title: Correction of B0-distortions in echo-planar-imaging-based perfusion-weighted MRI.
abstract: OBJECTIVE
  To evaluate and quantify a scheme for correcting susceptibility artifacts in spin-echo echo-planar-imaging-based dynamic susceptibility contrast (DSC) perfusion MRI of high-grade gliomas at 3 Tesla.
  
  
  METHODS
  Sixteen patients with a total of 78 scans were studied. DSC-MRI images were corrected using a displacement map generated from opposite phase-encoding polarity images. Two methods were used for quantification in the correction: (i) linear regression of pixel-by-pixel comparisons, performed both globally and relative to the anterior and posterior commissure plane (AC-PC plane), of T2-weighted images with both corrected and uncorrected raw DSC images; and (ii) counting significant (>2.0) normalized cerebral blood volume (nCBV) pixels from perfusion maps in the tumor region of interest.
  
  
  RESULTS
  Sixty-four of 78 datasets showed significant differences in the coefficient of correlation (r2) values. The difference between corrected and uncorrected r2 values was positive in all but one patient. Correction of B0- distortion significantly improved r2 in slices around the AC-PC plane. In 62% of the datasets, we observed an increased number of significant pixels in the corrected nCBV maps; 36% showed more significant pixels in uncorrected nCBV maps; 1% showed no difference.
  
  
  CONCLUSIONS
  Distortion correction of DSC-MRI may provide improved accuracy compared with uncorrected data, especially for tumors located below the corpus callosum and near the frontal sinuses.
authors.affiliation: Oslo University Hospital, Rikshospitalet, The Intervention Centre, Oslo, Norway; University of Oslo, Faculty of Medicine, Oslo, Norway.
authors.forename: Jonas
authors.initials: J
authors.lastname: Vardal
authors.forename: Raimo A
authors.initials: RA
authors.lastname: Salo
authors.forename: Christopher
authors.initials: C
authors.lastname: Larsson
authors.forename: Anders M
authors.initials: AM
authors.lastname: Dale
authors.forename: Dominic
authors.initials: D
authors.lastname: Holland
authors.forename: Inge Rasmus
authors.initials: IR
authors.lastname: Groote
authors.forename: Atle
authors.initials: A
authors.lastname: Bjørnerud
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D001932:Brain Neoplasms / Q000175:diagnosis / Q000473:pathology*; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D005910:Glioma / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D016014:Linear Models; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012494:Sampling Studies; D012680:Sensitivity and Specificity
chemical_list: D019786:Gadolinium DTPA
keywords: DSC-MRI; EPI; artifacts; correction; distortion; glioma