Dual-layer detector system and method for spectral imaging and contrast-enhanced digital breast tomosynthesis - Patent Application 20070123333

Abstract

A structure and method operable to detect radiation are described. The structure includes a dual layer detector imaging device that allows for one shot of x-rays for dual energy imaging. In one embodiment, the front layer of the detector includes a photon counting detector and the rear layer of the detector includes an energy integrating detector including a scintillating phosphor screen. In a further embodiment, the front detector layer includes a direct conversion x-ray detector and the second rear detector layer includes an indirect conversion x-ray detector. The imaging system further includes a spatial separation filter disposed proximate to the x-ray radiation source for absorbing x-ray radiation to separate the radiation into a low energy component for incidence on the imaging object and a high energy component. In one embodiment, the imaging object includes a contrast agent material having a characteristic K-edge atomic energy band level, and the separation filter absorbing x-ray radiation is close to the K-edge atomic energy band level.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 154,879, filed March 1, 2021, which is incorporated by reference herein in its entirety.

[0002] This application relates generally to radiation detectors and digital radiography and 3D digital breast imaging. [Background technology]

[0003] In digital radiography, the imaging system may include a flat panel detector (FPD) that includes a collection of layers such as a scintillator screen that absorbs radiation and generates pulses of visible light upon x-ray absorption, a pixelated array of photosensors, e.g., photodiodes (where the generated light is sensed), and a thin film transistor array to generate an electrical signal. The generated electrical signal may be used by the imaging system to generate a digital image. In some examples, the quality (e.g., sharpness, resolution) of the generated image may be affected by various phenomena such as light scattering and / or other phenomena.

[0004] Spectral X-ray imaging extracts material-specific images of a volume of interest. This technique is used in clinical radiography to provide additional diagnostic information about a patient's anatomy. Spectral imaging is performed by acquiring two or more X-ray transmission images (or "projections") of a volume of interest, each with a different X-ray energy, and applying post-processing techniques to identify its constituent materials by differences in their X-ray attenuation characteristics. One method for achieving energy separation between images is by temporal subtraction, where the X-ray source kVp (kilovolt peak) and / or filters are changed between successive X-ray projections.

[0005] Improving the contrast or signal-to-noise ratio (SNR) of material-selective x-ray images by using high-energy and low-energy projection measurements is described in U.S. Patent No. 4,029,963 to Alvarez. U.S. Patent No. 4,445,226 to Brody discloses a method for removing soft tissue or bone structures from x-ray images using a hybrid energy subtraction technique. U.S. Patent No. 8,792,617 to Baetz discloses a method for producing dual-energy x-ray images in mammography using two exposures, each with a different kVp and filtration. However, this method is prone to problems and artifacts due to patient body movement between the two exposures.

[0006] FIG. 1B illustrates a prior art approach 10 for dual energy subtraction, contrast injection following, or time-lapse subtraction before and after contrast injection methods employed in dual shot / single detector spectral mammography and spectral computed tomography (CT) systems. This approach uses rapid kV switching to produce alternating high and low energy projections. For example, in the dual shot approach of FIG. 1B, a first filter 20 is positioned in front of and in close proximity to the x-ray radiation source 15 to pass only low energy x-ray radiation 25 for incidence on the imaged object 12. A single detector 30, such as an x-ray photoconductor or scintillating screen, receives photons from the low energy x-ray radiation 25 transmitted through and not absorbed by the object 12, and associated circuitry converts these detected photons into electrical signals used to generate a first low energy (LE) image of the object. 1B, a second filter 40 is placed in front of and in close proximity to the X-ray radiation source 15 to pass only high energy X-ray radiation 45 for incidence on the imaged object 12. A single detector 30 receives photons from the high energy X-ray radiation 45 transmitted through and not absorbed by the object 12, and associated circuitry converts these detected photons into electrical signals that are used to generate a first high energy (HE) image of the object. Dual shot techniques employing two exposures can achieve a high degree of spectral separation between high and low energy images because they allow for changes in X-ray source kVp, filters, and image receptors during the acquisition workflow. While this versatility is desirable to achieve high contrast spectral imaging, this technique is inherently limited by misregistration artifacts resulting from subject body movement during acquisition.

[0007] Alternatively, U.S. Patent No. 9,526,466 to Karim discloses a method for producing dual energy x-ray images in mammography using stacked integrating multi-layer detectors, where the detectors are exposed to the x-ray beam simultaneously in the same x-ray exposure. However, this method has the disadvantage that the energy separation between the low and high energy images produced is limited, and there is no spectral separation filter as in the present disclosure, resulting in loss of contrast and SNR in the energy reduced images.

[0008] Finally, U.S. Patent No. 7,342,233 to Danielsson claims an apparatus with an array of photon-counting channels, each channel converting individual X-ray detection events into electrical pulses according to pulse height, with two sets of counters each counting pulses according to whether they are above or below a given threshold, producing high-energy and low-energy images in a single exposure. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 4,029,963 [Patent Document 2] U.S. Patent No. 4,445,226 [Patent Document 3] U.S. Patent No. 8,792,617 [Patent Document 4] U.S. Patent No. 9,526,466 [Patent Document 5] U.S. Patent No. 7,342,233 Summary of the Invention [Problem to be solved by the invention]

[0010] Thus, disclosed are structures, imaging systems and detectors that provide improved image quality and dose performance. The systems and imaging methods include single layer or dual layer detectors that enable one shot (single exposure) of X-rays for dual energy imaging, i.e., single shot energy discrimination. [Means for solving the problem]

[0011] In one example embodiment, a system including a single layer or dual layer detector includes a spectral separation filter positioned proximate to the output of an x-ray energy source to modulate the x-ray radiation into a low energy band and a high energy band to enable one shot of x-rays for dual energy imaging of an object.

[0012] In one embodiment, the imaging object can include a contrast agent material having a characteristic K-edge atomic energy band level, and the separation filter is made of a material that absorbs X-ray radiation near the K-edge atomic energy band level to produce two bands of X-ray radiation, a low energy (LE) radiation band and a high energy (HE) radiation band for dual energy imaging of the object.

[0013] The apparatus further comprises a single layer X-ray energy image detector including a forward X-ray imaging photon counting detector (PCD) for receiving incident X-ray radiation transmitted through the spectral separation filter and the imaged object and generating electrical signals capable of generating a first LE image of the imaged object and generating further electrical signals capable of generating a second HE image of the imaged object.

[0014] In one embodiment, the PCD is an amorphous-selenium (α-Se) X-ray photon-counting flat panel imager (SWAD) for detecting lower and higher energy photons to form both low and high energy images, respectively.

[0015] The apparatus may further comprise a spectral separation filter and a dual layer X-ray energy imaging detector including a first forward direct conversion X-ray imaging detector disposed on an underlying substrate for generating LE and HE images of the object, and a second backward indirect conversion X-ray imaging detector below the substrate for generating information to be combined with the HE image of the object.

[0016] In this embodiment, the first forward X-ray imaging detector may comprise a PCD such as an amorphous-selenium (α-Se) X-ray photon counting flat panel imager (SWAD) to detect both lower and higher energy photons used to form the respective low and high energy images. The second rearward X-ray imaging detector comprises an indirect conversion flat panel X-ray detector or a photon energy integrating detector and includes a material of atomic number selected to efficiently detect higher energy photons to form a high energy image used to enhance the higher energy image acquired by the first forward PCD.

[0017] In a further embodiment of the dual layer X-ray imaging detector, both the first forward X-ray imaging detector and the second X-ray imaging detector comprise integrated detectors. The forward integrated detector comprises a first pixel sensor for directly converting a first energy level band photons of the incident radiation transmitted through the imaged object into a first image signal configurable to form a low energy image of the imaged object. The rear integrated detector formed below the substrate comprises a second pixel sensor for converting a second energy level band photons of the incident radiation transmitted through the imaged object and through the forward integrated detector and the substrate into a second image signal configurable to form a high energy image of the imaged object.

[0018] According to a first aspect of the present invention there is provided an apparatus comprising: a separation filter for spectrally separating radiation from an X-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object; a substrate; and an X-ray photon counting detector formed on the substrate, the X-ray photon counting detector comprising an array of detector pixels, each detector pixel comprising a sensor for detecting interactions of individual X-ray photons of incident radiation transmitted through the imaged object for a fixed period of time, each detector pixel of the array having associated counting circuitry operable to generate a first electrical signal indicative of a respective count of a number of detected interactions of individual X-ray photons of the first energy level band and a second electrical signal indicative of a respective count of a number of detected interactions of individual X-ray photons of the second energy level band, the first electrical signal and the second electrical signal from the detector pixels of the array providing a respective energy spectrum image of the imaged object.

[0019] In a further aspect, an apparatus includes a separation filter for spectrally separating radiation from an X-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object, a first substrate, and an X-ray photon counting forward detector formed on the first substrate, the detector pixel array having a sensor for detecting interactions of individual X-ray photons of incident radiation transmitted through the imaged object for a fixed period of time, each detector pixel having an associated counting circuit operable to generate a first electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons of the first energy level band and a second electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons of the second energy level band, the detector pixels of the array having an associated counting circuit operable to generate a first electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons of the first energy level band and a second electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons of the second energy level band, the first and second electrical signals from the front detector pixel array provide respective energy spectrum images of the imaged object; an X-ray photon-counting forward detector formed on a second substrate and disposed below the first substrate, the rear detector comprising a scintillating screen for converting incident radiation containing X-ray photons of a second energy level band passing through the imaged object and transmitted through the front detector into photons; and a photosensor array disposed between the scintillating screen and the second substrate for the rear detector, the photosensor array operable to capture photons from the scintillating screen and convert the captured photons into a further electrical signal, the further electrical signal operable for combination with the second electrical signal from the front detector pixel array to obtain an image of the imaged object.

