Toshiba Medical Systems Corporation

Kabushiki Kaisha Toshiba

Xiaolan Wang

Yu Zou

Yuexing Zhang

Daniel Gagnon

Chunguang Cao

Zhou Yu

Miesher Rodrigues

Adam Petschke

Satoru Nakanishi

Zhengyan Wang

Changguo Ji

Alexander A Zamyatin

Yujie Lu

Richard Thompson

Sachin S Junnarkar

Yasuteru Kawai

A steam turbine exhaust chamber cooling device includes a plurality of spray nozzles, and the plurality of spray nozzles inject spray water from an injection port to the turbine exhaust chamber. Here, a center line of the injection port is inclined with respect to a radial direction of a turbine rotor so that the plurality of spray nozzles inject the spray water in a direction counter to a rotation direction of the turbine rotor. An inclination angle &#x3b1; at which the center line of the injection port is inclined to a forward side of the rotation direction with respect to the radial direction of the turbine rotor is in a relationship represented by the following formula (A),25&#xb0;&#x2264;&#x3b1;&#x2264;45&#xb0;&#x2003;&#x2003;(A).

Steam turbine exhaust chamber cooling device and steam turbine

A method and apparatus is provided to calculate scatter using a method to determine primary X-ray flux, first-scatter flux, and multiple-scatter flux using an integral formulation of a radiative transfer equation and using spherical-harmonic expansion. The integral for the primary X-ray flux does not include a spherical-harmonic expansion. The integral for the first-scatter flux includes an angle-dependent scatter cross-section. The integral for the multiple-scatter flux is performed iteratively, includes spherical harmonics, and includes a scatter cross-section expanded using Legendre polynomials. The integrals of attenuation along propagation rays can be accelerated using material decomposition of the attenuation coefficients. An anti-scatter-grid term can be included in the integrals to account for the effects of an anti-scatter grid on the fluxes prior to detection of the X-rays.

Scatter simulation with a radiative transfer equation using direct integral spherical harmonics method for computed tomography

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. The initial estimate can also be conditioned on the X-ray flux at the X-ray source.

More efficient method and apparatus for detector response correction and material decomposition of projection data obtained using photon-counting detectors

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.

Polar effect model, system, and method for photon counting detector in medical imaging systems including computed tomography

A computed tomography (CT) imaging apparatus for performing a scanogram includes a radiation source to emit X-rays; a plurality of photon-counting detectors (PCDs) arranged in a circular ring between the radiation source and a CT detector; and processing circuitry to perform a first scan to obtain projection data; determine a plurality of dark channels by comparing the obtained projection data to a predetermined threshold; add at least one adjacent padding channel to the determined plurality of dark channels to determine a plurality of shadowed channels; generate a correction map from the determined plurality of shadowed channels; and correct a scanogram obtained by a second scan based on the generated correction map. The apparatus reduces the shadow effects in the scanogram scan.

Method for scanogram scans in photon-counting computed tomography

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.

Wide X-ray spectrum photon counting computed tomography

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.

Count-weighted least squares parameter estimation for a photon-counting detector

A computed tomography (CT) apparatus and a method for identifying photon-counting detectors that are polarized due to high flux, thereby rendering the photon-counting detector inoperable. The data obtained from the photon-counting detectors that are determined to be polarized is skipped during an image pre-reconstruction phase. The data is further assigned a weight of zero during an image reconstruction phase in order to avoid imaging artifacts in the reconstructed CT image.

Method for identifying and processing detector polarization in photon-counting spectral X-ray detectors

Photon counting detectors are sparsely placed at predetermined positions in the fourth-generation geometry around an object to be scanned in spectral Computer Tomography (CT). An X-ray emitting source rotates radially outside the sparsely placed photon counting detectors. Furthermore, the integrating detectors are placed in the third-generation in combination to the sparsely placed photon counting detectors at predetermined positions in the fourth-generation geometry.

Method and system for spectral computed tomography (CT) with inner ring geometry

An apparatus and method of processing X-ray projection data obtained using photon-counting detectors and having multiple spectral components. The processing of the projection data includes correcting for nonlinear detector response, where the detector response model includes: pileup, ballistic deficit effects, polar effects, and characteristic X-ray escape. The processing of the projection data also includes a material decomposition mapping the projection data from spectral components into material components corresponding to high-Z and low-Z materials. The material decomposition includes a noise balancing process where the allocation of spectral components between a high-energy and a low-energy combination of spectral components is adjusted such that both high- and low-energy components have signal-to-noise ratios of similar magnitude. For computed tomography (CT) applications, material decomposition can be followed by image reconstruction and then image post-processing and presentation. For non-CT applications, material decomposition can be followed by image post-processing and presentation.

Pre-reconstruction calibration, data correction, and material decomposition method and apparatus for photon-counting spectrally-resolving X-ray detectors and X-ray imaging

A method and apparatus of aligning calibration projection data with object projection data to improve calibration corrections of the object projection data. In a first implementation, the method interpolates and upsamples both the calibration and object data, then shifts the upsampled calibration data to match a sub-view angular offset of the object data, and then performs calibration corrections before down-sampling the corrected object data. In a second implementation, the method continuously scans an object space&#x2014;with the object absent (present) in the object space&#x2014;to obtain calibration data (object absent) and object data (object present) both having the same sub-view angular offset. In a third implementation, the method obtains multiple scans having different sub-view angular offsets, organizes the scans into bins according to their respective sub-view angular offsets, and chooses the appropriate sub-view angular offsets bin for calibration corrections of the object data.

Computed tomography scanner calibration with angle correction for scan angle offset

A computed tomography (CT) imaging apparatus includes an X-ray source to emit X-rays; a plurality of photon-counting detectors (PCDs) arranged in a circular ring between the X-ray source and a CT detector; and processing circuitry to cause the X-ray source and the CT detector to perform a helical scan of an object to obtain projection data; extract, from the obtained projection data, a plurality of sets of projection data corresponding to a plurality of X-ray tube positions of the helical scan; and combine the plurality of sets of extracted projection data to obtain a scanogram.

A detector includes a photon-counting detector (PCD) layer and a cathode layer arranged adjacent to the PCD layer. The detector further includes a plurality of pixilated anodes arranged adjacent to the photon-counting detecting layer on a side opposite to the cathode layer. The detector also includes a plurality of collimator segments arranged above the cathode layer so as to block a portion of X-ray photons emitted from an X-ray source from reaching the anodes, where each collimator segment is arranged above a portion of at least one anode.

Apparatus and method for collimating X-rays in spectral computer tomography imaging

A method for performing reconstruction for a region of interest (ROI) of an object is provided. The method includes designating the ROI within the object, the ROI being located within a scan field of view (FOV) of a combined third- and fourth-generation CT scanner, the CT scanner including fixed photon-counting detectors (PCDs), and an X-ray source that rotates about the object in synchronization with a rotating detector. Further, the method includes determining, for each PCD, as a function of view angle, an on/off timing schedule, based on a size and location of the designated ROI, and performing a scan to obtain a first data set from the rotating detector and a second data set from the plurality of PCDs, while turning each PCD on and off according to the determined schedule. Finally, the method includes performing reconstruction using the first and second data sets to obtain ROI spectral images.

Method for spectral CT local tomography

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.

Growing community of inventors

Buffalo Grove, IL, United States of America

Xiaolan Wang