In vivo monitoring of renal tubule volume fraction using dynamic parametric MRI

Purpose The increasing incidence of kidney diseases is a global concern, and current biomarkers and treatments are inadequate. Changes in renal tubule luminal volume fraction (TVF) serve as a rapid biomarker for kidney disease and improve understanding of renal (patho)physiology. This study uses the amplitude of the long T2 component as a surrogate for TVF in rats, by applying multiexponential analysis of the T2‐driven signal decay to examine micromorphological changes in renal tissue. Methods Simulations were conducted to identify a low mean absolute error (MAE) protocol and an accelerated protocol customized for the in vivo study of T2 mapping of the rat kidney at 9.4 T. We then validated our bi‐exponential approach in a phantom mimicking the relaxation properties of renal tissue. This was followed by a proof‐of‐principle demonstration using in vivo data obtained during a transient increase of renal pelvis and tubular pressure. Results Using the low MAE protocol, our approach achieved an accuracy of MAE