Abstract: There is provided a method and corresponding system for image reconstruction based on energy-resolved x-ray data. The method comprises collecting (S1) at least one representation of energy-resolved x-ray data, and performing (S2) at least two basis material decompositions based on said at least one representation of energy-resolved x-ray data to generate at least two original basis image representation sets. The method further comprises obtaining or selecting (S3) at least two basis image representations from at least two of said original basis image representation sets, and processing (S4) said obtained or selected basis image representations by data processing based on machine learning to generate at least one representation of output image data.

Abstract: Disclosed is a calibration phantom for an x-ray imaging system having an x-ray source and an x-ray detector. The calibration phantom includes a combination of geometric objects of at least three different types and/or compositions including: a first object located in the middle, including a first material; a plurality of second objects arranged around the periphery of the first object, at least a subset of the second objects including a second material different than the first material, wherein the first object is relatively larger than the second objects; a plurality of third objects arranged around the periphery of the first object and/or around the periphery of at least a subset of the second objects, at least a subset of the third objects including a third material different than the first material and the second material, wherein the third objects are relatively smaller than the second objects.

Abstract: Disclosed is a method and corresponding system for correcting the pileup effect in energy-discriminating photon-counting detectors. According to a first aspect, there is provided a method for pileup correction in a non-paralyzable energy-discriminating photon-counting x-ray detector operating based on a number of energy bins. The method includes adding, for each of a number of energy bins, a correction term to the detected signal of the energy bin, the correction term being a product of two separable parameterized functions, each of which includes at least one parameter, where a first parameterized function depends on a weighted sum of the detected signal over the energy bins, and where a second parameterized function depends on the detected signal(s) in one or several energy bin(s). By assuming separability and ignoring any cross correlations, the number of parameters and the complexity of the pileup correction algorithm are reduced substantially.

Abstract: An x-ray imaging apparatus includes an x-ray source and detector with multiple detector elements. The source and detector are on a support that rotates around a subject, enabling projections at different view angles. The apparatus operates the x-ray source in switched kVp mode for alternately applying different voltages, including lower and higher voltages, during rotation to enable lower-energy and higher-energy exposures over the projections, providing for lower-energy projections and higher-energy projections. The x-ray detector is a photon-counting multi-bin detector allocating photon counts to multiple energy bins, and the apparatus selects counts from at least a subset of the bins to provide corresponding photon count information for both lower- and higher-energy projections.

Abstract: Disclosed is a method and corresponding system for correcting the pileup effect in energy-discriminating photon-counting detectors. According to a first aspect, there is provided a method for pileup correction in a non-paralyzable energy-discriminating photon-counting x-ray detector operating based on a number of energy bins. The method includes adding, for each of a number of energy bins, a correction term to the detected signal of the energy bin, the correction term being a product of two separable parameterized functions, each of which includes at least one parameter, where a first parameterized function depends on a weighted sum of the detected signal over the energy bins, and where a second parameterized function depends on the detected signal(s) in one or several energy bin(s). By assuming separability and ignoring any cross correlations, the number of parameters and the complexity of the pileup correction algorithm are reduced substantially.

Abstract: An x-ray imaging apparatus includes an x-ray source and detector with multiple detector elements. The source and detector are on a support that rotates around a subject, enabling projections at different view angles. The apparatus operates the x-ray source in switched kVp mode for alternately applying different voltages, including lower and higher voltages, during rotation to enable lower-energy and higher-energy exposures over the projections, providing for lower-energy projections and higher-energy projections. The x-ray detector is a photon-counting multi-bin detector allocating photon counts to multiple energy bins, and the apparatus selects counts from at least a subset of the bins to provide corresponding photon count information for both lower- and higher-energy projections.

Abstract: Disclosed is a calibration phantom for an x-ray imaging system having an x-ray source and an x-ray detector. The calibration phantom includes a combination of geometric objects of at least three different types and/or compositions including: a first object located in the middle, including a first material; a plurality of second objects arranged around the periphery of the first object, at least a subset of the second objects including a second material different than the first material, wherein the first object is relatively larger than the second objects; a plurality of third objects arranged around the periphery of the first object and/or around the periphery of at least a subset of the second objects, at least a subset of the third objects including a third material different than the first material and the second material, wherein the third objects are relatively smaller than the second objects.

Abstract: A method for imaging an object to be reconstructed includes acquiring projection data corresponding to the object. Furthermore, the method includes generating a measured sinogram based on the acquired projection data and formulating a forward model, where the forward model is representative of a characteristic of the imaging system. In addition, the method includes generating an estimated sinogram based on an estimated image of the object and the forward model and formulating a statistical model based on at least one of pile-up characteristics and dead time characteristics of a detector of the imaging system. Moreover, the method includes determining an update corresponding to the estimated image based on the statistical model, the measured sinogram, and the estimated sinogram and updating the estimated image based on the determined update to generate an updated image of the object. Additionally, the method includes outputting a final image of the object.