[0020] In a further aspect, an apparatus comprises a separation filter that spectrally separates radiation from an X-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object, the second energy level band being of greater energy than the first energy level band; a glass substrate; a forward integrated detector formed on the glass substrate, the forward integrated detector comprising a first pixel sensor for directly converting first energy level band X-ray photons of the incident radiation transmitted through the imaged object into a first image signal configurable to form a low-energy image of the imaged object; and a rear integrated detector formed below the glass substrate, the rear integrated detector comprising a second pixel sensor for indirectly converting second energy level band X-ray photons of the incident radiation transmitted through the imaged object and through the forward integrated detector and the substrate into a second image signal configurable to form a high-energy image of the imaged object.

[0021] Further to this aspect, the forward integrated detector comprises a first photoconductive layer for converting incident radiation containing X-ray photons of a first energy level band transmitted through the imaged object into electric charges, and a first charge storage array disposed between the first photoconductive layer and the substrate for accumulating electric charges associated with the converted X-ray photons.

[0022] Further to this aspect, the rear integrated detector comprises a scintillating screen for converting incident radiation containing X-ray photons of a second energy level band transmitted through the imaged object into photons, and a photosensor array disposed between the second scintillating screen and the substrate and operable to capture the photons from the second scintillating screen and convert the captured photons into a second image signal.

[0023] Further to this aspect, the imaged object includes a contrast agent material having a characteristic K-edge atomic energy band level, and the separation filter has an X-ray absorption edge for absorbing X-ray radiation near, e.g., within 10 keV of, the K-edge atomic energy band level of the contrast agent material.

[0024] Further features as well as the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings, in which like reference numbers indicate identical or functionally similar elements. [Brief description of the drawings]

[0025] [Figure 1A] FIG. 1 illustrates an example dual layer detector imaging system that enables one shot of X-rays for dual energy imaging in accordance with an embodiment of the present disclosure. [Figure 1B] FIG. 1 depicts a standard single detector system requiring two shots of X-ray exposure for dual energy imaging. [Figure 2A] 1 is an example diagram illustrating a comparison of HE and LE spectral separation for a dual shot / single detector approach and a dual layer detector approach. [Figure 2B] 1 is an example diagram illustrating a comparison of HE and LE spectral separation for a dual shot / single detector approach and a dual layer detector approach. [Figure 2C] 1 is an example diagram illustrating a comparison of HE and LE spectral separation for a dual shot / single detector approach and a dual layer detector approach. [Figure 2D] 1 is an example diagram illustrating a comparison of HE and LE spectral separation for a dual shot / single detector approach and a dual layer detector approach. [Figure 2E] 1 is an example diagram illustrating a comparison of HE and LE spectral separation for a dual shot / single detector approach and a dual layer detector approach. [Figure 2F] 2C is a table summarizing example average LE and average HE spectral energy band values ​​obtained for each of the embodiments of FIGS. 2A through 2E. [Figure 3A] FIG. 1B illustrates the effect of filter thickness and top detector material (T1) thickness on the spectral separation achieved for an embodiment depicting the dual-detector spectral imaging approach of FIG. 1A. [Figure 3B] FIG. 1B illustrates the effect of filter thickness and top detector material (T1) thickness on the spectral separation achieved for an embodiment depicting the dual-detector spectral imaging approach of FIG. 1A. [Figure 3C] FIG. 1B illustrates the effect of filter thickness and top detector material (T1) thickness on the spectral separation achieved for an embodiment depicting the dual-detector spectral imaging approach of FIG. 1A. [Figure 3D] 1B is a table summarizing the resulting improvement in image quality, as measured by SDNR, for different thicknesses of the front and rear detector layers for the single shot / dual layer detector of FIG. 1A. [Figure 4] FIG. 1 illustrates a first embodiment of a spectral imaging system including a single-shot / single-layer detector for generating dual LE and HE spectral images of an object. [Diagram 5] 1 is a cross-sectional schematic diagram of a fully assembled SWAD device used as a forward detector in a single-detector or dual-detector spectral imaging approach according to one embodiment. [Figure 6] FIG. 6 illustrates the results of an example of a simulated pixel response of a photon-counting SWAD device as illustrated in FIG. 5. [Figure 7] FIG. 1 illustrates a second embodiment of a spectral imaging system including a single-shot / dual-layer detector to generate dual LE and HE spectral images of an object. [Figure 8] FIG. 1 illustrates a further embodiment of a spectral imaging system including a single shot / dual layer detector to generate dual LE and HE spectral images of an object. [Figure 9] FIG. 13 illustrates a further embodiment of a spectral imaging system including a single shot / dual layer detector including a direct conversion X-ray front X-ray detector layer and an indirect conversion rear X-ray detector layer X-ray detector. [Figure 10]FIG. 13 illustrates a further embodiment of a spectral imaging system including a dual-shot exposure / dual-layer detector with either a source array or a step-shoot tomography system in accordance with an aspect of the present disclosure. [Figure 11A] 1 depicts simulated result images of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. [Figure 11B] 1 depicts simulated result images of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. [Figure 11C] 1 depicts simulated result images of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. [Figure 11D] 1 depicts simulated result images of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. [Figure 11E] 1 depicts simulated result images of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. [Figure 12] 11C, 11D and 11E are tables depicting signal difference to noise ratios in the simulated contrast-enhanced dual-energy mammography results. [Figure 13A] 1A-1D depict respective LE DBT, HE DBT and CE DBT image slices illustrating the problems to be overcome with prior art dual-shot imaging techniques. [Figure 13B] 1A-1D depict respective LE DBT, HE DBT and CE DBT image slices illustrating the problems to be overcome with prior art dual-shot imaging techniques. [Figure 13C]1A-1D depict respective LE DBT, HE DBT and CE DBT image slices illustrating the problems to be overcome with prior art dual-shot imaging techniques. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The following detailed description of the embodiments of the present disclosure is made with reference to the accompanying drawings. In this disclosure, descriptions of relevant functions or structures known in the art are omitted for clarity in understanding the concepts of the present disclosure, so as to avoid obscuring the present disclosure with unnecessary details.

[0027] Spectral X-ray imaging extracts material-specific images of a volume of interest. This technique is used in clinical radiography to provide additional diagnostic information about a patient's anatomy. Spectral imaging is performed by acquiring two or more X-ray transmission images (or "projections") of a volume of interest, each with a different X-ray energy, and applying post-processing techniques to identify its constituent materials by differences in their X-ray attenuation characteristics.

[0028] In embodiments herein, there are two methods to achieve energy separation between images: 1. Temporal subtraction, where the x-ray source kVp and / or filters are changed between successive x-ray projection images, or 2. Single shot energy discrimination, where multiple detectors sensitive to different energy spectra are provided. In one embodiment herein, single shot energy discrimination is performed using a single photon counting detector (PCD), where two or more energy bins are used to form multiple energy specific images from a single x-ray projection image. In a further embodiment, single shot energy discrimination is performed using a dual detector including a photon counting detector and a photon energy integrating detector (EID), which are used to form multiple energy specific images from a single x-ray projection image. A further embodiment implements single shot energy discrimination using a dual detector including two photon EIDs to form multiple energy specific images from a single x-ray projection image. A further embodiment contemplates a dual detector to form multiple energy specific images using two or more radiation exposures (multiple shots). The two methods can be combined to further enhance energy discrimination for spectral imaging.

[0029] Spectral imaging using single-shot energy discrimination is free of misregistration artifacts due to body motion, and as further described herein, when used in spectral DBT applications can provide more complete and more accurate diagnostic information about the breast compared to conventional 2D full-field digital mammography (FFDM), spectral FFDM, and conventional DBT. This information includes 3D breast tissue density, 3D microcalcification distribution and type, 3D distribution of contrast agent (e.g., iodine), and 3D component alteration of a subject's breast lesion (e.g., mass). This disclosure describes spectral imaging system implementations that can be used to provide one or all of the above information, for example, in spectral DBT.

[0030] FIG. 1A illustrates one embodiment of a dual layer detector spectral imaging system 100 that enables one shot of x-rays for dual energy imaging of an object 12 .

[0031] In one embodiment, the spectral imaging system 100 includes an X-ray source 15, which may be an X-ray tube that generates X-rays, or other device capable of generating X-rays. The X-ray source may irradiate a subject with X-ray radiation through a spectral separation filter, where the subject may absorb some of the X-rays, resulting in attenuation of the X-rays. The attenuated X-rays may be directed toward the dual detector structure 101 as incident X-rays 122.

[0032] In either embodiment, the dual-layer X-ray spectral imaging detector approach includes an X-ray filter 120 positioned in front of and proximate to the X-ray radiation source 15 to absorb a portion of the X-ray radiation output of the radiation source 15 such that the X-ray radiation 122 passes simultaneously at two energy levels, a first LE energy level including an emission band with energies below the X-ray absorption edge of the separation filter, and a second HE energy level including an emission band with energies above the X-ray absorption edge of the separation filter. The system 100 includes a dual-layer X-ray imaging detector to receive the incident X-ray radiation 122 transmitted through the object 12. The dual-layer X-ray imaging detector is configured as a stack 101 including a first forward detector 110 disposed on a substrate 125 and a second rear detector 150 disposed beneath the substrate 125 or attached beneath the substrate 125 using, for example, a radio-transparent adhesive. In one embodiment, the forward detector 110 can include a photon counting detector (PCD) or a photoconductor type photon integrated detector. The rear detector 150 may include an integrated photon detector. In these embodiments, the substrate may include a substrate 125 of glass or a similar material.

