Hepatic Cavernous Hemangiomas: Relationship between Speed of Intratumoral Enhancement during Dynamic MRI and Apparent Diffusion Coefficient on Diffusion-Weighted Imaging

Objective: To investigate the relationships between the apparent diffusion coefficients (ADCs) on diffusion-weighted imaging (DWI) and the speed of contrast-enhancement in hepatic hemangiomas. Materials and Methods: Sixty-nine hepatic hemangiomas (${\geq}$ 1 cm) were evaluated with DWI, by using multiple b values (b = 50, 400, $800s/mm^{2}$), followed by a gadolinium-enhanced dynamic MRI. The lesions were classified into three groups, according to the speed of contrast-enhancement on the portal phase. ADCs were measured on the ADC map automatically, and were calculated by using the two different b values ($mADC_{50-400}$ with b values = 50 and 400; $mADC_{400-800}$ with b values = 400 and $800s/mm^{2}$). Results: The mean ADCs (${\times}$ $10^{-3}mm^{2}/s$) were significantly higher in the rapid group (1.9 ${\pm}$ 0.44) than in the intermediate (1.7 ${\pm}$ 0.35, p = 0.046) or the slow groups (1.4 ${\pm}$ 0.34, p = 0.002). There were significant differences between the rapid and the slow groups in $mADC_{50-400}$ (2.12 vs. 1.48; p = 0.008) and $mADC_{400-800}$ (1.68 vs. 1.22, p = 0.010), and between the rapid and the intermediate groups in $mADC_{50-400}$ (2.12 vs. 1.79, p = 0.049). Comparing $mADC_{50-400}$ with $mADC_{400-800}$, there was a significant difference only in the rapid group (p = 0.001). Conclusion: Higher ADCs of rapidly-enhancing hemangiomas may be related to richer intralesional vascular perfusion. Also, the restricted diffusion may be attributed to the difference of structural characteristics of hemangioma.