The efficacy of MR techniques in the detection and assessment of renal injury in clinically relevant animal models of renal disease
In the present studies, the ability of some nuclear magnetic resonance techniques to provide a detailed picture of the extent and time-course of NMR-detectable tissue changes in response to renal insult was assessed. In the animal models of renal disease used, the comparison of NMR data with histological results shows that the proton NMR relaxation times of renal tissues have adequate specificity to observe differences in kidney response to different types of nephrotoxic insult and to accurately locate them. Depending on the toxin used and the damage it induces to the kidney, spin-lattice or spin-spin relaxation time may be more sensitive in detecting and monitoring the damage. This suggests that ex vivo NMR relaxation studies are useful for the interpretation of underlying biophysical mechanisms and, therefore, could constitute the link between physical parameters (characterising the results in magnetic resonance imaging studies) and physiological or pathological processes. This way they are expected to assist the identification of optimal acquisition conditions and imaging parameters in imaging studies of renal function. However, the studies undertaken stress the need for a strict protocol in NMR relaxation time measurements. The finding that physiological processes, such as ageing, and/or extrinsic factors, such as storage time and conditions, have the potential to alter tissue NMR and relaxation properties through changes in tissue water content and water environment indicates that the experimental conditions must be carefully controlled in order for reliable information to be obtained. In addition, caution should be taken when attempting to extrapolate the model-obtained information to humans, because of the complex mechanistic basis of toxic insult to the kidney.