[0033] In some embodiments herein, a spectral separation filter 120 at the x-ray source output uses a 100% 100% 100% 15 ... F1 From Z FN and TF1 From T FN The filter material is selected with an atomic number that selectively removes x-ray energy from the beam through preferential attenuation at energies near its K-edge, e.g., within 10 keV. The filter material, thickness, and order of its placement relative to the x-ray source are selected to form a filter energy transmission characteristic according to the initial energy spectrum, detector characteristics, and spectral information of the subject. For example, a material can be selected that has a K-edge (e.g., within 10 keV) close to that of a breast imaging contrast agent (e.g., iodine). Example separation filter materials can include Rh, Ag, Pd, In, and Sn filters.

[0034] In one embodiment, the dual layer detector imaging system 100 is specifically configured for digital breast tomosynthesis (DBT), particularly for acquiring high resolution three-dimensional (3D) x-ray images of the breast 12. In such an embodiment, the first forward detector 110 is a direct conversion flat panel x-ray detector ("forward detector") that is first exposed to the x-ray beam transmitted through the imaging subject, having a smaller atomic number, e.g., atomic number Z1 and thickness T1, and high spatial resolution. The atomic number and thickness of the forward detector material are chosen to preferentially absorb lower energy x-rays while transmitting higher energies, thereby enabling the formation of a low energy image. The high spatial resolution is utilized to preserve image detail information, i.e., small structures and sharp edges. In one example, the forward detector 110 is an amorphous selenium detector (e.g., Z1=34, T1=150 μm or 200 μm).

[0035] In one embodiment, the second rear detector 150 is an indirect conversion flat panel X-ray detector ("rear detector") with atomic number Z3>Z1 and thickness T3. The atomic number of the rear detector is chosen to efficiently detect higher energy photons to form a high energy image. The atomic number of the rear detector may be matched to the K-edge of the contrast agent, e.g., CsI:Tl for iodine, to improve the agent's prominence in the high energy image. The rear detector may include a scintillator that may be transparent or optically opaque structured or unstructured (e.g., columnar Cs:Tl or powder Gd2O2S:Tb) and may be provided with an optically reflective or absorbing backing. The scintillator is coupled to the photodetector array by direct deposition, pressure contact, or in some embodiments using a fiber optic plate to transmit the X-ray induced light image to the photodetector without light diffusion. The light sensor may be an α-Si:H photodiode, MIS type, or other type known in the art. The thin film transistor (TFT) switching elements may be of the α-Si:H type, metal oxide (MOTFT) type, or other types known in the art.

[0036] 2A to 2E illustrate respective diagrams depicting the ability of the dual-layer approach 100 of FIG. 1A to spectrally separate an X-ray energy spectrum into LE and HE spectral energy bands for incidence on an imaging object. For example, each of the diagrams of FIG. 2A to 2D shows an example diagram illustrating the spectral separation of X-ray radiation, in particular the number of photons received in the filtered radiation forming the LE and HE spectral imaging bands as a function of the photon energy (in keV) of the filtered radiation, as achieved by the dual-layer detector approach 100 of FIG. 1A for a W / Rh spectrum. A comparative diagram of the spectral separation of X-ray radiation and an example diagram depicting the number of photons received in the filtered radiation as a function of the photon energy (in keV) of the filtered radiation, as achieved by the dual-shot / single-detector approach 10 of FIG. 1B for a W / Rh spectrum, are additionally shown. In one example diagram shown in Figures 2A-2D, the detector is an amorphous selenium (α-Se) energy integrating detector (EID) with a thickness of 150 μm, and the spectral isolation filter is 200 μm thick and comprises rhodium.

[0037] In a first expression, FIG. 2A shows a comparison 201 of the spectral separation achieved for the single shot / dual layer detector approach of FIG. 1A compared to the dual shot / single layer detector approach of FIG. 1B. As shown in Figure 2A, the single shot / dual layer detector approach detects LE spectral radiation energy 214, which far exceeds the LE spectral radiation energy 204 detected by the dual shot / single layer detector approach of Figure 1B. Similarly, as shown in the diagram of Figure 2A, the single shot / dual layer detector approach detects HE spectral radiation energy 216, which exceeds the HE spectral radiation energy 206 as detected by the dual shot / single layer detector approach of Figure 1B. Additionally, the LE and HE radiation achieve a wide separation 215 of approximately 20 keV, resulting in improved LE and HE images.

[0038] 2B shows a comparison 221 of the spectral separation achieved for the single shot / dual layer detector approach of FIG. 1A using a k-edge band spectral separation filter for single shot LE / HE emission separation compared to the single layer detector approach of FIG. 1B using a non-K-edge filter for LE and HE spectral separation. As shown in FIG. 2B, the single shot / dual layer detector approach using a k-edge band filter detects LE spectral emission energy 234 and HE spectral emission energy 236 with respective spectral energy peak separation 225 of about 20 keV, which far exceeds the spectral separation achieved by the dual shot / single layer detector and non-k-edge band filtering approach of FIG. 1B, shown in FIG. 2B as LE spectral emission energy 224 and HE spectral emission energy 226, which have little or no spectral energy separation.

[0039] 2C shows a diagram 241 of the spectral separation achieved for the single shot / dual layer detector approach of FIG. 1A using a forward α-Se photoconductive detector 110, a rear CsI energy integrating scintillating detector 150, and a k-edge band spectral separation filter for single shot LE / HE emission separation. As shown in FIG. 2C, the single shot / dual layer detector approach using a forward α-Se photoconductive detector 110, a rear photon integrating detector 150, and a k-edge band spectral separation filter detects LE spectral emission energy 244 and HE spectral energy 246. An enhanced spectral energy peak separation 245 of over 20 keV is achieved between the LE and HE bands, resulting in improved LE and HE images.

[0040] 2D shows a diagram 261 of the spectral separation achieved for the single shot / dual layer detector approach of FIG. 1A using a forward α-Se photoconductive detector 110, a rear α-Se photoconductive detector 150, and a k-edge band spectral separation filter for single shot LE / HE radiation separation. As shown in FIG. 2D, the single shot / dual layer detector approach using a forward α-Se photon integrating detector 110, a rear α-Se photon integrating detector 150, and a k-edge band filter detects LE spectral radiation energy 254 and HE spectral energy 256. An enhanced spectral energy peak separation 255 of over 20 keV is achieved between the LE and HE bands, resulting in improved LE and HE images.

[0041] 2E shows a diagram 281 of the spectral separation achieved for the single shot / dual layer detector approach of FIG. 1A using a forward CsI energy-integrating scintillating detector 110, a rear CsI energy-integrating scintillating detector 150, and a k-edge band spectral separation filter for single shot LE / HE radiation separation. As shown in FIG. 2E, the single shot / dual layer detector approach using a forward CsI photon-integrating detector 110, a rear CsI photon-integrating detector 150, and a k-edge band filter detects a large amount of LE spectral radiation energy 274 and HE spectral energy 276.

[0042] Figure 2F is a table 290 illustrating a column 292 providing the average value of the detected LE spectral band energy in keV and a column 294 providing the average value of the detected HE spectral band energy in keV for the embodiment of Figures 2A-2E. As shown in Figure 2F, an average LE and average HE energy spectral separation of about 17 keV is achieved for the dual shot / single layer detector, whereas the dual layer detector configuration of Figure 1A using k-edge bandpass filtering and with a forward α-Se photoconductive detector 110 achieves a comparable average LE band separation and average HE band separation of about 13 keV.

[0043] 3A-3C illustrate the effect of filter thickness and top detector material (T1) thickness on the spectral separation achieved for an embodiment depicting the dual detector spectral imaging approach of FIG. 1A.

[0044] FIG. 3A particularly illustrates a comparison 300 of the LE and HE spectral energy separation achieved for the single shot / dual layer detector approach of FIG. 1A using two different thicknesses of rhodium spectral separation filter 120. In particular, as shown in FIG. 3A, the single shot / dual layer detector approach using a 200 μm thick Rh k-edge bandpass filter detects LE spectral emission energy 304 and HE spectral energy 306 with respective spectral energy peak separation 315 of about 20 keV, resulting in improved LE and HE images. For comparison, FIG. 3A depicts the LE spectral emission energy 305 and HE spectral energy 307 achieved for the single shot / dual layer detector approach using a 100 μm Rh k-edge bandpass filter. As shown in FIG. 3A, almost the same spectral energy separation is achieved with this single shot / dual layer detector approach.

[0045] FIG. 3B particularly illustrates a comparison 320 of the LE and HE spectral energy separation achieved for the single shot / dual layer detector approach of FIG. 1A using two different thicknesses of forward α-Se photoconductive detector 110 and a 200 micron thick RH spatial separation filter. In particular, as shown in FIG. 3B, the single shot / dual layer detector approach using a 200 μm thick forward α-Se photon integrating detector 110 detects LE spectral radiation energy 314 and HE spectral radiation energy 316 with respective spectral energy peak separation 325 of about 20 keV, resulting in improved LE and HE images. For comparison, FIG. 3B depicts the LE spectral radiation energy 317 and HE spectral radiation energy 319 achieved for the single shot / dual layer detector approach using a 150 μm thick forward α-Se detector 110. As shown in FIG. 3B, almost the same spectral energy separation is achieved with this single shot / dual layer detector approach.

[0046] 3C illustrates the effect of placing a filter material between the front detector layer 110 and the rear detector layer 150 on the single shot / dual layer detector approach of FIG. 1A. FIG. 3C particularly shows a comparison 350 of respective plots of the detector's Quantum detection efficiency measures as a function of detected photon energy level for different glass substrate thicknesses, e.g., front detector glass substrate thicknesses ranging between 300 microns and 700 microns, with the optional addition of a glass substrate 352 from the bottom detector (when it is in rear emission geometry). In the comparison, an optional Cu filter (or other higher z material) can be used.

