Head-to-head comparison of 11C-PiB and 18F-flutemetamol PET in transthyretin cardiac amyloidosis.

PURPOSE: Amyloid positron emission tomography (PET) tracers are increasingly used to detect cardiac amyloidosis (CA). 11C-Pittsburgh compound B (PiB) and 1⁸F-flutemetamol (FMM) have demonstrated diagnostic utility for CA. However, to our knowledge, no direct head-to-head comparison has been performed in cardiac imaging. This study compared the myocardial uptake patterns of PiB and FMM PET in patients with biopsy-confirmed wild-type transthyretin-CA (ATTRwt-CA). METHODS: Sixteen patients with ATTRwt-CA underwent PiB and FMM PET/CT. PET was performed dynamically for 25 min after tracer injection. Retention index (RI) images were derived from dynamic data, and standardized uptake value (SUV) images were calculated from static images acquired 10–20 min post-injection. Global myocardial uptake was assessed using myocardial-to-blood pool ratios (MBR-RI and MBR-SUV). Segmental uptake was evaluated using relative segmental uptake (RSU) and segmental MBR on 17-segment polar maps for 13 patients. RESULTS: Median RI-MBR values were 1.35 [1.28–1.63] for PiB and 1.50 [1.13–1.95] for FMM, showing a significant correlation (ρ = 0.580) without a significant difference. Median SUV-MBR values were 1.92 [1.64–2.20] for PiB and 1.87 [1.26–2.19] for FMM, with a strong correlation (ρ = .859) and no significant difference. Pooled segmental analysis demonstrated significant correlations for RSU (ρ = 0.635) and segmental MBR (ρ = 0.683). Concordance was preserved in both the treated and untreated subgroups. CONCLUSION: PiB and FMM PET provide highly concordant semi-quantitative assessments of myocardial amyloid burden in ATTRwt-CA. This first head-to-head cardiac comparison supports the need for harmonization strategies for cardiac amyloid PET in multicenter studies and longitudinal therapeutic monitoring.