2023
B1 inhomogeneity‐corrected T1 mapping and quantitative magnetization transfer imaging via simultaneously estimating Bloch‐Siegert shift and magnetization transfer effects
Jang A, Han P, Ma C, Fakhri G, Wang N, Samsonov A, Liu F. B1 inhomogeneity‐corrected T1 mapping and quantitative magnetization transfer imaging via simultaneously estimating Bloch‐Siegert shift and magnetization transfer effects. Magnetic Resonance In Medicine 2023, 90: 1859-1873. PMID: 37427533, PMCID: PMC10528411, DOI: 10.1002/mrm.29778.Peer-Reviewed Original ResearchConceptsBloch-Siegert shiftBloch-SiegertMagnetization transfer effectsMonte Carlo simulationsSpin-lattice relaxationSpin-bath modelMagnetization transferBinary spin-bath modelCarlo simulationsProton fractionOff-resonance irradiationIn vivo brain studiesBloch simulationsPhantom experimentsMagnetizationEstimationTransmitted fieldQuantitative magnetization transferMethod performanceMT effectSignal equation
2017
Feasibility study of using fall‐off gradients of early and late PET scans for proton range verification
Cho J, Grogg K, Min C, Zhu X, Paganetti H, Lee H, Fakhri G. Feasibility study of using fall‐off gradients of early and late PET scans for proton range verification. Medical Physics 2017, 44: 1734-1746. PMID: 28273345, PMCID: PMC5462437, DOI: 10.1002/mp.12191.Peer-Reviewed Original ResearchConceptsProton range verificationProton rangeMonte Carlo simulationsRange verificationFall-offIn-room positron emission tomographyCarlo simulationsResidual proton rangeDose fall-offPostirradiation delayPositron emission tomography imagingSOBP beamProton beamPositron emission tomographyPositron emission tomography scanPhantom studyIn-roomFunction of depthPhantomProtonOff-setMonteAcquisition timeBeamPositron emission tomography signal
2015
Fast Estimation of Image Variance for Time-of-flight PET Reconstruction
Wang M, Hu G, Fakhri G, Zhang H, Li Q. Fast Estimation of Image Variance for Time-of-flight PET Reconstruction. 2015, 1-4. DOI: 10.1109/nssmic.2015.7582040.Peer-Reviewed Original ResearchImage varianceMaximum likelihood expectation maximizationTOF-PETAhstract-The useLikelihood expectation maximizationFast algorithmExpectation maximizationReduction of computation timeComputation timeImage qualityMonte Carlo simulationsUniform diskFast estimationAlgorithmAnalytical expressionsCarlo simulationsVariance predictionImagesPET imagingPositron emission tomographyPhantomMaximization
2014
Towards coronary plaque imaging using simultaneous PET-MR: a simulation study
Petibon Y, Fakhri G, Nezafat R, Johnson N, Brady T, Ouyang J. Towards coronary plaque imaging using simultaneous PET-MR: a simulation study. Physics In Medicine And Biology 2014, 59: 1203-1222. PMID: 24556608, PMCID: PMC4061607, DOI: 10.1088/0031-9155/59/5/1203.Peer-Reviewed Original ResearchMeSH KeywordsComputer SimulationCoronary AngiographyCoronary StenosisHumansImage Interpretation, Computer-AssistedImaging, Three-DimensionalMagnetic Resonance AngiographyModels, CardiovascularMultimodal ImagingPhantoms, ImagingPositron-Emission TomographyReproducibility of ResultsSensitivity and SpecificityConceptsSimultaneous PET-MRChannelized Hotelling observerAttenuation mapMotion correctionPET-MRFluorodeoxyglucose-positron emission tomography imagingRespiratory motion fieldsMotion correction methodCho SNRMotion correction techniqueAnthropomorphic phantomUncorrected reconstructionsRespiratory motionXCAT phantomCoronary plaque imagingMonte Carlo simulationsPET reconstructionXCATActivity distributionCardiac gatingNon-rigid registrationHotelling observerCarlo simulationsPlaque imagingPhantom
2013
Determination of elemental tissue composition following proton treatment using positron emission tomography
Cho J, Ibbott G, Gillin M, Gonzalez-Lepera C, Min C, Zhu X, Fakhri G, Paganetti H, Mawlawi O. Determination of elemental tissue composition following proton treatment using positron emission tomography. Physics In Medicine And Biology 2013, 58: 3815-3835. PMID: 23681070, PMCID: PMC3763743, DOI: 10.1088/0031-9155/58/11/3815.Peer-Reviewed Original ResearchConceptsIn-room PET scannerProton treatmentSOBP beamPET scannerMonte Carlo simulationsTissue elemental compositionComposite decay curvePristine Bragg peakProton treatment planningIn-roomElemental tissue compositionCarlo simulationsDecay curvesRange verificationMonoenergetic beamsBeam rangeProton dosePhantom sectionsEmitted positronsPositron emission tomographyProton therapyBragg peakPhantom compositionDelivered dosePositron emission tomography imaging
