First Experience with [18F]FAZA PET Imaging in Kidney Allograft Dysfunction

Objectives: To evaluate 18F-labelled fluoroazomycinarabinoside ([18F]F-FAZA) PET in post-transplant patients and examine the association of its kinetic and uptake parameters with kidney allograft function measurements, including laboratory and histopathological assessments. Methods: In this prospective pilot study, renal transplant patients were evaluated with a dedicated positron emission tomography/magnetic resonance imaging (PET/MR) protocol between 2018 and 2023. Twenty patients with impaired kidney allograft function (cases) and ten sex- and time-post-transplant-matched control patients with stable transplant allograft function (controls) were included. All patients underwent [18F]F-FAZA PET/MR, including initial dynamic and delayed static imaging. Cases underwent an ultrasound-guided biopsy for histopathological assessments. Results: From the [18F]F-FAZA PET-derived parameters, dynamic total volume distribution (VT) was significantly higher in control patients than in cases (2.11 ± 0.55 vs. 1.62 ± 0.45; p = 0.026). When correlating [18F]F-FAZA PET parameters with creatinine levels and estimated glomerular filtration rate, VT was again the only variable that significantly correlated with both metrics. Regarding histopathological parameters, a significant positive correlation was found between k1 and vascular fibrous intimal thickening, a significant negative correlation between k3 and arteriolar hyalinosis, and k3/k4 (binding potential) was significantly correlated with the percentage of globally sclerotic glomeruli and arteriolar hyalinosis. Additionally, VT was significantly correlated with interstitial inflammation. SUVmean on the static PET was significantly correlated with the percentage of globally sclerotic glomeruli. Conclusions: Non-invasive assessment of renal microcirculation using dynamic [18F]F-FAZA PET is potentially feasible. The dynamic PET-derived parameters showed strong correlations with renal function. There were also correlations with various histopathological findings. Additionally, static [18F]F-FAZA PET-derived parameters showed complementary findings with hypoxia-related end-stage histopathological indicators.