Patent Application
20190353805
The subject matter disclosed herein relates to X-ray imaging systems and more particularly to a portable X-ray detector having a polymeric substrate.
A number of radiological imaging systems of various designs are known and are presently in use. Such systems generally are based upon generation of X-rays that are directed toward a subject of interest. The X-rays traverse the subject and impact a film or a digital detector. In medical diagnostic contexts, for example, such systems may be used to visualize internal tissues and diagnose patient ailments. In other contexts, parts, baggage, parcels, and other subjects may be imaged to assess their contents and for other purposes.
Increasingly, such X-ray systems use digital circuitry, such as solid-state detectors, for detecting the X-rays, which are attenuated, scattered or absorbed by the intervening structures of the subject. Solid-state detectors may generate electrical signals indicative of the intensities of received X-rays. These signals, in turn, may be acquired and processed to reconstruct images of the subject of interest.
As digital X-ray imaging systems have become increasingly widespread, digital X-ray detectors have become more portable for even greater versatility. Typically, a 2D flat panel array of silicon photo-detectors is fabricated on (e.g., via lithography) on a thin fragile glass substrate to form the X-ray detector panel or imaging panel. The panel is typically heavy and brittle. In addition, the detector includes additional components (e.g., panel support) to protect and limit the flexibility of the imaging panel. This results in a thicker and heavier detector. However, it is desirable to have a thin and lightweight X-ray detector.
Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible forms of the subject matter. Indeed, the subject matter may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In accordance with a first embodiment, a digital X-ray detector is provided. The digital X-ray detector includes a polymeric substrate. The digital X-ray detector also include a detector array configured to generate image data based on incident X-ray radiation disposed on the polymeric substrate, wherein the polymeric substrate extends beyond an edge of the detector array. The digital X-ray detector further includes scan electronics and readout electronics configured to acquire image data from the detector array, wherein the scan electronics, the readout electronics, or both the scan electronics and the readout electronics are directly disposed on the polymeric substrate.
In accordance with a second embodiment, a digital X-ray detector is provided. The digital X-ray detector includes a polymeric substrate. The digital X-ray detector also include a detector array configured to generate image data based on incident X-ray radiation disposed on the flexible polyimide substrate. The detector array includes a scintillator configured to convert the incident radiation into lower energy optical photons, a semi-hermetic coating or hermetic conductive coating is disposed on a side of the polymeric substrate opposite the scintillator and a flexible seal is disposed over the scintillator. The flexible seal is bonded to the polymeric substrate at a location beyond an edge of the detector array to semi-hermetically or hermetically seal the scintillator so that the edge of the polymeric substrate is also semi-hermetically or hermetically sealed.
In accordance with a third embodiment, a method for manufacturing a digital X-ray detector is provided. The method includes depositing a detector array configured to generate image data based on incident X-ray radiation on a polymeric substrate disposed on a glass substrate wherein the polymeric substrate extends beyond an edge of the detector array and then bends. The method also includes removing the glass substrate from the polymeric substrate. The method further includes directly disposing scan electronics, readout electronics, or both the scan electronics and the readout electronics on the polymeric substrate on the bend or after the bend of the polymeric substrate, wherein the scan electronics and the readout electronics are configured to acquire the image data from the detector array.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present subject matter, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.
The following embodiments describe a portable digital X-ray detector that includes a detector subsystem with a polymeric (e.g., flexible polyimide) substrate or panel. The polymeric substrate along with other flexible components of the detector subsystem (e.g., scintillator) makes the detector subsystem flexible and more rugged. The substrate may extend (and bend) beyond an edge of a detector array of the detector subsystem. In certain embodiments, scan and readout electronics may be disposed on the polymeric substrate at or beyond the bend. In certain embodiments, the scan and readout electronics disposed on the polymeric substrate may be located on the opposite side of detector subsystem (e.g., behind the imager) from where incident X-ray radiation is received to minimize exposure of the scan and readout electronics to radiation. The utilization of the polymeric substrate may also enable the imager to extend closer to the edge of the detector. In certain embodiments, components of a plurality of imager modules may be disposed in a tiled arrangement on the polymeric substrate to enable multiplexed readout of the image data.
Turning now to the drawings,
Source 12 is controlled by a power supply/control circuit 24 which furnishes both power and control signals for examination sequences. Moreover, detector 22 is coupled to a detector controller 26 which commands acquisition of the signals generated in the detector 22. Detector controller 26 may also execute various signal processing and filtration functions, such as for initial adjustment of dynamic ranges, interleaving of digital image data, and so forth. Both power supply/control circuit 24 and detector controller 26 are responsive to signals from a system controller 28. In general, system controller 28 commands operation of the imaging system to execute examination protocols and to process acquired image data. In the present context, system controller 28 also includes signal processing circuitry, typically based upon a general purpose or application-specific digital computer; and associated manufactures, such as optical memory devices, magnetic memory devices, or solid-state memory devices, for storing programs and routines executed by a processor of the computer to carry out various functionalities (e.g., gain calibration and gain correction), as well as for storing configuration parameters and image data; interface protocols; and so forth. In one embodiment, a general or special purpose computer system may be provided with hardware, circuitry, firmware, and/or software for performing the functions attributed to one or more of the power supply/control circuit 24, the detector controller 26, and/or the system controller 28 as discussed herein.
