Imaging equipment

Abstract

The imaging device includes: a first scintillator layer; an array of detector elements, wherein the array of detector elements includes first detector elements; a second scintillator layer, configured to receive radiation after the radiation has passed through the first scintillator layer and the array of detector elements, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; a first electrode, located closer to the first scintillator than the second scintillator; and a second electrode, located between the second scintillator and the first detector element; the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer; the second electrode is configured to allow light from the second scintillator layer to reach the first detector element.

Description

Technical Field

[0001] The field of application relates to imaging devices, and more particularly to medical imaging devices. Background Art

[0002] Imaging devices (e.g., x-ray imagers) have been used for both diagnostic and therapeutic purposes. One type of x-ray imager is a diagnostic imager configured to operate using a diagnostic radiation source. Another type of x-ray imager is a high DQE detector configured for use with a therapeutic radiation source. An x-ray imager may also be configured for use with both a diagnostic radiation beam and a therapeutic radiation beam.

[0003] Creating high DQE detectors for portal imaging presents significant technical challenges. One approach uses a thick pixelated scintillator array coupled to an electronic portal imaging device (EPID). Incoming x-ray photons deposit energy into the scintillator, which then generates photons via luminescence. These photons generate random polarization and direction vectors after the luminescence event and are transmitted throughout the scintillator, during which they can be reflected, refracted, and scattered. Eventually, many photons will cross the boundary between the scintillator and the photodiode array, be absorbed by the EPID's photodiodes, and be converted into an electrical current for readout and digitization. Although the technology is promising, performance can be suboptimal, and it is costly to cut the crystal scintillator into parallelepipeds and glue reflective spacers between them to reduce optical crosstalk.

[0004] In addition, in some cases, an x-ray imager (e.g., a diagnostic x-ray imager or a portal imager) may also include a scintillator coupled to a photodiode array. X-ray photons deposit energy in the scintillator, thereby generating photons with random directions and polarization vectors. A certain percentage of photons will pass through the scintillator, the photodiode boundary and deposit energy. The photodiode converts the photons into electron-hole pairs. After a sufficient amount of charge is collected, the signal is read out and digitized to form an image. In order to achieve a sufficiently high spatial resolution, optical blur needs to be minimized. This means that the photodiode signal associated with a given x-ray photon should be locally positioned to be laterally adjacent to the position where the x-ray photon interacts with the scintillator. A common approach to achieving this goal is by using a pixelated geometry that uses a reflective septum to limit the photons. Unfortunately, the manufacturing cost of this method is high and it is not very realistic to incorporate a large-area imager. Similarly, the process of cutting a crystal scintillator (e.g., Csl, CdWO4, BGO) into parallelepipeds, pasting reflective septa between them, and then combining pixels into a complete array can be very expensive. Another disadvantage of pixelated geometries is the loss of fill factor (and associated quantum efficiency) due to the finite thickness of the spacers.

[0005] Furthermore, the x-ray conversion efficiency of current amorphous silicon-based flat-panel imagers for megavoltage radiation is very low. Only about 1.3% of x-ray photons are used for imaging. In other words, more than 98% of the imaging dose is lost and not used for image formation. Approaches using thicker scintillators are either very expensive (because the scintillator must be pixelated) or must present very high imaging performance (due to the added blur). Summary of the invention

[0006] The imaging device includes: a first scintillator layer; an array of detector elements, wherein the array of detector elements includes first detector elements; and a second scintillator layer, configured to receive radiation after the radiation passes through the first scintillator layer and the array of detector elements, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer; and wherein the imaging device further includes: a first electrode, which is closer to the first scintillator than the second scintillator; and a second electrode, which is located between the second scintillator and the first detector element, wherein the second electrode is configured to allow light from the second scintillator layer to reach the first detector element; and / or a first neutral density filter located between the first scintillator layer and the first detector element and / or a second neutral density filter located between the second scintillator layer and the first detector element.

[0007] The imaging device includes: a first scintillator layer; an array of detector elements, wherein the array of detector elements includes a first detector element; a second scintillator layer, configured to receive radiation after the radiation passes through the first scintillator layer and the array of detector elements, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; a first electrode, located closer to the first scintillator than the second scintillator; and a second electrode, located between the second scintillator and the first detector element; wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer; and wherein the second electrode is configured to allow light from the second scintillator layer to reach the first detector element.

[0008] Optionally, the first electrode is located between the first scintillator and the first detector element, and wherein the first electrode is configured to allow light from the first scintillator layer to reach the first detector element.

[0009] Optionally, the second electrode is made of an opaque conductive material but is etched with a pattern to allow light to pass through the second electrode.

[0010] Optionally, the second electrode has a polygonal pattern.

[0011] Optionally, the first detector element has a first portion configured to generate a first electrical signal in response to light from the first scintillator layer and a second portion configured to generate a second electrical signal in response to light from the second scintillator layer.

[0012] Optionally, the first portion is a top side of the first detector element and the second portion is a bottom side of the first detector element.

[0013] Optionally, the first portion includes a first photodiode and the second portion includes a second photodiode, and wherein the first photodiode and the second photodiode form a side-by-side configuration.

[0014] Optionally, the second electrode is at least partially transparent to light.

[0015] Optionally, the second electrode includes a first opening to allow light from the second scintillator layer to pass through the first opening.

[0016] Optionally, the second electrode comprises a second opening.

[0017] Optionally, the first opening comprises a circular opening, a square opening, a rectangular opening or a slot.

[0018] Optionally, the second electrode has an annular configuration.

