title: Diffusion-weighted PROPELLER MRI for quantitative assessment of liver tumor necrotic fraction and viable tumor volume in VX2 rabbits.
abstract: OBJECTIVE
  To test the hypothesis that diffusion-weighted (DW)-PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI provides more accurate liver tumor necrotic fraction (NF) and viable tumor volume (VTV) measurements than conventional DW-SE-EPI (spin echo echo-planar imaging) methods.
  
  
  METHODS
  Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 10 VX2 liver tumors, DW-PROPELLER and DW-SE-EPI scans were performed at contiguous axial slice positions covering each tumor volume. Apparent diffusion coefficient maps of each tumor were used to generate spatially resolved tumor viability maps for NF and VTV measurements. We compared NF, whole tumor volume (WTV), and VTV measurements to corresponding reference standard histological measurements based on correlation and concordance coefficients and the Bland-Altman analysis.
  
  
  RESULTS
  DW-PROPELLER generally improved image quality with less distortion compared to DW-SE-EPI. DW-PROPELLER NF, WTV, and VTV measurements were strongly correlated and satisfactorily concordant with histological measurements. DW-SE-EPI NF measurements were weakly correlated and poorly concordant with histological measurements. Bland-Altman analysis demonstrated that DW-PROPELLER WTV and VTV measurements were less biased from histological measurements than the corresponding DW-SE-EPI measurements.
  
  
  CONCLUSIONS
  DW-PROPELLER MRI can provide spatially resolved liver tumor viability maps for accurate NF and VTV measurements, superior to DW-SE-EPI approaches. DW-PROPELLER measurements may serve as a noninvasive surrogate for pathology, offering the potential for more accurate assessments of therapy response than conventional anatomic size measurements.
authors.affiliation: Department of Radiology, Northwestern University, Chicago, Illinois 60611, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Deng
authors.forename: Sumeet
authors.initials: S
authors.lastname: Virmani
authors.forename: Joseph
authors.initials: J
authors.lastname: Young
authors.forename: Kathleen
authors.initials: K
authors.lastname: Harris
authors.forename: Guang-Yu
authors.initials: GY
authors.lastname: Yang
authors.forename: Alfred
authors.initials: A
authors.lastname: Rademaker
authors.forename: Gayle
authors.initials: G
authors.lastname: Woloschak
authors.forename: Reed A
authors.initials: RA
authors.lastname: Omary
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Larson
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D007091:Image Processing, Computer-Assisted; D008113:Liver Neoplasms / Q000473:pathology*; D009336:Necrosis; D011817:Rabbits