title: Comparison of biexponential and monoexponential model of diffusion weighted imaging in evaluation of renal lesions: preliminary experience.
abstract: OBJECTIVE
  To obtain intravoxel incoherent motion (IVIM) parameters with biexponential analysis of multiple b-value diffusion-weighted imaging (DWI) and compare these parameters to apparent diffusion coefficient (ADC) obtained with monoexponential modeling in their ability to discriminate enhancing from nonenhancing renal lesions.
  
  
  METHODS
  Twenty-eight patients were imaged at 1.5 T utilizing contrast-enhanced (CE) magnetic resonance imaging (MRI) and breath-hold DWI using 8 b values (range: 0-800 s/mm(2)). Perfusion fraction (f(p)), tissue diffusivity (D(t)), and pseudo-diffusion coefficient (D(p)) were calculated using segmented biexponential analysis. ADC(total) and ADC(0-400-800) were calculated with monoexponential fitting of the DWI data. f(p), D(t), D(p), ADC(total), and ADC(0-400-800) were compared between enhancing and nonenhancing renal lesions. Receiver operating characteristic analysis was performed for all DWI parameters. f(p) was correlated with percent enhancement.
  
  
  RESULTS
  There were a total of 31 renal lesions (15 enhancing and 16 nonenhancing) in 28 patients on CE-MRI. f(p) of enhancing masses was significantly higher (27.9 vs. 6.1) and D(t) was significantly lower (1.47 vs. 2.40 ×10(-3) mm(2)/s). IVIM parameters f(p) and D(t) demonstrated higher accuracy in differentiating enhancing from nonenhancing renal lesions compared with monoexponential parameters ADC(0-400-800) and ADC(total), with area under the curve of 0.946, 0.896, 0.854, and 0.675, respectively. There was a good correlation between f(p) and percent enhancement (r = 0.7; P < 0.001).
  
  
  CONCLUSIONS
  IVIM parameters f(p) and D(t) obtained with biexponential fitting of multi-b value DWI have higher accuracy compared with ADC (obtained with monoexponential fit) in discriminating enhancing from nonenhancing renal lesions. Furthermore, f(p) demonstrates good correlation with percent enhancement and can provide information regarding lesion vascularity without the use of exogenous contrast agent.
authors.affiliation: Department of Radiology, New York University Langone Medical Center, NY 10016, USA. hersh.chandarana@nyumc.org
authors.forename: Hersh
authors.initials: H
authors.lastname: Chandarana
authors.forename: Vivian S
authors.initials: VS
authors.lastname: Lee
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hecht
authors.forename: Bachir
authors.initials: B
authors.lastname: Taouli
authors.forename: Eric E
authors.initials: EE
authors.lastname: Sigmund
mesh_terms: D000704:Analysis of Variance; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000295:instrumentation*; D006801:Humans; D007668:Kidney / Q000098:blood supply / Q000473:pathology* / Q000502:physiology; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008962:Models, Theoretical; D010477:Perfusion; D012372:ROC Curve; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D003287:Contrast Media