[0047] 3D is a table 375 summarizing the resulting improvement in image quality as measured by signal difference to noise ratio (SDNR) 380 for different thicknesses of front detector layer 110 and rear detector layer 150 for the single shot / dual layer detector of FIG. 1A. In the first row, a single shot / dual layer detector having a front α-Se detector 110 of about 200 μm thickness and a rear CsI photon integrating detector 150 of about 400 μm thickness and a Rh filter of about 200 μm thickness allows detection of an average LE spectral emission energy of 27.5 keV and an average HE spectral energy of about 40.9 keV, providing an improved SDNR of about 6.01 at an x-ray tube source loading of about 108.2 mA. In the second row, a single shot / double layer detector with a front α-Se detector 110 of about 200 μm thickness and a rear CsI photon integrated detector 150 of about 400 μm thickness and a Rh filter of about 100 μm thickness allows detection of an average LE spectral emission energy of 28.0 keV and an average HE spectral energy of about 39.6 keV, providing an improved SDNR of about 5.22 at an X-ray tube source loading of about 18.2 mA. Similarly, a single shot / double layer detector with a front α-Se detector 110 of about 150 μm thickness and a rear CsI photon integrated detector 150 of about 400 μm thickness and a Rh filter of about 200 μm thickness allows detection of an average LE spectral emission energy of 26.8 keV and an average HE spectral energy of about 39.9 keV, providing an improved SDNR of about 6.31 at an X-ray tube source loading of about 108.2 mA.

[0048] 1A for imaging an object 12, with each embodiment specifically configured for Digital Breast Tomosynthesis (DBT), i.e., 3D breast spectral imaging. The 3D spectral X-ray imaging system comprises six components: 1) a spectral separation filter at the output of the X-ray source, which is a filter of atomic number Z, for modulating the X-ray energy spectrum incident on the imaging subject; F1 From Z FN and thickness T F1 From T FNand 2) a direct conversion flat panel X-ray detector ("front detector") that is first exposed to the X-ray beam transmitted through the imaged object, the direct conversion flat panel X-ray detector having a smaller atomic number Z1 and thickness T1 and high spatial resolution. 3) a filter at the exit surface of the detector having an atomic number Z 2F From Z NF and thickness T 2F From T 2F and a filter that modulates the x-ray energy spectrum leaving the front detector; 4) a second indirect conversion flat panel x-ray detector ("back detector") having atomic number Z3>Z1 and thickness T3; 5) a combined double layer detector in a dual shot x-ray exposure that can be implemented in a switchable kVp and filter DBT system providing up to four images for multiple material resolution; and 6) various combinations of photon counting detector (PCD) variants of α-Se flat panel imagers such as a top (front) detector (e.g., a field shaped multiwell avalanche detector or SWAD).

[0049] FIG. 4 shows a first embodiment of a spectral imaging system including a single shot / single layer detector 400. This first embodiment includes a combination of a spectral separation filter 120 positioned in front of and close to the X-ray radiation source 15 to absorb a portion of the X-ray radiation output of the radiation source 15. The spectral imaging system includes a single direct conversion flat panel X-ray detector, such as a photon counter detection (PCD) device 401, disposed on a substrate, such as a glass substrate 225. As described in more detail below, the PCD 401 includes a flat panel imager, such as an amorphous selenium (α-Se) based field shaping multi-well avalanche detector (SWAD), for photon counting at each pixel location. The α-Se X-ray photon counting flat panel SWAD imager layer 401 converts received photons into electrical pulses having a pulse height commensurate with the energy level of the received photons. At each pixel location in the PCD layer, the semiconductor thresholding and counting circuitry 230 detects the pulse height to distinguish between LE and HE photons received at the PCD layer from incident radiation that is not absorbed by (i.e., not transmitted through) the object 12. The thresholding circuitry can include a first thresholding circuit for rejecting noise signals and a second pulse thresholding circuit used to compare the height of the received pulse against a pulse height threshold. At a pixel, both the LE counter circuit and the HE counter circuit count the number of photon interactions as an electronic pulse received at that pixel location. Photons received from radiation that exceed the pulse height threshold can be counted as HE photons, and a HE accumulation "bin" maintains a photon count value in memory storage associated with that pixel location. Similarly, at the same pixel location, photons received from radiation that are below the pulse height threshold can be counted as LE photons, and a LE "bin" maintains a LE photon count value in memory storage associated with that pixel location.

[0050] As shown in FIG. 4, a data acquisition circuit 98 including a programmed processor 99 and memory configured to communicate with each other can receive count values ​​from each of the LE and HE bins and process these values ​​to produce respective LE and HE spectral images of the object.

[0051] For an embodiment employing a photon-counting detector (PCD) variant of an α-Se X-ray photon-counting flat panel imager (SWAD) as the top (front) detector, Figure 5 depicts a cross-sectional schematic of a fully assembled SWAD device. In the cross-sectional schematic of a fully assembled SWAD device 500 in Figure 5, two distinct regions are depicted: (1) a bulk region 510 formed by a thin film of α-Se for X-ray absorption, and (2) a multi-well sensing region 525 made up of a multi-well 526 and a number of pillars 550 disposed directly over the readout electronics, such as the semiconductor pixel thresholding and CMOS counting circuitry 230 of Figure 4. The sidewalls of the well 526 are formed by dielectric pillars 550 with two grid electrodes 530, 535 embedded therein, which can be utilized to create a localized high electric field within the well region for tunable avalanche gain and electrostatic shielding of the pixel electrodes for high speed unipolar time differential charge sensing. When the grid electrodes 530, 535 are energized, the electric field lines above the well bend, creating a field shaping effect that guides floating carriers into the well. The strength of the electric field in the well can be adjusted to create a localized high electric field region where carriers can undergo avalanche gain, while maintaining a low electric field throughout the bulk, just above the readout electronics. Additionally, the embedded grid electrodes act as Frisch grids, electrostatically shielding the pixel electrodes from sensing any carrier motion in the bulk, while creating a strong near-field effect that causes the collected signal to increase rapidly as carriers enter the well and undergo avalanche gain. The bulk region (~200 μm) is an order of magnitude thicker than the well region to provide good x-ray absorption and minimize the effect of depth-dependent avalanche gain. The common high-voltage electrode 560 is energized positively so that fast carriers (holes, in α-Se) can be collected.

[0052] FIG. 6 illustrates simulated pixel response results 600 for a photon-counting SWAD device as illustrated in FIG. 5, where a 300 micron thick α-Se bulk layer is exposed to a 49 kVp W spectrum filtered with 237 microns Cu, and a 4 cm thick breast has a 50% / 50% fibroglandular / adipose tissue composition. Pixel responses are shown for both 75 micron and 100 micron pixel sizes. Simulation results 600 are based on a multi-pixel geometry, whereby the pixel response shown includes a spectrum collected by a single central pixel along with crosstalk from eight neighboring pixels, capturing the spatial energy effects of charge sharing.

[0053] In one embodiment, the use of a photon-counting variant of an α-Se X-ray photon-counting flat panel imager (SWAD) as the top detector provides a low-cost alternative to other photon-counting detectors (PCDs) that use crystalline Cd(Zn)Te. Its energy resolution and count rate depend on the geometry of a Frisch grid built on top of a CMOS photon-counting integrated circuit network. With an avalanche gain of 10 and a linear Frisch grid, count rates of 100k counts per second (cps) are possible, with an energy resolution of 3 keV.

[0054] 7 illustrates a second embodiment of a spectral imaging system including a single shot / dual layer detector 700. This embodiment includes a spectral separation filter 120 positioned in front of and proximate to the x-ray radiation tube source 15 to absorb a portion of the x-ray radiation output of the source 15.

[0055] In one embodiment, a spectral separation filter 120 at the x-ray source output is made of one or more materials, e.g., atomic number Z, to modulate the x-ray energy spectrum 122 incident on the imaging subject 12. F1 From Z FN and thickness T F1 From T FNThe filter material is chosen with an atomic number that selectively removes x-ray energy from the beam through preferential attenuation at energies near its K-edge, e.g., within 10 keV. The filter material, thickness and order of its placement relative to the x-ray source are chosen to shape the filter energy transmission characteristics according to the initial energy spectrum, the detector characteristics and the spectral information of the subject. For example, a material can be selected that has a K-edge close to that of a breast imaging contrast agent (e.g., iodine). An example separation filter material can include Rh, Ag and Sn filters 120.

[0056] The spectral imaging system 700 includes a direct conversion forward photon counter detection (PCD) device 701 disposed on a substrate, such as the glass substrate 225. As in the embodiment of FIG. 4, the PCD 701 includes a flat panel imager, such as an amorphous selenium (α-Se) based SWAD, for photon counting at each pixel location. The α-Se flat panel SWAD imager layer 701 converts received photons into electrical pulses having a pulse height commensurate with the energy level of the received photons. At each pixel location in the PCD layer, thresholding and counting circuitry 230 detects the pulse height to distinguish either LE photons or HE photons received at the PCD layer from incident radiation that is not absorbed by the object 12 (i.e., transmitted through the object). The thresholding circuitry can include a pulse thresholding circuit that is used to compare the height of the received pulse against a pulse height threshold. At a pixel, both the LE counter circuitry and the HE counter circuitry count the number of photon interactions as electronic pulses received at that pixel location. Photons received from the radiation that exceed the pulse height threshold can be counted as HE photons, and an HE accumulation "bin" maintains a photon count value in memory storage associated with that pixel location. Similarly, photons received from the radiation at the same pixel location that are below the pulse height threshold can be counted as LE photons, and an LE "bin" maintains a LE photon count value in memory storage associated with that pixel location.