2008
Sequential and simultaneous dual‐isotope brain SPECT: Comparison with PET for estimation and discrimination tasks in early Parkinson disease
Trott C, Fakhri G. Sequential and simultaneous dual‐isotope brain SPECT: Comparison with PET for estimation and discrimination tasks in early Parkinson disease. Medical Physics 2008, 35: 3343-3353. PMID: 18697558, PMCID: PMC2673561, DOI: 10.1118/1.2940605.Peer-Reviewed Original ResearchConceptsEnergy resolutionTime-of-flight PET scannerRealistic Monte Carlo simulationsAcquisition energy windowSequential SPECTSystem energy resolutionGamma cameraEnergy windowThree-head cameraPET scannerEmission energyMonte Carlo simulationsDual-isotope SPECTSimultaneous SPECTBrain PETTwo-headed cameraCarlo simulationsProdromal disease stagesIdentical physiological conditionsSpatial resolutionDiscrimination taskStriatal sizeActivity concentrationsEarly identification of PDCamera head
2006
Monte Carlo Modeling of Cascade Gamma Rays in PET
Zhu X, Fakhri G. Monte Carlo Modeling of Cascade Gamma Rays in PET. 2011 IEEE Nuclear Science Symposium Conference Record 2006, 6: 3522-3525. DOI: 10.1109/nssmic.2006.353759.Peer-Reviewed Original ResearchCascade gamma raysGamma raysGamma-ray emitting isotopesDetector dead timeMonte Carlo modelPET imagingGamma eventsScatter fractionQuantitative PET imagingTorso phantomSingles ratesMonte Carlo simulationsDecrease of intensityHigh-activity regionsPhantom experimentsReconstructed volumePhantomRaysCarlo simulationsDead timeDetectorReconstructed imagesCascade typeImage intensityMonteSimultaneous Dual Tracer PET Using Generalized Factor Analysis of Dynamic Sequences
Fakhri G, Sitek A, Guérin B. Simultaneous Dual Tracer PET Using Generalized Factor Analysis of Dynamic Sequences. 2006, 4: 2128-2130. DOI: 10.1109/nssmic.2006.354334.Peer-Reviewed Original Research
2005
Realistic Monte Carlo PET Simulation with Pixellated Block Detectors, Light Sharing and Randoms Modeling
Guérin B, Fakhri G. Realistic Monte Carlo PET Simulation with Pixellated Block Detectors, Light Sharing and Randoms Modeling. 2005, 3: 1563-1567. DOI: 10.1109/nssmic.2005.1596617.Peer-Reviewed Original ResearchPET scannerBlock detectorsPhoton transportRandom coincidencesSimSET softwareMonte Carlo transport codeNEMA NU 2Model of photon transportEnergy weighted averageModel photon transportLight-sharingEnergy spectrumNU 2Light sharingTransport codeCrystal elementsMonte Carlo simulationsPET simulationsVery good agreementInteraction pointPET acquisitionDetection crystalAttenuation distributionDetectorCarlo simulations
2002
Quantitative Simultaneous 99MTc/123I Spect: Design Study and Validation With Monte Carlo Simulations and Physical Acquisitions
Fakhri G, Maksud P, Kijewski M, Zimmerman R, Moore S. Quantitative Simultaneous 99MTc/123I Spect: Design Study and Validation With Monte Carlo Simulations and Physical Acquisitions. IEEE Transactions On Nuclear Science 2002, 49: 2315. DOI: 10.1109/tns.2002.803819.Peer-Reviewed Original ResearchMonte Carlo simulationsBrain phantomCarlo simulationsSimultaneous dual-isotope imagingIterative ordered subsetsDigital brain phantomDual-isotope SPECT studyVariable collimator responseArtificial neural networkPhysical acquisitionEnergy windowNonuniform attenuationCollimator responseDual-isotope imagingPhantom acquisitionsScatter correctionClinical cameraNeural networkMontePhantomIsotope imagingCorrected projectionsSPECT studiesProjector/backprojectorClinical application
2001
A New Scatter Compensation Method for Ga-67 Imaging Using Artificial Neural Networks
Fakhri G, Moore S, Maksud P. A New Scatter Compensation Method for Ga-67 Imaging Using Artificial Neural Networks. IEEE Transactions On Nuclear Science 2001, 48: 799. DOI: 10.1109/23.940166.Peer-Reviewed Original ResearchK-shell X-raysEnergy window imagesAnthropomorphic torso phantomPoisson noise realizationsGa-67 studiesArtificial neural networkWindow imagesPhotoelectric absorptionPhoton interactionsTorso phantomCoherent scatteringMonte Carlo simulationsScatter correctionGa-67Neural networkReconstructed volumeCarlo simulationsCollimatorArtificial neural network learningError back propagationNoise realizationsScatteringGa-67 imagingActivity estimationOutput layerAbsolute activity quantitation in simultaneous 123I/99mTc brain SPECT.
