like.

As noted above, an exemplary imaging system utilized in a present embodiment may be a CT scanning system50, as depicted in greater detail inFIG. 2. The CT scanning system50may be a multi-slice CT (MSCT) system that offers a wide axial coverage, high rotational speed of the gantry, and high spatial resolution. Alternately, the CT scanning system50may be a volumetric CT (VCT) system utilizing a cone-beam geometry and an area detector to allow the imaging of a volume, such as an entire internal organ of a subject, at high or low gantry rotational speeds. The CT scanning system50is illustrated with a gantry52that has an aperture54through which a patient18may be moved. A patient table56may be positioned in the aperture54of the gantry52to facilitate movement of the patient18, typically via linear displacement of the table56by the linear positioning subsystem28(seeFIG. 1). The gantry52is illustrated with the source of radiation12, such as an X-ray tube that emits X-ray radiation from a focal point. For cardiac imaging, the stream of radiation is directed towards a cross section of the patient18including the heart.

In typical operation, the X-ray source12projects an X-ray beam64from the focal point and toward detector array22. The collimator14(seeFIG. 1), such as lead or tungsten shutters, typically defines the size and shape of the X-ray beam that emerges from the X-ray source12. The detector22is generally formed by a plurality of detector elements, which detect the X-rays that pass through and around a subject of interest, such as the heart or chest. Each detector element produces an electrical signal that represents the intensity of the X-ray beam at the position of the element during the time the beam strikes the detector. The gantry52is rotated around the subject of interest in a direction58so that a plurality of radiographic views may be collected by the computer36(seeFIG. 1). Furthermore, in accordance with exemplary aspects of the present technique, the detector array22may include a plurality of detector modules60. The detector22may be assembled by tiling a plurality of detector modules60with gaps62between the detector modules62to allow for some manufacturing tolerance on the widths of the detector modules60.

Thus, as the X-ray source12and the detector22rotate, the detector22collects data related to attenuated X-ray beams66. Data collected from the detector22then undergoes pre-processing and calibration to condition the data to represent the line integrals of the attenuation coefficients of the scanned objects. The processed data, commonly called projections, may then be filtered and backprojected to generate an image of the scanned area. An image may be reconstructed, in certain modes, using projection data for less or more than 360 degrees of rotation of the gantry52.

Turning now toFIG. 3, a cross-sectional side view70of an exemplary detector assembly for use in the system depicted inFIG. 1is illustrated. In a presently contemplated configuration, the detector assembly70is shown as including a first detector layer72having a top side and a bottom side. The first detector layer72may be arranged such that the top side of the first detector layer72is arranged to receive radiation before the bottom side of the first detector layer72. It may also be noted that the first detector layer72may include a scintillator or direct conversion sensor material, in certain embodiments. More particularly, the scintillator may include a wide variety of scintillators, such as, but not limited to, gadolinium oxysulfide (GOS) or cesium iodide (CsI) or yttrium oxide (Y2O3). Further, the direct conversion material may include semiconductors such as, but not limited to, silicon, gallium arsenide, mercury iodide (Hg2I), cadmium telluride (CdTe) or cadmium zinc telluride (CZT).

Moreover, the first detector layer72may be configured to operate in a photon counting mode with energy binning. In addition, the first detector layer72may be configured to operate in an integration mode. Alternatively, the first detector layer76may be configured to switch between the photon counting mode and the integration mode.

Also, in one embodiment, the thickness of the first detector layer72may be selected to have a relationship to the amount of desired flux to be transmitted through the first detector layer72to a second detector layer. Accordingly, the thickness of the first detector layer72may be in a range from about 0.1 to 1 mm. For example, for low atomic number sensor materials like silicon, the attenuation may be low and the thickness of the first detector layer72may accordingly be in a range from about 0.1 mm to about 10 mm. In a similar fashion, for high atomic number sensor materials like GOS, CsI, Hg2I, Y2O3, the thickness of the first detector layer72may be in a range from about 0.1 mm to about 2 mm. These thin first detector layers may be formed by a deposition process, screen printing or by bonding a monolithic sensor material.

