Malignant Liver Lesions

Abstract

Imaging techniques applied to medical practice depend on two major characteristics: the ability to consistently define anatomically coherent findings and adequate contrast between tissues. MR diffusion-weighted imaging (DWI) uses the signal loss associated with the random thermal motion of water molecules in the presence of magnetic field gradients to derive a quantitative parameter (the so-called apparent diffusion coefficient—ADC) that directly reflects the translational mobility of the water molecules in the tissues [1]. It is fundamentally different from the conventional morphological and hemodynamically based imaging techniques [2]. Early abdominal applications of DWI were limited due to susceptibility effects, suboptimal fat suppression and artifacts related to random and periodic motion [3, 4]. Many of these issues have not been completely solved but are today minimized considering current hardware and software improvements. As such, DWI has become an indispensable day-to-day tool for liver imaging, proving its value on various clinical scenarios, from focal liver lesion detection to characterization and/or diffuse liver disease assessment. Specific advantages consist on its short examination time, independence of exogenous sources of contrast, and the ability to provide qualitative and quantitative information [5, 6]. The following chapter addresses the most common current clinical applications of DWI in the setting of liver malignancies, considering basic methodologies on how to assess diffusion-weighted images in qualitative and quantitative manner and reviewing clinical results for oncologic applications.