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


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/mm(2)) 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) mm(2)/s) were significantly higher than at minimum blood flow (2.2 ± 0.11 × 10(-3) mm(2)/s) (P < 0.001), while medullary ADC-values did not differ significantly (maximum blood flow: 2.2 ± 0.18 × 10(-3) mm(2)/s; minimum blood flow: 2.15 ± 0.14 × 10(-3) mm(2)/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.


CONCLUSIONS
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.
University Düsseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Düsseldorf, Germany.
Philipp
P
Heusch
Hans-Jörg
HJ
Wittsack
Patric
P
Kröpil
Dirk
D
Blondin
Michael
M
Quentin
Janina
J
Klasen
Gael
G
Pentang
Gerald
G
Antoch
Rotem S
RS
Lanzman
D000328:Adult; D016880:Anisotropy; D001783:Blood Flow Velocity; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000098:blood supply* / Q000473:pathology*; D007679:Kidney Medulla / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D015233:Models, Statistical; D009038:Motion; D012079:Renal Circulation; D012119:Respiration; D013997:Time Factors