The use of diffusion tensor imaging in quantifying the effect of dexamethasone on brain tumours.

The role of dexamethasone in the treatment of patients with brain tumours remains poorly understood. In this study the self-diffusion parameters of extracellular water within primary intracranial tumours and peritumoural tissue, and their response to dexamethasone, have been measured using MR diffusion tensor imaging. Maps of the mean diffusivity <D> and two measures of diffusion anisotropy were obtained from six patients before, and typically 48-72h after, commencing dexamethasone treatment. A significant decrease in <D> of either tumour (p < 0.02) or oedematous brain (p < 0.04) was observed in three patients. No significant changes were noted in either of the two calculated diffusion anisotropy indices before and after steroid treatment in any of the six patients.