WO2024129635A1

WO2024129635A1 - Active surface sensor

Info

Publication number: WO2024129635A1
Application number: PCT/US2023/083480
Authority: WO
Inventors: Luca Bogoni; Xiaohui Wang
Original assignee: Carestream Health, Inc.
Priority date: 2022-12-14
Filing date: 2023-12-12
Publication date: 2024-06-20

Abstract

A DR detector, that includes plurality of imaging pixels forming an imaging surface for capturing a radiographic image, contains a plurality of sensors for recording local spatial positions of each of the sensors. A processor calculates a geometry and spatial position of the imaging surface relative to an x-ray source using the recorded local spatial positions of the plurality of sensors.

Description

ACTIVE SURFACE SENSOR

[0001] The subject matter disclosed herein relates to a digital radiographic imaging system and method using a conformable digital radiographic detector. In particular, the present disclosure relates to determining a relative spatial orientation of a conformable image receptor surface of the detector with respect to an x-ray source.

[0002] During radiographic image capture using an x-ray source, when a surface of a digital radiographic (DR) detector is used as a frame of reference (reference surface) it is necessary to determine its location and pose relative to the x- ray source. When the surface is visible, the pose and location can be computed using various sensors, such as stereopsis, laser-range, structured lighting, and/or accelerometers, to recover data defining a spatial position of the reference surface. On the other hand, when the reference surface is hidden, while it might be possible to compute it using depth sensors such as ultrasound, or x-ray imaging, in practice obstructions and noise may prevent accurate localization of the surface. Furthermore, if such surface is transparent to the sensor employed, localization may be impossible.

[0003] In the context of medical imaging applications, an example of such a hidden surface is represented by a surface of the DR detector. Specifically, when the DR detector is portable (out-of-bucky), and not used in a fixed structure with a known configuration (in-bucky), its location and pose relative to an x-ray source is not known. Computation of a DR detector’s pose and location are essential for positioning the source such that its emitted x-rays reach the plane of the DR detector orthogonally as much as possible. Knowing this spatial relation precisely allows capturing a projection of a patient's anatomy and thus acquiring clinically meaningful x-ray images. Solutions have been introduced to address the out-of-bucky localization of the DR detector, thus affording accurate computation of the reference surface even when it's hidden, such as when the DR detector is under a patient or under patient bedding.

[0004] If the DR detector, however, is not a rigid plane but conformable, its surface will deform to adjust to the patient body. In doing so, the planar constraint used for source alignment and image reconstruction are violated. In such a scenario, the recovered image acquisition will be distorted and, over time, not repeatable. Unpredictable distortions hinder clinical interpretation and lack of repeatability make longitudinal clinical comparison impossible. Recovery of the local deformations of non- visible deformable surfaces, such as in the case of a fully deformable DR detector, is ill-posed when using any of the traditional approaches which presently has no solution.

[0005] Hence, unless it is possible to address these limitations, comfortable DR detectors won’t be used clinically. The present invention, while extending to to an embodiment of a comfortable DR detector and a method of using such a detector, introduces solutions and processes aimed at addressing these limitations and recovering a depth map for hidden surfaces. The present invention proposes to measure deformation of a hidden surface by incorporating, within the surface, a mechanism for computing spatial information while also communicating the surface deformation(s). The ability to compute the deformation within the surface, avoiding the need of an external sensor, and also communicating the computation data makes the surface an active self-contained surface sensor.

[0006] Such an active surface sensor is based on an innovative approach that combines a network of novel tile-sensors and a practical approach to configure the sensors to accurately measure surface deformations. This innovation includes a set of primary aspects that define the sensor and its ability to measure deformations; secondary aspects pertaining to additional desirable properties of the active sensor’s surface such as the ability to deform only under a force acting on the surface, e.g., pressure/weight, and, upon removal of the force, return the surface to a non-deformed state; and tertiary aspects address calibration and validation of the active surface sensor to determine and guarantee the accuracy of the sensor.

[0007] The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE INVENTION

[0008] A DR detector includes a plurality of imaging pixels forming an imaging receptor surface for capturing a radiographic image. The DR detector contains a plurality of tile-sensors for recording local spatial positions of each of the sensors. A processor calculates a geometry and spatial position of the imaging surface relative to an x-ray source using the recorded local spatial positions of the plurality of tile-sensors.