[0019] Optionally, the second electrode has a grid configuration, and the first opening is one of a plurality of grid holes.

[0020] Optionally, the second electrode comprises a chromium layer.

[0021] Optionally, the second electrode comprises ITO or another transparent conductor.

[0022] Optionally, the first detector element comprises a hardware component, and wherein the second electrode and the hardware component are in a side-by-side configuration.

[0023] Optionally, the second electrode comprises a conductor extending along at least a portion of a periphery of the second electrode and one or more optical openings surrounded by the periphery.

[0024] Optionally, the hardware component includes at least a portion of a thin film transistor (TFT).

[0025] Optionally, the second electrode further comprises one or more additional conductors extending within a space surrounded by the periphery of the second electrode.

[0026] Optionally, the imaging device further comprises a substrate, wherein the array of detector elements is secured to the substrate, wherein the substrate has a first side and an opposing second side, the first side being closer to the radiation source than the second side.

[0027] Optionally, the array of detector elements is closer to the first side of the substrate than to the second side, or vice versa.

[0028] Optionally, the first portion of the first detector element is closer to the first side of the substrate than the second portion.

[0029] Optionally, the thickness of the substrate is less than 2 mm.

[0030] Optionally, the imaging device further comprises a focusing element layer located between (1) the detector element array and (2) the first scintillator layer or the second scintillator layer.

[0031] Optionally, the first scintillator layer is non-pixelated, the second scintillator layer is non-pixelated, or both the first scintillator layer and the second scintillator layer are non-pixelated.

[0032] Optionally, one or both of the first scintillator layer and the second scintillator layer are pixelated.

[0033] Optionally, the imaging device further comprises an optical grid coupled to the first scintillator layer or the second scintillator layer.

[0034] Optionally, the imaging device further comprises a first optical grid coupled to the first scintillator layer and a second optical grid coupled to the second scintillator layer.

[0035] Optionally, the imaging device further includes a first plate coupled to the first scintillator layer and a second plate coupled to the second scintillator layer, wherein the first scintillator layer and the second scintillator layer are located between the first plate and the second plate.

[0036] Optionally, the imaging device further comprises a first neutral density filter located between the first scintillator layer and the first detector element and / or a second neutral density filter located between the second scintillator layer and the first detector element.

[0037] Optionally, the first neutral density filter and / or the second neutral density filter are configured to improve a signal-to-noise ratio of an imaging device.

[0038] Optionally, the signal-to-noise ratio of the imaging device is based on: (1) the corresponding quantum efficiency (QE1, QE2) of the first scintillator layer and the second scintillator layer, (2) the corresponding detection quantum efficiency (DQE1, DQE2) of the first scintillator layer and the second scintillator layer, (3) the corresponding optical yield (αl, α2) of the first scintillator layer and the second scintillator layer, (4) the optical sensitivity (p1, p2) of the first detector element associated with the first scintillator and the second scintillator, respectively, or (5) any combination of the above.

[0039] Optionally, the first electrical signal has a first characteristic value (e1), and the second electrical signal has a second characteristic value (e2); and wherein min(e1, e2) / max(e1, e2) is greater than a threshold value.

[0040] Optionally, the first characteristic value (e1) is a function of the quantum efficiency QE1 of the first scintillator layer, the optical yield αl of the first scintillator layer, and the optical sensitivity p1 of the first detector element associated with the first scintillator layer; and wherein the second characteristic value (e2) is a function of the quantum efficiency QE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

[0041] Optionally, the first characteristic value (e1) is a function of the detection quantum efficiency DQE1 of the first scintillator layer, the optical yield αl of the first scintillator layer, and the optical sensitivity p1 of the first detector element associated with the first scintillator layer; and wherein the second characteristic value (e2) is a function of the detection quantum efficiency DQE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

[0042] Optionally, the threshold is greater than 0.5.

[0043] Optionally, the threshold is greater than 0.7.

[0044] The imaging device includes: a first scintillator layer; a detector element array, wherein the detector element array includes a first detector element; a second scintillator layer, wherein the detector element array is located between the first scintillator layer and the second scintillator layer; and a first neutral density filter located between the first scintillator layer and the first detector element and / or a second neutral density filter located between the second scintillator layer and the first detector element; wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer.

[0045] Optionally, the first neutral density filter and / or the second neutral density filter are configured to improve a signal-to-noise ratio of an imaging device.

[0046] Optionally, the signal-to-noise ratio of the imaging device is based on (1) the corresponding quantum efficiencies (QE1, QE2) of the first scintillator layer and the second scintillator layer, (2) the corresponding detection quantum efficiencies (DQE1, DQE2) of the first scintillator layer and the second scintillator layer, (3) the corresponding optical yields (αl, α2) of the first scintillator layer and the second scintillator layer, (4) the optical sensitivities (p1, p2) of the first detector element associated with the first scintillator and the second scintillator, respectively, or (5) any combination of the above.

[0047] Optionally, the first electrical signal has a first eigenvalue (e1) and the second electrical signal has a second eigenvalue (e2); and wherein the first neutral density filter and / or the second neutral density filter is configured such that min(e1, e2) / max(e1, e2) is greater than a threshold.

[0048] Optionally, the first characteristic value (e1) is a function of the quantum efficiency QE1 of the first scintillator layer, the optical yield αl of the first scintillator layer, and the optical sensitivity p1 of the first detector element associated with the first scintillator layer; and wherein the second characteristic value (e2) is a function of the quantum efficiency QE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

[0049] Optionally, the first characteristic value (e1) is a function of the detection quantum efficiency DQE1 of the first scintillator layer, the optical yield αl of the first scintillator layer, and the optical sensitivity p1 of the first detector element associated with the first scintillator layer; and wherein the second characteristic value (e2) is a function of the detection quantum efficiency DQE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

[0050] Optionally, the threshold is greater than 0.5.

