Parametric Cardiac Imaging with 18 F-Flutemetamol PET to Evaluate the Impact of Tafamidis in Patients with Transthyretin Cardiac Amyloidosis

In transthyretin cardiac amyloidosis (ATTR-CA), static 18F-flutemetamol PET–derived SUVs do not adequately capture intricate tracer kinetics, limiting the accurate quantification of amyloid burden. We developed dynamic parametric PET imaging methods to improve the quantification of myocardial amyloid burden in ATTR-CA. Methods: Twelve treatment-naïve ATTR-CA patients underwent 60-min dynamic cardiac 18F-flutemetamol PET/CT at baseline and after 6 mo of treatment with tafamidis. Image-derived input functions were corrected for blood-to-plasma ratios and metabolites. Myocardium blood volume fraction was estimated using a 1-tissue compartment model (0–10 min), and volume-of-distribution (VT) images were generated using the multilinear analysis 1 method (2–20 min). VT was correlated with echocardiography, 82Rb myocardial blood flow, and biomarkers. Results: The mean myocardial blood volume fraction was 22% ± 6%. A 2-tissue reversible model with metabolite- and plasma-corrected input functions provided optimal kinetic fits. Multilinear analysis 1 using 2- to 20-min PET data produced VT images with the lowest variance. VT decreased significantly after 6 mo of treatment with tafamidis (from 2.11 ± 0.33 to 1.96 ± 0.20, P = 0.046). Conclusion: Dynamic 18F-flutemetamol PET enabled robust quantification of myocardial amyloid burden using metabolite-corrected 2-compartment modeling. VT imaging demonstrated sensitivity to treatment-related changes in ATTR-CA.