Noise-induced bias in low-direction diffusion tensor MRI: replication of Monte-Carlo simulation with in-vivo scans

Clinical neuroimaging studies involving diffusion tensor MRI (DTI) require precise estimation of diffusion properties for statistical analysis. Tensor derived measures such as fractional anisotropy (FA) and trace are often analyzed for hypothesis testing. Given the limited scanning time typically available for studies, careful selection of scanning protocols and processing methods is essential for accurate and precise measurements. Analysis of the effect of MR noise on tensor derived measures has shown a negative bias in FA when the principal eigenvector of tensor is aligned with a gradient direction [1][2][3]. This bias can lead to a correlation between FA and tensor orientation in protocols with low numbers of gradient directions. We extend the results of simulation experiments by showing evidence of predicted anisotropy bias in in-vivo data.