2019
Time of flight PET reconstruction using nonuniform update for regional recovery uniformity
Kim K, Kim D, Yang J, Fakhri G, Seo Y, Fessler J, Li Q. Time of flight PET reconstruction using nonuniform update for regional recovery uniformity. Medical Physics 2019, 46: 649-664. PMID: 30508255, PMCID: PMC6501218, DOI: 10.1002/mp.13321.Peer-Reviewed Original ResearchConceptsSignal-to-noise ratio regionVariant step sizeSignal-to-noise ratioNesterov momentumOS-SQSUniform recoveryOS-EMStep sizeNon-TOF PETOrdered subsetsQuad-core CPUEarly stopping criterionGraphics processing unitsTime-of-flight PET reconstructionReconstruction methodPET reconstruction methodsNesterov's momentum methodImage qualityPET reconstructionTOF-PETOverall signal-to-noise ratioActive regionLow activity regionsComputer simulationsRecovery ratio
2017
Joint estimation of activity image and attenuation sinogram using time-of-flight positron emission tomography data consistency condition filtering
Li Q, Li H, Kim K, Fakhri G. Joint estimation of activity image and attenuation sinogram using time-of-flight positron emission tomography data consistency condition filtering. Journal Of Medical Imaging 2017, 4: 023502-023502. PMID: 28466027, PMCID: PMC5405780, DOI: 10.1117/1.jmi.4.2.023502.Peer-Reviewed Original ResearchData consistency conditionsMaximum likelihood attenuation correction factorsAttenuation sinogramConsistency conditionsJoint estimationJoint log-likelihood functionPET emission dataAttenuation correction factorsTime-of-flight (TOFActive imagingJoint estimation methodLog-likelihood functionPoisson noiseReconstruction resultsAttenuation correctionSinogram filteringPrevent convergenceEmission dataSinogramPositron emission tomography dataEstimation methodComputer simulationsPositron emission tomographyIterative methodCorrection factor
2016
Penalized MLAA with Spatially-Encoded Anatomic Prior in TOF PET/MR
Kim K, Yang J, Fakhri G, Seo Y, Li Q. Penalized MLAA with Spatially-Encoded Anatomic Prior in TOF PET/MR. 2016, 1-4. DOI: 10.1109/nssmic.2016.8069514.Peer-Reviewed Original ResearchSynthetic CT imagesAlternating direction methodAttenuation correctionImage qualityMR-based attenuation correctionTOF-PET dataPET emission dataPET image qualityTime-of-flight (TOFDirection methodCost functionCT imagesPET/MR scannersNoise componentsConsistency conditionsAnatomical MRIterative processComputer simulationsPET dataMLAAPET/MR scansImagesBone signalEmission dataTOFValidation of Bayesian analysis of compartmental kinetic models in medical imaging
Sitek A, Li Q, Fakhri G, Alpert N. Validation of Bayesian analysis of compartmental kinetic models in medical imaging. Physica Medica 2016, 32: 1252-1258. PMID: 27692754, PMCID: PMC5720163, DOI: 10.1016/j.ejmp.2016.09.010.Peer-Reviewed Original ResearchConceptsAccurate estimation of uncertaintyComputer simulationsMedical imagesPosterior distributionDistributed noiseTime series of imagesClosed-formSeries of imagesData setsKinetic parametersMarkov chain Monte Carlo methodsPosterior distributions of kinetic parametersNon-linear least squares methodAccurate estimationComputerLeast-squares methodKinetic modelEstimation of kinetic parametersF18-fluorodeoxyglucoseBayesian estimationImagesStatistical inferenceMonte Carlo methodEstimates of uncertaintyInformation
2015
Penalized Direct Estimation of Parametric Images in PET