[0051] Optionally, the threshold is greater than 0.7.

[0052] Optionally, the second scintillator layer is configured to receive radiation after the radiation has passed through the array of detector elements.

[0053] Optionally, the imaging device further comprises a first electrode located between the first scintillator and the first detector element, wherein the first electrode is configured to allow light from the first scintillator layer to reach the first detector element.

[0054] Optionally, the imaging device further comprises a second electrode configured to allow light from the second scintillator layer to reach the first detector element.

[0055] Optionally, the first detector element has a first portion configured to generate a first electrical signal in response to light from the first scintillator layer and a second portion configured to generate a second electrical signal in response to light from the second scintillator layer.

[0056] Optionally, the first portion is a top side of the first detector element and the second portion is a bottom side of the first detector element.

[0057] Optionally, the first portion includes a first photodiode and the second portion includes a second photodiode, and wherein the first photodiode and the second photodiode form a side-by-side configuration.

[0058] Optionally, the second electrode is at least partially transparent to light.

[0059] Optionally, the second electrode includes a first opening to allow light from the second scintillator layer to pass through the first opening.

[0060] Optionally, the second electrode comprises a second opening.

[0061] Optionally, the first opening comprises a circular opening, a square opening, a rectangular opening or a slot.

[0062] Optionally, the second electrode has an annular configuration.

[0063] Optionally, the second electrode has a grid configuration, and the first opening is one of a plurality of grid holes.

[0064] Optionally, the second electrode comprises a chromium layer.

[0065] Optionally, the second electrode comprises ITO or another transparent conductor.

[0066] Optionally, the first detector element comprises a hardware component, and wherein the second electrode and the hardware component are in a side-by-side configuration.

[0067] Optionally, the second electrode comprises a conductor extending along at least a portion of a periphery of the second electrode and one or more optical openings surrounded by the periphery.

[0068] Optionally, the second electrode further comprises one or more additional conductors extending within a space surrounded by the periphery of the second electrode.

[0069] Optionally, the hardware component includes at least a portion of a thin film transistor (TFT).

[0070] Optionally, the imaging device further comprises a substrate, wherein the array of detector elements is secured to the substrate, wherein the substrate has a first side and an opposing second side, the first side being closer to the radiation source than the second side.

[0071] Optionally, the imaging device further comprises a focusing element layer located between (1) the detector element array and (2) the first scintillator layer or the second scintillator layer.

[0072] Optionally, the imaging device further comprises an optical grid coupled to the first scintillator layer or the second scintillator layer.

[0073] Optionally, the imaging device further comprises a first optical grid coupled to the first scintillator layer and a second optical grid coupled to the second scintillator layer.

[0074] Optionally, the imaging device further includes a first plate coupled to the first scintillator layer and a second plate coupled to the second scintillator layer, wherein the first scintillator layer and the second scintillator layer are located between the first plate and the second plate.

[0075] Optionally, the thickness of the substrate is less than 2 mm.

[0076] Other and further aspects and features will become apparent from a reading of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The accompanying drawings illustrate the design and utility of the embodiments, wherein the same elements are referred to by common reference numerals. These drawings are not necessarily drawn to scale. In order to better understand how to obtain the above and other advantages and purposes, a more specific description of the embodiments illustrated in the accompanying drawings will be presented. These drawings depict only exemplary embodiments and are therefore not to be considered as limiting the scope of the claims.

[0078] Figure 1 A radiation system with an imaging device according to some embodiments is illustrated.

[0079] Figure 2 An imaging device according to some embodiments is illustrated.

[0080] Figure 3 Detector elements according to some embodiments are illustrated.

[0081] Figure 4 Another detector element according to other embodiments is illustrated.

[0082] Figure 5A-5E Examples of electrodes in various embodiments are shown.

[0083] Figure 6 Another imaging device according to other embodiments is illustrated.

[0084] Figure 7 Another imaging device according to other embodiments is illustrated. DETAILED DESCRIPTION

[0085] Various embodiments are described below with reference to the accompanying drawings. It should be noted that the drawings are not drawn to scale, and throughout the drawings, elements of the same structure or function are represented by the same reference numerals. It should also be noted that these figures are only used to facilitate the description of the embodiments. They are not an exhaustive description of the invention, nor are they a limitation on the scope of the invention. Additionally, the illustrated embodiments do not need to have all the aspects or advantages shown. The aspects or advantages described in conjunction with a particular embodiment are not necessarily limited to that embodiment, and even if not illustrated, or not explicitly described, may also be practiced in any other embodiment.

[0086] Figure 1 A radiation therapy system 10 is illustrated. The system 10 includes an arm gantry 12, a patient support 14 for supporting a patient 20, and a control system 18 for controlling the operation of the arm gantry 12 and the delivery of radiation. The system 10 also includes: a radiation source 22, which projects a radiation beam 26 toward the patient 20 when the patient 20 is supported on the support 14; and a collimator system 24 for changing the cross-sectional shape of the radiation beam 26. In different embodiments, the radiation source 22 can be configured to generate a cone beam, a fan beam, or other types of radiation beams. In addition, in other embodiments, the source 22 can be configured to generate a proton beam, an electron beam, or a photon beam as a form of radiation for treatment purposes. In addition, in other embodiments, the system 10 can have other forms and / or configurations. For example, in other embodiments, the system 10 can have a ring gantry 12 instead of the arm gantry 12.

