Renal Spatial Profile of IVIM Parameters: Humans and Dogs

Intrarenal diffusion dynamics were studied by comparing the spatial profile of Intravoxel Incoherent Motion (IVIM) parameters in humans and dogs. Despite previous renal IVIM studies in humans, limited data exists on canine kidneys, and cross-species studies, to evaluate the canine kidney model, are sparse. To address these gaps, this study evaluates the spatial heterogeneity of renal IVIM parameters, including diffusion (D), pseudo-diffusion (D*), and perfusion fraction (fp), across different kidney regions. Nine healthy human participants and eight beagles were scanned using similar diffusion-weighted imaging (DWI) protocols on a 3T MRI. Kidneys were divided into nine anatomical regions, categorized by cortical, outer, and inner medullary layers from the cranial to caudal poles. Using Bayesian fitting, IVIM parameters were extracted, and differences were analyzed across regions. Results showed significant spatial variation in IVIM parameters for both species. In humans, D values were higher in cortical regions compared to the medulla, while D* and fp showed elevated values in inner medullary regions. Conversely, dogs reported consistently higher D values across all regions, with significant differences in D* and fp profiles compared to humans. Canine cortical regions displayed higher perfusion fractions than medullary regions, unlike the trends observed in human kidneys. This cross-species analysis provides insights into renal microcirculation and diffusion, highlighting distinct spatial profiles in human and canine kidneys. The findings may advance the understanding of renal physiology and pathophysiology, supporting the relevance of canine models in translational kidney research. Further studies are required to validate these observations and improve imaging protocols for enhanced reproducibility and accuracy in renal IVIM assessments.