Diffusion-weighted MRI of kidneys in healthy volunteers and living kidney donors

• Magnetic resonance diffusion-weighted imaging of kidneys.
• Apparent diffusion coefficient in healthy individuals.
• Monoexponential model of diffusion.

AimTo establish the normal apparent diffusion coefficient (ADC) values in healthy kidneys, comparing them with the literature, and assessing the correlation between ADC values, creatinine blood level, and glomerular filtration rate (GFR).Materials and methodsTwenty-four healthy volunteers and 26 living kidney donors were examined on a 1.5 T magnetic resonance imaging (MRI) unit. Two diffusion-weighted imaging (DWI) sequences were included in the study protocol (protocol 1 with 16 b-values, protocol 2 with 10 b-values) before the examination blood and urine samples were collected. The GFR was calculated using Cockcroft & Gault and MDRD (Modification of Diet In Renal Disease) formulas and the ADC values were measured separately for the cortex and medulla of each kidney by two independent observers. All statistical analyses were performed using the STATISTICA (version 10.0) software package. Data were analysed using an unpaired t-test; p<0.05 indicated a statistically significant difference.ResultsThe average ADC value for protocol 1 for the cortex was 2.26×10−3 mm2/s, for the medulla 2.21×10−3 mm2/s. In protocol 2, the respective values were 2.13×10−3 mm2/s and 2.06×10−3 mm2/s. Neither statistically significant interobserver differences nor correlation between ADC values, GFR, and creatinine serum level were observed.ConclusionThe reference ADC values were established. The measurements show high interobserver consistency. The differences in ADC values reported in the literature suggest dependence on the equipment and methodology and point to the necessity of obtaining ADC norms for each MRI unit.