El Fakhri G, Moore S, Maksud P, Aurengo A, Kijewski M. Absolute activity quantitation in simultaneous 123I/99mTc brain SPECT. Journal Of Nuclear Medicine 2001, 42: 300-8. PMID: 11216530.Peer-Reviewed Original ResearchMeSH KeywordsAlzheimer DiseaseBenzamidesBrainCerebellumCerebral CortexCerebrovascular CirculationCorpus CallosumHumansIodine RadioisotopesMonte Carlo MethodNeural Networks, ComputerParkinson DiseasePhantoms, ImagingPutamenPyrrolidinesRadiopharmaceuticalsSensitivity and SpecificityTechnetium Tc 99m ExametazimeTomography, Emission-Computed, Single-PhotonConceptsOrdered-subset expectation maximizationDistance-dependent collimator responseActivity quantitationActivity distributionIterative ordered-subsets expectation maximizationZubal brain phantomAsymmetric windowsSimulated normal populationPathological studiesDecay photonsBrain SPECTCollimator responseNonuniform attenuationDual-isotope imagingBrain phantomMonte Carlo simulationsCorpus callosumNormal populationPartial volume effectsCarlo simulationsCortical lobesAssessment of brain perfusionScatteringCross-talkBrain perfusionAbsolute Quantitation in Simultaneous 99mTc/123I Brain SPECT Using ANN: Design Optimization and Validation
Fakhri G, Maksud P, Moore S, Zimmerman R, Kijewski M. Absolute Quantitation in Simultaneous 99mTc/123I Brain SPECT Using ANN: Design Optimization and Validation. 2001, 3: 1429-1431. DOI: 10.1109/nssmic.2001.1008605.Peer-Reviewed Original ResearchMonte Carlo simulationsBrain phantomSimultaneous dual-isotope imagingDigital brain phantomDual-isotope SPECT studyVariable collimator responseCarlo simulationsNon-uniform attenuationI-123 imagingEnergy windowCollimator responseDual-isotope imagingPhantom acquisitionsOSEM algorithmArtificial neural networkPhysical acquisitionScatter correctionClinical cameraBrain structuresPhantomIsotope imagingMonteSPECT studiesActivity concentrationsTc-99
2000
Scatter and cross-talk corrections in simultaneous Tc-99m/I-123 brain SPECT using constrained factor analysis and artificial neural networks
Fakhri G, Maksud P, Kijewski M, Haberi M, Todd-Pokropek A, Aurengo A, Moore S. Scatter and cross-talk corrections in simultaneous Tc-99m/I-123 brain SPECT using constrained factor analysis and artificial neural networks. IEEE Transactions On Nuclear Science 2000, 47: 1573-1580. DOI: 10.1109/23.873018.Peer-Reviewed Original ResearchSpectral factor analysisTc-99mEnergy window methodDigital brain phantomCross-talk correctionI-123 imagingUnscattered photonsTc-99m activityBrain phantomMonte Carlo simulationsI-123Dual-isotope studiesPhotonsCarlo simulationsTc-99Simultaneous imagingAssessment of brain perfusionCross-talkBrain structuresBrain SPECTArtificial neural networkBrain perfusionPhantomClinical potentialCaudate nucleusRelative impact of scatter, collimator response, attenuation, and finite spatial resolution corrections in cardiac SPECT.