In accordance with aspects of the present technique, the first detector layer72may also include a plurality of first coupling gaps74. As previously noted with reference toFIG. 2, the detector22(seeFIG. 2) may include gaps62(seeFIG. 2) between the plurality of detector modules60(seeFIG. 2), where the gaps62are configured to allow for some manufacturing tolerance on the widths of the detector modules60. Accordingly, in a presently contemplated configuration, these first coupling gaps74may be configured to accommodate the manufacturing tolerance of the width of the detector module. The presence of these first coupling gaps74advantageously facilitates relatively easy assembly of the detector modules into the detector. More particularly, during assembly, the detector modules may be easily placed into the detector without physical interference at the boundaries of the detector modules. Furthermore, these first coupling gaps74may be configured to facilitate coupling between the top side and the bottom side of the first detector layer72. For example, the first coupling gaps74may be configured to aid in routing of electronics configured to electrically couple the top side and the bottom side of the first detector layer72. Furthermore, the plurality of first coupling gaps74may have a width in a range from about 5 microns to about 50 microns, in certain embodiments.

Additionally, in accordance with further aspects of the present technique, the detector assembly70may include a second detector layer76having a corresponding top side and a bottom side. In one embodiment, the second detector layer76may be disposed adjacent to the bottom side of the first detector layer72. Further, the second detector layer76may be arranged such that the top side of the second detector layer76is arranged to receive radiation before the bottom side of the second detector layer76. Also, the second detector layer76may include either scintillators or direct conversion sensor materials as previously described with reference to the first detector layer72. Additionally, the second detector layer76may be configured to operate in a photon counting mode or an integration mode, as noted with reference to the first detector layer72.

As will be appreciated, a portion of the incident flux may be transmitted through the first detector layer72to the second detector layer76. The second detector layer76may therefore be configured to have a thickness sufficient to prevent the flux incident on the second detector layer76from being transmitted through the thickness of the second detector layer76. Accordingly, the second detector layer76may have a thickness in a range from about 3 mm to about 5 mm. It may be noted that a plurality of pixels in the second detector layer76may be disposed at an offset with respect to a plurality of pixels in the first detector layer72. This offset arrangement of pixels in each of the first detector layer72and the second detector layer76advantageously results in higher resolution. More particularly, in regards to spatial resolution, sampling of the incident radiation may be optimal when the pixels of the first detector layer72are superimposed with respect to that of the second detector layer76by an offset of ½ of the pixel pitch dimension. In certain embodiments, the plurality of pixels in the second detector layer76may be disposed at an offset of about one half of the pixel pitch with respect to a plurality of pixels in the first detector layer72. The layout of the pixel array in the second detector layer76may be a uniform array with pixel position gaps corresponding to the physical gaps between detector modules and the uniform array is disposed with an offset of ½ of the pixel spacing.

Moreover, in accordance with further aspects of the present technique, the second detector layer76may include a plurality of second coupling gaps78. These second coupling gaps78may be configured to facilitate coupling the first detector layer72to associated electronics, such as read out electronics, for example. In one embodiment, the second coupling gaps78may be configured to aid in routing of electronics configured to electrically couple the first detector layer72to associated electronics. It may be noted that the plurality of second coupling gaps78may be configured to have a width that is substantially larger than the width of the plurality of first coupling gaps74as the plurality of second coupling gaps78may be configured to facilitate passage of the interconnect structures from the first detector layer72, while the plurality of first coupling gaps74may be configured to accommodate mechanical tolerance during manufacture and assembly. In a presently contemplated configuration, the plurality of second coupling gaps78may have a width in a range from about 20 microns to about 300 microns. In contrast, the plurality of first coupling gaps74may have a width in a range from about 5 microns to about 50 microns, as previously noted.

In the presently contemplated configuration illustrated inFIG. 3, the detector assembly70may also include one or more first interconnect structures80. Each of the one or more first interconnect structures80may be configured to facilitate transfer of a first set of image data acquired via the first detector layer72to backplane electronics92, for instance. In one embodiment, the first interconnect structures80may include a flexible interconnect structure, where the flexible interconnect structure includes one or more copper traces disposed on a polyimide film. One end of the first interconnect structures80may be operationally coupled to the first detector layer72. More particularly, one end of the first interconnect structure80may be configured to be in operative association with the bottom side of the first detector layer72. The other end of the first interconnect structures80may be coupled to a first set of electronics82, where the first set of electronics82may include readout electronics.

