title: Impact of the calculation algorithm on biexponential fitting of diffusion-weighted MRI in upper abdominal organs.
abstract: OBJECTIVE
  To compare the variability, precision, and accuracy of six different algorithms (Levenberg-Marquardt, Trust-Region, Fixed-Dp , Segmented-Unconstrained, Segmented-Constrained, and Bayesian-Probability) for computing intravoxel-incoherent-motion-related parameters in upper abdominal organs.
  
  
  METHODS
  Following the acquisition of abdominal diffusion-weighted magnetic resonance images of 10 healthy men, six distinct algorithms were employed to compute intravoxel-incoherent-motion-related parameters in the left and right liver lobe, pancreas, spleen, renal cortex, and renal medulla. Algorithms were evaluated regarding inter-reader and intersubject variability. Comparability of results was assessed by analyses of variance. The algorithms' precision and accuracy were investigated on simulated data.
  
  
  RESULTS
  A Bayesian-Probability based approach was associated with very low inter-reader variability (average Intraclass Correlation Coefficients: 96.5-99.6%), the lowest inter-subject variability (Coefficients of Variation [CV] for the pure diffusion coefficient Dt : 3.8% in the renal medulla, 6.6% in the renal cortex, 10.4-12.1% in the left and right liver lobe, 15.3% in the spleen, 15.8% in the pancreas; for the perfusion fraction Fp : 15.5% on average; for the pseudodiffusion coefficient Dp : 25.8% on average), and the highest precision and accuracy. Results differed significantly (P < 0.05) across algorithms in all anatomical regions.
  
  
  CONCLUSIONS
  The Bayesian-Probability algorithm should be preferred when computing intravoxel-incoherent-motion-related parameters in upper abdominal organs.
authors.affiliation: Department of Diagnostic, Pediatric, and Interventional Radiology, Inselspital University Hospital, Bern, Switzerland.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Barbieri
authors.affiliation: Department of Diagnostic and Interventional Radiology, University Hospital, Zürich, Switzerland.
authors.forename: Olivio F
authors.initials: OF
authors.lastname: Donati
authors.affiliation: Department of Diagnostic, Pediatric, and Interventional Radiology, Inselspital University Hospital, Bern, Switzerland.
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Froehlich
authors.affiliation: Department of Diagnostic, Pediatric, and Interventional Radiology, Inselspital University Hospital, Bern, Switzerland.
authors.forename: Harriet C
authors.initials: HC
authors.lastname: Thoeny
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D000328:Adult; D000465:Algorithms; D001499:Bayes Theorem; D003198:Computer Simulation; D038524:Diffusion Magnetic Resonance Imaging; D064368:Healthy Volunteers; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007672:Kidney Cortex / Q000000981:diagnostic imaging; D007679:Kidney Medulla / Q000000981:diagnostic imaging; D008099:Liver / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009038:Motion; D010179:Pancreas / Q000000981:diagnostic imaging; D011336:Probability; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio; D013154:Spleen / Q000000981:diagnostic imaging
keywords: Bayesian; abdominal; algorithm; intravoxel-incoherent-motion; least-squares; segmented