Abstract: A global optimization and apparatus to decompose spectral computed tomography (CT) projection data into basis materials. A cost function is defined to represent the difference between the measured projection data and calculated attenuation data using projection lengths for the basis materials with corresponding material models and a detector model to calculate the detector response. The cost function may have many local minima and only one global minima. A global optimization method is then used to obtain the projection lengths corresponding to the global minimum of the cost function. The global optimization method can be either a single-stage optimization method, or can be performed in multiple stages, e.g., a first coarse optimization stage followed by a second fine optimization stage using the final values of the first stage as the inputs into the second stage. The global optimization method can be a stochastic optimization method.

Abstract: A CT scanner apparatus includes an X-ray source mounted on a gantry of the CT scanner apparatus. The CT scanner apparatus also includes a first X-ray detector mounted on the gantry opposite to the X-ray source, and configured to detect X-rays emitted from the X-ray source and transmitted through an object. The CT scanner apparatus also includes a fixed, sparse array of second X-ray detectors. Each of the second X-ray detectors includes a plurality of stacked scintillators and a photosensor adjacent to a sidewall of the stacked scintillators in a side-readout configuration.

Abstract: A photon-counting detector apparatus is configured to receive X-rays transmitted from an X-ray source. The photon-counting detector apparatus includes a first photon-counting detector having a first detecting material configured to detect photons using a first set of energy bins. The photon-counting detector apparatus also includes a second photon-counting detector arranged above the first photon-counting detector relative to an incidence direction of the X-rays transmitted from the X-ray source. The second photon-counting detector has a second detecting material configured to detect photons using a second set of energy bins. The first set of energy bins differs from the second set of energy bins.

Abstract: A method and apparatus is provided to reconstruct a collective image of a multiple method/geometry imaging system (e.g., a hybrid computed tomography system having energy-integrating detectors arranged in a third-generation geometry and photon-counting detectors arranged in a fourth generation geometry), wherein a splitting-based iterative algorithm using modified dual variables is used in the image reconstruction. Whereas a separate image for each method/geometry of the multiple method/geometry imaging system can be obtained by solving the distinct system-matrix equation corresponding to each respective method/geometry, the collective image is obtained by simultaneously solving a collective optimization problem including all respective system-matrix. The collective image is obtained more efficiently using variable splitting to subdivide the optimization into subproblems that are solved in an iterative fashion.

Abstract: A computed tomography (CT) imaging apparatus includes a radiation source configured to emit X-rays; a plurality of photon-counting detectors configured to detect X-rays emitted by the radiation source and generate a photon counting signal based on the detected X-rays; and processing circuitry to obtain a kV-waveform used by the radiation source to generate the X-rays during a scan of an object, and adjust at least one energy threshold dividing the photon counting signal into a plurality of spectra bins in accordance with the obtained kV-waveform.

Abstract: An apparatus and method of processing X-ray projection data including spectral computed tomography (CT) projection data. The spectral CT data is decomposed into material projection lengths using a material-decomposition method that includes an initial-estimate method to provide an initial projection-lengths estimate. The initial-estimate method can include first reconstructing an image using non-spectral CT data, and then subdividing the reconstructed image into materials according to the relative attenuation density of areas within the reconstructed image (e.g., high attenuation areas correspond to a high attenuation material such as bone). The projection length estimates of each material are then obtained by forward projecting the corresponding subdivision of the reconstructed image. Also, the initial estimate can be obtained/refined by selecting the projection lengths with smallest cost-function value from randomly chosen projection lengths within a sample space.

Abstract: A computed tomography (CT) apparatus and a method for determining response of a photon-counting detector of a CT scanner. Based on a count rate of an incident spectrum and a dead time parameter of the photon-counting detector, a highest pileup order that has a contribution towards an output spectrum of the photon-counting detector greater than a threshold corresponding to the pileup order is determined. In computing the overall output spectrum of the photon-counting detector, only the spectra corresponding to pileup orders lower than or equal to the highest pileup order are considered.

Abstract: Method, system, and programs for providing content recommendation are disclosed. A first set of candidate content items may be generated based on a user profile, and a second set of candidate items may be generated based on the likelihood that the user will click a corresponding candidate content item in the second set. The candidate content items in the first and second sets may be ranked together using a learning model and presented to the user as content recommendations based on their rankings. The likelihood that the user will click a given candidate content item in the second set may be estimated based on similarities between the given content item and content items related to the given content item. Such a similarity may be computed based on activities performed by users who have viewed both the given content item and a related content item.

Abstract: A computed-tomography apparatus that includes a CT scanner including an X-ray source and a detector covering respective angle ranges in the axial and transaxial planes of the CT scanner. The CT detector includes first detector elements disposed on a first surface to capture incident X-ray photons emitted from the X-ray source, and second detector elements sparsely disposed on a second surface different from the first surface, the second surface being farther away from the scanner than the first surface, the second detector elements being smaller in number than the first detector elements. Each of the second detector elements is reachable only by X-ray photons originating in a small angle range around a line connecting the X-ray source and a center of the surface of the detector element, the small angle range being determined by the predetermined distance separating the first and second surfaces and a size of the detector element.

Abstract: An apparatus and a method are provided for calculating an output spectrum of a photon-counting detector based on an incident spectrum. The apparatus includes processing circuitry to determine a plane extending from a top face of the photon-counting detector that includes regions that all possible incident rays will transverse; divide the determined plane into subregions; calculate a detector response function for each of the subregions; determine an overall detector response function by summing the calculated detector response function for each of the subregions and normalizing the summation by an area of the determined plane; and calculate the output spectrum based on the overall detector response function and the incident spectrum.

