Dual-screen digital radiography with asymmetric reflective screens

Abstract

To provide a structure in application to digital radiographic imaging in which the quality of the images produced in the digital radiographic imaging is affected by various phenomena, such as light scattering.SOLUTION: A structure operable to detect radiation is described. The structure may include a first screen of a first thickness and a second screen of a second thickness greater than the first thickness. The structure may further include a photosensor array disposed between the first screen and the second screen. A back side of the first screen may face incident radiation directed toward the structure. The first screen may include a first reflective layer that may reflect the light photons scattered among the first screen toward the photosensor array. The second screen may face the photosensor array such that the first screen and the second screen are oriented in opposite directions. The second screen may include a second reflective layer that may reflect the light photons that passed through the photosensor array toward the photosensor array.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross-reference to related applications. This application claims priority to U.S. Provisional Application No. 62 / 540,620, filed Aug. 3, 2017, and U.S. Provisional Application No. 62 / 711,883, filed Jul. 30, 2018.

[0002] This application generally relates to radiation detectors and digital radiography.

Background Art

[0003] In digital radiography, an imaging system may include a screen that absorbs radiation and generates light. The generated light is sensed by an array of light sensors to generate an electrical signal. The generated electrical signal is used by the imaging system to generate a digital image. In some examples, the quality of the generated image (e.g., sharpness, resolution, etc.) is affected by various phenomena such as light scattering.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In some examples, structures generally applicable to digital radiography are described.

Means for Solving the Problems

[0005] The structure may include a first screen having a first thickness and a second screen having a second thickness greater than the first thickness. The structure may further include a photosensor array disposed between the first screen and the second screen. The first screen is oriented to face the photosensor array, whereby the back surface of the first screen may face the incident radiation directed towards the structure. The first screen may include a first phosphor layer that converts the incident radiation directed towards the structure into photons. The first screen may further include a first reflective layer disposed on the back surface of the first screen. The first reflective layer may reflect the photons scattered in the first phosphor layer towards the photosensor array. The second screen is oriented to face the photosensor array, whereby the first screen and the second screen may be oriented in opposite directions. The second screen may include a second phosphor layer. The second screen may further include a second reflective layer disposed on the back surface of the second screen. The second reflective layer may reflect the photons that have passed through the photosensor array back towards the photosensor array. The photosensor array may be operable to capture photons and convert the captured photons into an electrical signal.

[0006] In some examples, an imaging system is generally described. The imaging system can include a processor configured to communicate with a structure. The structure can include a first screen having a first thickness and a second screen having a second thickness greater than the first thickness. The structure can further include an optical sensor array disposed between the first screen and the second screen. The first screen is oriented to face the optical sensor array, whereby the back surface of the first screen can face the incident radiation directed towards the structure. The first screen can include a first phosphor layer that converts the incident radiation directed towards the structure into photons. The first screen can further include a first reflective layer disposed on the back surface of the first screen. The first reflective layer can reflect the photons scattered in the first phosphor layer towards the optical sensor array. The second screen is oriented to face the optical sensor array, whereby the first screen and the second screen can be oriented in opposite directions. The second screen can include a second phosphor layer. The second screen can further include a second reflective layer disposed on the back surface of the second screen. The second reflective layer can reflect the photons that have passed through the optical sensor array back towards the optical sensor array. The optical sensor array can be operable to capture photons and convert the captured photons into an electrical signal. The processor can be configured to receive the electrical signal from the structure and generate an image using the electrical signal.

[0007] In some examples, an X-ray apparatus is generally described. The apparatus can include a radiation detector, an X-ray radiation source, and a processor. The X-ray radiation source can be operable to irradiate an object disposed between the X-ray radiation source and the radiation detector with X-rays. The radiation detector can include a first screen having a first thickness and a second screen having a second thickness greater than the first thickness. The radiation detector can further include an optical sensor array disposed between the first screen and the second screen. The first screen is oriented to face the optical sensor array, whereby the back surface of the first screen can face the X-rays irradiated on the radiation detector. The first screen can include a first phosphor layer that converts X-rays into photons. The first screen can further include a first reflective layer disposed on the back surface of the first screen. The first reflective layer can reflect photons scattered in the first phosphor layer toward the optical sensor array. The second screen is oriented to face the optical sensor array, whereby the first screen and the second screen can be oriented in opposite directions. The second screen can include a second phosphor layer. The second screen can further include a second reflective layer disposed on the back surface of the second screen. The second reflective layer can reflect photons that have passed through the optical sensor array back toward the optical sensor array. The optical sensor array can be operable to capture photons and convert the captured photons into an electrical signal. The processor can be configured to input the electrical signal from the radiation detector and generate an image of the object using the electrical signal.

