Vessel Branch Segmentation of Phase Contrast Vastly undersampled PRojection Magnetic Resonance ImagingOverviewPhase Contrast MRPC VIPRMotivationTheory (Chung et al.)Theory in PracticeMethodsResults: SegmentationSlide 10Results: CenterlineConclusionsDepartments of Radiology and Medical PhysicsDepartments of Radiology and Medical PhysicsUniversity of Wisconsin-MadisonUniversity of Wisconsin-MadisonVessel Branch Segmentation of Phase Contrast Vastly undersampled PRojection Magnetic Resonance Imaging Kevin Johnson Kevin JohnsonOverview•Background•Motivation•Theory–Phase Coherence Mixture Model–Discrepancies •Methods–Segmentation–Traces•Results•ConclusionsPhase Contrast MR •MRI–Fourier encodes atoms of non-zero spin–Complex Acquisition •Phase Contrast MR–Encoded velocity in phase–5-Images per Acquisition:1H DensityVascularVelocity A/P Velocity L/R Velocity S/IPC VIPR •Highly efficient acquisition•More accurate than conventional methods•High Resolution (0.5x0.5x0.5mm)Motivation•Phase image is difficult to analyze due to noise•Segmentations allows visualization•In neurological cases vasculature is complex–Need to separate branchesFrydrychowicz et al. ICVTS 2006. 340-342Theory (Chung et al.) •Phase Coherence•May allow for automated separation-)(,)(cNssjilpcsjivvcCM}0|,{)(2cssWsscNjisjisMixture Model Phase Coherence ThresholdsTheory in Practice•Phase Coherence Histogram•Simply due to the higher accuracy–In paper they had phase offsets –Shift PDF of Tissue–No effect on backgroundMethods•Segmentation1) Determine phase coherence2) Threshold phase coherence (T=0)3) Threshold CD Image (T manually set)4) Take intersection of images5) Open image6) Determine connected regions7) Remove small regions•Centerline1) Filter with LPF2) Initialize by 3D watershed filling up to threshold3) 3D Watershed with bridges built as connectivityResults: SegmentationComplex Difference Initial Threshold Eroded ImageDilated Image Cleanup/Connectivity3D Final ResultResults: Segmentation•Separate out individual components•Remove componentsECA Branch ICA Branch Sap Vein BranchNo ECA/SAPUn-segmentedResults: Centerline Initial ConnectivityConnectivity (50% max)FinalConclusions•Phase Coherence mixture model ineffective for PC VIPR •Segmentation effective at separating components•Small vessels lost due to opening mask•Center line effective in most vessels•Failures in cases of complex
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