[0009] In one embodiment, a digital radiographic imaging system includes a DR detector having an imaging surface comprising a plurality of imaging pixels for capturing a radiographic image. A plurality of tile-sensors each comprising a subset of the imaging pixels and each comprising a sensor for recording a local spatial position of the tile-sensor. A processor calculates a geometry and spatial position of the imaging surface using the recorded local spatial positions from the plurality of tile-sensors.

[0010] In one embodiment, a method includes capturing a radiographic image of a patient using a conformable DR detector wherein the conformable DR detector comprises an image receptor surface divided into a plurality of sections each disposed at a different angle with respect to each other. Spatial position data is received from the plurality of sensors in the DR detector and a spatial pose for each of the plurality of sections of the conformable DR detector is determined using the received plurality of spatial position data.

[0011] With respect to a deformable DR detector imaging surface, a depth map of a deformable surface may be computed from a mesh of neighboring tilesensors having associated spatial positions, dimensions, and curvatures. These tilesensors may be discrete physical components or contiguous neighboring locations on a deformable imaging receptor surface. A tile-sensor affords the ability to compute the pose of a tile, when discrete, or a surface curvature, when contiguous, relative to a reference surface, such as an image receptor surface of a DR detector. An aggregation process performed by a processor may combine the tile-sensors' data into a network of sensors defining the complete image receptor surface of the DR detector. The surface deformation of the network of sensors may be computed by using the aggregated tile-sensors’ pose and geometry data when discrete, or curvature and location data when contiguous.

[0012] A tile-sensor’s pose is predicated on each tile having one or more pose sensors, such as accelerometers, limited circuitry for processing, local storage, and means of communicating information including an ID, tile geometry, and pose. Collectively, these electronic components that define a tile-sensor may be referred to herein as integrated tile electronics components (ITEC).

[0013] Such an active surface sensor is the result of an efficient and cost effective aggregation of individual tile-sensors into a network of tile-sensors. Communicatively connecting all ITECs that are present on a surface, whether discrete or contiguous, enables the computation of a depth map for the surface relative to a preferred reference surface, such as an initial planar surface position. The proposed surface sensor yields surface information for a contiguous or discrete tile topology while preserving tile geometry, guaranteeing flexibility and durability.

[0014] This active surface sensor actively computes a deformation map by leveraging the collection of tile-sensors embedded at or near the surface itself, rather than having the surface being measured as a byproduct of using external measuring capabilities. While the embodiment for the active surface sensor presented in this document is presented using accelerometers, any such sensors meeting the ability to relate pose could be used, such as capacity elastomer sensors.

[0015] This description of the active surface sensor focuses on a primary goal of the functionality of capturing the deformation of the surface as it bends and folds upon a force being applied, such as the weight of a patient. The secondary aspects capture surface properties that pertain to the material composition of the surface, such as using flexible or rigid tile-sensors arranged adjacent to each other. These properties induce and control how the active surface sensor surface responds to forces whether globally or locally across the image receptor surface. [0016] The stiffness of a tile-sensor describes and introduces controls, whether active or passive, to manage an amount of data defining its deformation. An allowed amount of deformation may be altered as part of a configuration step or dynamically. Hence, deformation may be configured according to a stiffness matrix defining the stiffness relation between loci on the imaging receptor surface, with such matrix allowing local stiffness variability based on use and applicability. The elasticity of a tile-sensor describes properties of the surface material related to how it might stretch, bend and/or deform under given local forces. This not only allows for local compliance but also affords the ability to capture local deformations and better represent the topology of the underlying image receptor surface. Restoration of a tilesensor describes how the active surface sensor may be resilient to return to an original preferred default surface shape, e.g., planar, polyhedral, hemispherical, cylindrical, or sinusoidal, after the forces acting on the surface subside.

[0017] Calibration and validation aspects of the active surface sensor may be used to determine and/or guarantee the accuracy of each tile-sensor. A calibration process may be applicable for each individual tile-sensor, whether discrete or contiguous, and for the active surface sensor as a whole. Thus, the present invention addresses the need to determine the pose of the surface for a deformable DR detector so as to enable correct image reconstruction. After correctly determining relative spatial locations of the entire image receptor surface, an acquired radiographic image can be reconstructed while accounting for potential projective distortions.

