Diffusion-weighted MRI moves beyond brain to other body parts

August 1, 2008 Diagnostic Imaging. Diffusion-weighted MRI moves beyond brain to other body parts Monitoring water mobility offers an approach to cancer imaging that complements anatomy-based techniques without their radiation risks BY VINCENT VANDECAVEYE, M.D., FREDERIK DE KEYZER, M.SC., AND ROBERT HERMANS, M.D., PH.D. -------------------------------------------------------------------------------- MR imaging can be used for many applications in oncology. Its main roles in cancer imaging are determining locoregional tumor extent, characterizing tumors, and monitoring treatment. MRI, like CT, relies on morphological criteria for lesion differentiation. This reliance, however, can make it difficult to detect small cancerous deposits and to differentiate tumor recurrence from treatment-induced tissue changes. Although differences in signal intensity on T1- and T2-weighted sequences help lesion differentiation—in hepatic lesions, for example—definite tissue characterization based on these sequences alone is often not possible.1 Administration of a contrast agent frequently improves lesion conspicuity and characterization, but the resulting increase in sensitivity sometimes comes at the cost of specificity. In cases of hepatic cirrhosis, for example, it can be difficult to differentiate between benign and malignant nodules that enhance in the arterial phase.2 Otherwise, gadolinium-based contrast agents have only a minor impact on nodal staging.

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