The role of quantitative diffusion-weighted imaging in characterization of hypovascular liver lesions: A prospective comparison of intravoxel incoherent motion derived parameters and apparent diffusion coefficient.

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), and hypovascular liver metastases (HLM). METHODS: Seventy-four prospectively enrolled patients (21 IMC, and 53 HLM) 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 reliability was tested using a intraclass correlation coefficient. 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 characteristic (ROC) curve analysis. RESULTS: The interobserver agreement was good for ADC (0.802), and excellent for D, D*, and ƒ (0.911, 0.927, and 0.942, respectively). ADC, and D values were significantly different among IMC and HLM (both p < 0.05), while there was no significant difference among these lesions for ƒ and D* (p = 0.101, and p = 0.612, respectively). ROC analysis showed higher diagnostic performance of D in comparison to ADC (AUC = 0.879 vs 0.821). CONCLUSION: IVIM-derived parameters in particular D, in addition to ADC, could help in differentiation between most common hypovascular malignant liver lesions, intrahepatic mass-forming cholangiocarcinoma and hypovascular liver metastases.

Intrahepatic mass-forming cholangiocarcinoma and solitary hypovascular liver metastases: is the differential diagnosis using diffusion-weighted MRI possible?

Background Intrahepatic mass-forming cholangiocellular carcinoma (IMC) is the second most common primary liver tumor. The differentiation between IMC and solitary hypovascular liver metastases (SHLM) represents a diagnostic challenge due to many overlapping magnetic resonance imaging (MRI) features. Purpose To determine the value of diffusion-weighted imaging (DWI) in addition to conventional MRI for the distinction between intrahepatic mass-forming cholangiocarcinoma and solitary hypovascular liver metastases. Material and Methods Fifty-three patients with pathologically proven IMC (n = 31) and SHLM (n = 22) who had undergone MRI and DWI before surgery or percutaneous biopsy were enrolled in this study. The following MRI features were analyzed: the size and shape of the lesion, presence of capsular retraction and segmental biliary dilatation, T2-weighted (T2W) signal intensity, the presence of target sign on DWI and enhancement pattern. Apparent diffusion coefficient (ADC) values were calculated for each lesion ( b = 800 s/mm2). Univariate and multivariate logistic regression analyses were used to identify significant differentiating features between IMCs and SHLMs. Results Univariate analysis revealed that following parameters favor diagnosis of IMCs over SHLMs: lobulating shape, heterogeneous T2W signal intensity, capsular retraction, segmental biliary dilatation, target sign on DWI and rim-like enhancement on arterial phase followed by progressive enhancement in delayed phases. ADC values measured in the periphery of the lesion were significantly lower in IMCs in comparison to SHLMs. Multivariate analysis revealed that target sign on DWI was the most significant predictor of IMCs. Conclusion Qualitative DWI analysis with target sign significantly improves diagnostic accuracy for differentiation among IMC and SHLM lesions.