Furthermore, proper reconstructions will guarantee that radiographic image acquisitions will be repeatable making longitudinal clinical comparison possible.

[0018] The summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. In fact, many of the elements described as related to a particular embodiment can be used together with, and possibly interchanged with, elements of other described embodiments. Many changes and modifications may be made within the scope of the present invention.

[0019] This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings below are intended to be drawn neither to any precise scale with respect to relative size, angular relationship, relative position, or timing relationship, nor to any combinational relationship with respect to interchangeability, substitution, or representation of a required implementation., emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which:

[0021] FIG. 1 is a schematic perspective view of an exemplary x-ray imaging system using a conformable DR detector having tile-sensors;

[0022] FIG. 2A is a schematic diagram of a tile-sensor with a two dimensional imaging pixel array;

[0023] FIG. 2B is a diagram of an electronic read out circuit; [0024] FIG. 3A is a perspective diagram of an exemplary conformable DR detector utilizing a plurality of tile-sensors;

[0025] FIG. 3B is a cross section diagram of the conformable DR detector of FIG. 3A;

[0026] FIG. 4A is a MATLAB illustration of an exemplary global surface paraboloid deformation showing dominant deformation along x, but none along y;

[0027] FIG. 4B is a MATLAB illustration of an exemplary global surface paraboloid deformation showing deformation along x and y axes; and

[0028] FIG. 5 is an example from a MATLAB peaks function illustrating an exemplary deformation of the active surface sensor.

DETAILED DESCRIPTION OF THE INVENTION

[0029] This application claims priority to U.S. Patent Application Serial No. 63/432,459, filed December 14, 2022, in the name of Bogoni et al., and entitled ACTIVE SURFACE SENSOR, which is hereby incorporated by reference herein in its entirety.

[0030] FIG. 1 is a perspective view of a digital radiographic (DR) imaging system 10 that may include a conformable DR detector 40 (shown undeformed and without a housing for clarity of description), an x-ray source 14 configured to generate radiographic energy (x-ray radiation), a processing system 34 for controlling operation of the DR imaging system 10, and a digital monitor, or electronic display, 26 configured to display one or more images 24 captured by the DR detector 40, according to one embodiment. The DR detector 40 may include a two dimensional array 12 of tile-sensors 22, each containing a plurality of imaging pixels or photosensors, arranged in an electronically addressable formation, such as rows and columns (FIG. 2 A). The DR detector 40 may be positioned to receive x-rays 16 emitted by the x-ray source 14 that pass through a patient 20 during a radiographic imaging procedure. As shown in FIG. 1, the radiographic imaging system 10 may use an x-ray source 14 that emits collimated x-rays 16, e.g. an x-ray beam, selectively aimed at and passing through a preselected area 18 of patient 20 such that the emitted x-rays 16 fall on an imaging receptor surface comprised of tile- sensors 22 of the DR detector 40. The x-ray beam 16 may be attenuated by varying degrees along its plurality of rays according to the structure, e.g., varying thickness, of the patient 20, which attenuated x-rays are detected by the imaging pixels in tile sensors 22. The deformed or planar DR detector 40 may be initially positioned, as much as possible before deformation under the weight of patient 20, in a perpendicular relation to a central ray 17 of the plurality of rays 16 emitted by the x-ray source 14. The array 12 of individual tile-sensors 22 may be individually electronically addressed by the processing system 34 according to their location in array 12. The orientation, configuration, shape, number, size, and placement, relative to other components in DR detector 40, of tile-sensors 22, as shown in FIG. 1 , is arbitrary and does not limit the scope of any embodiments disclosed herein. The tile-sensors 22 of one DR detector 40 may range in number from four, to hundreds, or even thousands, based on the individual sizes of tile-sensors and available computing power. The tile-sensors 22 may each be controlled and operate independently from neighboring tile-sensors 22, or they may each be electrically connected to one or all, e.g. four, of their adjacent, neighboring tile sensors 22 via common gate lines and data lines (FIG. 2A). The tile-sensors 22 may each be scanned individually and independently by readout circuitry 28, 30, to acquire radiographic image data captured therein and spatial orientation data stored therein, or the tile-sensors 22 may each wirelessly transmit image data and spatial orientation information as described herein. If tile-sensors 22 are electrically connected to adjacent, neighboring tile-sensors 22 using common gate and data lines, then the scanned radiographic image data may be transmitted to common readout circuits 28, 30, as in standard DR detectors. In addition, spatial orientation data as recorded in each of the tile-sensors 22 may be transmitted to the processing system 34. In one exemplary embodiment, the photosensitive cells in tilesensors 22 may be scanned by common electronic scanning circuit 28 so that the image data from the array 12 may be transmitted to common electronic read-out circuit 30 and further transmitted to processing system 34. [0031] An on board voltage controller 32 is electrically connected to the two- dimensional array 12 to provide power. The tile-sensors 22 and circuits 28, 30, 32, and on-board processor 36, as described herein, forming DR detector 40 may be attached to a flexible, deformable backing sheet 38, such as a carbon fiber sheet, so that the relative orientation and spatial placement as between all the components of DR detector 40 described herein are maintained when the DR detector 40 is not in a deformed state, i.e., not in use during patient imaging. The deformable backing sheet 38, as described herein, may include a multi-layer sheet that provides additional features, e.g., scatter protection, for the deformable DR detector 40.

