Quantitative arterial spin labelling perfusion measurements in rat models of renal transplantation and acute kidney injury at 3T.

Objectives: To employ ASL for the measurement of renal cortical perfusion in particular renal disorders typically associated with graft loss and to investigate its potential to detect and differentiate the related functional deterioration i.e., in a setting of acute kidney injury (AKI) as well as in renal grafts showing acute and chronic transplant rejection.

Materials And Methods: 14 Lewis rats with unilateral ischaemic AKI and 43 Lewis rats with renal grafts showing acute or chronic rejections were used. All ASL measurements in this study were performed on a 3T MR scanner using a FAIR True-FISP approach to assess renal blood flow (RBF). Perfusion maps were calculated and the cortical blood flow was determined using a region-of-interest based analysis. RBF of healthy and AKI kidneys as well as of both rejection models, were compared. In a subsample of 20 rats, creatinine clearance was measured and correlated with cortical perfusion.

Results: RBF differs significantly between healthy and AKI kidneys (P<0.001) with a mean difference of 213±80ml/100g/min. Renal grafts with chronic rejections show a significantly higher (P<0.001) mean cortical perfusion (346±112ml/100g/min) than grafts with acute rejection (240±66ml/100g/min). Both transplantation models have a significantly (P<0.001) lower perfusion than healthy kidneys. Renal creatinine clearance is significantly correlated (R=0.85, P<0.001) with cortical blood flow.

Conclusion: Perfusion measurements with ASL have the potential to become a valuable diagnostic tool, regarding the detection of renal impairment and the differentiation of disorders that lead to a loss of renal function and that are typically associated with graft loss.