Purpose: To characterize the diffusion time (Δeff) dependence of apparent diffusion coefficient (ADC) and intravoxel incoherent motion-related parameters in the human kidney at 3 T.
Methods: Sixteen healthy volunteers underwent an MRI examination at 3 T including diffusion-weighted imaging at different Δeff ranging from 24.1 to 104.1 ms. The extended mono-exponential ADC and intravoxel incoherent motion models were fitted to the data for each Δeff and the medullary and cortical ADC, (pseudo-)diffusion coefficients (D* and D) and flow-related signal fraction (f) were calculated.
Results: When all the data were used for fitting, a significant trend toward higher ADC with increasing Δeff was observed between 24.1 and 104.1 ms (median and interquartile range: 2.38 [2.19, 2.47] to 2.84 [2.36, 2.90] × 10-3 mm2/s for cortex, and 2.28 [2.18, 2.37] to 2.82 [2.58, 3.11] × 10-3 mm2/s for medulla). In contrast, no significant differences in ADC were found when only the data acquired at b-values higher than 200 s/mm2 were used for fitting. When the intravoxel incoherent motion model was applied, cortical and medullary f increased significantly (cortex: 0.21 [0.15 0.27] to 0.37 [0.32, 0.49] × 10-3 mm2/s; medulla: 0.15 [0.13 0.29] to 0.41 [0.36 0.51] × 10-3 mm2/s). No significant changes in cortical and medullary D and D* were observed as diffusion time increased.
Conclusion: Renal perfusion and tubular flow substantially contribute to the observed increase in ADC over a wide range of Δeff between 24 and 104 ms.
Keywords: diffusion time; diffusion‐weighted imaging (DWI); intravoxel incoherent motion (IVIM); renal DWI.
© 2024 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.