[0032] The DR detector 40 may communicate with processing system 34 over a connected cable 33 (wired), or the DR detector 40 and the processing system 34 may be each equipped with a wireless transceiver to exchange radiographic image data, spatial information, and/or instructions wirelessly 35. The processing system 34 may include a processor and electronic memory (not shown) to control operations of the DR detector 40 as described herein, and to request, receive, store and process image data as well as spatial orientation data from individual tile-sensors 22, or processing system 34 may receive image data and spatial information data aggregated by common electronic scanning circuit 28 and common electronic read-out circuit 30. The image processing system 34 may also be used to control activation of the x-ray source 14 during a radiographic imaging procedure, controlling an x-ray tube electric current magnitude, and thus the fluence of x-rays in x-ray beam 16, and/or the x-ray tube voltage, and thus the energy level of the x-rays in x-ray beam 16. A portion or all of the acquisition control and image processing functions performed by processing system 34 may be performed in the detector 40 using an on-board processing system 36 which may include a processor and electronic memory to control operations of the DR detector 40 as described herein, including control of tile-sensors 22 and circuits 28, 30, 32, and to store and process image and tile-sensor orientation data similar to the functions of standalone processing system 34. The processing system 36 may control image transmission, image processing and image correction on board the detector 40 based on stored programming and/or based on instructions or other commands transmitted from the processing system 34. [0033] FIG. 2A is a schematic diagram of a tile-sensor 22. Each tile-sensor 22 includes a plurality of photosensors, or imaging pixels, 222 formed as an array 212 of photosensors 222 that are addressable by row and column. The array 212 of photosensor cells 222 may each include a photodiode 270 and a thin film transistor (TFT) 271 each having gate (G), source (S), and drain (D) terminals. In embodiments of DR detector 40 disclosed herein, the two-dimensional array 212 of photosensor cells 222 may be formed in a device layer that abuts adjacent layers of the tile-sensor 22 structure, which adjacent layers may include a rigid substrate layer such as glass or a flexible substrate layer such as polyimide. A gate driver circuit 228 may be electrically connected to each of the photosensors 222 via a plurality of gate lines 283 which control a voltage applied to the gates of TFTs 271 for reading out image data over data lines 284 from each photosensor 222 in tile-sensor 22. The image data may be transmitted from the data lines 284 to ITEC 290 to be transmitted therefrom to processing system 34 individually for each tile sensor 22. If the detector 40 uses a common gate line/data line configuration, then the common gate lines 283 for each tile-sensor 22 may be electrically connected to electronic scanning circuit 28 (FIG. 1) via common gate lines electrically connected to each, and across, horizontally neighboring tile-sensors 22 to signal data read out from each of tile-sensors 22. Similarly, electronic read out circuit 30 may be electrically connected to data lines 284 to aggregate image data read out from the array of tile-sensors 22 if the detector 40 uses a common gate line/data line configuration, wherein the common data lines 284 may be electrically connected to common electronic read out circuit 30 and to all vertically neighboring tile-sensors 22. ITEC circuit 290, as described herein, includes a processor and electronic memory for storing spatial position data and image data; a wireless transceiver 291, such as a WiFi transceiver; and an accelerometer 292, preferably a three dimensional, or three-axes, accelerometer for detecting spatial position/orientation data to be stored in ITEC 290. The voltage controller 32 (FIG. 1) is connected to voltage line 232 for controlling a voltage of the photodiodes 270 using distribution lines 285 at each of the photosensors 222. As is well-know, a scintillator, or wavelength converter, may be disposed over the array 212 of photosensors 222 to convert incident x-ray radiographic energy to visible light energy. Thus, the schematic diagram of FIG. 2A represents one tile-sensor 22 of a deformable, or conformable, DR detector 40. The ellipses 240 on each side of tile-sensor 22 indicate that neighboring tile-sensors 22 may be adjacent on all four sides and include the same electronic configuration as as shown in FIG. 2A.

