The invention relates generally to the field of medical imaging, and in particular to radiographic imaging and digital radiographic (DR) detectors and more particularly to amorphous silicon or polycrystalline radiographic detector arrays.
There is a need for improvements in the consistency and/or quality of medical x-ray images, particularly when obtained by an x-ray apparatus designed to operate with a-Si DR x-ray detectors.
An aspect of this application is to advance the art of medical digital radiography.
Another aspect of this application to address in whole or in part, at least the foregoing and other deficiencies in the related art.
It is another aspect of this application to provide in whole or in part, at least the advantages described herein.
An aspect of this application to is to provide methods and/or apparatus to address and/or reduce disadvantages caused by the use of portable (e.g., wireless) digital radiography (DR) detectors and/or radiography imaging apparatus using the same.
An aspect of this application to is to provide methods and/or apparatus that can provide active pixels in amorphous or polycrystalline semiconductor DR x-ray detectors.
In accordance with one embodiment, the present invention can provide a digital radiographic area detector that can include an imaging array including a plurality of active pixels, each active pixel including at least one polycrystalline or amorphous silicon electrically chargeable photosensor and thin-film transistors; a bias control circuit to provide a bias voltage to the photosensors for a portion of the imaging array; first conductive lines (e.g., scanlines) coupled to a plurality of active pixels arranged along a first direction in the portion of the imaging array; second conductive lines (e.g., datalines) coupled to a plurality of active pixels arranged along a first direction in the portion of the imaging array; circuits to provide signal sensing for the portion of the imaging array coupled to the second conductive lines; and charge conversion circuitry to convert voltage values output by the active pixels to a corresponding charge values for input to the signal sensing circuits. In one embodiment, the imaging array includes a-IGZO devices.
These objects are given only by way of illustrative example, and such objects may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently achieved by the disclosed invention may occur or become apparent to those skilled in the art. The invention is defined by the appended claims.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings.
The elements of the drawings are not necessarily to scale relative to each other.
The following is a description of exemplary embodiments of the invention, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures.
Where they are used, the terms “first”, “second”, and so on, do not necessarily denote any ordinal or priority relation, but may be used for more clearly distinguishing one element or time interval from another.
The array 12 can be divided into a plurality of individual cells 22 that can be arranged rectilinearly in columns and rows. As will be understood to those of ordinary skill in the art, the orientation of the columns and rows is arbitrary, however, for clarity of description it will be assumed that the rows extend horizontally and the columns extend vertically.
In exemplary operations, the rows of cells 22 can be scanned one (or more) at a time by scanning circuit 28 so that exposure data from each cell 22 may be read by read-out circuit 30. Each cell 22 can independently measure an intensity of radiation received at its surface and thus the exposure data read-out provides one pixel of information in an image 24 to be displayed on a monitor 26 normally viewed by the user. A bias circuit 32 can control a bias voltage to the cells 22.
Each of the bias circuit 32, the scanning circuit 28, and the read-out circuit 30, can communicate with an acquisition control and image processing circuit 34 that can coordinate operations of the circuits 30, 28 and 32, for example, by use of an electronic processor (not shown). The acquisition control and image processing circuit 34, can also control the examination procedure, and the x-ray tube 14, turning it on and off and controlling the tube current and thus the fluence of x-rays in beam 16 and/or the tube voltage and hence the energy of the x-rays in beam 16.
The acquisition control and image processing circuit 34 can provide image data to the monitor 26, based on the exposure data provided by each cell 22. Alternatively, acquisition control and image processing circuit 34 can manipulate the image data, store raw or processed image data (e.g., at a local or remotely located memory) or export the image data.
Exemplary pixels 22 can include a photo-activated image sensing element and a switching element for reading a signal from the image-sensing element. Image sensing can be performed by direct detection, in which case the image-sensing element directly absorbs the X-rays and converts them into charge carriers. However, in most commercial digital radiography systems, indirect detection is used, in which an intermediate scintillator element converts the X-rays to visible-light photons that can then be sensed by a light-sensitive image-sensing element.
Examples of image sensing elements used in image sensing arrays 12 include various types of photoelectric conversion devices (e.g., photosensors) such as photodiodes (P-N or PIN diodes), photo-capacitors (MIS), photo-transistors or photoconductors. Examples of switching elements used for signal read-out include MOS transistors, bipolar transistors and p-n junction components.
There are numerous types of x-ray equipment and configurations designed for specific radiographic procedures that can use area detectors. These can include wall-stand, floor-mount, chest, table units or mobile units; designed for supine, upright, or other patient orientations.