[0008] In addition to the structures and operations of the various embodiments, further features are described in detail below with reference to the accompanying drawings. In the drawings, like reference numerals indicate identical or functionally similar elements.

Brief Description of the Drawings

[0009]

Figure 1

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Mode for Carrying Out the Invention

[0010] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In describing the invention, in order to clarify the understanding of the concept of the invention and avoid unnecessary details from obscuring the invention, related functions or structures widely known in the art are omitted.

[0011] In the application of digital radiography, an active matrix indirect flat panel imager (AMFPI) can be used. In some examples, the AMFPI can include a single intensifying screen and can be created by placing a sensor array (e.g., a thin film transistor array) under the intensifying screen. Thereby, the AMFPI can operate by allowing X-rays to be incident from above the intensifying screen. The thickness of the single intensifying screen can be based on a trade-off between X-ray absorption rate and spatial resolution. For example, increasing the thickness can improve the absorption rate and sensitivity, but can also cause a decrease in resolution due to light scattering in the phosphor layer of the intensifying screen.

[0012] In screen-film radiography, a dual screen system can include a dual emulsion film disposed between two partitions divided from a single intensifying screen. Such a configuration can reduce light scattering because the distance between the incident radiation and the film is shortened, but can cause a crossover phenomenon where photons penetrate the film emulsion and are reflected from the opposite partition.

[0013] As will be further described below, the structures according to the present disclosure (e.g., the structure 100 of FIG. 1) can address some of the drawbacks of various digital radiography systems and film-screen radiography systems.

[0014] FIG. 1 shows an example of a structure 100 that can be utilized to implement dual-screen digital radiography with an asymmetric reflection screen, arranged in accordance with at least a portion of the embodiments described herein. The structure 100 can include a first screen 110, a second screen 120, an optical sensor array 105, and a substrate 107. The first screen 110 can be oriented such that the back surface of the first screen faces the incident radiation (e.g., incident X-ray 102) directed towards the structure 100. The optical sensor array 105 can be disposed between the first screen 110 and the second screen 120. The first screen 110 and the second screen 120 can be oriented in opposite directions such that the first screen 110 and the second screen 120 face each other. In the orientation of the structure 100 shown in FIG. 1, the back surface of the first screen 110 can be the upper surface of the structure 100, and the back surface of the second screen 120 can be the bottom surface of the structure 100. The thickness of the screen 110 in FIG. 1 can be smaller than the thickness of the second screen 120. The first screen 110 can be disposed on top of the optical sensor array 105 such that the incident X-ray 102 is incident on the first screen 110. In some examples, since the thickness of the first screen 110 is smaller than the thickness of the second screen 120, the first screen 110 can be disposed on top of the optical sensor array 105.

[0015] Screen 110 may include a scintillation phosphor layer 114 and a reflective layer 112. Here, the reflective layer 114 can be made of a material with a high reflectivity. Screen 120 may include a scintillation phosphor layer 122 and a reflective layer 124. Here, the reflective layer 124 can be made of a material with a high reflectivity. For example, the reflective layers 114, 124 may be coated with a layer of a white material such as titanium dioxide. The sizes of the reflective layers 114, 124 may be the same or different, and the coating materials of the reflective layers 114, 124 may be the same or different. Each of the phosphor layers 114, 124 may include phosphor crystals capable of capturing the incident X-rays 102 and converting the captured X-rays into photons. In some examples, the thickness of the phosphor layer 114 is smaller than the thickness of the phosphor layer 124, whereby the screen 110 can be thinner than the screen 120. In some examples, the screens 110, 120 can each be of a granular type (e.g., Gd02S2:Tb) or cylindrical (e.g., CsI:TI), or a combination of both. In some examples, to enhance the structural stability, an additional support for the thicker screen (e.g., screen 120) may optionally be disposed under the reflective layer 122.