[0034] FIG. 2B is a diagram of electronic read out circuit 30. If the detector 40 uses a common gate line/data line configuration, then the common data lines 284 may be electrically connected to each, and across, vertically neighboring tile-sensor 22 through to read electronic out circuit amplifiers 286 to receive and transfer data signals to analog multiplexer 287 and to analog-to-digital converter (ADC) 288 for streaming out the digital radiographic image data at desired rates.

[0035] FIG. 3A shows a perspective view of an exemplary portable conformable DR detector 40 according to an embodiment disclosed herein. The conformable DR detector 40 may include a flexible substrate to allow the DR detector 40 to capture radiographic images in a deformed orientation. The flexible substrate may be fabricated to provide an adjustable curvature in two or three dimensions, as desired. The DR detector 40 may include a similarly flexible housing portion 301 that surrounds a multilayer structure comprising a flexible tile-sensor array portion comprising a plurality of tile-sensors 22 which, in the example embodiment of FIG. 3A, includes an array of forty-nine tile sensors 22. The housing portion 301 of the DR detector 40 may include a continuous, flexible material, such as a carbon fiber plastic, polymeric, or other plastic based material, surrounding an interior volume of the DR detector 40 that includes components as described herein wherein control and read out circuitry may be positioned below the tile-sensors 22.

[0036] With reference to FIG. 3B, there is illustrated in schematic form an exemplary cross-section view along section 3B-3B of the exemplary embodiment of the conformable DR detector 40 of FIG. 3A. The multi-layer structure of each of the tile-sensors 22 are schematically illustrated in FIG. 3B and, as may be seen in the figure, are disposed within an interior volume 350 enclosed by a flexible housing 301 attached to a flexible top cover 312, and may include a flexible scintillator layer 304 over the two-dimensional tile-sensor array 12 comprising tile-sensors 22. The scintillator layer 304 may be directly under, e.g., directly abutting, the top cover 312, and the tile-sensor array 12 may be directly under the scintillator 304. Alternatively, a flexible layer 306 may be positioned between the scintillator layer 304 and the top cover 312 as part of the multilayer structure to allow adjustable curvature of the multilayer structure and to provide shock absorption. The flexible layer 306 may be selected to provide an amount of flexible support for both the top cover 312 and the scintillator 304, and may comprise a thin foam rubber type of material.

[0037] A substrate layer 320 may be disposed under each of the tile sensors 22 of the array 12, such as a rigid glass layer, in one embodiment, or flexible substrate comprising polyimide or carbon fiber upon which the tile-sensors 22 may be formed to allow adjustable curvature of the array 12. The substrate layer 320 may be attached to a thin flexible carbon fiber backing layer 38, which may also include a radioopaque shield layer, such as lead, and may be used as an x-ray blocking layer to help prevent scattering of x-rays passing through the substrate layer 320 as well as to block x-rays reflected from other surfaces in the interior volume 350. Readout electronics, including the scanning circuit 28, the read-out circuit 30, the voltage controller 32, and processing system 36 may be formed underneath the array 12. The tile-sensor array 12 may be electrically connected to the electronics over a flexible electrical connector 328 which may comprise a plurality of flexible, sealed conductors known as chip-on-film (COF) connectors.