In the embodiment illustrated in
Referring now to
As noted above, the polymeric substrate 34 may be polyimide. The polyimide substrate may include the following thermal properties. The polyimide substrate may include a coefficient of thermal expansion ranging from approximately 25 to 30 ppm/° C. (at a test condition of approximately 100 to 200° C.). The polyimide substrate may include heat shrinkage ranging from −0.022 to −0.030% (at a test condition of 150° C. for 30 minutes).
As to other components of the digital detector 22, the electronics 42 control the operation of the detector 22. In particular, electronics 42 enable the acquisition of image data from the digital detector array 40. The electronics 42 may include scan and readout electronics including circuit boards, data modules, scanning modules, and other circuitry.
The scintillator 43 converting incident X-rays to visible light. The scintillator 43, which may be fabricated from cesium iodide (CsI), gadolinium oxysulfide (GOS), or other scintillating materials, is designed to emit light proportional to the energy and the amount of the X-rays absorbed. As such, light emissions will be higher in those regions of the scintillator layer where either more X-rays were received or the energy level of the received X-rays was higher. Since the composition of the subject will attenuate the X-rays projected by the X-ray source to varying degrees, the energy level and the amount of the X-rays impinging upon the scintillator 43 will not be uniform across the scintillator layer. This variation in light emission will be used to generate contrast in the reconstructed image.
The light emitted by the scintillator 43 is detected by a photosensitive layer on the imager 44. The photosensitive layer includes an array of photosensitive elements or detector elements to store an electrical charge in proportion to the quantity of incident light absorbed by the respective detector elements. Generally, each detector element has a light sensitive region and a region including electronics to control the storage and output of electrical charge from that detector element. The light sensitive region may be composed of a photodiode, which absorbs light and subsequently creates and stores electronic charge. After exposure, the electrical charge in each detector element is read out using logic-controlled electronics 42. In certain embodiments, due to the flexibility of the substrate 34, the detector 22 may include more than one scintillator and/or more than one imager.
Each detector element is generally controlled using a transistor-based switch. In this regard, the source of the transistor is connected to the photodiode, the drain of the transistor is connected to a readout line, and the gate of the transistor is connected to a scan control interface disposed on the electronics 42 in the detector 22. When negative voltage is applied to the gate, the switch is driven to an OFF state, thereby preventing conduction between the source and the drain. Conversely, when a positive voltage is applied to the gate, the switch is turned ON, thereby allowing the photodiode to be recharged, with the amount of charge being a function of the diode depletion as an indication of incident energy, which is detected on the readout line. Each detector element of the detector array 40 is constructed with a respective transistor (e.g., a thin-film transistor).
Specifically during exposure to X-rays, negative voltage is applied to all gate lines resulting in all the transistor switches being driven to or placed in an OFF state. As a result, any charge depletion experienced during exposure reduces the charge of each detector element. During read out, positive voltage is sequentially applied to each gate line. That is, the detector is an X-Y matrix of detector elements and all of the gates of the transistors in a line are connected together so that turning ON one gate line simultaneously reads out all the detector elements in that line. A multiplexer may also be used to support read out of the detector elements in a faster fashion. The output of each detector element is then input to an output circuit (e.g., a digitizer) that digitizes the acquired signals for subsequent image reconstruction on a per pixel basis. In a typical reconstruction, each pixel of the reconstructed image corresponds to a single detector element of the digital detector array 40.
The enclosure 38 protects the detector components from damage when exposed to an external load or an impact. The enclosure 38 includes a front side 46 to receive radiation 48 (e.g., during front side irradiation). In certain embodiments, the detector 22 may also be may receive radiation on the back side 50 (e.g., during back side irradiation). In certain embodiments, the detector 22 may be utilized for both front side and back side irradiation. The enclosure 38 may be formed of materials such as a metal, a metal alloy, a plastic, a composite material, or a combination of the above. In certain embodiments, the material has low X-ray attenuation characteristics. In one embodiment, the enclosure 38 may be formed of a lightweight, durable composite material such as a carbon fiber reinforced plastic material, carbon reinforced plastic material in combination with foam cores, or a graphite fiber-epoxy composite. Some embodiments may include one or more material compositions having a non-conductive matrix with conductive elements disposed therein, and may provide electromagnetic interference shielding to protect the internal components of the detector 22 from external electronic noise. Additionally, the enclosure 38 may be designed to be substantially rigid with minimal deflection when subjected to an external load.
In certain embodiments, the detector 22 may include additional layers of digital detector arrays. One digital detector array could act as an ion chamber by measuring X-ray dose. Another digital detector array may be utilized for autosensing the beginning of irradiation. The image data maybe selectively read out from the digital detector arrays.
Technical effects of the disclosed embodiments include providing a detector that includes a detection subsystem including a flexible polymeric substrate (e.g., polyimide). The flexible substrate, in conjunction with other flexible detector components (e.g., scintillator, seal, etc.), provides a more flexible detector assembly and more rugged detector assembly. In addition, the flexible substrate may enable the expansion of the detector array closer to the edges of the detector. In certain embodiments, the flexible substrate may enable fewer electronic components (e.g., data modules) and enable multiplexed readout of the image data.
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 languages of the claims.
