Peritumoral edema of meningiomas and metastatic brain tumors: differences in diffusion characteristics evaluated with diffusion-tensor MR imaging

Introduction We prospectively compared the fractional anisotropy (FA) and mean diffusivity (MD) of the peritumoral edema of meningiomas and metastatic brain tumors with diffusion-tensor magnetic resonance (MR) imaging. Methods The study protocol was approved by the local ethics committee, and written informed consent was obtained. Preoperative diffusion-tensor MR imaging was performed in 15 patients with meningiomas and 11 patients with metastatic brain tumors. Regions of interest (ROI) were placed in the peritumoral edema and normal-appearing white matter (NAWM) of the contralateral hemisphere to measure the FA and MD. The FA and MD ratios were calculated for each ROI in relation to the NAWM of the contralateral hemisphere. Changes in peritumoral MD and FA, in terms of primary values and ratios, were compared using a two-sample t-test; P < 0.05 was taken as indicating statistical significance. Results The mean MD values ( x 10(-3) mm(2)/s) of the peritumoral edema for metastases and meningiomas, respectively, were 0.902 +/- 0.057 and 0.820 +/- 0.094, the mean MD ratios were 220.3 +/- 22.6 and 193.1 +/- 23.4, the mean FA values were 0.146 +/- 0.026 and 0.199 +/- 0.052, and the mean FA ratios were 32.3 +/- 5.9 and 46.0 +/- 12.1. All the values were significantly different between metastases and meningiomas (MD values P= 0.016, MD ratios P= 0.006, FA values P= 0.005, FA ratios P= 0.002). Conclusion The peritumoral edema of metastatic brain tumors and meningiomas show different MD and FA on diffusion-tensor MR imaging.