[0087] In the illustrated embodiment, the radiation source 22 is a therapeutic radiation source for providing therapeutic energy. In other embodiments, the radiation source 22, in addition to being a therapeutic radiation source, may also be a diagnostic radiation source for providing diagnostic energy for imaging purposes. In this case, the system 10 will include an imager (e.g., an imager 80) located at an operating position relative to the source 22 (e.g., below the support 14). In further embodiments, the radiation source 22 may be a therapeutic radiation source for providing therapeutic energy, wherein the therapeutic energy may be used to acquire an image. In this case, in order to acquire imaging using therapeutic energy, the imager 80 is configured to generate an image in response to the radiation having therapeutic energy (e.g., an MV imager). Moreover, in some embodiments, the imager 80 may be a portal imager configured to perform portal imaging. In some embodiments, the therapeutic energy is typically 160 kiloelectronvolts (keV) or higher, more typically 1 megaelectronvolt (MeV) or higher, and the diagnostic energy is typically those energies below the high energy range, more typically below 160keV. In other embodiments, the therapeutic energy and the diagnostic energy may have other energy levels. In some embodiments, the radiation source 22 is capable of generating x-ray radiation at multiple photon energy levels. For example, the accelerator can have an energy range of 1mv to 20mv, producing x-rays with an energy range of 10kV to 160kv. In other cases, the energy range can be between about 10kev to about 20Mev. In further embodiments, the radiation source 22 can be a diagnostic radiation source. In this case, the system 10 can be a diagnostic system with one or more moving parts. In the illustrated embodiment, the radiation source 22 is carried by the arm frame 12. Alternatively, the radiation source 22 can be located in a bore (e.g., coupled to a ring frame).

[0088] In the illustrated embodiment, control system 18 includes a processing unit 54 (e.g., a processor) coupled to controller 40. Control system 18 may also include a monitor 56 for displaying data and an input device 58 (e.g., a keyboard or mouse) for inputting data. Operation of radiation source 22 and gantry 12 is controlled by controller 40, which provides power and timing signals to radiation source 22 and controls the speed and position of gantry 12 based on signals received from processing unit 54. Although controller 40 is shown as a separate component from gantry 12 and processing unit 54, in alternative embodiments, controller 40 may be part of gantry 12 or processing unit 54.

[0089] In some embodiments, the system 10 can be a treatment system that is configured to deliver a therapeutic radiation beam toward a patient 20 at different gantry angles. During the treatment process, the source 22 rotates around the patient 20 and delivers the therapeutic radiation beam toward the patient 20 from different gantry angles. When the source 22 is at different gantry angles, the collimator 24 is operated to change the shape of the beam to correspond to the shape of the target tissue structure. For example, the collimator 24 can be operated so that the shape of the beam is similar to the cross-sectional shape of the target tissue structure. In another example, the collimator 24 can be operated so that different parts of the target tissue structure receive different amounts of radiation (e.g., during IMRT).

[0090] In different embodiments, imager 80 may have different configurations. Figure 2 An imaging device 200 according to some embodiments is illustrated. In some embodiments, the imaging device 200 can be used to implement the imager 80. As shown, the imaging device 200 includes a first scintillator layer 202 and a detector element array 204. In some embodiments, each detector element 204 can include one or more amorphous silicon (a:Si) detectors. The imaging device 200 also includes a second scintillator layer 206. As shown, the detector element array 204 is located between the first scintillator layer 202 and the second scintillator layer 206. The second scintillator layer 206 is configured to receive radiation after the radiation passes through the detector element array 204. The imaging device 200 also includes electrodes 210, 212, which are coupled to a corresponding one of the detector elements 204. Each detector element 204 is configured to generate a first electrical signal in response to light from the first scintillator layer 202, and to generate a second electrical signal in response to light from the second scintillator layer 206.

[0091] In the illustrated embodiment, each detector element 204 has a first electrode 210 electrically coupled thereto and a second electrode 212 coupled thereto. The first electrode 210 and the second electrode 212 are located on opposite sides of the detector element 204 and are configured to receive opposite charges of electron-hole pairs generated in the detector element 204 in response to detected light. In the illustrated embodiment, the second electrode 212 has a configuration for allowing light from the second scintillator layer 206 to reach the detector element 204. Furthermore, in some embodiments, the first electrode 210 also has a configuration for allowing light from the first scintillator layer 202 to reach the detector element 204. In some embodiments, the detector element 204 can be implemented using a photodiode. Furthermore, in some embodiments, the electrodes 210 and 212 can be considered as part of a photodiode, or as terminals separately coupled to a photodiode.

[0092] In some embodiments, the detector element 204 has a first portion configured to generate a first electrical signal in response to light 202 from the first scintillator layer and a second portion configured to generate a second electrical signal in response to light 206 from the second scintillator layer. In some cases, the first portion 240 is a top side 250 of the detector element 204 and the second portion 242 is a bottom side 252 of the detector element 204 ( Figure 3 In other cases, the first portion 240 and the second portion 242 may form a side-by-side configuration ( Figure 4 ).

[0093] Moreover, in some embodiments, the first portion may include a first photodiode element and the second portion may include a second photodiode element. In this specification, the term "photodiode element" refers to one or more circuit elements on a detector pixel that are associated with converting photon energy into an electrical signal. This includes, but is not limited to, (multiple) photodiodes, (multiple) switching transistors, (multiple) amplifying transistors, direct conversion elements, or combinations thereof. The first scintillator layer 202 and the second scintillator layer 206 are configured to receive radiation and generate photons in response to the radiation. The first photodiode element is configured to generate an electrical signal in response to photons provided from the first scintillator layer 202, and the second photodiode element is configured to generate an electrical signal in response to photons provided from the second scintillator layer 206. The electrical signal is then read out and digitized to form an image. In some embodiments, a circuit is provided that combines the signals from the first and second photodiode elements of each detector element 204 to form each pixel in the image.