Moreover, as noted hereinabove, the detector assembly70may also include a plurality of first set of electronics82corresponding to the plurality of first interconnect structures80. In one embodiment, each of the plurality of first set of electronics82may be disposed adjacent to a respective first interconnect structure80. Additionally, each of the plurality of first set of electronics82may be operatively coupled to the respective first interconnect structure80and configured to process the first set of image data. For example, the first set of electronics82may include Application Specific Integrated Circuits (ASICs), Floating Point Gate Arrays (FPGAs), Digital Signal Processing (DSP) chips, passive signal conditioning circuits, or power regulation circuits. As will be appreciated, the first set of image data may include analog signals acquired via the first detector layer72. The ASICs82may be configured to convert the analog signals of the first set of image data to corresponding digital signals. These digitals signals representative of the first set of image data may then be communicated to a host computer via the backplane electronics92, for instance.

Further, in certain embodiments, the digital readout data may be connected to the backplane electronics92via connectors84. Accordingly, the connectors84may be configured to operatively couple the first interconnect structures80to the backplane electronics92. In one embodiment, the connectors84may include make-break connectors, for example.

With continuing reference toFIG. 3, the detector assembly70may also include one or more second interconnect structures86. As previously noted with reference to the first interconnect structures80, each of the one or more second interconnect structures86may be configured to facilitate transfer of a second set of image data acquired via the second detector layer76to the backplane electronics92, for instance. In certain embodiments, the second interconnect structures86may include flexible interconnect structures, where the flexible interconnect structures include one or more copper traces disposed on a polyimide film. One end of the second interconnect structures86may be operationally coupled to the second detector layer76. Furthermore, as described with reference to the first interconnect structure80, one end of the second interconnect structures86may be configured to be in operative association with the bottom side of the second detector layer76. Additionally, the other end of the second interconnect structures86may be coupled to a second set of electronics88, where the second set of electronics88may include readout electronics.

Also, the detector assembly70may include a plurality of second set of electronics88, as noted hereinabove. The second set of electronics88may be disposed adjacent to the second interconnect structures86. As illustrated in the embodiment ofFIG. 3, each of the plurality of second set of electronics88may be disposed adjacent to a respective second interconnect structure86. Furthermore, each of the plurality of second set of electronics88may be operatively coupled to the respective second interconnect structure86and configured to process the second set of image data. The second set of electronics88may include ASICs, where the ASICs may be configured to convert the analog signals in the second set of image data acquired via the second detector layer76to corresponding digital signals. Additionally, the second set of electronics may also include FPGAs, DSPs, signal conditioning passive components, or power regulation circuits. The digital signals may subsequently be communicated to a host computer via the backplane electronics92, for instance. Reference numeral90is representative of a mating connector plug for the connector84.

In accordance with aspects of the present technique, the detector assembly70may also include an exemplary support structure94configured to provide support to the first detector layer72and the second detector layer76. The support structure94will be described in greater detail with reference toFIG. 5.

The detector assembly70may also include an anti-scatter collimator96. In certain embodiments, the anti-scatter collimator96may be disposed adjacent to the top side of the first detector layer72. As will be appreciated, the anti-scatter collimator96may be configured to selectively attenuate incident radiation that is at an angle with respect to surface-normal direction. In certain embodiments, the anti-scatter collimator96may include an arrangement of one or more thin attenuating lamina plates or cells located at pixel boundaries. This arrangement of lamina plates may be configured to selectively pass X-rays that travel at normal incidence to the detector plane, while selectively attenuating the X-rays that travel at a non-normal incidence to the detector plane.

It may be noted that the first set of electronics82and the second set of electronics88may be susceptible to damage when exposed to X-ray radiation. In order to prevent any damage to the first set of electronics82and the second set of electronics88, the detector assembly70may include an X-ray shield98. In a presently contemplated configuration, the X-ray shield98may be disposed adjacent to the support structure94such that the X-ray shield98is positioned between the support structure94and the first set of electronics82and the second set of electronics88.

By implementing the detector assembly70as described hereinabove, a detector assembly70with multiple layers may be constructed, where the detector assembly70is configured to have a plurality of coupling gaps to allow for passage of electronic packaging materials. Additionally, loss of information due to missing pixels in the plurality of second coupling gaps78may be compensated for by interpolation within the second set of image data or by combining image data from the multiple layers, as will be described in greater detail with reference toFIGS. 6-9. For example, if the first detector layer72is saturated due to sensitivity to high flux rate, then the second set of image data may be used to substitute for the first set of image data. Additionally, if the first detector layer72includes an energy sensitive detector, such as a photon counting detector with energy binning, then the first set of image data may advantageously be overlaid or otherwise combined with the second set of image data to generate an image with combined material and density information. Furthermore, data from the first detector layer72and the second detector layer76may be combined to generate material discrimination information by utilizing the different energy selectivity of the first and second detector layers72,76. Such energy selectivity may be caused due to the beam hardening of the spectrum in the second detector layer76due to the attenuation of the first detector layer72. Additionally, the method may include applying a material discrimination algorithm to the combined image data by utilizing the different spectral sensitivity and/or photon counting capabilities of the first and second detector layers72,76.