[0016] The optical sensor array 105 may include a photosensitive storage element 108 that may include a plurality of switching elements 106. The substrate 107 may be disposed between the optical sensor array 105 and the phosphor layer 124 with a small optical thickness. The photosensitive storage element 108 and the switching element 106 may be disposed on the upper surface of the substrate 107. The optical sensor array 105 may be an a-Si:H n-i-p photodiode, a MIS type, or other type. The optical sensor array 105 is sensitive to light incident from any surface and may have a low transmittance at the wavelengths emitted by the screens 110, 120. For example, the optical sensor array 105 may have a high light absorption rate (90% or more) at the wavelengths of the light emitted by the screens 110, 120 so that the effects of pixel crosstalk and crossover can be reduced. In one example, the substrate 107 may be a thin glass, plastic, or cellulose with a thickness of less than 30 microns, preferably less than 10 microns. The optical sensor array 105 can capture photons and convert the captured photons into electrical signals, and the electrical signals can be used by a device (separate from the structure 100) to generate a digital image. For example, each switching element 106 corresponds to a pixel of an image, and by switching specific columns, rows, and pixel groups, a group of pixel values can be read out to generate an image.

[0017] In one example, the structure 100 can be a component of an imaging system that generates an image. In operation, the phosphor layer 114 can receive the incident X-ray 102 and convert the incident X-ray 102 into light. When the converted light reaches the photosensor array 105, the photosensor array 105 can capture photons from the converted light and convert the photons into an electrical signal. In the example shown in FIG. 1, when the incident X-ray 102 reaches the phosphor layer 114, the crystals in the phosphor layer 114 can convert the X-ray into photons 140. The photons 140 can scatter within the phosphor layer 114. A portion of the scattered photons can be directed towards the photosensor array 105, and other scattered photons can be directed away from the photosensor array 105. The reflective layer 112 can reflect the scattered photons towards the photosensor array 105 so that the photosensor array 105 can capture the scattered photons.

[0018] In some examples, the incident X-ray 102 may not be completely captured by the phosphor layer 114 (e.g., the phosphor layer 114 may not have enough crystals to convert all the incident X-rays). The un-captured X-rays pass through the photosensor array 105, and the crystals in the phosphor layer 124 of the second screen 120 convert the captured X-rays into photons 150. The photons 150 can scatter within the phosphor layer 124. A portion of the scattered photons can be directed towards the photosensor array 105, and other scattered photons can be directed away from the photosensor array 105. The reflective layer 122 can reflect the scattered photons towards the photosensor array 105 so that the photosensor array 105 can capture the scattered photons. Thus, the second screen 120 facilitates recapturing photons from the reflected light of the screen 110 that were not absorbed by the photosensor array 105.

[0019] In some examples, the light converted from the upper screen 110 (facing the incident X-rays) can be weighted by adjusting the optical properties of the photosensor array 105. The light from the screen 110 may contain more information from the low-energy portion of the incident X-ray spectrum due to the effects of beam hardening. Also, by emphasizing this, the visibility of low-contrast objects in the image generated by the imaging system utilizing the structure 100 can be improved.

[0020] In one example, the process is implemented by a computer device or a hardware processor to construct the structure 100. Also, the process can start with the step of performing a radiography inspection to determine the beam quality or the half-value layer (HVL) of the phosphor layers 114, 124. Next, using a mathematical model, performance metrics such as the signal-to-noise ratio (SNR), modulation transfer function (MTF), etc. can be determined as a function of the ratio of the weights or thicknesses of the coatings of the two screens 110, 120. Thereafter, based on the results of the radiography inspection and the performance metrics, the thickness ratio of the phosphor layers 114, 124 that can provide ideal performance in the desired implementation of the structure 100 is selected.