A related art area detector is shown in
The embodiment of
To comply with ISO 4090.2001(E) standard, packaging of the detector array and supporting electronics becomes very challenging. There is limited space for these components in all directions (X, Y, Z). First, flex circuits connecting the detector array and electronics need to be wrapped underneath the array. Second, use of a self-contained battery and battery pack within the DR detector is preferred. In order to comply with the 16 mm cassette thickness, the self-contained battery and battery pack needs to be extremely thin. It is noted that the present invention is not limited to a self-contained battery, but could be energized through an external power source detector array. For durability reasons, the detector array 208 is attached to a stiffener 210 in an embodiment of the present invention. The stiffener is made of a lightweight composite that has similar thermal coefficient of expansion to the substrate material, but significantly higher bending stiffness than the substrate.
As shown in
In a hydrogenated amorphous silicon (a-Si:H) based indirect flat panel imager of
Device electronics required for proper operation of the detector can be mounted within the cavity 206 and can include electronic components 220 (e.g., processors, FPGAs, ASICs, chips, etc.) that can be mounted on one or more separate and/or interconnected circuit boards 226.
This application describes various exemplary radiographic detector architectures and their glass interface (e.g., imaging array) to external Readout IC's (ROICs).
Architectures/embodiments described herein include: 1) traditional passive pixel design (related art), 2) voltage accepting ROIC, 3) V to Q (Voltage to Charge) conversion on glass, and 4) V to Q (Voltage to Charge) conversion on ROICs.
Certain exemplary embodiments described herein include, but are not limited to radiographic detector architectures and their glass interface to external Readout IC's (ROICs).
An exemplary difference between
There is no current ROIC commercially available for a radiographic area detector that allows for voltage input, only charge as an input. Certain exemplary embodiments according to the application can use an architecture that uses the ROIC 550 that can accept voltage input. The ROIC 550 internal design as shown in the
Active pixel implementations herein are not intended to be limited to 3T pixels but also alternative pixels such as 4T pixels. In one embodiment, active pixel embodiments can use amorphous indium-gallium-zinc-oxide (IGZO) materials and/or IGZO process technology. In one embodiment, active pixel embodiments can use a-Si materials and/or a-Si process technology.
An active pixel structure including 3 or more TFT elements along with a biasing TFT element can output a voltage onto conductive data lines. A typical 3T active pixel structure can output a signal voltage first, which is proportional to the light accumulated onto the photo-detector element. A 3T active pixel structure can then output a reset voltage second as a function of enabling the reset transistor element within an active pixel structure. The voltage difference can be translated to a charge difference by using a voltage to charge element between the active pixel structure and a charge input accepting ROIC structure. This charge difference can be sensed by a charge input accepting ROIC for further conditioning.
When implementing various embodiment integrations on silicon chip and glass, all of the necessary components are desired to be on the glass, which includes the column circuit, buffers and ADC. In the case of CMOS technology, the device characteristics are so good that this makes sense and is fully realizable. However even though a-IGZO is better than a-Si in its device characteristics, it is still no match for CMOS. Maintaining CMOS readout data rate speeds is unlikely and full a-IGZO ADC on glass is also unlikely.
Certain exemplary embodiments described herein include an interface on glass that can change voltage to charge (V to Q) to provide an active pixel on glass for low noise and/or maintain the high readout performance using external ROICs. These exemplary embodiments using column circuit implementation on glass can provide better imaging array performance.
Note that in one embodiment, the column circuit design is not a switched capacitor in nature that can be what typical architectures use. No switches are required for the voltage to charge conversion embodiment as shown in
Benefits of the embodiment of
Active pixel implementations herein are not intended to be limited to 3T pixels but also alternative pixels such as 4T pixels. In one embodiment, active pixel embodiments can use IGZO materials and/or IGZO process technology. In one embodiment, active pixel embodiments can use a-Si materials and/or a-Si process technology. In one embodiment, adding switches for multiple capacitors (e.g., changing the size, with various sizes) can allow for increasing an allowable gain range. In one embodiment, alternative designs can use switches for binning implementation (e.g., horizontal).
Exemplary embodiments according to the application occur at/nearby the sensor (e.g., a-Si, a-IGZO) on glass interface to the ROICs (e.g., formed in crystal silicon that are damaged by X-rays). Generally, ROICs are positioned to the side (outside the imaging area) or underneath the imaging array and protected by a lead shield.
In certain exemplary embodiments, digital radiographic imaging detectors can include thin-film elements such as but not limited to thin-film photosensors and thin-film transistors. Thin film circuits can be fabricated from deposited thin films on insulating substrates as known to one skilled in the art of radiographic imaging. Exemplary thin-film circuits can include a-IGZO devices such as a-IGZO TFTs or PIN diodes, Schottky diodes, MIS photocapacitors, and be implemented using amorphous semiconductor materials, polycrystalline semiconductor materials such as metal oxide semiconductors. Certain exemplary embodiments herein can be applied to digital radiographic imaging arrays where switching elements include thin-film devices including at least one semiconductor layer. Certain exemplary embodiments herein can be applied to digital radiographic imaging arrays where the DR detector is a flat panel detector, a curved detector or a detector including a flexible imaging substrate.