Referring now toFIG. 4, a cross-sectional side view110of another exemplary tileable layered detector assembly for use in the system10(seeFIG. 1) is illustrated. In one embodiment, the detector assembly110may include at least one first detector module. According to aspects of the present technique, the first detector module may include a first detector layer112having a top side and a bottom side. Additionally, the first detector layer112may also include a plurality of first coupling gaps114. As previously noted with reference toFIG. 3, the plurality of first coupling gaps114may be configured to accommodate mechanical tolerance during manufacture and assembly. Additionally, the plurality of first coupling gaps114may be configured to facilitate coupling the top side and the bottom side of the first detector layer112.

The first detector module112may also include a first interconnect structure116configured to facilitate transfer of a first set of image data acquired via the first detector layer112to backplane electronics130. As previously described with reference toFIG. 3, the first interconnect structure116may include a flexible interconnect layer having a plurality of copper traces disposed on a polyimide film. In addition, the first detector module may include a first set of electronics118that may be configured to process the first set of image data acquired via the first detector layer112. In certain embodiments, the first set of electronics118may include ASIC, FPGAs, DSPs, signal conditioning passive components, or power regulation circuits configured to convert analog image data into corresponding digital image data, which may then be transferred to the backplane electronics130. Connectors120that may be coupled to the first interconnect structures116may be employed to facilitate operatively coupling the first interconnect structures116to the backplane electronics130.

In accordance with further aspects of the present technique, the detector assembly110may also include a second detector module. This second detector module may include a second detector layer122, a second interconnect structure126and a second set of electronics128. The second detector layer122may have a corresponding top side and a bottom side and may be configured to acquire a second set of image data. In addition, the second detector layer122may also include a plurality of second coupling gaps124that may be configured to facilitate passage of the first interconnect structure116from the first detector layer112to the backplane electronics130. As previously noted, the plurality of second coupling gaps124may be configured to be substantially larger than the plurality of first coupling gaps114.

Moreover, the second interconnect structure126may be configured to facilitate transfer of the second set of image data acquired via the second detector layer122to backplane electronics130. Further, the second set of electronics128may be configured to process the second set of image data acquired via the second detector layer122. In certain embodiments, the second set of electronics128may include ASICs, FPGAs, DSPs, signal conditioning passive components, or power regulation circuits configured to convert analog image data into corresponding digital image data, which may then be transferred to the backplane electronics130. Connectors120that are coupled to the second interconnect structures126may be employed to facilitate operatively coupling the second interconnect structures126to the backplane electronics130. Reference numeral132is representative of a mating connector plug for the connector120.

In accordance with aspects of the present technique, a plurality of first detector modules and a plurality of second detector modules may be disposed on a support structure134. As previously noted, the support structure134may include a plurality of slots that may be configured to facilitate passage of the plurality of first detector modules and the plurality of second detector modules. Accordingly, the plurality of first detector modules and the second detector modules may be aligned and mechanically secured to the support structure134following an alignment process. In one embodiment, such alignment may be performed with optical pick-and-place equipment, for example, that will register the pixel positions of different pixels into a uniform array and the array to a fiducial marking on the support structure134. It may be noted that other equipment known in the art, such as, but not limited to, fixtures that reference to the sidewall of the module, may also be employed to perform the alignment step. Also, in a presently contemplated configuration, the detector assembly110may include an anti-scatter collimator136disposed adjacent to the first detector layer112, where the anti-scatter collimator136may be configured to include attenuating lamina, as previously described. Furthermore, the anti-scatter collimator136may also be aligned and fixed to the support structure134.

As previously noted with reference toFIG. 3, an X-ray shield, such as the X-ray shield98(seeFIG. 3), may be disposed such that the plurality of ASICs are protected from potentially damaging X-ray radiation. In the embodiment of the tileable layered detector assembly110illustrated inFIG. 4, an X-ray shield (not shown) may be disposed adjacent to each of the ASICs. In other words, in certain embodiments, an X-ray shield may be disposed on top of the first set of electronics118. Additionally, an X-ray shield may also be disposed on top of the second set of electronics128.

