Patent application number | Description | Published |
20080217540 | Incorporation of axial system response in iterative reconstruction from axially compressed data of cylindrical scanner using on-the-fly computing - A method and system for reconstructing PET image data from a cylindrical PET scanner by incorporation of axial system response. The method includes the steps of: assuming the decomposition of axial components into individual line-of-response (LOR) contributions, approximating each LOR spreading in image space as depth-independent, implementing each LOR response, combining the LORs to produce large span projection data, implementing the back projector as a transposed matrix, and assembling the LOR projections and spans for each azimuthal angle. | 09-11-2008 |
20080219525 | Acceleration of Joseph's method for full 3D reconstruction of nuclear medical images from projection data - A method for interpolating at least one oblique line of response ray representing nuclear image projection data through a rectangular volume and a system for using the method. The method consists of steps of interpolating all the direct rays in a rectangular volume, making a projected ray by projecting the oblique ray onto a surface of the rectangular volume, matching the projected ray to a coinciding interpolated direct ray, shearing the rectangular volume to match the projected ray, and interpolating the oblique ray in the sheared volume. | 09-11-2008 |
20090072131 | Estimation of Crystal Efficiency With Axially Compressed Sinogram - The present invention provides a method for estimating crystal efficiency in a PET detector that takes axial compression into account. It does so via an iterative methodology in which a μ-map is first generated and then is used to obtain a solution for the equation | 03-19-2009 |
20090072155 | TIME-OF-FLIGHT (TOF) POSITRON EMISSION TOMOGRAPHY (PET) RECONSTRUCTION FROM TIME-TRUNCATED PROJECTION DATA - A method of TOF-PET image reconstruction using time-truncated TOF-PET projection data. The time-truncated TOF-PET data is obtained by narrowing the scanner time window to a smaller “time window field of view,” which reduces the field of view of a TOF-PET scanner. This results in a lower list mode stream transfer rate, which can be useful in high count rate data acquisitions, in particular | 03-19-2009 |
Patent application number | Description | Published |
20100057819 | Iterative Algorithms for Variance Reduction on Compressed Sinogram Random Coincidences in PET - The use of the ordinary Poisson iterative reconstruction algorithm in PET requires the estimation of expected random coincidences. In a clinical environment, random coincidences are often acquired with a delayed coincidence technique, and expected randoms are estimated through variance reduction (VR) of measured delayed coincidences. In this paper we present iterative VR algorithms for random compressed sinograms, when previously known methods are not applicable. Iterative methods have the advantage of easy adaptation to any acquisition geometry and of allowing the estimation of singles rates at the crystal level when the number of crystals is relatively small. Two types of sinogram compression are considered: axial (span) rebinning and transaxial mashing. A monotonic sequential coordinate descent algorithm, which optimizes the Least Squares objective function, is investigated. A simultaneous update algorithm, which possesses the advantage of easy parallelization, is also derived for both cases of the Least Squares and Poisson Likelihood objective function. | 03-04-2010 |
20100067758 | Point Spread Function Radial Component Implementation in Joseph's Forward Projector - Point spread function (PSF) radial filtering in a line of response space. Modeling a radial component, R, of a point spread filter as a function of at least a radial projection index ρ, a radial image space coordinate r, and an azimuth θ. The index ρ is characterized by an asymmetrical Gaussian distribution having where σleft(r) and σright(r) derived from point source measurements, and an adjustment σ | 03-18-2010 |
20100072375 | Iterative algorithms for crystal efficiencies estimations from TOF compressed normalization data - Time-of-flight (TOF) clinical data collected during a PET scan are very sparse and have significant size. These data undergo TOF axial rebinning and azimuthal mashing if histogrammed data-based reconstruction algorithms are used. In a clinical environment, TOF compression is typically performed by the hardware rebinner. Normalization data, acquired on a regular basis and used for estimation of some norm components, are compressed by the hardware rebinner in a similar manner. This disclosure presents simple update iterative algorithms for crystal efficiencies norm component estimation from TOF compressed normalization data. Previously known methods are not directly applicable since the compression procedure significantly complicates normalization data model equations. The iterative algorithms presented herein have advantages of being easily adapted to any acquisition geometry, and of allowing estimation of parameters at crystal level when a number of crystals is relatively small. A monotonic sequential coordinate descent algorithm, which optimizes the Least Squares objective function, is presented. A simultaneous update algorithm, which possesses the advantage of easy parallelization, is also presented. | 03-25-2010 |
20100074500 | SYSTEM AND METHOD FOR 3D TIME OF FLIGHT PET FORWARD PROJECTION BASED ON AN EXACT AXIAL INVERSE REBINNING RELATION IN FOURIER SPACE - Methods and systems for reconstructing a nuclear medical image from time-of-flight (TOF) positron emission tomography (PET) imaging data are disclosed. Measured three-dimensional (3D) TOF-PET data, including direct two-dimensional (2D) projections and oblique 3D projection data, are acquired from a PET scanner. A model 3D image is preset, a modeled 2D TOF sinogram is generated from the model 3D image, and a modeled 3D TOF sinogram is generated from the 2D TOF sinogram based on an exact inverse rebinning relation in Fourier space. The model 3D image is corrected based on the 3D TOF sinogram and is provided as the reconstructed nuclear medical image. Techniques disclosed herein are useful for facilitating efficient medical imaging, e.g., for diagnosis of various bodily conditions. | 03-25-2010 |
