Intrasession and Intersession Repeatability of Diffusion Tensor Imaging in Healthy Human Liver

Objective: The aim of this study was to evaluate the effect of signal to noise ratio (SNR) and number of gradient directions (NGD) on intra- and intersession repeatability of liver diffusion tensor imaging (DTI) metrics. Methods: At each of 3 liver DTI scan sessions, liver diffusion was assessed in 5 healthy volunteers using a 6-direction DTI scan performed 9 separate times (ie, number of signal averages [NSA]). In addition, 4 combinations of NSA and NGD were acquired (NSA/NGD = 1/30, 3/10, 3/12, and 5/6) to determine the combined effect to DTI metrics, which was based on intersubject variability and intrasession (V-intra) and intersession (V-inter) repeatability. Results: Intersubject variability was less than 20%, whereas V-intra and V-inter repeatability were less than 5% and less than 10%, respectfully. V-inter was not affected by the NGD used. Decreases in V-inter(FA), V-inter(lambda(1)), V-inter (RD), and V-inter(MD) were observed with increasing NSA, and hence SNR. Conclusion: Increased SNR may improve intrasession and intersession repeatability of liver DTI metrics. Scan repeatability was not influenced by NGD.