As will be appreciated, various applications such as medical and industrial imaging, biomedical non-invasive diagnostics, non-destructive testing (NDT) and non-destructive evaluation (NDE) of materials, security and baggage scanning, may entail the use of detector assemblies that encompass large areas. For example, in the field of medical diagnostics, such as, but not limited to ultrasound and mammography, it may be desirable to employ detector assemblies that encompass large areas. For instance, in order to obtain enhanced image quality it may be desirable to employ large area detectors that are capable of covering a relatively large portion of the anatomy in a single gantry rotation. In particular, cardiac images with enhanced image quality may be obtained via the use of such large area detectors as the entire image data set may be acquired in a relatively short period of time especially when the heart is in a slow moving phase. In a similar fashion, security applications such as baggage scanning may entail use of detector assemblies that encompass large areas. In accordance with exemplary aspects of the present technique, a detector assembly that encompasses a large area is presented. It may be noted that the term “large area” detector assembly is used to represent a detector assembly that has a square area in a range from about 10 cm2to about 50 cm2.

Although the embodiments of the tileable layered detectors depicted inFIGS. 3-4are illustrated as having a planar configuration, it may be appreciated that the tileable layered detectors may also be configured to exhibit an arc shape or a partial arc shape. In certain embodiments, the arc-shaped detector may be configured to have a width of about 75 cm to about 1.5 meters.

The large area detector assembly may be formed by tiling a plurality of first detector modules and a plurality of second detector modules. As used herein, the terms “tiling” and “tileable” refer to placing detector modules adjacent to one another or otherwise arranged in a pattern to form an array in a manner analogous to floor tiles. In one embodiment, a second detector module may be disposed adjacent to a first detector module to form a detector sub-group. Subsequently, a plurality of such detector sub-groups may be tiled to form a large area detector assembly. Alternatively, a plurality of first detector modules may be arranged to form a first detector sub-group. Similarly, a second detector sub-group may be formed by arranging a plurality of second detector modules. A large area detector assembly may then be formed by tiling a plurality of first detector sub-groups and a plurality of second detector sub-groups. As described hereinabove, the plurality of first detector modules and the plurality of second detector modules may be aligned and mechanically fixed on the support structure134, while the plurality of slots on the support structure134may be utilized to facilitate the passage of these detector modules.

In the embodiment illustrated inFIG. 4, the detector assembly110is shown as including one backplane130. In other words, a plurality of first detector modules and a plurality of second detector modules may be coupled to a single larger backplane, such as the backplane130, for example, as depicted in the embodiment ofFIG. 4. However, in certain other embodiments, the detector assembly110may include more than one backplane. More particularly, the detector assembly110may include a first backplane (not shown) that is operatively coupled to the plurality of first detector modules. Similarly, a second backplane (not shown) may be operatively coupled to the plurality of second detector modules in the detector assembly110.

By implementing the detector assembly110as described hereinabove, a large area detector assembly may be constructed. Additionally, in the detector assembly110respective sets of electronics may be integrated into the corresponding detector modules. More particularly, the first set of electronics118may be integrated with the corresponding first detector layer112, while the second set of electronics128may be integrated with the corresponding second detector layer122. Consequently, the respective interconnect structures, such as the first interconnect structures116and the second interconnect structures126may be configured to facilitate only digital communication and power functionality. The interconnect structures116,126may thereby be configured to have a relatively small size, consequently allowing relatively smaller slots in the support structure134.

Turning now toFIG. 5, an exploded view144of an exemplary support assembly for use in the detector assemblies ofFIGS. 3-4is illustrated. In the illustrated embodiment, the support assembly144is shown as including a support structure146. In accordance with aspects of the present technique, the support structure146may be configured to keeping a plurality of first detector modules and a plurality of second detector modules in place by restraining one or more degrees of freedom. In one embodiment, the support structure146may include stainless steel, low-expansion iron/nickel alloys such as FeNi36or FeNi42, aluminum, engineering plastics, such as ULTEM® polyetherimide, LEXAN® polycarbonate, aluminum silicon carbide (AlSiC), or a laminate or metal matrix composite (MMC) material.