[0057] As shown in FIG. 7, a data acquisition circuit 98 including a programmed processor 99 and memory configured to communicate with each other can receive count values ​​from each of the LE and HE bins and process these values ​​to generate respective LE and HE spectral images of the object.

[0058] In one embodiment, the single shot / dual layer detector 700 further includes an indirect conversion flat panel X-ray detector layer 751 formed on the second glass substrate 226 and mounted beneath the substrate 225 using, for example, a radio transparent adhesive. In one embodiment, the indirect conversion flat panel X-ray detector layer 751 is an energy integrated detector (EID) such as columnar (col-) CsI. Generally, however, the rear EID detector 751 is made of a material having an atomic number greater than the atomic number of the material of the first X-ray detector layer 701.

[0059] The rear EID included in the single shot / dual layer detector 700 includes a scintillating phosphor layer (phosphor screen) to convert X-ray energy photons into light quanta that can be sensed by an associated photosensor (photodetector) array circuitry 235 configured to indirectly capture the energy of the light quanta from the X-rays transmitted through the object. For example, the EID phosphor layer may include phosphor crystals that can capture the incident X-rays and convert the captured X-rays into light quanta. Although not shown, the top surface of the X-ray detector layer 751 may include a reflective layer, where the reflective layer may be made of a highly reflective material. For example, the reflective layer may be coated with a layer of a white material such as titanium dioxide. The reflective layer may reflect scattered photons toward the photosensor array 235 so that the photosensor array 235 captures any scattered photons. Thus, in some examples, the incident X-rays may not be captured enough by the front detector (e.g., PCD layer) 701 to count all photon interactions. X-rays that are not captured may pass through the PCD layer 701, and crystals in the phosphor screen of the EID layer 751 may convert the captured X-rays into photons for detection.

[0060] In one embodiment, the rear screen 751 may include a scintillating phosphor layer, or material such as phosphor crystals that can capture photons. In some examples, the phosphor layer may be of powder or granular type (e.g., GdO2S2:Tb, CaWO4, BaFCl:Eu). In other examples, the screen phosphor may be composed of nanometer-sized particles such as quantum dots, rather than the micron-sized particles typical of "standard" screens such as GdO2S2:Tb. In yet other examples, the scintillating material may be composed of a perovskite type. The rear detector phosphor screen may emit photons in the visible light range (e.g., photon bursts).

[0061] The rear detector phosphor screen may comprise a structured scintillating layer. For example, the rear detector phosphor screen may include a scintillating phosphor needle structure capable of capturing photons. In some examples, the rear detector phosphor screen may be a vacuum deposited needle structure composed of CsI:Tl. In some examples, different types of scintillating materials and combinations of types may be used in the rear screen.

[0062] The photosensor array 235 may include a photosensitive storage element and may include a plurality of switching elements (not shown). The second substrate 226 may be of small optical thickness and in an alternative embodiment may be disposed between the photosensor array 235 and the phosphor layer 751. The photosensitive storage element and the switching element may be disposed on top of the substrate 226. The photosensor array may be composed of α-Si:H nip photodiodes, MIS type or other types. The photosensor array may be sensitive to the top side incident light and may have low transmittance at the wavelengths emitted by the phosphor screen of the EID layer 751. For example, the photosensor array 235 may have high optical absorption (greater than 90%) at the wavelengths of light emitted by the screen of the layer 751 so that pixel crosstalk and crossover effects may be reduced. In one example, the substrate 226 may be glass, plastic or cellulose with a thickness of 700 microns. The photosensor array 235 may capture light quanta and convert the captured light quanta into electrical signals that may be used by data acquisition electronics (separate from the detector 700) to generate a digital image. For example, each switching element may correspond to a pixel of the image, such that switching of a particular column, row, or group of pixels may result in the readout of a group of pixel values ​​to generate the image.

[0063] In the system of FIG. 7, i.e., a single shot / dual layer detector 700 combining an α-Se PCD forward detector with an energy integrating CsI rear detector, the thickness of the α-Se is typically 200-300 microns. Photons transmitted from the α-Se PCD are generally above 33 keV and can be integrated by the CsI detector and added to the top energy bin of the α-Se PCD to ensure high quantum efficiency and SNR. In one embodiment, the number of photons in the high energy region of the SWAD PCD is roughly 1 / 3 of the total number of photons detected by the SWAD and CsI EID together. The addition of the CsI EID as a rear detector provides a significant improvement in the signal difference to noise ratio (SDNR) of the spectral image.

[0064] As shown in FIG. 7, a data acquisition circuit 98 including a programmed processor 99 can receive the integrated HE photon energy values ​​from each of the pixels and post-process these values ​​to enhance the image quality of the HE spectrum image of the object.

[0065] FIG. 8 illustrates a further embodiment of a spectral imaging system including a single shot / dual layer detector 800. This embodiment optionally includes a spectral separation filter 120 or a conventional X-ray spectral imaging filter positioned in close proximity to the front of the X-ray radiation tube source 15. As in the embodiment of FIG. 7, the spectral imaging system 800 includes a direct conversion forward photon counter detection (PCD) device 801 disposed on a substrate, such as a glass substrate 225. The PCD 801 includes a flat panel imager, such as an amorphous selenium (α-Se) based SWAD, for counting photons at each pixel location. The α-Se flat panel SWAD imager layer 801 converts received photons into electrical pulses having a pulse height commensurate with the energy level of the received photons. At each pixel location in the PCD layer, thresholding (binning) and counting circuitry 230 distinguishes between LE photons and received HE photons and stores the respective counts of detected LE and HE photons received at a particular pixel. The thresholding and counting circuitry interfaces with data acquisition circuitry 98, which includes a programmed processor 99 that receives the LE or HE photons accumulated at each pixel to generate respective LE and HE spectral images.

[0066] The single shot / dual layer detector 800 embodiment of Figure 8 further includes an indirect conversion flat panel X-ray detector layer 851 formed on the second substrate 226 and mounted beneath the substrate 225 using, for example, an adhesive. In one embodiment, the indirect conversion flat panel X-ray detector layer 851 is an energy integrating detector (EID) such as CsI. Typically, the rear EID detector 851 is made of a material having an atomic number greater than the atomic number of the material of the first X-ray detector layer 801.

[0067] The addition of a CsI EID layer 851 as a rear detector, as in the embodiment of Figure 7, provides a significant improvement in the signal difference to noise ratio (SDNR) of the spectral image as this layer captures photons transmitted from the α-Se PCD, primarily above 33 keV, i.e., HE photons, which are integrated by the CsI detector and added to the top energy bin of the α-Se PCD, ensuring high quantum efficiency and SNR. In particular, a data acquisition circuit 98 including a programmed processor 99 can receive the integrated HE photon energy values ​​from each of the pixels and post-process these values ​​to enhance the image quality of the HE spectral image of the object.

[0068] FIG. 9 illustrates a further embodiment of a spectral imaging system including a single shot / dual layer detector 900. The embodiment of FIG. 9 includes a combination of a spectral separation filter 120 positioned in front of and in close proximity to the X-ray radiation source 15 to absorb a portion of the X-ray radiation output of the radiation source 15. The spectral imaging system includes a direct conversion flat panel X-ray forward detector 901 disposed on a substrate, such as a glass substrate 225. The direct conversion flat panel X-ray forward detector 901 is first exposed to an X-ray beam transmitted through an imaging subject. In one embodiment, the direct conversion flat panel X-ray detector layer 901 is an energy integrating detector (EID) including a photoconductive material, such as, but not limited to, α-Se. In this embodiment, the α-Se EID flat panel X-ray detector layer 901 absorbs X-ray photons and excites electrons in the photoconductor to a conductive state in the conduction band of the material. In the presence of an electric field, the electrons in the conduction band move along the electric field lines. Thus, charge released by absorption of X-ray radiation can be collected by applying an electric potential across the α-Se EID material. The semiconductor pixel circuitry 930 disposed between the forward imaging detector 901 and the substrate 225 may include a capacitor array, or similar charge storage matrix, for storing collected charge released by absorption of X-ray radiation.

[0069] In one embodiment, the forward detector is made of a material with atomic number Z1 and thickness T1, and high spatial resolution chosen to allow for the formation of low energy images by preferentially absorbing lower energy x-rays while transmitting higher energies. The high spatial resolution is utilized to preserve image detail information, i.e., small structures and sharp edges. An amorphous selenium detector (Z1=34, T1=150 μm) is an example of a forward detector material.

[0070] As further shown in FIG. 9, pixel circuitry 930 including a charge storage matrix disposed between the forward imaging detectors 901 connects to data acquisition circuitry 98 including a programmed processor 99 and memory for receiving values ​​associated with the accumulated LE or HE photons at each pixel and processing this data to generate respective LE and HE spectral images.

[0071] In this embodiment, a further spectral filter 940 is placed at the exit face of the front detector 901 and is shown sandwiched between the forward integrated detector 901 and the substrate 225 to modulate the X-ray energy spectrum exiting the forward detector 901. This filter 940 has atomic number Z 2F From Z NF and T 2F From T 2F The filter 940 may comprise one or more materials having a thickness in the range of 100 nm to 150 nm. In particular, the material of the filter 940 is chosen to attenuate low energy photons and facilitate the fabrication of the device, for example glass used as a substrate to fabricate the active matrix of the forward detector. The thickness of the filter 940 is adjusted to the desired compromise between energy modulation and system sensitivity.