Abstract: A method for imaging an object to be reconstructed includes acquiring projection data corresponding to the object. Furthermore, the method includes generating a measured sinogram based on the acquired projection data and formulating a forward model, where the forward model is representative of a characteristic of the imaging system. In addition, the method includes generating an estimated sinogram based on an estimated image of the object and the forward model and formulating a statistical model based on at least one of pile-up characteristics and dead time characteristics of a detector of the imaging system. Moreover, the method includes determining an update corresponding to the estimated image based on the statistical model, the measured sinogram, and the estimated sinogram and updating the estimated image based on the determined update to generate an updated image of the object. Additionally, the method includes outputting a final image of the object.

Abstract: There is provided a method of image reconstruction based on energy-resolved image data from a photon-counting multi-bin detector or an intermediate storage. The method includes processing (S1) the energy-resolved image data by performing at least two separate basis decompositions using different number of basis functions for modeling linear attenuation, wherein a first basis decomposition is performed using a first smaller set of basis functions to obtain at least one first basis image representation, and wherein a second basis decomposition is performed using a second larger set of basis functions to obtain at least one second basis image representation. The method also includes reconstructing a first image based on the at least one first basis image representation obtained from the first basis decomposition, and combining the first image with information representative of the at least one second basis image representation.

Abstract: There is provided a method of image reconstruction based on energy-resolved image data from a photon-counting multi-bin detector or an intermediate storage. The method includes processing (Si) the energy-resolved image data by performing at least two separate basis decompositions using different number of basis functions for modeling linear attenuation, wherein a first basis decomposition is performed using a first smaller set of basis functions to obtain at least one first basis image representation, and wherein a second basis decomposition is performed using a second larger set of basis functions to obtain at least one second basis image representation. The method also includes reconstructing a first image based on the at least one first basis image representation obtained from the first basis decomposition, and combining the first image with information representative of the at least one second basis image representation.

Abstract: There is provided a method for at least partly determining the orientation of an edge-on x-ray detector with respect to the direction of x-rays from an x-ray source. The method includes obtaining (S1) information from measurements, performed by the x-ray detector, representing the intensity of the x-rays at a minimum of two different relative positions of a phantom in relation to the x-ray detector and the x-ray source, the phantom being situated between the x-ray source and the x-ray detector and designed to embed directional information in the x-ray field when exposed to x-rays. The method also includes determining (S2) at least one parameter associated with the orientation of the x-ray detector with respect to the direction of x-rays based on the obtained information from measurements and a geometrical model of the spatial configuration of the x-ray detector, x-ray source and phantom.

Abstract: There is provided a method of image reconstruction based on energy-resolved image data from a photon-counting multi-bin detector or an intermediate storage. The method comprises processing (S1) the energy-resolved image data by performing at least two separate basis decompositions using different number of basis functions for modeling linear attenuation, wherein a first basis decomposition is performed using a first smaller set of basis functions to obtain at least one first basis image representation, and wherein a second basis decomposition is performed using a second larger set of basis functions to obtain at least one second basis image representation. The method also comprises reconstructing a first image based on said at least one first basis image representation obtained from the first basis decomposition, and combining the first image with information representative of said at least one second basis image representation.

Abstract: There is provided a method for at least partly determining the orientation of an edge-on x-ray detector with respect to the direction of x-rays from an x-ray source. The method includes obtaining (S1) information from measurements, performed by the x-ray detector, representing the intensity of the x-rays at a minimum of two different relative positions of a phantom in relation to the x-ray detector and the x-ray source, the phantom being situated between the x-ray source and the x-ray detector and designed to embed directional information in the x-ray field when exposed to x-rays. The method also includes determining (S2) at least one parameter associated with the orientation of the x-ray detector with respect to the direction of x-rays based on the obtained information from measurements and a geometrical model of the spatial configuration of the x-ray detector, x-ray source and phantom.

Abstract: There is provided a method of image reconstruction based on energy-resolved image data from a photon-counting multi-bin detector or an intermediate storage. The method comprises processing (S1) the energy-resolved image data by performing at least two separate basis decompositions using different number of basis functions for modeling linear attenuation, wherein a first basis decomposition is performed using a first smaller set of basis functions to obtain at least one first basis image representation, and wherein a second basis decomposition is performed using a second larger set of basis functions to obtain at least one second basis image representation. The method also comprises reconstructing a first image based on said at least one first basis image representation obtained from the first basis decomposition, and combining the first image with information representative of said at least one second basis image representation.

Abstract: A method and corresponding arrangement for reconstructing an image based on spectral image data acquired for at least two different effective energies includes: obtaining a first set of spectral image data related to an object to be imaged and a second set of spectral image data related to a calibration phantom including at least one reference material; performing basis decomposition based on the first set of spectral image data, providing estimated basis images of the object to be imaged with respect to associated basis functions; performing basis decomposition based on the second set of spectral image data, providing calibrated estimates of reference basis coefficients corresponding to the at least one reference material; and determining image values representing the object based on a system model of an imaging system to be emulated, the estimated basis images and their associated basis functions, and the calibrated estimates of reference basis coefficients.