Pilot Study on Dynamic Long-Axial Field-of-View [¹⁸F]FDG PET/CT in Liver Transplant Recipients as a Non-Invasive...

Background/Objectives: Routine liver biopsies play an important role in monitoring liver allografts but carry non-negligible risks. This pilot study assesses the feasibility of dynamic long-axial field-of-view (LAFOV) [¹⁸F]FDG PET/CT as a non-invasive alternative to biopsy. Methods: Liver transplant (LTx) recipients meeting the inclusion criteria of ≥10 months post-transplantation and scheduled routine biopsy were prospectively enrolled, along with healthy controls. All participants underwent dynamic LAFOV [¹⁸F]FDG PET/CT, followed by biopsy in LTx recipients, who were stratified by inflammatory severity using the BANFF score. Hepatic kinetic parameters (K1, k2, k3, k4) and SUVmean/SUVmax were compared using Mann-Whitney U tests. Correlations were assessed using Spearman's rank correlation. A p-value < 0.05 was considered significant. Analyses were performed in RStudio (version 2024.12.10563). Results: Sixteen LTx recipients (mean age 48.6 years; seven female, nine male) and eight healthy controls (mean age 35.4 years; six female, two male) were included. Healthy controls had mean k3 and k4 values of 0.0037 min^-1 ± 0.0003 min^-1 and 0.0019 min^-1 ± 0.0011 min^-1, respectively. LTx recipients showed significantly higher k3 and k4 values, both when including and excluding patients with biopsy-confirmed inflammation. Descriptive comparisons between LTx recipients with and without significant inflammation (n = 3) showed no clear differences. Spearman analysis showed no significant correlations between the BANFF score and kinetic parameters. The strongest degree of correlation was found between BANFF score and k3, indicating a moderate positive but non-significant association (k3: rs = 0.396, p = 0.128). Conclusions: Elevated k3 and k4 values in LTx recipients were not explained by allograft inflammation, suggesting altered FDG kinetics post-transplant. These differences may confound [¹⁸F]FDG PET interpretation. Larger studies are needed to assess the clinical applicability of dynamic LAFOV [¹⁸F]FDG PET/CT.