[0094] In the illustrated embodiment, the electrode 212 is at least partially transparent to light. In some cases, the electrode 212 may include a first opening 260 to allow light from the second scintillator layer 206 to pass through ( Figure 5A ). In addition, in some embodiments, the electrode 212 may include a plurality of openings (e.g., a first opening and a second opening) to allow light from the second scintillator layer 206 to pass through. The first opening may include a circular opening, a square opening, a rectangular opening, or a slot. In some embodiments, the electrode 212 may have a ring configuration ( Figure 5B In further embodiments, the electrode 212 may have a grid configuration, and the opening 260 is one of a plurality of grid holes ( Figure 5C ). In some embodiments, Figure 5DAs shown, the electrode 212 can have a shape that accommodates the (multiple) components of the detector element 204. As shown, the electrode 212 is generally square, accommodating the (multiple) components 490 of the detector element 204 at the corners or (multiple) sides of the electrode 212. The (multiple) components 490 can be photodiodes or hardware components (e.g., at least a portion of a thin film transistor (TFT), a trace, a wire, a circuit, etc.). In other embodiments, the electrode 212 can have a rectangular, circular, hexagonal, or other custom shape. The electrode 212 is positioned near the (multiple) components 490 of the detector element 204 in a side-by-side configuration and defines an opening 260 that allows light to travel through. In some embodiments, the opening 260 can be a space without any material. In other embodiments, the opening 260 can be filled or covered by an optically transparent material, which can be conductive or non-conductive. In the embodiment shown, the electrode 212 has a conductor 500 (e.g., a wire or trace) extending along the perimeter of the electrode 212. In other embodiments, the conductor 500 may not extend around the entire perimeter of the electrode 212, but may extend partially around the perimeter to define an open loop of the electrode 212. Furthermore, in other embodiments, the electrode 212 may include additional conductor(s) 502 ( Figure 5E ).like Figure 5E As shown in the embodiment of FIG. 2 , the electrode 212 has additional conductors 502 extending in the same direction within the perimeter of the electrode 212. Such a configuration defines a plurality of openings 260 (e.g., slots) to allow light to pass through. In other embodiments, the electrode 212 may include additional conductors extending in other directions (e.g., in a horizontal direction to form a grid of holes with the vertical conductors 502).

[0095] It should be noted that the term "opening" (eg, opening 260) may refer to a space without any material that allows light to travel therethrough, or may refer to a material that has at least some optical transparency to allow light to travel therethrough.

[0096] Furthermore, in other embodiments, the electrode 212 may be made of a non-transparent conductive material but etched with a pattern to allow light to pass through. For example, the electrode may have a polygonal pattern, or any custom pattern etched to allow light to pass through.

[0097] In any of the embodiments described herein, the electrode 212 can include a chromium layer. Additionally, in some embodiments, the electrode 212 can include indium tin oxide (ITO) or another transparent conductor.

[0098] return Figure 2, the imaging device 200 further includes a glass substrate 220, wherein the detector element array 204 is fixed to the glass substrate 220. In the embodiment shown, the glass substrate 220 has a first side 222 and an opposite second side 224, wherein the first side 222 is closer to the radiation source than the second side 224. The thickness of the glass substrate 220 can be less than 2 mm, more preferably less than 1 mm, and even more preferably less than 0.7 mm. In addition, in some embodiments, the substrate 220 is greater than 0.1 mm or greater than 0.15 mm. In other embodiments, the thickness of the glass substrate 220 can be greater than 2 mm. In some embodiments, the detector element array 204 is located closer to the first side 222 of the glass substrate 220 than the second side 224. It has been found that any blurring effect (due to light traveling from the second scintillator layer 206 through the glass substrate 220 to the detector elements 204) is minimal or does not significantly reduce image quality. Therefore, the imaging device 200 does not require any optical filter to be coupled between the second scintillator layer 206 and the glass substrate 220 to improve image resolution. However, if improvement is desired, the imaging device 200 may include such an optical filter, or a kernel-based algorithm may be utilized to improve the resolution of images generated by the imaging device 200 .

[0099] In other embodiments, the substrate 220 may be made of other materials other than glass. For example, in other embodiments, the substrate 220 may be made of plastic.

[0100] In other embodiments, the detector element array 204 is located closer to the second side 224 of the glass substrate 220 than the first side 222. This configuration is advantageous because the detector elements 204 are in close proximity to the scintillator layer 206 so that photons exiting the scintillator layer 206 can be immediately received by the detector elements 204.

[0101] Furthermore, in some embodiments, a first portion of first detector element 204 is located closer to first side 222 of glass substrate 220 than second side 224, and a second portion of first detector element 204 is located closer to second side 224 of glass substrate 220 than first side 222. In other embodiments, both the first portion and the second portion of detector element 204 may be located closer to first side 222 of glass substrate 220 than second side 224. In further embodiments, both the first portion and the second portion of detector element 204 may be located closer to second side 224 of glass substrate 220 than first side 222.

