Focal Liver Lesion Classification and Characterization in Noncirrhotic Liver: A Prospective Comparison of Diffusion-Weighted Magnetic Resonance–Related Parameters

Purpose: The objective of this study was to prospectively verify if diffusion-weighted magnetic resonance (DwMR)–related parameters such as perfusion fraction ( f ) and slow diffusion coefficient (D), according to Le Bihan theory, are more effective than apparent diffusion coefficient (ADC) for classification and characterization of the more frequent focal liver lesions (FLLs) in noncirrhotic liver. Methods: Sixty-seven patients underwent standard liver magnetic resonance imaging (MRI) and free-breath multi-b DwMR study. Two regions of interest were defined by 2 observers, including 1 FLL for each patient (21 hemangiomas, 21 focal nodular hyperplasias, 25 metastases) and part of surrounding parenchyma, respectively. For every FLL, D, f, and ADC were estimated both as absolute value and as ratio between FLL and surrounding parenchyma by fitting the reduced equation of the bicompartmental model to experimental data; t test, analysis of variance, and receiver operating characteristic analysis were performed. Results: t Test showed significant differences in ADClesion, flesion, Dlesion, ADCratio, and Dratio values between benign and malignant FLLs, more pronounced for ADClesion (P < 0.0009) and ADCratio (P = 0.001). Applying cutoff values of 1.55 × 10−3 mm2/s (ADClesion) and 0.89 (ADCratio), the DwMR study presented sensitivities and specificities, respectively, of 84% and 80% (for ADClesion), 72% and 80% (ADCratio). Conclusions: Apparent diffusion coefficient (by fitting procedures) better performs than do D and f in FLL classification, especially when its values are less than 1.30 or greater than 2.00 × 10−3 mm2/s. Key Words: focal liver lesion, diffusion-weighted imaging, apparent diffusion coefficient (ADC), slow diffusion coefficient (D), perfusion fraction (f), IVIM theory