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

Abstract

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. 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 (Vintra) and intersession (Vinter) repeatability. Intersubject variability was less than 20%, whereas Vintra and Vinter repeatability were less than 5% and less than 10%, respectfully. Vinter was not affected by the NGD used. Decreases in Vinter(FA), Vinter(λ1), Vinter(RD), and Vinter(MD) were observed with increasing NSA, and hence SNR. Increased SNR may improve intrasession and intersession repeatability of liver DTI metrics. Scan repeatability was not influenced by NGD.