[0072] Further included is an indirect conversion flat panel X-ray detector layer 951 formed on the second substrate 226 and mounted beneath the substrate 225, for example using an adhesive. In one embodiment, the indirect conversion flat panel X-ray detector layer 951 is an energy integrated detector (EID) of a material such as CsI. This second indirect conversion flat panel X-ray back detector may be a material with an atomic number Z3 greater than the atomic number Z1 of the front detector material, and is of thickness T3. In one embodiment, the atomic number of the back detector is chosen to efficiently detect higher energy photons to form a high energy image. It may be matched to the K-edge of the contrast agent, for example CsI:Tl for iodine, to improve the contrast of the agent in the high energy image. The scintillator screen of the back detector may be transparent, or may be optically opaque structured or unstructured (e.g., columnar Cs:Tl or powder Gd2O2S:Tb), and may be provided with an optically reflective or absorbing backing. The scintillator is coupled to the photodetector or photodetector array 235 by direct deposition, pressure contact, or in some embodiments using a fiber optic plate to transmit the X-ray induced light image to the photodetector without light diffusion. The light sensor may be an α-Si:H photodiode, MIS type or other type known in the art. The thin film transistor (TFT) switching element may be an α-Si:H type, a metal oxide thin film (MOTFT) type, or other type known in the art.

[0073] As further shown in FIG. 9, a data acquisition circuit 98 including a programmed processor 99 can receive integrated HE photon energy values ​​from each of the pixels and post-process these data to enhance the image quality of the HE spectral image of the object.

[0074] Figure 10 depicts a further embodiment of a spectral imaging system including a dual shot exposure / dual layer detector 1000 with a switchable kVp and filter placement system. The embodiment of Figure 10 includes a combination of a low energy spectral filter 124 positioned in front of and proximate to the X-ray radiation source 15 during a first exposure, e.g., to provide a LE radiation portion of the X-ray radiation output of the radiation source 15, e.g., 28 keV, and additionally includes a high energy spectral filter 126 positioned in front of and proximate to the X-ray radiation source 15 during a second exposure, e.g., to provide a HE radiation portion of the X-ray radiation output of the radiation source 15, e.g., 49 keV.

[0075] The dual layer detector 1000 of FIG. 10 corresponds to the dual layer detector 900 of FIG. 9 and includes a direct conversion flat panel X-ray forward detector 1001 disposed on a substrate, such as a glass substrate 225. The direct conversion flat panel X-ray forward detector 1001 is first exposed to an X-ray beam transmitted through the imaged object 12. In one embodiment, the direct conversion flat panel X-ray detector layer 1001 is an energy integrating detector (EID) including a photoconductive material, such as, but not limited to, α-Se. In this embodiment, the α-Se EID flat panel X-ray detector layer 1001 absorbs X-ray photons and excites electrons in the photoconductor to a conductive state in the conduction band of the material. In the presence of an electric field, the electrons in the conduction band move along the electric field lines. Thus, charge released by absorption of X-ray radiation can be collected by applying an electric potential across the α-Se EID material. The semiconductor pixel circuitry 1030 disposed between the forward imaging detector 1001 and the substrate 225 may include a capacitor array, or similar charge storage matrix, for storing collected charge released by absorption of X-ray radiation.

[0076] In one embodiment, the forward detector is made of a material with atomic number Z1 and thickness T1, and high spatial resolution chosen to allow for the formation of low energy images by preferentially absorbing lower energy x-rays while transmitting higher energies. The high spatial resolution is utilized to preserve image detail information, i.e., small structures and sharp edges. An amorphous selenium detector (Z1=34, T1=150 μm) is an example of a forward detector material.

[0077] As further shown in FIG. 10, pixel circuitry 1030 including a charge storage matrix disposed between the forward imaging detectors 1001 connects with data acquisition circuitry 98 including a programmed processor 99 for receiving values ​​associated with the accumulated LE photons at each pixel and processing this data to generate an LE spectral image.

[0078] In this embodiment, a further spectral filter 1040 is placed at the exit face of the front detector 1001 and is shown sandwiched between the forward integrated detector 1001 and the substrate 225 to modulate the X-ray energy spectrum leaving the forward detector 1001. This filter 1040 has atomic number Z 2F From Z NF and T 2F From T 2F The filter 1040 may comprise one or more materials having a thickness in the range of 100 nm to 100 nm. In particular, the material of the filter 1040 is chosen to attenuate low energy photons and facilitate the fabrication of the device, for example glass used as a substrate to fabricate the active matrix of the forward detector. The thickness of the filter 1040 is adjusted to the desired compromise between energy modulation and system sensitivity.

[0079] Further included is an indirect conversion flat panel X-ray detector layer 1051 formed on the second substrate 226 and mounted beneath the substrate 225 using, for example, a radiolucent adhesive. In one embodiment, the indirect conversion flat panel X-ray detector layer 1051 is an energy integrated detector (EID) of a material such as CsI. This second indirect conversion flat panel X-ray back detector may be a material with an atomic number Z3 greater than the atomic number Z1 of the front detector material and is of thickness T3. In one embodiment, the atomic number of the back detector is chosen to efficiently detect higher energy photons to form a high energy image. It may be matched to the K-edge of the contrast agent, e.g., CsI:Tl for iodine, to improve the contrast of the agent in the high energy image. The scintillator screen of the back detector may be transparent or optically opaque structured or unstructured (e.g., columnar Cs:Tl or powder Gd2O2S:Tb) and may be provided with an optically reflective or absorbing backing. The scintillator is coupled to the photodetector or photodetector array 235 by direct deposition, pressure contact, or in some embodiments using a fiber optic plate to transmit the X-ray induced light image to the photodetector without light diffusion. The light sensor may be an α-Si:H photodiode, MIS type or other type known in the art. The thin film transistor (TFT) switching element may be an α-Si:H type, a metal oxide thin film (MOTFT) type, or other type known in the art.

[0080] As further shown in FIG. 10, a data acquisition circuit 98 including a programmed processor 99 can receive integrated HE photon energy values ​​from each of the pixels and post-process these data to generate an HE spectral image of the object.

[0081] In an exemplary operation, in a double shot (double exposure) method, a first exposure is made with a low energy beam and appropriate filters, e.g., 28 keV and Rh, and a second exposure is made with a higher energy beam and filters, e.g., 49 keV and Cu. Artifacts due to body movement may be present, but can be reduced by aligning appropriate filters in front of the source at successive time instances using fast keV switching and a rotatable filter wheel. In the simplest case, image data from two detector layers are added to form LE and HE images for use in dual energy subtraction. That is, results from both the front and rear detectors from the first (28 keV) exposure are added to form the LE image, and results from both detectors from the second (49 keV) exposure are added to form the HE image. For the 28 keV exposure, the contribution of the CsI layer detector is smaller because a larger absorption occurs in the front detector Se layer. For the 49 keV exposure, the contribution of CsI is large since many of the higher energy x-rays penetrate the Se layer. Advantages include (i) greater energy separation in the LE and HE images, (ii) the LE images appear much more similar to what conventional mammograms do at 28 keV, and (iii) the CsI layer results in greater x-ray absorption of the HE beam than Se alone. Additionally, the four sets of image data can be informative for multiple material compositions.

[0082] 11A to 11E depict simulated result images 1100 of digital mammography, contrast-enhanced dual-energy mammography, digital breast tomosynthesis, and contrast-enhanced digital breast tomosynthesis. The top half of each image is from a digital breast phantom (with breast structure) and the bottom half is homogeneous breast tissue with a density of 25%. Each of the iodine object sets is arranged in a 4×4 array 1101 and 1102 and is inserted into both the upper and lower halves of the phantom. The iodine objects are spheres with diameters of 2, 3, 5, and 8 mm, and iodine concentrations of 1, 2, 3, and 5 mg / ml, respectively.

[0083] In the simulated images, FIG. 11A shows a simulated digital mammography image resulting from the use of a single layer detector composed of a 50 μm thick Rh spatial separation filter (28 kVp) and a 300 μm thick α-Se detector.

[0084] FIG. 11B shows a simulated digital mammography image resulting from the use of a single-layer detector composed of a 237 μm thick Cu filter (49 kVp) and a 300 μm thick α-Se front detector.

[0085] FIG. 11C shows a contrast-enhanced dual-energy mammography image (e.g., the dual-layer detector of FIG. 9 ) composed of a 200 μm thick Rh spatial separation filter (49 kVp), a 200 μm thick α-Se front detector, 700 μm thick glass, and a 400 μm thick pillared CsI rear detector.

[0086] FIG. 11D shows a contrast-enhanced dual-energy mammography image (e.g., dual-layer detector in FIG. 9 ) composed of a 237 μm thick Cu spatial separation filter (49 kVp), a 200 μm thick α-Se front detector, a 700 μm thick glass substrate, and a 400 μm thick pillared CsI rear detector.

[0087] FIG. 11E shows a contrast-enhanced dual-energy mammography image (e.g., the dual-layer detector in FIG. 9 ) composed of a 200 μm thick Rh spatial separation filter (49 kVp), a 200 μm thick columnar CsI front detector, a 700 μm thick glass substrate, and a 400 μm thick columnar CsI rear detector.

[0088] FIG. 12 shows a table 1150 depicting the signal difference to noise ratios in the simulated contrast-enhanced dual energy mammography results of FIG. 11C, FIG. 11D and FIG. 11E. As shown in table 1150, an optimal SDNR of 2.83 is achieved for the lower half image portion, e.g., image half 1160 of FIG. 11C, when compared to the SDNR of 1.65 achieved for the upper half 1170 of the image as obtained using the simulated single shot / dual layer detector of FIG. 9, constructed with a 200 μm thick Rh spatial separation filter (49 kVp), a 200 μm thick α-Se front detector, 700 μm thick glass and a 400 μm thick pillared CsI rear detector. Similarly, the SDNR value is increased for the lower half image portions of FIG. 11D and FIG. 11E, when compared to the respective SDNR of 65 achieved for their corresponding upper image portions. As shown, the embodiment of Figures 11C, 11D implementing a dual layer α-Se front detector and a CsI rear detector performs better than the dual layer embodiment using CsI front and rear detectors.

