Fiber Orientation Mapping Using Gradient Echo MRI: R2* Mapping Vs Frequency Difference Mapping

Samuel James Wharton¹, Richard Bowtell¹

Recent work has shown that magnitude images acquired using gradient echo (GE) techniques at high field are sensitive to the fiber-orientation in white matter. Here, we show that frequency difference mapping (FDM) based on acquisition of multi-echo GE data allows the strong fiber-orientation contrast in phase images to be exploited in producing high resolution, 3D fiber-orientation maps. This approach was tested on post-mortem brain samples by comparing the resulting orientation maps to DTI data and fiber-orientation maps generated from simultaneously acquired R2* maps. The results suggest that FDM at high field may be used for high resolution fiber-orientation mapping.