El Fakhri G, Buvat I, Benali H, Todd-Pokropek A, Di Paola R. Relative impact of scatter, collimator response, attenuation, and finite spatial resolution corrections in cardiac SPECT. Journal Of Nuclear Medicine 2000, 41: 1400-8. PMID: 10945534.Peer-Reviewed Original ResearchConceptsDepth-dependent collimator responseSpatial resolution correctionCollimator responseFinite spatial resolutionBull's-eye mapCardiac SPECTActivity quantitationAttenuation correctionScatter correctionResolution correctionSpatial resolutionCollimator response correctionsSignal-to-noise ratioFrequency-distance principleImpact of scatteringLeft ventricleMonte Carlo simulationsCardiac phantomScatteringCarlo simulationsLV cavityAbsolute quantitationImproved contrastLV regionsProcessing schemeA new scatter compensation method for Ga-67 imaging using artificial neural networks
Fakhri G, Moore S, Maksud P. A new scatter compensation method for Ga-67 imaging using artificial neural networks. 2011 IEEE Nuclear Science Symposium Conference Record 2000, 2: 13/48-13/52 vol.2. DOI: 10.1109/nssmic.2000.949989.Peer-Reviewed Original ResearchK-shell X-raysEnergy window imagesAnthropomorphic torso phantomScatter correction methodPoisson noise realizationsGa-67 studiesPhotoelectric absorptionPhoton interactionsWindow imagesTorso phantomArtificial neural networkCoherent scatteringMonte Carlo simulationsScatter correctionGa-67Reconstructed volumeNeural networkCarlo simulationsCollimatorNoise realizationsScatteringGa-67 imagingArtificial neural network learningPrimary distributionError backpropagation
1999
Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study
El Fakhri G, Buvat I, Pélégrini M, Benali H, Almeida P, Bendriem B, Todd-Pokropek A, Di Paola R. Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study. European Journal Of Nuclear Medicine And Molecular Imaging 1999, 26: 437-446. PMID: 10382086, DOI: 10.1007/s002590050409.Peer-Reviewed Original ResearchConceptsDepth-dependent collimator responseCollimator responseMonte Carlo simulationsActivity underestimationSingle-photon emission tomographyCarlo simulationsSignal-to-noise ratioSpatial resolutionCardiac phantomFWHM spatial resolutionCardiac single-photon emission tomographyQuantitative accuracyAnthropomorphic cardiac phantomPhysical effectsInfluence of scatteringEffect of scatteringScatter countsFull-widthIncreased SNRPoor spatial resolutionScatteringMap homogeneityPhantomMonteImaging systemMonte Carlo evaluation of quantitation in simultaneous Tc-99m/I-123 brain SPECT using constrained spectral factor analysis
Fakhri G, Moore S, Kijewski M, Maksud P, Todd-Pokropek A. Monte Carlo evaluation of quantitation in simultaneous Tc-99m/I-123 brain SPECT using constrained spectral factor analysis. 2011 IEEE Nuclear Science Symposium Conference Record 1999, 3: 1392-1396 vol.3. DOI: 10.1109/nssmic.1999.842815.Peer-Reviewed Original ResearchSpectral factor analysisTc-99mEnergy window methodDigital brain phantomI-123 imagingUnscattered photonsTc-99m activityBrain phantomFiltered-backprojectionMonte Carlo simulationsPrimary spectraDual-isotope studiesI-123Monte Carlo evaluationPhotonsCarlo simulationsSimultaneous imagingMonteBrain structuresBrain SPECTTc-99PhantomCaudate nucleusSpectraPixel values
1998
Artificial neural network as a tool to compensate for scatter and attenuation in radionuclide imaging.
Maksud P, Fertil B, Rica C, El Fakhri G, Aurengo A. Artificial neural network as a tool to compensate for scatter and attenuation in radionuclide imaging. Journal Of Nuclear Medicine 1998, 39: 735-45. PMID: 9544691.Peer-Reviewed Original ResearchConceptsEnergy spectrumCompton scatteringRadioactive sourcesImages of radioactive sourcesScatter correctionArtificial neural networkNeural networkNumerical Monte Carlo simulationsMonte Carlo simulationsPelvis scansIncident photonsMultilayer neural networkProjection imagesScatteringComptonCarlo simulationsDiffusion mediaSource distributionSpectrum acquisitionEnergyGeometric sourcesHomogeneous mediumCorrectionSpectraNetwork