title: Intravoxel incoherent motion model-based analysis of diffusion-weighted magnetic resonance imaging with 3b-values for response assessment in locoregional therapy of hepatocellular carcinoma.
abstract: OBJECTIVE
  The aim of this study was to evaluate an intravoxel incoherent motion (IVIM) model-based analysis of diffusion-weighted imaging (DWI) for assessing the response of hepatocellular carcinoma (HCC) to locoregional therapy.
  
  
  METHODS
  Respiratory-gated DWI (b=0, 50, and 800 s/mm2) was retrospectively analyzed in 25 patients who underwent magnetic resonance imaging at 1.5 T before and 6 weeks following the first cycle of transarterial chemoembolization therapy, transarterial ethanol-lipiodol embolization therapy, and transarterial radioembolization therapy. In addition to the determination of apparent diffusion coefficient, ADC(0,800), an estimation of the diffusion coefficient,D', and the perfusion fraction,f', was performed by using a simplified IVIM approach. Parameters were analyzed voxel-wise. Tumor response was assessed in a central slice by using a region of interest (ROI) covering the whole tumor. HCCs were categorized into two groups, responders and nonresponders, according to tumor size changes on first and second follow ups (if available) and changes of contrast-enhanced region on the first follow up.
  
  
  RESULTS
  In total, 31 HCCs were analyzed: 17 lesions were assigned to responders and 14 were to nonresponders. In responders, ADC(0,800) andD' were increased after therapy by ~30% (P=0.00004) and ~42% (P=0.00001), respectively, whereasf' was decreased by ~37% (P=0.00094). No significant changes were found in nonresponders. Responders and nonresponders were better differentiated by changes inD' than by changes in ADC(0,800) (area under the curve =0.878 vs 0.819 or 0.714, respectively).
  
  
  CONCLUSIONS
  In patients with HCCs undergoing embolization therapy, diffusion changes were better reflected byD' than by conventional ADC(0,800), which is influenced by counteracting perfusion changes as assessed byf'.
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Petra
authors: P
authors: Mürtz
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Arndt-Hendrik
authors: AH
authors: Penner
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Anne-Kristina
authors: AK
authors: Pfeiffer
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Alois M
authors: AM
authors: Sprinkart
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Claus C
authors: CC
authors: Pieper
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Roy
authors: R
authors: König
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Wolfgang
authors: W
authors: Block
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Hans H
authors: HH
authors: Schild
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Winfried A
authors: WA
authors: Willinek
authors: Department of Radiology, University of Bonn, Bonn, Germany.
authors: Guido M
authors: GM
authors: Kukuk
keywords: DWI; HCC; IVIM; MRI; locoregional therapy; therapy monitoring