title: Minimizing the Acquisition Time for Intravoxel Incoherent Motion Magnetic Resonance Imaging Acquisitions in the Liver and Pancreas.
abstract: OBJECTIVE
  The aim of this study was to determine the combination of b-values and signal averages for diffusion-weighted image acquisitions that render the minimum acquisition time necessary to obtain values of the intravoxel incoherent motion (IVIM) model parameters in vivo in the pancreas or liver with acceptable reproducibility.
  
  
  METHODS
  For 16 volunteers, diffusion-weighted images, with 14 b-values and 9 acquisitions per b-value, were acquired in 2 scan sessions. The IVIM model was fitted to data from lesion-sized regions of interest (ROIs) (1.7 cm(3)) as well as organ-sized ROIs in the pancreas and liver. By deleting data during analyzes, the IVIM model parameters, D and f, could be determined as a function of the number of b-values as well as the number of measurements per b-value taken along. For the IVIM model parameters, we examined the behavior reproducibility, in the form of the within-subject coefficient of variation (CVw), as a function of the amount of data taken along in the fits. Finally, we determined the minimum acquisition time required as a function of CVw.
  
  
  RESULTS
  For the lesion-sized ROI, the intersession CVws were 8%/46% and 13%/55% for D/f in the pancreas and liver, respectively, when all data were taken along. For 1.2 times larger CVws, acquisition in the pancreas could be done in 5:15 minutes using 9 acquisitions per b-value at b = 0, 30, 50, 65, 100, 375, and 500 mm(-2)s and for the liver in 2:15 using 9 acquisitions per b-value at b = 0, 40, and 500 mm(-2)s.
  
  
  CONCLUSIONS
  Acquiring 7 b-values in the pancreas and 3 b-values in the liver only decreases the reproducibility by 20% compared with an acquisition with 14 b-values. The understanding of the behavior of reproducibility as a function of b-values and acquisitions per b-values scanned will help researchers select the shortest IVIM protocol.
authors.affiliation: From the Departments of *Radiology, and †Radiation Oncology, Academic Medical Center, Amsterdam; ‡Department of Radiology, University Medical Center Utrecht, Utrecht; §Department of Medical Oncology, and ∥Laboratory for Experimental Oncology and Radiobiology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Gurney-Champion
authors.forename: Martijn
authors.initials: M
authors.lastname: Froeling
authors.forename: Remy
authors.initials: R
authors.lastname: Klaassen
authors.forename: Jurgen H
authors.initials: JH
authors.lastname: Runge
authors.forename: Arjan
authors.initials: A
authors.lastname: Bel
authors.forename: Hanneke W M
authors.initials: HW
authors.lastname: van Laarhoven
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
mesh_terms: D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008099:Liver / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009038:Motion; D010179:Pancreas / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D013997:Time Factors