[0102] The scintillator layers 202, 206 can be selectively selected to suit the desired imaging task. For example, the first scintillator layer 202 can be copper and Lanex TM, while the second scintillator layer 206 can be CdWO4, Csl or BGO, and vice versa. In addition, in some embodiments, GOS with copper stacking plates can also be used for the first scintillator layer 202, the second scintillator layer 206, or both. When implemented in the second scintillator layer 206, the stacking plate is positioned below the GOS. Scintillator options suitable for the first scintillator layer 202 and / or the second scintillator layer 206 include, but are not limited to, LKH-5, CdWO4, Csl, with or without stacking plates. The first scintillator layer 202 and the second scintillator layer 206 can be the same or different.

[0103] In some embodiments, the first scintillator layer 202 may be non-pixelated, the second scintillator layer 206 may be non-pixelated, or both the first scintillator layer 202 and the second scintillator layer 206 may be non-pixelated. In other embodiments, one or both of the first scintillator layer 202 and the second scintillator layer 206 may be pixelated.

[0104] When the imaging device 200 is used, the imaging device 200 is positioned so that the first scintillator layer 202 receives radiation from the radiation source before the second scintillator layer 206. The first scintillator layer 202 receives the radiation and generates photons in response to the received radiation. The photons are detected by the detector elements 204, and the detector elements 204 generate electrical signals (imaging signals) in response to the photons detected from the first scintillator layer 202. Part of the radiation is not absorbed by the first scintillator layer 202, passes through the detector elements 204 and the glass substrate 220 and reaches the second scintillator layer 206. The second scintillator layer 206 receives the radiation and generates photons in response to the received radiation. The photons from the second scintillator layer 206 travel in the opposite direction toward the radiation direction and reach the detector elements 204. The detector elements 204 generate electrical signals (imaging signals) in response to the photons detected by the corresponding detector elements 204. Therefore, each detector element 204 generates two electrical signals based on the photons from the first scintillator layer and the second layer of scintillator. The two electrical signals from each detector element 204 are combined, for example via circuitry, to form an image signal for an image pixel. The imaging signal may be transmitted to a device (eg, a processor) that determines an image based on the imaging signal and / or to a medium for storage.

[0105] In order to enable each detector element 204 to detect photons from both the first scintillator layer 202 and the second scintillator layer 206, the detector element 204 needs to be able to detect photons from two opposite directions. In some embodiments, the detector element 204 has a photodiode, which is configured to detect photons from two opposite directions. Alternatively, the detector element 204 may have a first photodiode to detect photons from the first scintillator layer 202, and a second photodiode to detect photons from the second scintillator layer 206. The first photodiode and the second photodiode may be arranged on the top side and the bottom side of the detector element 204, respectively. Therefore, in this embodiment, there are two photodiodes for each pixel, one of which is inverted. In addition, in order to allow photons from the second scintillator layer 206 to reach the detector element 204, the electrode 212 is configured to allow light to pass through. For example, the electrode 212 may have one or more openings (such as Figure 5A-5C 2 (shown) to allow light to pass through to reach the detector element 24. Additionally or alternatively, the electrode 212 can be made of ITO or a combination of ITO and other materials, so that the electrode 212 is at least partially transparent. Furthermore, alternatively or additionally, the electrode 212 can be implemented using a thin layer of chrome.

[0106] The above embodiments illustrate an inverted geometry, which has advantages because it increases the number of photons detected by the detector element 204. In addition, by adding the second scintillator layer 206, the conversion efficiency of the imaging device 200 is improved. Additionally, the above method of using scintillator layers on opposite sides of the detector element 204 significantly reduces artifacts and does not add significant cost. In addition, the above multi-scintillator layer method is superior to imaging devices using thick non-pixelated scintillators or thick pixelated scintillators. A thick scintillator layer without pixelation will blur the signal and thus reduce the image resolution. In addition to blurring, light generated on the upper part of the thick scintillator layer travels a longer distance and is more attenuated than light generated on the lower part of the thick scintillator layer. Therefore, efficiency does not scale with thickness. The above method of using two scintillator layers can be viewed as splitting the thick scintillator layer into two layers and placing the two scintillator layers on opposite sides of the detector element 204. This reduces blurring because the light has to travel a shorter distance, which reduces unnecessary light attenuation. In addition, as previously mentioned, thick pixelated scintillators will solve the light scattering problem in thick non-pixelated scintillators, but manufacturing large-area pixelated scintillators is very expensive. Adding the second scintillator layer 206 below the detector element 204 only increases the cost of the relatively inexpensive second scintillator layer 206. In some embodiments, the substrate 220 is configured to have a thinner thickness, which can reduce the distance that light travels from the scintillator layer 206 to the detector element 204, thereby reducing the blurring effect.

[0107] In any embodiments described herein, the imaging device 200 may not require any optical grid between the first scintillator layer 202 and the detector elements 204, and may not require any optical grid between the second scintillator layer 206 and the detector elements 204. In other embodiments, the imaging device 200 may also optionally include an optical grid coupled between the first scintillator layer 202 and the detector elements 204 and / or an optical grid coupled between the second scintillator layer 206 and the detector elements 204. The optical grid is configured to allow "on-angle" light generated by the second scintillator 206 to be transmitted toward the detector elements 204, while blocking "off-angle" light.

[0108] In some embodiments, the imaging device 200 may further include a focusing element layer 280 disposed between the detector element array 204 and the second scintillator layer 206 ( Figure 6 ). The focusing element layer 280 is configured to direct the light generated by the second scintillator 206 to the detector element 204, thereby improving the resolution of the image. The focusing element layer 280 may include an optical fiber array, a brightness enhancement film (BEF), an optical grid, an optical filter, or any optical device capable of conveying light rays (e.g., using Fresnel refraction and / or reflection). In other embodiments, a focusing element is not required, and the imaging device 200 does not include a focusing element between the detector element 204 and the second scintillator layer 206.