In a presently contemplated configuration, the support structure146may include a plurality of slots. For example, the support structure146may include a plurality of first slots148configured to facilitate passage of the first interconnect structures, such as the first interconnect structures80(seeFIG. 3), for example. It may be noted that the plurality of first slots148may have a width that is configured to accommodate the thickness of the first interconnect structures80. Accordingly, the plurality of first slots148may have a width in a range from about 0.5 mm to about 5 mm.

Moreover, the support structure146may also include a plurality of second slots150configured to allow the second interconnect structures, such as the second interconnect structures86(seeFIG. 3), to pass through. As noted hereinabove, the plurality of second slots150may have a width that is dependent upon the thickness of the plurality of second interconnect structures86. Thus, the plurality of second slots150may have a width in a range from about 0.5 mm to about 5 mm. It may be noted that in certain embodiments, the width of the plurality of second slots150may be the same as the width of the plurality of first slots148. Alternatively, in certain other embodiments, the width of the plurality of second slots150may be different from the width of the plurality of first slots148.

In accordance with further aspects of the present technique, each of the plurality of first slots148and second slots150on the support structure146may also be configured to accommodate passage of both the first interconnect structures and the second interconnect structures. Consequently, the plurality of slots may have a width in a range from about 0.5 mm to about 5 mm, in certain embodiments.

As described hereinabove, the plurality of first detector modules and the plurality of second detector modules may be aligned and mechanically secured to the support structure146. It may also be noted that the plurality of first detector modules and the plurality of second detector modules may be thermally controlled by the support structure146. Thermal control may be accomplished by securing heating elements and temperature sensing elements to the support structure146. As will be appreciated, power to the heating elements may be controlled by comparing the temperature read by the temperature sensing elements to a preset reference point. In certain embodiments, a commercially available proportional-integral-derivative (PID) controller may be employed to facilitate thermally controlling the support structure146.

As illustrated inFIG. 5, the support assembly144may also include one or more detector rails. As will be appreciated, the one or more detector rails may include a steel structure with precise alignment features configured to align the detector modules or sub-units within the intended geometry of the imaging system. In the embodiment illustrated inFIG. 5, the support assembly144is shown as including a first detector rail152and a second detector rail154. The support structure146may be secured to the first detector rail152and the second detector rail154with the aid of one or more bolts156that may be configured to fit through a plurality of threaded holes158that may be disposed on the support structure146. However, other forms of securing the support structure146to the one or more detector rails152,154may also be employed. Additionally, an anti-scatter collimator (not shown), such as the anti-scatter collimator96(seeFIG. 3), may be aligned and secured to the one or more detector rails152,154.

As described hereinabove, a layered, tileable detector assembly includes at least a first detector layer and a second detector layer. Accordingly, a first set of image data may be acquired via the first detector layer, while the second detector layer may be used to acquire a second set of image data. These sets of image data may then be employed to facilitate material decomposition and reconstruction of the acquired image data. In other words, the two sets of image data may be accordingly processed to generate a reconstructed image and material specific images.

FIG. 6is a flow chart170depicting an exemplary method for imaging employing the tileable layered detector illustrated inFIGS. 3-4. In accordance with aspects of the present technique, a method for imaging using the exemplary tileable layered detector is presented. The method starts at step172where a first layer sinogram may be generated using a first set of image data acquired via a first detector layer in the detector assembly, such as the detector assemblies70(seeFIG. 3),110(seeFIG. 4). Similarly, step174may entail generation of a second layer sinogram using a second set of image data acquired via a second detector layer in the detector assembly.

As previously noted, the second detector layer is described as having a plurality of second coupling gaps configured to facilitate passage of a plurality of first interconnect structures. The presence of the plurality of second coupling gaps in the second detector layers may result in “missing” data in the second set of image data. More particularly, missing pixels in the plurality of second coupling gaps may result in loss of information in the second set of image data. Additionally, as previously described with reference toFIG. 4, an X-ray shield may be disposed on top of each of the first set of electronics118(seeFIG. 4) and the second set of electronics128(seeFIG. 4). The presence of the X-ray shield thereby results in degrading and/or blocking out of image data in the second layer sinogram. In one embodiment, loss of information may be circumvented by employing a relatively “thin” interconnect layer for the first interconnect structures that pass through the plurality of second coupling gaps. For example, the first interconnect structures may include thin, flexible, laminate electronics that have a thickness less than about 0.1 mm.