[0021] For example, in order to maximize the detective quantum efficiency (DQE) of an imaging system that utilizes structure 100, the thicknesses of the two scintillation phosphor layers 114, 124 can be selected. DQE is the output signal-to-noise ratio (SNR) per input quantum, and DQE depends on the spatial frequency and the X-ray exposure level. The basic limitation of DQE performance is given by the product of the X-ray absorption rate and the following two noise factors. One quantizes the variation in the magnitude of the response to absorption events (Swank factor), and the other quantifies the variation in the spatial response to events (Lubberts factor). The Lubberts factor indicates a decrease in DQE due to the variation in the spatial spread of light caused by X-ray absorption events occurring at various distances from the photosensor array. In an example of maximizing the detective quantum efficiency, the thinner (smaller thickness) of the two scintillation phosphor layers 114, 124 can be selected to be between 30% and 45% of the total thickness of the two scintillation phosphor layers 114, 124.

[0022] In some examples, the thicknesses of the two scintillation phosphor layers 114, 124 can be selected to maximize the modulation transfer function (MTF) of the imaging system that utilizes structure 100. To maximize the MTF, the thinner of the two scintillation screens is selected to be between 20% and 40% of the total thickness of the scintillation layers.

[0023] In one example, structure 100 is a component of an imaging system. The imaging system can include structure 100, a processor, and a memory that are configured to communicate with each other. The first screen 110 of structure 100 can receive incident X-rays 102 and convert the incident X-rays into photons. The reflective layer 114 can reflect photons scattered within the first phosphor layer 112 toward the photosensor array 105. The reflective layer 124 of the second screen 120 can reflect photons that have passed through the photosensor array 105 back toward the photosensor array 105. The photosensor array 105 can convert the captured photons into electrical signals and output the electrical signals to the processor. The processor can store the electrical signals in the memory and generate an image using the electrical signals.

[0024] In one example, the structure 100 can be a radiation detector in a device that includes an x-ray source and a processor. The x-ray source can be an x-ray tube that generates x-rays, or other device that can generate x-rays. An object, such as a subject, can be disposed between the x-ray source and the structure 100. The x-ray source irradiates the object with x-rays, and the object can absorb a portion of the x-rays, causing attenuation of the x-rays. The attenuated x-rays can be directed towards the structure 100 as incident x-rays 102. The first screen 110 of the structure 100 can receive the incident x-rays 102 and convert the incident x-rays into photons. The reflective layer 114 can reflect photons scattered within the first phosphor layer 112 towards the photosensor array 105. The reflective layer 124 of the second screen 120 can reflect light that has passed through the photosensor array 105 back towards the photosensor array 105. The photosensor array 105 can capture the photons and convert the captured photons into an electrical signal. The processor can receive the electrical signal from the radiation detector and be operable to generate an image of the object using the electrical signal.

[0025] FIG. 2 shows an example of a structure 200 that can be utilized to implement dual-screen digital radiography with an asymmetric reflective screen, arranged in accordance with at least a portion of the embodiments described herein. FIG. 2 may be described below with reference to FIG. 1 and the above description.

[0026] The structure 200 can include a first screen 110, a second screen 120, a photosensor array 205, and an optical fiber plate 202. The photosensor array 205 can include a photosensitive storage element 108 that includes a plurality of switching elements 106. The optical fiber plate 202 can have an optical thickness that is substantially 0, such as a negligible optical thickness and a physical thickness of 1 to 3 mm. In some examples, the numerical aperture of the optical fibers of the optical fiber plate 202 can be relatively large.

[0027] Figure 3 shows graphs of the Lubberts factor and DQE of an imaging system that utilizes a dual screen structure (structures 100 and / or 200) with a white backing (e.g., reflective layers 112, 122) and a resolution of 5 lp / mm (line pairs per millimeter).

[0028] In graph 302, the total thickness of the two screens of the dual screen structure is 160 microns (0.160 mm). Here, the back surface (the surface including reflective layer 112) of the thinner screen (the first screen 110) is at the 0 micron position, and the back surface (the surface including reflective layer 114) of the thicker screen (the second screen 120) is at the 160 micron position. As shown in graph 302, the optimal DQE point is 0.06 mm. That is, the optimal position of the photosensor array (e.g., photosensors 105, 205) with respect to the total thickness is a position 0.06 mm (60 microns) away from the 0 micron point, or the back side of the thinner screen where the incident X-rays are received. When the photosensor array is placed at the 0.06 mm point, the thickness ratio of the two screens that maximizes DQE is approximately 37%.

