Optimization of Number of Diffusion Gradient Directions on anisotropy indices and deterministic fiber tracking for diffusion tensor imaging

For MR diffusion tensor imaging (DTI), the imaging parameter of Number of Diffusion Gradient Direction (NDGD) plays a great role in the acquisition of raw data. Up till now, a consensus hasn´t been reached on the selection of NDGD in DTI protocols for the computation of anisotropy indices and the deterministic fiber tracking. In this paper, we proposes a scheme for optimizing the NGDG in clinical DTI protocols. A case of low-grade glioma patient was acquired by five DTI protocols with five different NDGDs 6, 11, 15, 21, and 31. The DTI raw data of each NDGD was processed by the software of DTI Studio. The two DTI indices of relative anisotropy (RA) and fractional anisotropy (FA) were firstly calculated, and then the deterministic fiber tracking was conducted. Finally, the experimental results were evaluated by an experienced radiologist quantitatively and qualitatively. The results showed that the NDGD = 6 was suitable for the computation of DTI indices and the deterministic fiber tracking. The optimization of NDGD ensures the accuracy of tensor computation, and it is helpful for the data acquisition of DTI.