To investigate the ability of T₁ mapping and intravoxel incoherent motion imaging (IVIM) parameters for evaluating renal allografts at the early stage after renal transplantation.

This prospective study protocol was approved by the local ethics committee, and written informed consent was obtained from all subjects. Sixty two recipients 2 to 4 weeks after kidney transplantation and 20 healthy volunteers (control group) underwent routine MRI, T₁ mapping, and IVIM imaging (11 b values, 0 to 700 s/mm²). Recipients were divided into two groups base on their estimated glomerular filtration rate (eGFR): 37 recipients with good allograft function (eGFR ≥60 ml·min^-1·1.73 m^-2) and 25 recipients with impaired allograft function (eGFR<60 ml·min^-1·1.73 m^-2). The ADC, true diffusion coefficient (ADC_slow), pseudo-diffusion coefficient (ADC_fast), perfusion fraction (f) and T₁ values were measured on both cortex and medulla. Differences among groups were compared using the one-way analysis of variance. Correlations between eGFR and the parameters in renal allografts were assessed by using Pearson correlation analysis. ROC was performed to assess the diagnostic utilities of using these parameters to discriminate allografts with impaired function from good function.

Excepting for cortical T₁, ADC_fast and medullary T₁, f values, allografts with good function showed no differences in other parameters compared with healthy control. Excepting for medullary T₁ and ADC_fast, the other values showed significantly differences in allografts with impaired function compared to allografts with good function (all P<0.05). Excepting for medullary f and ADC_fast values, allografts with impaired function showed significantly differences in the parameters compared with good function group(all P<0.05). In renal allografts, excepting for medullary T₁, ADC_fast, and f values, cortical T₁ exhibited a negative correlation with renal function, and there was a significant positive correlation between eGFR and other parameters. Cortical T₁ value showed high sensitivity(91.9%) to discriminate renal allografts with different function, with the threshold of 17.36× 10² ms, and ADC value showed high specificity(96.0%)with the threshold of 1.98×10^-3 mm²/s.

T₁ mapping and IVIM technique may be useful for detecting renal allograft dysfunction, and be a reliable imaging for evaluating and monitoring allograft function.

Kidney transplantation; Magnetic resonance imaging; Renal insufficiency