Detection of impaired renal allograft function in paediatric and young adult patients using arterial spin labelling MRI (ASL-MRI)

Abstract

The study aimed to discriminate renal allografts with impaired function by measuring cortical renal blood flow (cRBF) using magnetic resonance imaging arterial spin labelling (ASL-MRI) in paediatric and young adult patients. We included 18 subjects and performed ASL-MRI on 1.5 T MRI to calculate cRBF on parameter maps. cRBF was correlated to calculated glomerular filtration rate (GFR) and compared between patient groups with good (GFR ≥ 60 mL/min/1.73 m²) and impaired allograft function (GFR < 60 mL/min/1.73 m²). Mean cRBF in patients with good allograft function was significantly higher than in patients with impaired allograft function (219.89 ± 57.24 mL/min/100 g vs. 146.22 ± 41.84 mL/min/100 g, p < 0.008), showing a highly significant correlation with GFR in all subjects (r = 0.75, p < 0.0001). Also, the diffusion-weighted imaging (DWI-MRI) apparent diffusion coefficient (ADC) and Doppler measurements of peak-systolic and end-diastolic velocities and the resistive index (PS, ED, RI) were performed and both methods showed no significant difference between groups. ADC implied no correlation with GFR (r = 0.198, p = 0.464), while PS indicated moderate correlation to GFR (r = 0.48, p < 0.05), and PS and ED moderate correlation to cRBF (r = 0.58, p < 0.05, r = 0.56, p < 0.05, respectively). Cortical perfusion as non-invasively measured by ASL-MRI differs between patients with good and impaired allograft function and correlates significantly with its function.

Figure 1

Multi-slice perfusion weighted images (PWI) in two representative patients with: (a) good allograft function (GFR ≥ 60 ml/min/100 g) and (b) impaired allograft function (GFR < 60 ml/min/100 g).

Figure 2

Axial ADC maps with representative circular regions of interest (ROI) placed in the renal cortex in: (a) patient with GFR ≥ 60 mL/min/1.73 m² and (b) patient with GFR ≥ 60 mL/min/1.73 m² (notice the difference in ADC values of anterior and posterior aspect of the kidney, with moderate diffusion restriction in posterior aspect after intraoperative vascular incident; this DWI appearance resolved after few months from transplantation).

Figure 3

Box plot showing a comparison of perfusion values in patients with GFR < 60 and GFR ≥ 60 mL/min/1.73 m²; an outlier from group 2 (GFR ≥ 60 mL/min/1.73 m²) falling out of the boxplot corresponds to the participant number 10 in Table 1.

Figure 4

Scatter plot showing a positive correlation coefficient between cRBF and GFR; r = 0.75, p < 0.0001.

Figure 5

(a) Positioning of the middle slice; (b) Quantitative Perfusion Map representing cRBF (ml/min/100 g) imaged in a patient with good allograft function (GFR ≥ 60 ml/min/100 g) and (c) Quantitative Perfusion Map representing cRBF (ml/min/100 g) imaged in a patient with impaired allograft function (GFR < 60 ml/min/100 g).

Figure 6

ROC curve of cRBF measured by ASL-MRI for distinguishing allografts with impaired function from allografts with good function.