[0029] In Figure 3, graph 304 shows the Lubberts factor, DQE, and Swank factor of an imaging system that uses a dual screen structure (structures 100, 200, 300, etc.) without a reflective layer. As shown in graph 304, the DQE is lower than the DQE shown in graph 302. This indicates that including a reflective layer increases the DQE of the imaging system. The Lubberts factor indicates a decrease in DQE due to the change in the spatial spread of light resulting from X-ray absorption events that occur at various distances from the photosensor array.

[0030] Figure 4 shows an example of performance measurement results for dual screen digital radiography with an asymmetric reflective screen arranged according to at least some of the embodiments described herein. Figure 4 below may be described with reference to the above descriptions of Figures 1 - 3.

[0031] Graph 402 shows some calculation results when a single intensifying screen is subdivided into two parts with different relative thicknesses and the light sensor array at different positions shown on the x-axis of Graph 402 is sanded. Similar to the example in FIG. 3, the dual screen structure (e.g., structure 100 and / or 200) regarding Graph 402 includes a white backing (reflective layers 112, 122) and a resolution of 5 lp / mm (line pairs per millimeter). The total thickness of the two screens is 160 microns. An incident X-ray beam of 70 kVp, RQA5 is incident from the left. The MTF and the normalized noise power spectrum (NNPS) are shown in Graph 402 for each configuration. The optimal MTF point is 0.04 mm. That is, the optimal position of the light sensor array (e.g., the light sensor arrays 105, 205 described above) relative to the total thickness is a position 0.04 mm (40 microns) away from the 0 micron point, or the back of the thinner screen that is receiving the incident X-ray. The thickness ratio of the two screens for maximizing the MTF by making the light sensor array 0.06 mm is about 25%.

[0032] FIG. 5 shows the difference between the standard configuration of an X-ray detector and the dual screen configuration described in the present disclosure. As shown in FIG. 5, the standard configuration includes one scintillator and the glass substrate is the bottommost layer of the detector. In the dual screen configuration, another screen ("screen 2") thicker than the upper screen ("screen 1") under the glass substrate is added, and there is reflective backing on both the upper screen and the lower screen.

[0033] FIG. 6 shows experimental results suggesting the difference in MTF between the standard or conventional one-screen configuration and the dual screen configuration described in the present disclosure. As shown in FIG. 6, the modeled MTF of the dual screen configuration is greater than the modeled MTF of the conventional configuration in both the high-sensitivity configuration and the high-resolution configuration. Also, as shown in FIG. 6, the measured MTF of the dual screen configuration is greater than the measured MTF of the conventional configuration in both the high-sensitivity configuration and the high-resolution configuration.

[0034] Figure 7 shows the experimental results suggesting the difference in DQE between the normal single-screen configuration and the dual-screen configuration described in the present disclosure. The experimental results shown in Figure 7 are based on experiments using the RQA9 incident X-ray beam. As shown in Figure 7, the measured DQE of the dual-screen configuration is larger than that of the conventional configuration.

[0035] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to limit the present invention. When used in this specification, the singular forms "a" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, when used in this specification, the terms "comprising" and / or "including" specify the presence of the specified functions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other functions, integers, steps, operations, elements, and / or components.

[0036] In the following claims, if there are corresponding multiple structures, materials, acts, etc. of steps and functional elements, they are intended to include any structure, material, or act for performing the function in combination with other specifically claimed claim elements. The description of the present invention is presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications suitable for the intended particular uses.

Claims

1. a first screen having a first thickness; a second screen having a second thickness greater than the first thickness; a photosensor array disposed between the first screen and the second screen; A structure comprising: the first screen is oriented toward the photosensor array such that a rear surface of the first screen faces incident radiation directed toward the structure; The first screen comprises: a first phosphor layer for converting the incident radiation directed at the structure into photons; a first reflective layer disposed on a back surface of the first screen, the first reflective layer reflecting the photons scattered in the first phosphor layer towards the photosensor array; Equipped with the second screen is oriented to face the photosensor array such that the first screen and the second screen are oriented in opposite directions; The second screen comprises: a second phosphor layer; and a second reflective layer disposed on a back surface of the second screen, the second reflective layer reflecting the photons that have passed through the photosensor array back towards the photosensor array; and Equipped with the photosensor array captures the photons and converts the captured photons into an electrical signal; structure.

