Comparison of Diffusion and DCE-MRI as Markers for Response to Therapy in HCC Patients

Introduction: Both diffusion tensor and diffusion weighted MRI have been used extensively in the evaluation of neurological disorders including stroke, Alzheimer’s disease, and multiple sclerosis [1 – 3]. More recently, interest has grown in the use of diffusion MRI to evaluate and predict response to therapy in various cancers [4 – 6]. Diffusion tensor imaging, which is most useful in the brain for mapping the layout of white matter bundles, is not particularly applicable to the analysis of cancers, where an orderly arrangement of barriers to diffusion is not expected. Apparent diffusion coefficient (ADC), however, can be a useful proxy for cellular density within a tumor. In this study, we have evaluated the practicality and utility of using changes in ADC as an indicator of response to therapy in hepatocellular cancer (HCC). In the first phase of the study, 12 normal volunteers were imaged twice with a temporal separation of roughly 40 minutes between scans. ADC values were then calculated for regions of normal liver tissue and these results were used to estimate the scan-rescan coefficient of variability (CoV) for this measurement. In the second phase of the study, seven HCC patients were imaged at baseline and again after (1) administration of an anti-angiogenic agent, and (2) chemoembolization. Patients were also imaged at each time point using DCE-MRI [7], and changes in ADC were correlated with changes seen in blood flow and vascular permeability.