Abstract: An apparatus and method for reducing the X-ray flux in a computed-tomography (CT) scanner that includes a rotating X-ray source and a plurality of stationary photon-counting detectors configured to capture incident X-ray photons emitted from the X-ray source. A bowtie filter equipped with an edge filter that can be positioned in a reconfigurable manner such that the high X-ray flux at the leading edge of an X-ray fan beam incident on the detector is reduced. The CT apparatus includes a processor that is configured to compute the displacement of the edge filter in either a static or dynamic manner such that that the intensity of X-ray flux at the detectors in within acceptable operating limits.

Abstract: A computed tomography (CT) imaging system is provided including processing circuitry configured to obtain a plurality of basis images that are combined to generate a target image; de-noise the basis images using a noise-reduction method to generate de-noised basis images; calculate noise maps of the basis images by subtracting the de-noised basis images from the basis images; calculate a weight for each of the noise maps using the target image and the calculated noise maps; and generate a reduced-noise target image using the target image, the calculated noise maps, and the calculated weights.

Abstract: An X-ray computer tomography apparatus includes at least one X-ray tube generating X-rays, first detector elements (energy integrating type) and second detector elements (photon counting type) detecting an intensity and spectrum of the X-rays transmitted through the object respectively, at least one data acquisition circuit acquiring first projection data and second projection data smaller in data amount than the first projection data detected by the first and second detector elements respectively, an arithmetic circuit computing a minimum value of a cost function based on the first and second projection data by executing an iterative reconstruction algorithm, and reconstruction circuit reconstructing an image of the object based on the first and second projection data, which correspond to the minimum value of the cost function.

Abstract: A computed-tomography apparatus that includes a CT scanner including an X-ray source and a detector covering respective angle ranges in the axial and transaxial planes of the CT scanner. The CT detector includes first detector elements disposed on a first surface to capture incident X-ray photons emitted from the X-ray source, and second detector elements sparsely disposed on a second surface different from the first surface, the second surface being farther away from the scanner than the first surface, the second detector elements being smaller in number than the first detector elements. Each of the second detector elements is reachable only by X-ray photons originating in a small angle range around a line connecting the X-ray source and a center of the surface of the detector element, the small angle range being determined by the predetermined distance separating the first and second surfaces and a size of the detector element.

Abstract: A method and apparatus for estimating a parameter vector including a plurality of parameters of a detector response model of a photon-counting detector. The method includes calculating a modeled spectrum based on an input spectrum and an initial value of the plurality of parameters. For each detector, a difference between the normalized photon count of the measured spectrum and the normalized modeled spectrum is calculated. A root mean square error (RMSE) between the measured and modeled spectra is obtained by squaring the normalized difference and weighting the normalized difference by a weighting factor. The parameter vector is updated until an optimum RMSE value is achieved. Upon determining optimal values of the parameter vector, measured data that is obtained via a patient scan is corrected based on the optimal parameter vector.

Abstract: A method and an apparatus for determining primary and secondary escape probabilities for a large photon-counting detector without pile-up. A model for the detector with no pile-up is formulated and used for spectrum correction in a computed tomography scanner. The method includes computing primary K-escape and secondary K-escape probabilities occurring at a certain depth within the photon-counting detector. Further, a no pile-up model for the photon-counting detector is formulated by determining a response function, based on the computed primary and secondary K-escape probabilities and geometry of the photon-counting detector. The method includes obtaining a measured CT scan of an object and further performs spectrum correction by determining the incident input spectrum based on the response function and the measured spectrum of the large photon-counting detector.

Abstract: A spectral computed tomography (CT) ordered subsets (OS) reconstruction method using two sets of projection data having a different number of views is provided. The method includes obtaining a first set of projection data that includes single-energy CT data for a first number of views, obtaining a second set of projection data that includes spectral CT data for a second number of views, wherein the first and second numbers are integers and the second number is smaller than the first number, partitioning the first set of projection data into N equal-sized subsets of projection data, including the second set of projection data in each of the N subsets of projection data to generate N expanded subsets of projection data, and performing OS reconstruction with the N expanded subsets of projection data to generate a reconstructed CT image.

Abstract: A control circuit for a computer-aided tomography (CT) system includes an input that receives a master timing signal and an input that receives a first timing signal. The control circuit includes a mode detection circuit that determines the scan mode of the CT system based on the master timing signal and a first timing signal, where the frequency of the first time signal is lower than the frequency of the master timing signal. The control circuit also includes a circuit that generates a second timing signal based on the master timing signal and the scan mode, where the second timing signal that has a lower frequency than the master timing frequency but a higher frequency than the frequency of the first timing signal.

Abstract: An apparatus is provided to reconstruct an image using combined third-generation energy-integrating computed tomography projection data and fourth-generation spectrally resolved computed tomography projection data. The apparatus includes processing circuitry configured to obtain first projection data representing projection data from an energy-integrating detector; obtain second projection data representing projection data from a photon-counting spectrally discriminating detector; and reconstruct a first combined-system basis image and a second combined-system basis image by solving a combined-system matrix equation using the first projection data and the second projection data.

Abstract: A spectral computed tomography scanner apparatus, including a rotating X-ray source, a plurality of fixed energy-discriminating detectors, a processor that generates a shadow map that indicates, for each detector/view angle, a shadow state of the detector, the shadow state indicating that one of X-rays are completely blocked by a second detector and do not reach the detector, the X-rays are partially blocked by the second detector and partially reach the detector, the X-rays are not blocked by any of the detectors and reach the detector, and the detector is not with the scan field of view at the view angle, and a controller configured to cause the scanner apparatus to perform a scan of an object over a first range of view angles to collect view data, wherein the processor is configured to perform scatter correction using the collected view data and the generated shadow map.