The role of intravoxel incoherent motion (IVIM) parameters in characterization of hypovascular liver lesions: the raw diffusion weighted images and IVIM data

Background: The utility of intravoxel incoherent motion (IVIM) related
parameters in differentiation of hypovascular liver lesions is still
unknown. Purpose: The purpose of this study was to evaluate the value of
IVIM related parameters in comparison to apparent diffusion coefficient
(ADC) for differentiation among intrahepatic mass-forming
cholangiocarcinoma (IMC), hypovascular liver metastases (HLM) and primary
hepatic lymphoma (PHL). Methods: Seventy-seven prospectively enrolled
patients (21 IMC, 53 HLM, and 3 PHL) underwent 1,5T magnetic resonance
examination with IVIM diffusion-weighted imaging using seven b values
(0-800 s/mm2). Two independent readers performed quantitative analysis of
IVIM-related parameters and ADC. Interobserver agreement was tested using
a Pearson/Spearman-correlation. Results: ADC, true diffusion coefficient
(D), perfusion-related diffusion coefficient (D*), and perfusion fraction
(ƒ) were compared among the lesions using Kruskal-Wallis H test. The
diagnostic accuracy of each parameter was assessed by receiver operating
curve (ROC) analysis. ADC, and D were significantly different among IMC
and HLM with higher diagnostic performance of D (AUC=0.879 vs 0.821).
Patients with PHL had significantly lower ADC, D and ƒ compared with IMC
(p<0.001, p<0.001, and p=0.041, respectively) with highest
diagnostic accuracy of D (AUC=0.905). D and ƒ were lower in PHL in
comparison to HLM (p=0.031, and p=0.01). Good interobserver agreement was
found among two readers (r=0.811 for ADC, 0.902 for D, 0.899 for D*, and
0.911 for ƒ maps). Conclusion: IVIM-derived parameters in particular D, in
addition to ADC, could help in differentiation among most common
hypovascular malignant liver lesions. Moreover, they can be used for
characterization of rare hypovascular entities such as primary hepatic
lymphoma.