Impact of blood flow on diffusion coefficients of the human kidney: A time-resolved ECG-triggered diffusion-tensor imaging (DTI) study at 3T

Abstract

Purpose: To evaluate the impact of renal blood flow on apparent diffusion coefficients (ADC) and fractional anisotropy (FA) using time-resolved electrocardiogram (ECG)-triggered diffusion-tensor imaging (DTI) of the human kidneys. Materials and Methods: DTI was performed in eight healthy volunteers (mean age 29.1 ± 3.2) using a single slice coronal echoplanar imaging (EPI) sequence (3 b-values: 0, 50, and 300 s/mm2) at the timepoint of minimum (20 msec after R wave) and maximum renal blood flow (200 msec after R wave) at 3T. Following 2D motion correction, region of interest (ROI)-based analysis of cortical and medullary ADC- and FA-values was performed. Results: ADC-values of the renal cortex at maximum blood flow (2.6 ± 0.19 × 10-3 mm2/s) were significantly higher than at minimum blood flow (2.2 ± 0.11 × 10-3 mm2/s) (P < 0.001), while medullary ADC-values did not differ significantly (maximum blood flow: 2.2 ± 0.18 × 10-3 mm2/s; minimum blood flow: 2.15 ± 0.14 × 10-3 mm2/s). FA-values of the renal medulla were significantly greater at maximal blood (0.53 ± 0.05) than at minimal blood flow (0.47 ± 0.05) (P < 0.01). In contrast, cortical FA-values were comparable at different timepoints of the cardiac cycle. Conclusion: ADC-values in the renal cortex as well as FA-values in the renal medulla are influenced by renal blood flow. This impact has to be considered when interpreting renal ADC- and FA-values. J. Magn. Reson. Imaging 2013;37:233-236. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.