[0038] When x-ray imaging system 10 is used in x-ray imaging, a patient may be placed between the source 14 and portable DR detector 40. When the DR detector 40 is positioned under a patient, it is likely to be partially or completely covered by bedding as well as additional devices, e.g., breathing tubes or lines. Previous solutions for determining the relative spatial position of the source 14 and DR detector 40 included adding one or more accelerometers placed at corners of a planar panel detector or using scouting imaging with ultra-low exposure energy. The captured image could then be used to recover known geometrical characteristics and thus the pose of the detector. When the detector is defined by a rigid planar surface, such a pose of the detector may be easily determined. Correct detector pose computation is essential for positioning the source orthogonal to the plane of the detector and thus capturing a true projection of the patient anatomy and thus acquiring a clinically meaningful x-ray image. Pose and distance can also be used to adjust for projective distortions, e.g., key-stoning.

[0039] As the DR detector 40 is bendable and conformable in multidimensions, its surface will deform to adjust to the patient body weight. When DR detector 40 surface deformations are introduced, the planar constraint used for source alignment and image reconstruction is violated. In such a scenario, an active surface sensor as described herein may be used as a means to obtain from the tile-sensors 22 both local as well as global information about the deformed image receptor surface. Thus, a surface deformation can be computed from a network aggregation of tilesensors 22 placed at or near the active surface sensor itself, as described herein.

[0040] A deformable DR detector surface may be approximated by using a mesh of neighboring tile-sensors 22 each having associated locations, dimensions, spatial orientation, and curvatures. These tile-sensors 22 may be discrete physical components or contiguous neighboring locations on a deformable surface. As a localized sensor on the surface, a tile-sensor 22 affords the ability to compute the spatial pose of the tile-sensor 22, when discrete, or a surface curvature at a particular location within a tile-sensor neighborhood, when contiguous, relative to an initial, i.e., before deformation, planar reference surface.

[0041] The present invention discloses a spatial pose computation as follows: by attaching at least one accelerometer 292 per tile-sensor 22 as part of its ITEC 290 (whether discrete or at location on a contiguous surface), the accelerometer 292 will allow determining the orientation of the tile-sensor's normal relative to gravity. In one embodiment, a configuration may include three accelerometers per tile-sensor 22 to reduce spatial pose estimation errors. In one embodiment, an accelerometer 292 with two or three axes may be used. Sizes of such accelerometers are on the order of a few millimeters. When considering the choice of an accelerometer 292, trade off considerations make be taken to optimize between cost, redundancy, size, and accuracy. [0042] This approach effectively miniaturizes and distributes an established solution to compute the pose for a large flat panel detector and applies it to the individual tile-sensor 22. In the limiting case, the flat surface is represented by a single tile-sensor. As the selected size of the tile-sensor 22 is reduced to smaller sizes and possibly different topologies, the functionality of the pose estimation is applicable to the individual tile-sensor 22 and thus each of the underlying quantized surface portions can be computed. This similarly applies when the tile-sensor 22 is not discrete, but is considered as a loci on a surface. Each tile-sensor's pose may be specified by a single accelerometer 292. If more than one accelerometer 292 per tilesensor 22 is used, a small circuit may be added to integrate the spatial pose information from each of the accelerometers. Each tile-sensor 22 may also include an RF sensor, or transceiver, 291 as part of its ITEC 290, or another type wireless sensor and/or transceiver that may be wirelessly interrogated so as to recover the spatial pose data of each individual tile-sensor 22. Alternatively, a wired connector may be employed, as disclosed herein. Additional local storage and computational capabilities may be included as part of the ITEC 290 circuitry associated with each tile-sensor 22. A tile-sensor 22 may be considered as a neighborhood of photosensors, or imaging pixels, 222 on a DR detector surface with associated ITEC components. It is understood that an ITEC 290 component as described herein enables each tile-sensor 22 to be treated as an individual unit directly externally accessible. In other configurations, the tile-sensor 22 may have minimal capability such as including only a single accelerometer with all the additional capabilities residing elsewhere in the DR detector 40.

