Role of DWI in the Evaluation of Intracranial Lesions

Diffusion weighted imaging is a specialized magnetic resonance imaging technique that depends upon the random movement of water molecules within and between the extracellular and intracellular spaces. It provides microscopic information from water protons that is not possible with conventional MRI imaging. Regions with restricted water mobility yield a higher signal and appear bright on DW imaging (Haaga JR et al 2009). Apparent diffusion coefficient (ADC) is a quantitative parameter calculated from DWI that combines the effect of capillary perfusion and water diffusion.. ADC value is calculated for each pixel of the image and is displayed as a parametric map. DWI is most applicable in the tissues which are dominated by isotropic water movement like grey matter in cerebral cortex and major brain nuclei.It has been used to study the normal brain and various diseases such as ischemia, tumors, epilepsy and white matter disorders (Chenevert et al 1990 and Rowley HA et al 1999). DWI provides useful information, increasing the sensitivity of MRI as a diagnostic tool, narrowing the differential diagnosis, providing the prognostic information, aiding the treatment planning and evaluating the response to treatment.