Recurrence and Metastasis of Lung Cancers Demonstrate Decreased Diffusion on Diffusion-Weighted MRI

Diffusion-weighted magnetic resonance imaging (DWI) exploits the random, translational motion, or so-called Brownian movement, of water molecules in biologic tissue (Le Bihan et al., 1988). Recently, DWI has been used to detect the restricted diffusion of water molecules in the body. The primary use of DWI has been in brain imaging, mainly for the evaluation of intracranial tumors, acute ischemic stroke and demyelinating diseases (Tien et al., 1994; Sorensen et al., 1996). Diffusion of water molecules in malignant tumors is generally restricted compared to that in normal tissue, resulting in a decreased apparent diffusion coefficient (ADC) value (Szafer et al., 1995; Takahara et al., 2004). MRI examination carries no risk of exposure to radiation, and the examination can be done in every hospital whereas hospitals equipped with PET-CT are limited because of the potential risk in handling the radioisotope of 18F-FDG. Furthermore, MRI examination is relatively more affordable compared to a PET-CT