[0043] An aggregation process may be used to combine tile-sensors 22 into a network of sensors that covers an entire surface of a DR detector 40. The concept of a mesh network of tile-sensors 22 has been introduced in telecommunication applications where independent and distributed WiFi nodes can connect dynamically and communicate with other nodes as a means to enhance robustness, reliance, and effective coverage of an area. In the present x-ray system context, however, communication between tile-sensors, while possible in some embodiments, is not an essential or a primary aspect. A mesh may refer to a layout of tile-sensors 22 on a DR detector 40 surface with the explicit intent to capture a representation of the topology of the surface using tile-sensors 22 placed at discrete locations. Based on the morphology of the DR detector 40 surface, whether discrete tile-sensors 22, or loci on a continuous surface, a resulting depth map of the surface may be approximated in term of discrete tile patches of potentially different convexities and sizes, or as an interpolation of measurements over various neighboring locations.

[0044] The present invention proposes different approaches for mounting the ITEC 290 components of a tile- sensor 22. While the ITEC 290 could be mounted prior to assembly when dealing with discrete tile-sensors 22, the present invention includes an approach to prepare the DR detector 40 into which ITEC 290 components will be mounted. The configurations identified herein provide a method for tilesensor aggregation into a mesh of tile-sensors 22 and defines some advantages of the present inventive approach. In one embodiment, each tile-sensor 22 may be electrically connected to adjacent ones by using common gate lines (e.g., horizontal) and data lines (e.g., vertical) connected to and across each of the tile-sensors 22, thus digitally joining each tile-sensor 22 to construct a grid of adjacent tile-sensors 22 as described herein. This may be facilitated using mechanical interfaces between tilesensors 22. one embodiment, bonding may be used by introducing an interface material between tile-sensors 22 having different properties. In such a situation whereas the tile areas would preserve a degree of stiffness, the individual bonding areas would afford relative flexibility and displacement. In one embodiment, a single carbon fiber sheet 38 of a given thickness may be etched for a given tile-sensor topology. The carbon fiber sheet 38, upon being etched, will allow its surface to comply to pressure and deform without rupturing. The initial thickness of the carbon fiber sheet 38 can be selected based on (a) within tile rigidity and (b) tradeoff between edge folding angle and stress/strain resilience required at the edge interface. Such etching may be accomplished using mechanical instrumentation or laser. It is understood that whereas the present description highlights carbon fiber, other materials may be used to meet the same requirement. In one embodiment, following tile etching, the etched areas may be filled with a flexible bonding material. This approach affords the DR detector 40 imaging surface to be presented as a uniform smooth surface while adding the benefit of increased flexibility and reducing potential damage in edge areas as a result of stress. In one embodiment, a composite material may be used to have more stiffness along the peripheral areas or along one direction and more flexibility in others. For instance, considering x and y axes for a surface, it may be preferable to have more flexibility along the x dimension. This will provide a preferred direction of compliance such as to allow roll up, but also for the placement of additional electronic components along the y-axis.

[0045] Upon completion of the definition of a mesh of tile-sensors 22, according to at least one of the approaches described herein, the ITEC 290 components may be connected according to a specific tile-sensor 22 topology. The resulting configuration of ITEC 290 components, mounted on a surface with distributed electrical connections for each ITEC 290 for power and communication, if not using a wireless capability, captures the functionality of the active surface sensor. In one embodiment, individual small sections of lead shielding 310 just large enough to cover the ITEC 290 components may be aligned with the components.

[0046] The ability to compute the surface deformation of the active surface sensor uses the aggregated tile-sensors’ spatial pose and geometry, when discrete, or curvature and location, when contiguous. As described herein, the active surface sensor may have a decentralized architecture where every single tile-sensor may be queried individually, by wire or wirelessly, to reconstruct a depth map; or a centralized architecture where the full active surface sensor can return a depth map. Alternatively, intermediary embodiments may be configured wherein sections of the tile-sensors 22 may be selectively queried externally, e.g., by rows or columns. Depending on the degree of interaction and type of information requested, the necessary ITEC 290 electronic components will need to be incorporated to support the desired sensor architecture. In a preferred embodiment, the active surface sensor will have an architecture that includes the capability to manage the inter tile-sensor communications and configurations and provide a single point of wired or wireless access. [0047] It may desirable that the DR detector 40 deform less along preferred directions along the borders. Considering a rectangular DR detector 40 surface, it may be desirable that the detector surface retain flexibility along the x-direction, but stiffness along the y-direction as illustrated in FIG. 4A. In another application it may be desirable to have equal, or possibly different deformability along both borders of the detector surface as illustrated in FIG. 4B. Additional flexibility of the active surface sensor may be introduced when allowing the surface to stretch such as illustrated in FIG. 5. In these cases, the active surface sensor, given well defined placement of the ITEC 290 components, can compute the surface deformation by interpolating between the local ITEC 290 displacement.