[0089] Figures 13A-13C depict images that, among other things, demonstrate a practical problem with DBT that the dual layer detector approach of the embodiment of Figures 7 and 9 is intended to overcome. In Figures 13A-13C, which depict respective LE DBT, HE DBT and CE DBT image slices, significant patient body motion is observed between the HE and LE images, a problem that would be exacerbated in DBT and CEDBT.

[0090] The embodiments of the system and method described herein overcome some of the shortcomings of various digital and film screen radiography systems by enabling a form of x-ray imaging that extracts material specific information from a volume of interest, e.g., the location and intensity of a contrast agent being injected into the body. Moreover, this is done in a single exposure, eliminating the problem of patient body movement during multiple exposures. Several methods of implementing the invention are disclosed, including the use of dual layer detectors and the use of photon counting detectors. The system and method enable the acquisition of clinically valuable information such as 3D breast tissue density, 3D microcalcification distribution and type, 3D distribution of contrast agent (e.g. iodine) and 3D component alteration of a subject's breast lesion (e.g., a mass) in a digital breast tomography system.

[0091] In mammography, spectral tomography imaging provides more complete and accurate diagnostic information about the breast compared to conventional 2D full-field digital mammography (FFDM), spectral FFDM and conventional DBT, including 3D breast tissue density, 3D microcalcification distribution and type, 3D distribution of contrast agent (e.g. iodine) and 3D component alteration of the breast lesion (e.g. lump) of interest.

[0092] Thus, systems and methods are disclosed herein that make it possible to perform material-selective chest imaging and enable acquisition of clinically valuable information, such as 3D location of contrast agents, while eliminating image artifacts due to patient body motion.

[0093] The terminology used herein is for the purpose of describing particular embodiments and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprises" and / or "comprising", as used herein, specify the presence of stated features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0094] Corresponding structures, materials, acts, and equivalents, if any, of all means-plus-function or step-plus-function elements in the following claims are intended to include any structure, material, or act for performing a function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or to limit the invention to the disclosed form. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. The present embodiment has been chosen and described in order to best explain the principles and practical applications of the invention, and to enable others skilled in the art to understand the invention in various modified forms as adapted to the particular use contemplated. [Explanation of symbols]

[0095] 10 Prior art approach, dual shot / single detector approach 12 Object, imaging object, imaging subject 15 X-ray source, X-ray radiation source, X-ray radiation tube source 20 First Filter 25 Low Energy X-Ray Radiation 30 Detector 40 Second Filter 45 High Energy X-ray Radiation 65 SDNR 98 Data Acquisition Network 99 Processors 100 Spectral imaging system, dual layer method, dual layer detector method 101 stack, dual detector structure 110 forward detector, forward α-Se photoconductive detector, forward α-Se photon integrating detector, forward CsI energy integrating scintillating detector, forward CsI photon integrating detector, forward detector layer 120 X-ray filter, Spectral separation filter, Rhodium Spectral separation filter 122 Incident X-rays, Incident X-ray radiation 124 Low Energy Spectral Filter 125 Board 126 High Energy Spectral Filter 150 Rear detector, Rear CsI energy integrating scintillating detector, Rear photon integrating detector, Rear α-Se photon integrating detector, Rear CsI photon integrating detector, Rear detector layer 201 Comparison of Spectral Separation 204 LE Spectral Radiant Energy 206 HE Spectral Radiant Energy 214 LE Spectral Radiant Energy 215 Separation 216 HE Spectral Radiation Energy 221 Comparison of Spectral Separation 224 LE Spectral Radiant Energy 225 Spectral energy peak separation, glass substrate 226 HE spectrum radiant energy, second substrate, second glass substrate 230 Counting circuit network, CMOS counting circuit network 234 LE Spectral Radiant Energy 235 Optical sensor (photodetector) array circuit network, optical sensor array, optical detector array 236 HE Spectral Energy 241 Spectral Separation Diagram 244 LE Spectral Radiant Energy 245 Spectral Energy Peak Separation 246 HE Spectral Energy 254 LE Spectral Radiant Energy 255 Spectral Energy Peak Separation 256 HE Spectral Energy 261 Spectral Separation Diagram 274 LE Spectral Radiant Energy 276 HE Spectral Energy 281 Spectral Separation Diagram 290 table 292 columns 294 columns Comparison of 300 LE and HE spectral separations 304 LE Spectral Radiant Energy 305 LE Spectral Radiant Energy 306 HE Spectral Energy 307 HE Spectral Energy 315 Spectral Energy Peak Separation 314 LE Spectral Radiant Energy 316 HE Spectral Energy 317 LE Spectral Radiant Energy 319 HE Spectral Radiant Energy 320 Comparison of Spectral Separation 325 Spectral Energy Peak Separation 350 Chart Comparison 352 Glass Substrate 375 table 380 Signal to Noise Ratio (SDNR) 400 single shot / single layer detector 401 Photon Counter Detection (PCD) Device, SWAD Imager Layer 500 SWAD Devices 510 Bulk Area 525 Multi-well sensing area 526 Multiwell 530, 535 Grid electrodes 550 Dielectric Pillar 560 High Voltage Electrode 600 simulated pixel response results, simulation results 700 Single Shot / Dual Layer Detector, Spectral Imaging System 701 Direct conversion forward photon counter detection (PCD) device, α-Se flat panel SWAD imager layer, photon counting detector, first X-ray detector layer 751 Rear EID detector, Indirect conversion flat panel X-ray detector layer, X-ray detector layer, Phosphor layer, EID layer 800 Single Shot / Dual Layer Detector, Spectral Imaging System 801 Direct conversion forward photon counter detection (PCD) device, α-Se flat panel SWAD imager layer, first X-ray detector layer, photon counting detector 851 Indirect conversion flat panel X-ray detector layer, rear EID detector, CsI EID layer, rear integrated detector 900 Double Layer Detector 901 Forward integrated detector, Direct conversion flat panel X-ray forward detector, X-ray forward detector, X-ray detector layer, α-Se EID flat panel X-ray detector layer, Forward imaging detector 930 Semiconductor pixel circuit network 940 Spectral Filter 951 Indirect conversion flat panel X-ray detector layer, rear integrated detector 1000 Double Layer Detector 1001 Direct conversion flat panel X-ray forward detector, Direct conversion flat panel X-ray detector layer, α-Se EID flat panel X-ray detector layer, Forward detector, Forward integrated detector 1030 Semiconductor pixel circuit network 1040 More Spectral Filters 1051 Indirect conversion flat panel X-ray detector layer 1100 Simulation result image 1101, 1102 4x4 array 1150 table 1160 Half of the image 1170 Top half of image

Claims

1. a separation filter for spectrally separating radiation from an x-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object; A substrate; an X-ray photon counting detector formed on the substrate; Equipped with the x-ray photon counting detector comprises an array of detector pixels, each detector pixel comprising a sensor for detecting interactions of individual x-ray photons of the incident radiation transmitted through the imaged object over a fixed period of time; each detector pixel of the array has associated counting circuitry operable to generate a first electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons in the first energy level band and a second electrical signal representative of a respective count of a number of detected interactions of individual X-ray photons in the second energy level band, the first electrical signal and the second electrical signal from the array of detector pixels providing a respective energy spectrum image of the imaged object.

2. each detector pixel sensor generates an electrical pulse having a height attribute commensurate with an energy level of an interacting x-ray photon, and each associated counting circuit of the array includes a pulse height threshold selector circuit for incrementing a count of detected interactions of individual x-ray photons having a height attribute at or above a particular threshold energy level used to distinguish between high and low energy levels; 2. The apparatus of claim 1, wherein the radiation in the first energy level band is of greater energy than the radiation in the second energy level band, and the particular threshold energy level corresponds to a pulse height attribute associated with the first energy level band.

3. the imaged object includes a contrast agent material having a characteristic K-edge atomic energy band level, the separation filter absorbs X-ray radiation near the K-edge atomic energy band level, the contrast agent is iodine, and the separation filter comprises a material selected from the group including Rh, Ag, Pd, In, and Sn; and / or 10. The apparatus of claim 1, wherein the sensor of each detector pixel comprises an amorphous selenium (α-Se) based field-shaped multiwell avalanche detector (SWAD).