Kim K, Fakhri G, Li Q. Penalized Direct Estimation of Parametric Images in PET. 2015, 1-4. DOI: 10.1109/nssmic.2015.7582182.Peer-Reviewed Original ResearchAlternating direction methodDirection methodHigh noise varianceIterative reconstruction processKinetic parameter imagesTV regularizationNoise varianceDirect reconstructionPhysiological kinetic parametersDirection estimationReconstruction processNeighboring voxelsCost functionRidge regressionRaw measurementsConventional direct methodComputer simulationsDynamic imagingSplitting methodKinetic parametersImagesBrain phantomAccurate parametric imagesPoisson likelihoodPotential imagesNon-Local and Motion-Based Low-Rank Regularizations for Gated CT Reconstruction
Kim K, Fakhri G, Li Q. Non-Local and Motion-Based Low-Rank Regularizations for Gated CT Reconstruction. 2015, 1-3. DOI: 10.1109/nssmic.2015.7582219.Peer-Reviewed Original ResearchLow-rank regularizationNon-local weightsRegistration matrixLow-rank propertyMulti-frame imagesHigh noiseNon-local regularizationImage patchesMotion blurring artifactsConcurrent executionIterative reconstruction algorithmBlurring artifactsMotion-basedReconstruction algorithmMotion patternsNon-localReduce noiseImage qualityLow-dose conditionsComputer simulationsMotion artifactsNoiseGated computed tomographyGated CTRegularization
2014
Sparse-View Spectral CT Reconstruction Using Spectral Patch-Based Low-Rank Penalty
Kim K, Ye J, Worstell W, Ouyang J, Rakvongthai Y, Fakhri G, Li Q. Sparse-View Spectral CT Reconstruction Using Spectral Patch-Based Low-Rank Penalty. IEEE Transactions On Medical Imaging 2014, 34: 748-760. PMID: 25532170, DOI: 10.1109/tmi.2014.2380993.Peer-Reviewed Original ResearchConceptsLow-rank penaltySelf-similarity of patchesLog-likelihoodPoisson log-likelihoodCost functionSpectral CT reconstructionOriginal cost functionGPU implementationAlternating minimizationSensitive to intensity changesConventional algorithmsSpectral imagingEdge directionComputational costProcedure algorithmComputational advantagesAlgorithmX-ray transmissionComputer simulationsOptimization methodSpectral computed tomographySelf-similarityCT reconstructionX-rayGPUTof-Pet Ordered Subset Reconstruction Using Non-Uniform Separable Quadratic Surrogates Algorithm
Kim K, Ye J, Cheng L, Ying K, Fakhri G, Li Q. Tof-Pet Ordered Subset Reconstruction Using Non-Uniform Separable Quadratic Surrogates Algorithm. 2014, 963-966. DOI: 10.1109/isbi.2014.6868032.Peer-Reviewed Original ResearchSignal-to-noise ratioQuadratic surrogatesTOF-basedAlgorithm timeNoise ratioReconstruction algorithmReconstructed imagesAlgorithmConvergence rateImage qualityPET reconstructionTransmission reconstructionComputer simulationsTOF PET reconstructionTOF-PETEmission reconstructionAccurate imagingImagesSmall regionConvergenceComputerReconstructionNon-uniformityOSEM
2007
Fast Analytical Modeling of Compton Scatter Using Point Clouds and Graphics Processing Unit (GPU)
Sitek A, Fakhri G, Ouyang J, Maltz J. Fast Analytical Modeling of Compton Scatter Using Point Clouds and Graphics Processing Unit (GPU). 2007, 6: 4546-4548. DOI: 10.1109/nssmic.2007.4437122.Peer-Reviewed Original ResearchGraphics processing unitsComputation timeProcessing unitPoint cloudsNVIDIA Quadro FXCalculation speedEfficient geometric modelingScattered point cloudExorbitant computation timeComputing architectureImage samplesImaging modelResolution levelsComputational frameworkComputerGraphicsComputer simulationsArchitectureRepresentationCloudImage volumesNatural advantagesComputational modelCompton scatteringAccurate model