However, certain conditions may disallow use of such thin interconnect layers. In such situations, this loss of information in the second set of image data may be compensated by interpolating within the second set of image data across the plurality of second coupling gaps, in accordance with exemplary aspects of the present technique. Furthermore, the second detector layer being disposed further from the source of radiation than the first detector layer may have a different magnification within the imaging geometry. Accordingly, at step176, the second set of image data may be interpolated to compensate for the missing data and difference in magnification, thereby resulting in a “complete” second set of image data registered to the first set of data. As will be appreciated, interpolation methods, such as, but not limited to, linear interpolation methods, polynomial interpolation, or cubic splines may be used to facilitate interpolating the second set of image data over the plurality of second coupling gaps in the second detector layer. It may also be noted in the case where the pixels in the first detector layer and the second detector layer are positioned with an offset of ½ pixel spacing, the interpolation step may result in the generation of a data set with interlaced sampling.

As described hereinabove, the second set of image data may be interpolated within to compensate for the missing data and magnification mismatch to generate a complete second set of image data that is registered to the first set of image data. For example, regions of missing data in the second set of image data may be interpolated via the use of neighboring image data. Alternatively, in certain other embodiments, the first sinogram generated at step172may be used to facilitate interpolation of the second sinogram to compensate for the missing data.FIG. 7is a diagrammatic illustration of a sinogram190obtained via a second detector layer in the detectors illustrated inFIGS. 3-4. Reference numeral192is representative of a data channel number, while a view number is represented by reference numeral194. Additionally, reference numeral196is indicative of missing data in certain columns in the second layer sinogram190. The missing data in certain columns in the second layer sinogram190is due to the plurality of second coupling gaps in the second detector layer, as previously noted. Also, reference numeral198is representative of a portion of a column of missing data in the second layer sinogram190.

As previously described, the missing data196in the second layer sinogram190may be compensated by interpolating the data within the second layer sinogram190.FIG. 8is a schematic flow chart200illustrating an exemplary process of sinogram interpolation. More particularly, in accordance with aspects of the present technique, a method for interpolating the second layer sinogram190(seeFIG. 7) over a plurality of second coupling gaps in a second detector layer in a detector assembly, such as the detector assembly70(seeFIG. 3),110(seeFIG. 4), is presented. A portion of a first layer sinogram obtained via a first detector layer in the tileable layered detectors illustrated inFIGS. 3-4is represented by reference numeral202. Further, a data channel number is represented by reference numeral192, while reference numeral194is indicative of a view number, as previously described inFIG. 7. Additionally, image data in the first layer sinogram202may be generally represented by reference numeral208.

Referring further toFIG. 8, reference numeral212is indicative of a portion of a second layer sinogram, such as the second layer sinogram190(seeFIG. 7), obtained via a second detector layer in the tileable layered detector illustrated inFIGS. 3-4. Also, reference numeral214is representative of image data in the second layer sinogram212. As previously noted with reference toFIG. 7, reference numeral196is indicative of a column of missing data in the portion212of the second layer sinogram190. Further, as noted hereinabove, for certain data channel positions in the second layer sinogram212, there are no corresponding physical pixels due to the presence of the plurality of second coupling gaps in the second detector layer. Consequently, there is no one-to-one correspondence between the first layer sinogram202and the second layer sinogram212, particularly in region196. Reference numeral210is representative of image data in the first layer sinogram202that lies within the column196. In accordance with aspects of the present technique, image data210in the first layer sinogram202may be utilized to facilitate interpolation of the missing data in the second layer sinogram212. Consequent to the interpolation step176(seeFIG. 6), missing data216in the column196in the second layer sinogram212may be obtained. In one embodiment, a linear interpolation method may be employed in the interpolation step176, as previously noted.

Furthermore the mismatch in magnification may be such that the data points214in the second layer sinogram214do not correspond to the same projective rays of the data points208in the first layer sinogram202. Accordingly, the interpolation may be performed on all the second layer data to produce an interpolated array of points corresponding to the same projective rays and the data points208in the first layer sinogram202.

Alternatively, image data from other layers, such as the first detector layer, for example, may be combined with the second set of image data to recompense for the loss of information in the second set of image data. In other words, in one embodiment, image data acquired via the first detector layer (i.e., the first layer sinogram202) may be combined with the second layer sinogram212to make up for the loss of information in the second set of image data. It may be appreciated that if the first detector layer is saturated due to sensitivity to high X-ray flux, the second set of image data may then be used to stand in for the first set of image data, and thereby permit reconstruction of the image data. For example, if the first detector layer includes an energy sensitive detector, then the corresponding first set of image data may be overlaid or otherwise combined with the second set of image data to facilitate forming an image with combined material and density information.