2. the photosensor array comprises a photosensitive storage element including a plurality of switching elements; The structure of claim 1.

3. a substrate disposed between the photosensor array and the second phosphor layer. The structure of claim 1.

4. the substrate being one of glass, plastic, and cellulose; The structure of claim 3.

5. a fiber optic plate disposed between the photosensor array and the second phosphor layer. The structure of claim 1.

6. a ratio of the first thickness to the second thickness maximizes a detection quantum efficiency of an imaging system utilizing the structure. The structure of claim 1.

7. a ratio of the first thickness to the second thickness that maximizes a modulation transfer function of an imaging system utilizing the structure. The structure of claim 1.

8. 1. An imaging system comprising a processor configured to communicate with a structure, the imaging system comprising: The structure comprises: a first screen having a first thickness; a second screen having a second thickness greater than the first thickness; a photosensor array disposed between the first screen and the second screen; Equipped with the first screen is oriented toward the photosensor array such that a rear surface of the first screen faces incident radiation directed toward the structure; The first screen comprises: a first phosphor layer for converting the incident radiation directed at the structure into photons; a first reflective layer disposed on a back surface of the first screen, the first reflective layer reflecting the photons scattered in the first phosphor layer towards the photosensor array; Equipped with the second screen is oriented to face the photosensor array such that the first screen and the second screen are oriented in opposite directions; The second screen comprises: a second phosphor layer; and a second reflective layer disposed on a back surface of the second screen, the second reflective layer reflecting the photons that have passed through the photosensor array back towards the photosensor array; and Equipped with the photosensor array captures the photons and converts the captured photons into an electrical signal; The processor, inputting the electrical signal from the structure; and configured to generate an image using the electrical signals; Imaging system.

9. the photosensor array comprises a photosensitive storage element including a plurality of switching elements; 9. The imaging system of claim 8.

10. a substrate disposed between the photosensor array and the second phosphor layer.

9. The imaging system of claim 8.

11. the substrate being one of glass, plastic, and cellulose; 11. The imaging system of claim 10.

12. a fiber optic plate disposed between the photosensor array and the second phosphor layer.

9. The imaging system of claim 8.

13. a ratio of the first thickness to the second thickness maximizes a detection quantum efficiency of an imaging system utilizing the structure.

9. The imaging system of claim 8.

14. a ratio of the first thickness to the second thickness that maximizes a modulation transfer function of an imaging system utilizing the structure.

9. The imaging system of claim 8.

15. A radiation detector; an x-ray source operable to emit x-rays at an object disposed between said x-ray source and said radiation detector; A processor; An apparatus comprising: The radiation detector comprises: a first screen having a first thickness; a second screen having a second thickness greater than the first thickness; a photosensor array disposed between the first screen and the second screen; Equipped with the first screen is oriented toward the photosensor array such that a rear surface of the first screen faces the x-rays emitted toward the radiation detector; The first screen comprises: a first phosphor layer that converts the x-rays directed at the structure into photons; a first reflective layer disposed on a back surface of the first screen, the first reflective layer reflecting the photons scattered in the first phosphor layer towards the photosensor array; Equipped with the second screen is oriented to face the photosensor array such that the first screen and the second screen are oriented in opposite directions; The second screen comprises: a second phosphor layer; and a second reflective layer disposed on a back surface of the second screen, the second reflective layer reflecting the photons that have passed through the photosensor array back towards the photosensor array; and Equipped with the photosensor array captures the photons and converts the captured photons into an electrical signal; The processor, inputting the electrical signal from the radiation detector; and configured to generate an image of the object using the electrical signals. Device.

16. the photosensor array comprises a photosensitive storage element including a plurality of switching elements; 16. The apparatus of claim 15.

17. a substrate disposed between the photosensor array and the second phosphor layer.

16. The apparatus of claim 15.

18. a fiber optic plate disposed between the photosensor array and the second phosphor layer.

16. The apparatus of claim 15.

19. a ratio of the first thickness to the second thickness maximizes a detection quantum efficiency of an imaging system utilizing the structure.

16. The apparatus of claim 15.

20. a ratio of the first thickness to the second thickness that maximizes a modulation transfer function of an imaging system utilizing the structure.

16. The apparatus of claim 15.

Images