[0109] In some embodiments, the imaging device 200 may optionally further include a first plate 300 coupled to the first scintillator layer 202 and a second plate 302 coupled to the second scintillator layer 206, wherein the first scintillator layer 202 and the second scintillator layer 206 are disposed between the first plate 300 and the second plate 302. Figure 7 During use, radiation may interact with the first plate 300 and the second plate 302 (in addition to the first scintillator layer 202 and the second scintillator layer 206 ) to create photons for detection by the detector elements 204 .

[0110] One consideration for maximizing the signal-to-noise ratio (SNR) is to equalize the signals from the first scintillator layer 202 and the second scintillator layer 206. Signal detection theory suggests that the amplitude of the electronic signal from the scintillator on each side (after the light signal is converted by the photodiode) should be proportional to the detection quantum efficiency (DQE) of the scintillator on that side. For example, if the same scintillator with the same thickness is used for the top and bottom sides, but the photodiode efficiency on the bottom side is, for example, 1 / 2 of the efficiency on the top side, then a 1 / 2x neutral density filter can be placed between the top scintillator and the detector element 204 to equalize the signal, or at least bring them closer to each other. Alternatively, different scintillators with different optical yields can be used on the top and bottom sides.

[0111] In some embodiments, the first electrical signal (generated based on light from the first scintillator layer 202) may have a first eigenvalue (e1), and the second electrical signal (generated based on light from the second scintillator layer 206) may have a second eigenvalue (e2). The first eigenvalue and the second eigenvalue may be the first electronic signal amplitude and the second electronic signal amplitude, respectively. The ratio min(e1, e2) / max(e1, e2) may be greater than a threshold. For example, the threshold may be greater than 0.5, greater than 0.7, greater than 0.9, etc. In any example, the threshold may be less than or equal to 1.0. In some embodiments, by selecting appropriate materials and thicknesses for the first scintillator layer 202 and the second scintillator layer 206, such a ratio may be achieved to be lower than a specified threshold. In other embodiments, the imaging device 200 may also optionally include a first neutral density filter located between the first scintillator layer 202 and the first detector element and / or a second neutral density filter located between the second scintillator layer 206 and the first detector element. The first neutral density filter and / or the second neutral density filter may be configured to improve the signal-to-noise ratio of the imaging device. For example, the first neutral density filter and / or the second neutral density filter may be configured such that min(e1, e2) / max(e1, e2) is greater than a threshold value.

[0112] In some embodiments, the signal-to-noise ratio 202 of the imaging device is based on: (1) the corresponding quantum efficiencies (QE1, QE2) of the first scintillator layer 202 and the second scintillator layer 206, (2) the corresponding detection quantum efficiencies (DQE1, DQE2) of the first scintillator layer 202 and the second scintillator layer 206, (3) the corresponding optical yields (αl, α2) of the first scintillator layer 202 and the second scintillator layer 206, (4) the optical sensitivities (p1, p2) of the first detector element associated with the first scintillator 202 and the second scintillator 206, respectively, or (5) any combination of the foregoing.

[0113] Furthermore, in some embodiments, the first characteristic value (e1) may be a function of the quantum efficiency QE1 of the first scintillator layer 202, the optical yield α1 of the first scintillator layer 202, and the optical sensitivity p1 of the (multiple) detector elements associated with the first scintillator layer 202. And, the second characteristic value (e2) may be a function of the quantum efficiency QE2 of the second scintillator layer 206, the optical yield α2 of the second scintillator layer 206, and the optical sensitivity p2 of the (multiple) detector elements associated with the second scintillator layer 206.

[0114] In other embodiments, the first characteristic value (e1) may be a function of the detection quantum efficiency DQE1 of the first scintillator layer, the optical yield α1 of the first scintillator layer, and the optical sensitivity p1 of the (multiple) detector elements associated with the first scintillator layer. And, the second characteristic value (e2) may be a function of the detection quantum efficiency DQE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the (multiple) detector elements associated with the second scintillator layer.

[0115] It should be understood that the terms "first scintillator layer" and "second scintillator layer" do not necessarily refer to the top scintillator layer and the bottom scintillator layer, respectively. For example, in other cases, the first scintillator layer may refer to the bottom scintillator layer, and the second scintillator layer may refer to the top scintillator layer.

[0116] It should be understood that the imaging device 200 embodiments described herein are not limited to portal imagers and any embodiment of the imaging device 200 described herein can be used with diagnostic radiation beams. The imaging device 200 can be part of a treatment machine, part of an imaging machine, or both.

[0117] In the above embodiments, various features have been described with reference to medical imaging. In other embodiments, any or all of the features described herein can be implemented for security applications. For example, in some embodiments, any imaging device 200 described herein can be used for cargo screening.

[0118] Although specific embodiments have been shown and described, it should be understood that it is not intended to limit the claimed invention to the preferred embodiments, and it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the claimed invention. Therefore, the description and drawings should be regarded as illustrative rather than restrictive. The claimed invention is intended to cover alternatives, modifications and equivalents.

