Are ADC histogram metrics repeatable?

Abstract

Purpose: The present study evaluated the repeatability of apparent diffusion coefficient (ADC) histogram metrics in clinical MRI.Methods: Twelve patients who underwent head MRI in our hospital from May to July in 2016 were included in the present study. All patients gave informed consent. Two sequential diffusion-weighted images with echo planar imaging (DWI-EPI) in the identical positioning were obtained. The b-factors of 0 and 1000 or 1500 s/mm2 were used, three orthogonal motion proving gradients (MPGs) were applied, and synthesized images were generated. The regions of interest (ROIs) were ssigned at the lesions on the 1st DWI and pasted onto the 2nd at the same size and location. Voxel-wise ADC was calculated by fitting the signal intensity change of each voxel into a mono-exponential curve. ADCs calculated from 1st and 2nd DWI were defined as ADC-1st and ADC-2nd, respectively. To investigate the repeatability of voxel-wise ADC in each lesion, ADC-1st and ADC-2nd were compared using Wilcoxon matched-pairs signed rank test and linear regression. To onsider repeatability of ADC histogram metrics for all lesions, minimal, 25%, median, 75%, maximum, mean, skewness, and kurtosis of ADC-1st and ADC-2nd for each lesion were compared using linear regression and Bland-Altman plot.Results: For repeatability of voxel-wise ADC, significant differences were observed between ADC-1st and ADC-2nd in 5 lesions. Linear regression did not show significance of the slope in 5 lesions. As for repeatability of ADC histogram metrics, all ADC histogram metrics except skewness and kurtosis showed significance of the slope in linear regression (p<0.0001) and high repeatability in Bland-Altman plot.Conclusion: The histogram metrics of voxel-wise ADC like minimum, 25%, median, 75%, maximum, and mean show high repeatability, but skewness and kurtosis did not