Diffusion-Weighted MRI: Role in the differential Diagnosis of the Brain Tumors

Abstract

Diffusion-weighted MRI (or diffusion-weighted imaging, DWI) is a method that is based upon random (Brownian) movements of water molecules. In diffusion-weighted imaging, additional gradients (which are the strong magnetic fields) are applied in very short durations. If restricted diffusion is present, increased signal is obtained. However, the diffusion-weighted images also have T2 characteristics and therefore, lesions that are very bright on T2 weighted images may still appear bright on diffusion weighted sequences. To overcome this “T2 shine-through” effect, apparent diffusion coefficient (ADC) maps are produced by getting three orthogonal measurements, taking the average, for each voxel.1 Areas with restricted diffusion appears dark on ADC images;