[0048] A calibration process for each individual tile-sensor 22, whether discrete or contiguous, and for the active surface sensor as a whole, can be achieved by placing the tile-sensor 22 onto a known surface of a given morphology. Examples of type of morphologies are shown in FIGS. 4A-4B. By relating the known surface morphology to what is computed and returned by the active surface sensor, error calibration can be performed to remove or reduce it to a desired tolerance. The calibration process may be repeated using a variety of surfaces to validate that all sensors are properly calibrated. Thus, for instance, the calibrating surface may have a cylinder or other known surface, which might be automatically moved or rotated across either axis of alignment to alter or vary the curvature of the resting surface. By comparing the surface parametric model to the surface obtained from the active surface sensor, the calibrating matrix can be obtained to minimize errors. A validation process may be performed by using the mechanism from the calibration process, however, proper validation with an independent mechanism such as depth sensor, e.g., laser range sensor, may be used to determine a reference depth map. Upon proper alignment of the active surface sensor, and upon satisfying the required design tolerance, accuracy of the depth from the active surface sensor can be assessed.

[0049] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method, or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.), or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “service,” “circuit,” “circuitry,” “module,” and/or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

[0050] Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc readonly memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0051] Program code and/or executable instructions embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages. These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. [0052] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

CLAIMS:

1. A digital radiographic imaging system comprising: an imaging surface comprising a plurality of imaging pixels for capturing a radiographic image; a plurality of tile-sensors each comprising a subset of the imaging pixels and each comprising a sensor for recording a local spatial position of a corresponding tile-sensor; and a processor to calculate a geometry and spatial position of the imaging surface using the recorded local spatial positions of the plurality of tile-sensors.

2. The system of claim 1, wherein the plurality of tile-sensors are each formed on a rigid substrate.

3. The system of claim 1, wherein the processor generates a human viewable 3D map of the imaging surface for display by the imaging system according to the calculated geometry and spatial position of the imaging surface.

4. The system of claim 1 , wherein each of the plurality of tilesensors are disposed at a different angle with respect to each other.

5. The system of claim 1, wherein each of the plurality of tilesensors include an accelerometer for sensing a local spatial position of a corresponding tile-sensor and for generating spatial position data therefor.

6. The system of claim 5, wherein each of the plurality of tilesensors includes a transmitter for wirelessly transmitting the spatial position data to the processor.

7. The system of claim 1, wherein the calculated spatial position of the imaging surface includes deformations of the imaging surface along at least two orthogonal axes of the imaging surface.

8. Method comprising: capturing a radiographic image of a patient using a conformable DR detector, the conformable DR detector comprising an image receptor surface divided into a plurality of sections each disposed at a different angle with respect to each other; receiving a plurality of spatial position data from each of a plurality of sensors in the DR detector; and determining a spatial pose for each of the plurality of sections of the conformable DR detector using the received plurality of spatial position data.

9. The method of claim 8, further comprising disposing the plurality of sections each along a different plane with respect to each other.

10. The method of claim 8, further comprising digitally displaying a three dimensional map of the imaging surface of the conformable digital radiographic DR detector using the spatial position data.

11. The method of claim 8, further comprising forming the plurality of sections on a rigid substrate.

12. The method of claim 8, further comprising mounting an accelerometer to each of the plurality of sections for sensing a local spatial position of a section and for generating spatial position data therefor.

13. The method of claim 12, further comprising wirelessly transmitting the spatial position data from each of the sections.

14. The method of claim 13, further comprising wirelessly transmitting spatial position data that defines deformations of the imaging surface along at least two orthogonal axes of the imaging surface.