Certain exemplary embodiments herein can be applied to digital radiographic imaging arrays where photoelectric conversion elements include at least one semiconductor layer, and that at least one semiconducting layer can include amorphous silicon, micro-crystalline silicon, poly-crystalline silicon, single-crystal silicon-on-glass (SiOG), organic semiconductor, and metal oxide semiconductors. Certain exemplary embodiments herein can be applied to digital radiographic imaging arrays where switching elements include at least one semiconductor layer, and that at least one semiconducting layer can include amorphous silicon, micro-crystalline silicon, poly-crystalline silicon, single-crystal silicon-on-glass (SiOG), organic semiconductor, and metal oxide semiconductors.
The present application contemplates methods and program products on any computer readable media for accomplishing its operations. Exemplary embodiments according to the present application can be implemented using an existing computer processor, or by a special purpose computer processor incorporated for this or another purpose or by a hardwired system.
Also known in the art are digital radiographic imaging panels that utilize an array of pixels comprising an X-ray absorbing photoconductor, such as amorphous Selenium (a-Se), and a readout circuit. Since the X-rays are absorbed in the photoconductor, no separate scintillating screen is required.
It should be noted that while the present description and examples are primarily directed to radiographic medical imaging of a human or other subject, embodiments of apparatus and methods of the present application can also be applied to other radiographic imaging applications. This includes applications such as non-destructive testing (NDT), for which radiographic images may be obtained and provided with different processing treatments in order to accentuate different features of the imaged subject.
Priority is claimed from commonly assigned, copending U.S. Provisional Patent Application Ser. No. 61/790,618 filed Mar. 15, 2013 in the name of Ravi K MRUTHYUNJAYA et al., titled RADIOGRAPHIC DETECTOR USING POLYCRYSTALLINE ACTIVE PIXEL ARCHITECTURE USING VOLTAGE TO CHARGE CONVERSION ON GLASS, the contents of which are incorporated fully herein by reference.
As will be appreciated by one skilled in the art, the present invention may be embodied as a system, method, or computer program product. Accordingly, an embodiment of the present invention may be in the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, and other suitable encodings) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit” or “system.” Furthermore, the present invention may take the form of a computer program product embodied in a computer-readable storage medium, with instructions executed by one or more computers or host processors. This medium may comprise, for example: magnetic storage media such as a magnetic disk (such as a hard drive or a floppy disk) or magnetic tape; optical storage media such as an optical disc, optical tape, or machine readable bar code; solid state electronic storage devices such as solid state hard drives, random access memory (RAM), or read only memory (ROM); or any other physical device or medium employed to store a computer program. The computer program for performing the method of the present invention may also be stored on computer readable storage medium that is connected to a host processor by way of the internet or other communication medium.
Those skilled in the art will readily recognize that the equivalent of such a computer program product may also be constructed in hardware. The computer-usable or computer-readable medium could even be paper or another suitable medium upon which executable instructions are printed, as the instructions can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport computer instructions for use by, or in connection with, an instruction execution system, apparatus, or device.
In accordance with one embodiment of the application, a digital radiographic area detector can include an imaging array including a plurality of active pixels, each active pixel comprising at least one amorphous IGZO electrically chargeable photosensor and at least three thin-film transistors; a bias control circuit to provide a bias voltage to the photosensors for a portion of the imaging array; first conductive lines coupled to a plurality of active pixels arranged along a first direction in the portion of the imaging array; second conductive lines coupled to a plurality of active pixels arranged along a second direction in the portion of the imaging array; circuits to provide signal sensing for the portion of the imaging array coupled to the second conductive lines; and charge conversion circuitry to convert voltage values output by the active pixels to a corresponding charge values for input to the signal sensing circuits during readout of a signal from the portion of the imaging array.
In accordance with one embodiment of the application, a digital radiographic area detector can include an imaging array including a plurality of active pixels, each active pixel including at least one amorphous silicon/a-IGZO electrically chargeable photosensor and at least three thin-film transistors; circuits to provide signal sensing for the portion of the imaging array coupled to conductive data lines; and charge conversion circuitry to convert voltage values output by the active pixels to a corresponding charge values for input to the signal sensing circuits during readout of a signal from a portion of the imaging array, where the active pixels are configured to output voltage on second conductive lines and the charge conversion circuitry comprises a first circuit formed in crystal silicon at ROICs formed in crystal silicon to convert the signal sensing circuits to accept voltage. In one embodiment, the ROICs are configured to input the voltage as input signals to output corresponding digital data. In one embodiment, the imaging array includes a-IGZO devices.
While the invention has been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention can have been disclosed with respect to only one of several implementations, such feature can be combined with one or more other features of the other implementations as can be desired and advantageous for any given or particular function. The term “at least one of” is used to mean one or more of the listed items can be selected. The term “about” indicates that the value listed can be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US14/27862 | 3/14/2014 | WO | 00 |
Number | Date | Country | |
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61790618 | Mar 2013 | US |