Z. Rumboldt, S. Tipnis, D. Vicent, M.V. Spampinato, G. Goldsberry, W. Huda

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XIX Symposium Neuroradiologicum. Iterative Reconstruction Algorithm for Head CT. Z. Rumboldt, S. Tipnis, D. Vicent, M.V. Spampinato, G. Goldsberry, W. Huda. Medical University of South Carolina Charleston, SC, USA. Background. CT images traditionally reconstructed - PowerPoint PPT Presentation

Text of Z. Rumboldt, S. Tipnis, D. Vicent, M.V. Spampinato, G. Goldsberry, W. Huda

  • Z. Rumboldt, S. Tipnis, D. Vicent,M.V. Spampinato, G. Goldsberry, W. HudaMedical University of South CarolinaCharleston, SC, USAXIX Symposium NeuroradiologicumIterative Reconstruction Algorithm for Head CT

  • BackgroundCT images traditionally reconstructed using filtered back projection techniques(FBP)FBP limitations: geometry, data completeness, radiation doseIncreased spatial resolution is directlycorrelated with increased image noise

  • BackgroundITERATIVE IMAGE RECONSTRUCTION approaches recently proposed and introducedmay allow for improved image quality and lower noise(2 Alternative Forced Choice methodology)iterative reconstruction may allow decouplingof spatial resolution and image noise

    need for a substantial increase in computation power compared to conventional FBP reconstruction

  • After an image is reconstructed, reprojection simulates the CT measurement process, with the image as the object, followed by corrections

  • Each time the image is updated, processing algorithmenhances spatial resolution at higher object contrasts & reduces image noise in low contrast areas

  • PurposeNovel Methodology

    Comparison with normal scans for lesion detection, not side by sideClinical evaluation of potential noise reduction andimproved lesion detection

  • Material and MethodsPart 1

    10 adult head CTs both FBP and IRIS

    2 neuroradiologists evaluated simultaneously both sets for each patient at 3 levels - MCP, BG, and centrum semiovale (30 levels in all) for noise and artifacts

    raters blinded for the algorithm had 3 choices: preference for A, for B, no preference

  • Materials and MethodsTotal screened 228 Age range selected 25 through 8524 abnormal subjects - 30 lesions: 21 hypo 7 hyper 1 mixed 1 iso

    12 normal subjects selected to matchPart 2

  • Materials and MethodsIn house software (MUSC, Matthew Daniels, website accessible on campus network)

    Displayed pairs of single slice CT - Abnormal on LeftLocation and description of lesion givenRating scale 1 to 101 = Barely discernable 10 = Definitely see lesion

    PATHOLOGY COMPARED TO THE NORMAL 3 sets for each pair: FBP, NBC, IRIS

  • Materials and MethodsFBPNBCIRIS

  • FBP

  • IRIS

  • NBC

  • Every reader trained on practice set prior to studyIndividual randomization for every reader

    AnalysisRatios of the obtained values: IRIS/FBP NBC/FBPMaterials and MethodsEvery reader trained on practice set prior to studyIndividual randomization for every readerEvery reader trained on practice set prior to studyIndividual randomization for every reader

  • FBPIRISResults

  • ResultsIn all evaluated images (30 levels) noise was considered lower with IRIS compared to FBP

    Artifacts were less prominent in 11 of the 30 evaluated levels using IRIS and in 3 using FBP (no preference was found for 16 levels)Part 1

  • IRISNBCResults

  • ResultsIRISNBC

  • Rater 1Part 2

    FBP (d)NBC (d')IRIS (d")d'/dd"/d1313.001.001333.003.008770.880.886320.500.336250.330.834761.751.509670.670.786731.170.503351.001.673351.001.671242.004.006731.170.503451.331.677150.140.714771.751.757590.711.293571.672.338881.001.002462.003.004471.001.752422.001.002783.504.004671.501.753862.672.003782.332.6776100.861.435531.000.603471.332.3387100.881.254641.501.00

  • Results

    Rater 1NBC/FBPIRIS/FBP

    Avg. Hypo1.341.48Std.Dev. Hypo0.770.94

    Avg. Hyper1.511.61Std.Dev. Hyper0.720.75

    Average1.451.61Std. Dev0.820.97

  • AVG. HYPO RATIO1.341.481.691.491.071.22SD HYPO RATIO0.770.942.131.210.430.41

    AVG. HYPER RATIO1.511.611.121.181.021.05SD HYPER RATIO0.720.750.480.470.180.26

    AVG. RATIO1.451.611.541.421.091.24SD RATIO0.820.971.821.040.410.45

    NBCIRISNBCIRISNBCIRIS

    Rater 1Rater 2Rater 3

  • Results

    Pooled ResultsNBCIRIS

    Pooled Avg. Hypo1.371.40Pooled Std.Dev. Hypo1.340.91

    Pooled Avg. Hyper1.221.28Pooled Std.Dev. Hyper0.530.56

    Pooled Average1.361.42Pooled Std. Dev1.180.87

  • ConclusionIterative reconstruction algorithm decreases noise in Head CT images It seems to improve lesion detection

    It may allow decreased radiation doseNo clear difference between IRIS and NBC

    **MR (2/12/2010)