It may be noted that in certain embodiments, step176may be an optional step. As described hereinabove, use of relatively thin first interconnect structures that pass through the plurality of second coupling gaps aids in circumventing loss of information, thereby mitigating the need for an interpolation step.

With returning reference toFIG. 6, at step178, the first layer sinogram generated at step172may be subject to a processing step to generate a processed first layer sinogram. In certain embodiments, the processing steps may include a filtering step, a scaling step, or both. It may be noted that other processing such as beam hardening correction or material decomposition may also be applied to the first layer sinogram. Subsequently, at step180a first set of image data may be reconstructed using the processed first layer sinogram obtained consequent to step178. In certain embodiments, reconstruction algorithms, such as, but not limited to, filtered backprojection or iterative reconstruction may be employed to facilitate the reconstruction of the first set of image data. It may be noted that for cases where the first detector layer produces multi-energy bin data, multiple material images may be generated consequent to the processing and reconstruction steps.

Similarly, at step182, the second layer sinogram generated at step174or step176may be processed to generate a processed second layer sinogram. The processed second layer sinogram may then be employed to reconstruct a second set of image data at step184. Here again, reconstruction algorithms, such as, but not limited to, filtered backprojection and iterative reconstruction may be used to reconstruct the second image data set. Consequent to steps180and184, a reconstructed first set of image data and a reconstructed second set of image data are generated. Following steps180and184, the reconstructed first set of image data and the reconstructed second set of image data may be combined to generate a single combined image data set at step186.

In the exemplary process170illustrated inFIG. 6, the first layer sinogram and the second layer sinogram are combined after reconstruction of a respective first set of image data and a second set of image data, which are then employed to generate a combined image data set, as described hereinabove. Alternatively, the first layer sinogram and the second layer sinogram may be combined prior to a reconstruction step as will be described with reference toFIG. 9.

By employing the method of imaging illustrated inFIG. 6, optimal combination of the first set of image data and the second set of image data may be achieved. For example, if the first detector layer includes an energy discrimination (ED) detector, while the second detector layer includes an energy integration (EI) detector, color overlay of material information on a density image may be accommodated.

Turning now toFIG. 9, a flow chart220depicting another exemplary method for imaging employing the tileable layered detectors illustrated inFIGS. 3-4is illustrated. The method starts at step222where a first layer sinogram may be generated employing a first set of image data acquired via a first detector layer in the tileable layered detector. Similarly, a second layer sinogram may be generated employing a second set of image data acquired via a second detector layer in the tileable layered detector, at step224. Subsequently, at step226, the second layer sinogram may be interpolated to generate an interpolated second layer sinogram. As previously noted with reference toFIG. 6, the second layer sinogram may be interpolated within the second set of image data or may be combined with image data from the first detector layer, for example.

The first layer sinogram generated at step222and the interpolated second layer sinogram generated at step226may then be combined at step228to generate a combined image data set. Furthermore, the combined image data set may be processed at step230to generate a processed combined image data set. As previously noted, the processing step230may include a filtering step, a scaling step, or both. This processed combined image data set may then be utilized to generate an image at step232. In one embodiment, the processing step230may include a material decomposition step that may be configured to generate data which may be reconstructed to indicate material basis or atomic number images in step232.

By employing the method of imaging illustrated inFIG. 9, optimal combination of the first set of image data and the second set of image data of image to circumvent saturation associated with photon counting detectors may be achieved. For example, if the first detector layer includes a photon counting detector that is susceptible to corruption by saturation at a high flux rate, the second set of image data may be substituted for the first set of image data.

The detector assemblies70(seeFIG. 3),110(seeFIG. 4) are described as having a first detector layer and at least a second detector layer. These tileable layered detector assemblies may be used in the detector array22(seeFIG. 1) included in an imaging system, such as the imaging system10(seeFIG. 1). Such an imaging system may have material decomposition capability by leveraging the energy selectivity of the two layer data. In accordance with aspects of the present technique, it may be noted that these tileable layered detector assemblies may encompass the whole detector array. Alternatively, these tileable layered detector assemblies may be used to cover only a predetermined portion of the detector array22. Accordingly, in certain embodiments, predetermined portions of the detector array22may include the exemplary tileable layered detector assembly70,110, while the other portions of the detector array22may include single layer detectors.