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

<p class="western"><b>Background: </b><span>The utility of </span>intravoxel incoherent motion (IVIM) related parameters <span>in differentiation of hypovascular liver lesions is still unknown.</span></p> <p class="western"><b>Purpose: </b>The purpose of this study was to evaluate<b> </b>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).</p> <p class="western"><b>Methods:</b> 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 <i>b</i> 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. </p> <p class="western"><b>Results</b>: ADC, true diffusion coefficient (<i>D</i>), perfusion-related diffusion coefficient (<i>D</i>*), 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 <i>D</i> were significantly different among IMC and HLM with higher diagnostic performance of <i>D</i> (AUC=0.879 vs 0.821). Patients with PHL had significantly lower ADC, <i>D</i> and ƒ compared with IMC (<i>p</i>&lt;0.001, <i>p</i>&lt;0.001, and <i>p</i>=0.041, respectively) with highest diagnostic accuracy of <i>D</i> (AUC=0.905). <i>D</i> and ƒ were lower in PHL in comparison to HLM (<i>p</i>=0.031, and <i>p</i>=0.01). Good interobserver agreement was found among two readers (<i>r</i>=0.811 for ADC, 0.902 for <i>D</i>, 0.899 for <i>D</i>*, and 0.911 for ƒ maps).</p> <p class="western"><b>Conclusion</b>: IVIM-derived parameters in particular <i>D</i>, 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.</p>