20110127413 | Systems and Methods for Calibrating Time Alignment For A Positron Emission Tomography (PET) System - A representative positron emission tomography (PET) calibration system includes a PET scanner having a ring detector, a phantom that is placed at approximately the center of the ring detector, and a time alignment calibration manager that is coupled to the PET scanner. The time alignment calibration manager detects coincidence events from the phantom, calculates position of time of flight events from the ring detector based on the detected coincidence events, and calculates time offsets for the ring detector using a mean value calculation based on the calculated position of the time of flight events. | 06-02-2011 |
20120070050 | Time of Flight Scatter Distribution Estimation in Positron Emission Tomography - Estimating time-of-flight (TOF) scatter distribution in a positron emission tomography (PET) system. Obtaining PET TOF projection data: PET random coincidence data and PET TOF prompt coincidence events data. Reducing measured TOF projection data to non-TOF projection data. Reconstructing, unbiased, the non-TOF projection date. Forward projecting unbiased reconstructed non-TOF projection data to estimate TOF trues distribution. Subtracting: The estimated TOF trues distribution and the measured random coincidence, from measured TOF prompt coincidence events. | 03-22-2012 |
20120250965 | Method and System for Using a Modified Ordered Subsets Scheme for Attenuation Weighted Reconstruction - A method and system is provided for performing medical imaging. The method and system includes at least one radiation detector to detect radiation from a subject, and an image processor which determines attenuation paths for an image point, groups substantially similar attenuation path lengths for the same image point to form a modified subset group, and processing image data using the modified subset group in order to provide a reconstructed image substantially similar to an original image. | 10-04-2012 |
20130028496 | Simultaneous Reconstruction of Emission Activity and Attenuation Coefficient Distribution from TOF Data, Acquired with External Shell Source - Methods, and systems therefrom, for generating images from time of flight (TOF) data associated with a scan of at least one object using a positron emission tomography system are provided. The method includes providing initial values for an activity image to yield a current activity image. The method also includes estimating initial values for an attenuation map (μ-map) image based on the TOF data to yield a current μ-map image. The method further includes repeating, until at least one termination condition is met, the steps of updating the current activity image based on at least the current μ-map and a first update algorithm and updating the current μ-map image based on at least on the updated activity image and a second update algorithm. The method also includes outputting an image of the at least one object based on the current μ-map and the current activity image. | 01-31-2013 |
20140056500 | Generating Attenuation Correction Maps for Combined Modality Imaging Studies and Improving Generated Attenuation Correction Maps Using MLAA and DCC Algorithms - The DCC (Data Consistency Condition) algorithm is used in combination with MLAA (Maximum Likelihood reconstruction of Attenuation and Activity) to generate extended attenuation correction maps for nuclear medicine imaging studies. MLAA and DCC are complementary algorithms that can be used to determine the accuracy of the mu-map based on PET data. MLAA helps to estimate the mu-values based on the biodistribution of the tracer while DCC checks if the consistency conditions are met for a given mu-map. These methods are combined to get a better estimation of the mu-values. In gated MR/PET cardiac studies, the PET data is framed into multiple gates and a series of MR based mu-maps corresponding to each gate is generated. The PET data from all gates is combined. Once the extended mu-map is generated the central region is replaced with the MR based mu-map corresponding to that particular gate. On the other hand, in dynamic PET studies the uptake in the patient's arms reaches a steady state only after the tracer distributes throughout the body. Hence, for dynamic scans, the projection data of all frames is summed and used to generate the MLAA based extended mu-map for all frames. | 02-27-2014 |
20140194735 | Random Sinogram Variance Reduction in Continuous Bed Motion Acquisition - Random sinogram variance is reduced in continuous bed motion acquisition. The randoms are modeled as a product of transverse singles efficiencies. The random sinogram is assumed to be a smooth function in the axial direction, collapsing the parameterization for estimating the transverse singles efficiencies into a single, conceptual ring. By solving the product, the mean random values are used to smooth the randoms in image reconstruction with less noise and artifacts. | 07-10-2014 |
20140200848 | Normalization Coefficients in PET Continuous Bed Motion Acquisition - Normalization coefficients in are computed for positron emission tomography (PET) continuous bed motion acquisition (CBM). The normalization coefficients for the lines-of-response in CBM account for the change in decay of the injected isotope over time and/or changes in velocity of the bed motion. | 07-17-2014 |
20150036789 | Reconstruction with Partially Known Attenuation Information In Time of Flight Positron Emission Tomography - Reconstruction in positron emission tomography is performed with partially known attenuation. A PET-CT scanner is used to generate a PET image with time of flight emission information. To limit x-ray dose while providing increased sensitivity at the ends of the CT volume in the PET image, attenuation coefficients for oblique LORs passing outside the CT volume are determined from the time of flight emission information. The attenuation coefficients for LORs within the CT volume are derived from the CT data. An objective function may be maximized for the emission distribution without reconstructing the attenuation distribution. | 02-05-2015 |