4. The X-ray photon counting detector is a front detector formed on the substrate, and the apparatus further comprises a rear detector disposed below the substrate, the rear detector comprising: a scintillating screen for converting incident radiation containing x-ray photons of the first energy level band transmitted through the imaged object and through the front detector into light quanta; a photosensor array disposed between the scintillating screen and the substrate, the photosensor array operable to capture the photons from the scintillating screen and convert the captured photons into further electrical signals, the further electrical signals operable for combination with the first electrical signals from the array of detector pixels to obtain an image of the imaging object; Equipped with the rear detector is an integrated detector and the scintillating screen is made of a material that matches the characteristic K-edge atomic energy band level of the contrast agent material; and / or said scintillating screen being of structured or columnar type or of unstructured or granular type; and / or the rear detector is a cylindrical CsI energy-integrating detector; and / or the scintillating screen further comprises a backing comprising one of a reflective surface or an absorptive surface; and / or The optical sensor array includes: a plurality of photosensitive storage elements for capturing at least a portion of the photons from the scintillating screen; a plurality of switching elements, each of the plurality of switching elements corresponding to one of each of the plurality of photosensitive storage elements, a transparent metal bias layer, and a transparent 2D patterned metal layer facing the scintillating screen; The apparatus of claim 3 , comprising:

5. a separation filter for spectrally separating radiation from an x-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object; A first substrate; an x-ray photon counting forward detector formed on the first substrate, the x-ray photon counting forward detector comprising an array of detector pixels, each detector pixel comprising a sensor for detecting interactions of individual x-ray photons of the incident radiation transmitted through the imaged object for a fixed period of time, each of the array of detector pixels having associated counting circuitry operable to generate a first electrical signal representative of a respective count of a number of detected interactions of individual x-ray photons of the first energy level band and a second electrical signal representative of a respective count of a number of detected interactions of individual x-ray photons of the second energy level band, the first electrical signal and the second electrical signal from the array of detector pixels providing respective low and high energy spectral images of the imaged object; a rear detector formed on a second substrate and disposed below the first substrate; Equipped with The rear detector is a scintillating screen for converting incident radiation containing x-ray photons of the second energy level band transmitted through the imaged object and through the front detector into light quanta; a photosensor array disposed between the scintillating screen and the second substrate for the rear detector, the photosensor array operable to capture the photons from the scintillating screen and convert the captured photons into further electrical signals, the further electrical signals operable for combination with the second electrical signals from the array of detector pixels to obtain an image of the imaging object; An apparatus comprising:

6. each sensor of the front detector pixels generates an electrical pulse having a height attribute commensurate with an energy level of an interacting x-ray photon, and each associated counting circuit of the array includes a pulse height threshold selector circuit for incrementing a count of detected interactions of individual x-ray photons having a height attribute at or above a particular threshold energy level; 6. The apparatus of claim 5, wherein the radiation in the second energy level band is of greater energy than the radiation in the first energy level band, and the particular threshold energy level corresponds to a pulse height attribute associated with the first energy level band.

7. the imaging subject includes a contrast agent material having a characteristic K-edge atomic energy band level, and the isolation filter has an X-ray absorption edge for absorbing the X-ray radiation near the K-edge atomic energy band level; the contrast agent is iodine and the separation filter comprises a material selected from the group including Rh, Ag, Pd, In and Sn; and / or the rear detector is an integrating detector, and the scintillating screen is made of a material that matches the characteristic K-edge atomic energy band level of the contrast agent material; 6. The apparatus of claim 5, wherein the scintillating screen is of the structured or columnar type, or of the unstructured or granular type.

8. the sensor of each front detector pixel comprises an amorphous selenium (α-Se) based field shaped multi-well avalanche detector (SWAD) and the back detector is a pillared CsI energy integrating detector; and / or the scintillating screen further comprises a backing comprising one of a reflective surface or an absorptive surface; The optical sensor array includes: a plurality of photosensitive storage elements for capturing at least a portion of the photons from the scintillating screen; a plurality of switching elements, each of the plurality of switching elements corresponding to one of each of the plurality of photosensitive storage elements, a transparent metal bias layer, and a transparent 2D patterned metal layer facing the scintillating screen; The apparatus of claim 5 , comprising:

9. a separation filter for spectrally separating radiation from an x-ray radiation source into a first energy level band and a second energy level band for incident radiation on an imaged object, the second energy level band being of greater energy than the first energy level band; A glass substrate; a forward integrated detector formed on the glass substrate, the forward integrated detector comprising a first pixel sensor for directly converting a first energy level band of X-ray photons of the incident radiation transmitted through the imaged object into a first image signal configurable to form a low energy image of the imaged object; a rear integrated detector disposed below the glass substrate, the rear integrated detector comprising a second pixel sensor for indirectly converting second energy level band x-ray photons of the incident radiation passing through the imaged object and transmitted through the front integrated detector and the glass substrate into a second image signal configurable to form a high energy image of the imaged object; An apparatus comprising:

10. The forward integrated detector includes: a first photoconductive layer for converting incident radiation containing X-ray photons of the first energy level band transmitted through the imaged object into an electric charge; a first charge storage array disposed between the first photoconductive layer and the substrate for storing charges associated with the converted x-ray photons; and / or and / or a filter disposed at an exit face of the front detector, the filter including a material operable to modulate the x-ray radiation exiting the front detector and to attenuate x-ray photons in the first energy level band; 10. The apparatus of claim 9, wherein the first photoconductive layer of the front energy-integrating detector comprises an amorphous selenium material and the scintillating screen of the rear energy-integrating detector comprises a CsI material.

11. The rear integrated detector includes: a scintillating screen for converting incident radiation containing X-ray photons of the second energy level band transmitted through the imaged object, the forward integrated detector, and the glass substrate into light quanta; a photosensor array disposed between the scintillating screen and the glass substrate, the photosensor array operable to capture the photons from the second scintillating screen and convert the captured photons into the second image signal; The apparatus of claim 10 .

12. the imaging subject includes a contrast agent material having a characteristic K-edge atomic energy band level, the separation filter has an X-ray absorption edge for absorbing the X-ray radiation close to the K-edge atomic energy band level, and the scintillating screen is made of a material that matches the characteristic K-edge atomic energy band level of the contrast agent material; and / or said scintillating screen being of structured or columnar type or of unstructured or granular type; and / or the scintillating screen further comprises a backing comprising one of a reflective surface or an absorptive surface; and / or The optical sensor array includes: a plurality of photosensitive storage elements for capturing at least a portion of the photons from the scintillating screen; a plurality of switching elements, each of the plurality of switching elements corresponding to one of each of the plurality of photosensitive storage elements, a transparent metal bias layer, and a transparent 2D patterned metal layer facing the scintillating screen; The apparatus of claim 11 , comprising:

13. A source of X-ray radiation; and a first low energy band pass filter configured for alignment in front of the x-ray radiation source to allow transmission of a first low energy level band of x-ray radiation for incidence on an imaged object at a first time instance; a second high energy bandpass filter configured for subsequent alignment in front of the x-ray radiation source to allow transmission of a second high energy level band x-ray radiation for incidence on the imaged object at a second time instance; A dual layer X-ray radiation detector; Equipped with The dual layer X-ray radiation detector comprises: A glass substrate; a forward energy-integrating detector formed on the glass substrate, the forward energy-integrating detector comprising a first pixel sensor for directly converting photons of the first low energy level band of incident X-ray radiation transmitted through the imaged object during the first time instance into a first image signal and for directly converting photons of the second higher energy level band of incident X-ray radiation transmitted through the imaged object during the second time instance into a second image signal; a rear energy-integrated detector formed below the glass substrate, the rear energy-integrated detector comprising a second pixel sensor for indirectly converting photons of the first lower energy level band of incident X-ray radiation transmitted through the imaged object and through the forward energy-integrated detector and the glass substrate during the first time instance into a further first image signal, and for indirectly converting photons of the second higher energy level band of incident X-ray radiation transmitted through the imaged object and through the forward energy-integrated detector and the glass substrate during the second time instance into a further second image signal; Equipped with the first image signal from the front detector can be combined with the further first image signal from the rear detector to form a low energy image of the imaged object; An x-ray imaging system, wherein the second image signal from the front detector is combineable with the further second image signal from the rear detector to form a high energy image of the imaged object.

14. The rear energy integration detector includes: a scintillating screen for converting incident radiation containing X-ray photons of the first low energy level band and the second higher energy level band transmitted through the imaged object and through the forward integrated detector into photons; a photosensor array disposed between the scintillating screen and the glass substrate, the photosensor array operable to capture the photons from the scintillating screen and convert the captured photons into respective further first and further second image signals; and / or The forward energy integration detector includes: a photoconductive layer for converting incident radiation containing X-ray photons of the first lower energy level band and the second higher energy level band transmitted through the imaged object into respective electric charges; a charge storage array disposed between the first photoconductive layer and the glass substrate for storing the respective charges associated with the converted x-ray photons used to form the respective first and second image signals; The system of claim 13 , comprising:

15. 1. A method for x-ray imaging, comprising: Under the object to be imaged with incident X-ray radiation, A glass substrate; a forward energy integrating detector formed on the glass substrate and including a first pixel sensor; a rear energy integrating detector formed below the glass substrate and including a second pixel sensor; providing a dual layer X-ray radiation detector comprising: positioning a first low energy band pass filter in front of an x-ray radiation source to allow transmission of a first low energy level band of x-ray radiation for incidence on the imaged object at a first time instance; positioning a second high energy band filter in front of the x-ray radiation source to allow transmission of a second high energy level band x-ray radiation for incidence on the imaged object at a second time instance, the dual layer x-ray radiation detector receiving the first low energy level band x-ray radiation at the first time instance and receiving the second high energy level band x-ray radiation at the second time instance through the imaged object; using the first pixel sensor of the forward energy-integrating detector to directly convert photons of the first lower energy level band of incident X-ray radiation transmitted through the imaged object during the first time instance into a first image signal and directly convert photons of the second higher energy level band of incident X-ray radiation transmitted through the imaged object during the second time instance into a second image signal; using the second pixel sensor of the rear energy-integrated detector to indirectly convert photons of the first lower energy level band of the incident X-ray radiation transmitted through the imaged object and through the forward energy-integrated detector and the glass substrate during the first time instance into a further first image signal, and to indirectly convert photons of the second higher energy level band of the incident X-ray radiation transmitted through the imaged object and through the forward energy-integrated detector and the glass substrate during the second time instance into a further second image signal; forming a low energy image of the imaged object from the first image signal and the further first image signal; forming a high energy image of the imaged object from the second image signal and the further second image signal; 13. A method for x-ray imaging comprising:

Images