title: Systematic analysis of the intravoxel incoherent motion threshold separating perfusion and diffusion effects: Proposal of a standardized algorithm.
abstract: OBJECTIVE
  To systematically evaluate the dependence of intravoxel-incoherent-motion (IVIM) parameters on the b-value threshold separating the perfusion and diffusion compartment, and to implement and test an algorithm for the standardized computation of this threshold.
  
  
  METHODS
  Diffusion weighted images of the upper abdomen were acquired at 3 Tesla in eleven healthy male volunteers with 10 different b-values and in two healthy male volunteers with 16 different b-values. Region-of-interest IVIM analysis was applied to the abdominal organs and skeletal muscle with a systematic increase of the b-value threshold for computing pseudodiffusion D*, perfusion fraction Fp, diffusion coefficient D, and the sum of squared residuals to the bi-exponential IVIM-fit.
  
  
  RESULTS
  IVIM parameters strongly depended on the choice of the b-value threshold. The proposed algorithm successfully provided optimal b-value thresholds with the smallest residuals for all evaluated organs [s/mm2]: e.g., right liver lobe 20, spleen 20, right renal cortex 150, skeletal muscle 150. Mean D* [10(-3) mm(2)/s], Fp [%], and D [10(-3) mm(2)/s] values (±standard deviation) were: right liver lobe, 88.7 ± 42.5, 22.6 ± 7.4, 0.73 ± 0.12; right renal cortex: 11.5 ± 1.8, 18.3 ± 2.9, 1.68 ± 0.05; spleen: 41.9 ± 57.9, 8.2 ± 3.4, 0.69 ± 0.07; skeletal muscle: 21.7 ± 19.0; 7.4 ± 3.0; 1.36 ± 0.04.
  
  
  CONCLUSIONS
  IVIM parameters strongly depend upon the choice of the b-value threshold used for computation. The proposed algorithm may be used as a robust approach for IVIM analysis without organ-specific adaptation.
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Moritz C
authors.initials: MC
authors.lastname: Wurnig
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Olivio F
authors.initials: OF
authors.lastname: Donati
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Erika
authors.initials: E
authors.lastname: Ulbrich
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Filli
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Kenkel
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Bern, Switzerland.
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Thoeny
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Boss
mesh_terms: D000005:Abdomen / Q000033:anatomy & histology / Q000502:physiology; D000328:Adult; D000465:Algorithms; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology
keywords: diffusion-weighted imaging; intravoxel incoherent motion; magnetic resonance; pseudodiffusion