Claims

1. An imaging device, comprising: a first scintillator layer; an array of detector elements, wherein the array of detector elements comprises a first detector element; as well as a second scintillator layer configured to receive the radiation after the radiation has passed through the first scintillator layer and the array of detector elements, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer and to generate a second electrical signal in response to light from the second scintillator layer; and The imaging device further comprises: a first electrode closer to the first scintillator than the second scintillator; and a second electrode between the second scintillator and the first detector element, wherein the second electrode is configured to allow the light from the second scintillator layer to reach the first detector element; The second electrode is made of an opaque conductive material and includes an etched pattern or a first opening to allow the light from the second scintillator layer to pass through the pattern or the first opening to reach the first detector element. 2 . The imaging device of claim 1 , wherein the first electrode is between the first scintillator and the first detector element, and wherein the first electrode is configured to allow light from the first scintillator layer to reach the first detector element. 3 . The image forming apparatus according to claim 1 , wherein the second electrode has a polygonal pattern.

4. The imaging device of claim 1 , wherein the first detector element has: a first portion configured to generate the first electrical signal in response to the light from the first scintillator layer; and a second portion configured to generate the second electrical signal in response to the light from the second scintillator layer. 5 . The imaging device of claim 4 , wherein the first portion is a top side of the first detector element and the second portion is a bottom side of the first detector element.

6. The imaging device of claim 4, wherein the first portion includes a first photodiode and the second portion includes a second photodiode, and wherein the first photodiode and the second photodiode form a side-by-side configuration.

7. The imaging device of claim 1, wherein the second electrode is at least partially transparent to light.

8. The imaging device according to claim 1, wherein the second electrode includes a second opening. 9 . The imaging device according to claim 1 , wherein the first opening comprises a circular opening, a square opening, a rectangular opening, or a slot.

10. The imaging device according to claim 1, wherein the second electrode has a ring-shaped configuration. 11 . The imaging device according to claim 1 , wherein the second electrode has a grid configuration, and the first opening is one grid hole among a plurality of grid holes.

12. The image forming apparatus according to claim 1, wherein the second electrode comprises a chromium layer.

13. The imaging device of claim 1, wherein the second electrode comprises ITO or another transparent conductor.

14. The imaging device of claim 1, wherein the first detector element comprises a hardware component, and wherein the second electrode and the hardware component are in a side-by-side configuration.

15. The imaging device of claim 14, wherein the second electrode comprises a conductor extending along at least a portion of a periphery of the second electrode, and one or more optical openings surrounded by the periphery, the first opening being one of the one or more optical openings.

16. The imaging device of claim 15, wherein the second electrode further comprises one or more additional conductors extending within a space surrounded by the periphery of the second electrode.

17. The imaging device of claim 14, wherein the hardware component comprises at least a portion of a thin film transistor (TFT).

18. The imaging device of claim 1 further comprising a substrate, wherein the array of detector elements is secured to the substrate, wherein the substrate has a first side and an opposing second side, the first side being closer to a radiation source than the second side.

19. The imaging device of claim 18, wherein the array of detector elements is closer to the first side of the substrate than to the second side, or vice versa.

20. The imaging device of claim 18, wherein the first portion of the first detector element is closer to the first side of the substrate than to the second side.

21. The imaging device of claim 18, wherein the thickness of the substrate is less than 2 mm.

22. The imaging device of claim 1, further comprising a layer of focusing elements located between (1) the array of detector elements and (2) the first scintillator layer or the second scintillator layer.

23. The imaging device of claim 1, wherein the first scintillator layer is non-pixelated, the second scintillator layer is non-pixelated, or both the first scintillator layer and the second scintillator layer are non-pixelated.

24. The imaging device of claim 1, wherein one or both of the first scintillator layer and the second scintillator layer are pixelated.

25. The imaging device of claim 1, further comprising an optical grid coupled to the first scintillator layer or the second scintillator layer.

26. The imaging device of claim 1, further comprising a first optical grid coupled to the first scintillator layer, and a second optical grid coupled to the second scintillator layer.

27. The imaging device of claim 1, further comprising a first plate coupled to the first scintillator layer, and a second plate coupled to the second scintillator layer, wherein both the first scintillator layer and the second scintillator layer are between the first plate and the second plate.

28. An imaging device according to claim 1, wherein the signal-to-noise ratio of the imaging device is based on: (1) the corresponding quantum efficiencies (QE1, QE2) of the first scintillator layer and the second scintillator layer, (2) the corresponding detection quantum efficiencies (DQE1, DQE2) of the first scintillator layer and the second scintillator layer, (3) the corresponding optical yields (α1, α2) of the first scintillator layer and the second scintillator layer, (4) the optical sensitivities (p1, p2) of the first detector element associated with the first scintillator and the second scintillator, respectively, or (5) a combination of any of the above.

29. The imaging device according to claim 1, wherein the first electrical signal has a first characteristic value (e1), and the second electrical signal has a second characteristic value (e2); and wherein min(e1, e2) / max(e1, e2) is greater than a threshold value.

30. The imaging device of claim 29, wherein the first characteristic value (e1) is a function of a quantum efficiency QE1 of the first scintillator layer, an optical yield α1 of the first scintillator layer, and an optical sensitivity p1 of the first detector element associated with the first scintillator layer; and Therein the second characteristic value (e2) is a function of the quantum efficiency QE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

31. The imaging device of claim 29, wherein the first characteristic value (e1) is a function of a detection quantum efficiency DQE1 of the first scintillator layer, an optical yield α1 of the first scintillator layer, and an optical sensitivity p1 of the first detector element associated with the first scintillator layer; and The second characteristic value (e2) is a function of the detection quantum efficiency DQE2 of the second scintillator layer, the optical yield α2 of the second scintillator layer, and the optical sensitivity p2 of the first detector element associated with the second scintillator layer.

32. The imaging device of claim 29, wherein the threshold is greater than 0.

5.

33. The imaging device of claim 29, wherein the threshold is greater than 0.7.

Images