F-18 meta-fluorobenzylguanidine PET imaging of myocardial sympathetic innervation

Background I-123 meta-iodobenzylguanidine (MIBG) imaging has long been employed to noninvasively assess the integrity of human norepinephrine transporter-1 and, hence, myocardial sympathetic innervation. Positron-emitting F-18 meta-fluorobenzylguanidine (MFBG) has recently been developed for potentially superior quantitative characterization. We assessed the feasibility of MFBG imaging of myocardial sympathetic innervation. Methods 16 patients were imaged with MFBG PET (30-minute dynamic imaging of chest, followed by 3 whole-body acquisitions between 30 minutes and 4-hour post-injection). Blood kinetics were assessed from multiple samples. Pharmacokinetic modeling with reversible 1- and 2-compartment models was performed. Kinetic rate constants were re-calculated from truncated datasets. All patients underwent concurrent MIBG SPECT. Results MFBG myocardial uptake was rapid and sustained; the mean standardized uptake value (SUV (mean +/- standard deviation)) was 5.1 +/- 2.2 and 3.4 +/- 1.9 at 1 hour and 3-4-hour post-injection, respectively. The mean K-1 and distribution volume (V-T) were 1.1 +/- 0.6 mL/min/g and 34 +/- 22 mL/cm(3), respectively. Both were reproducible when re-calculated from truncated 1-hour datasets (Intraclass Correlation Coefficient of 0.99 and 0.91, respectively). Spearman's rho = 0.86 between MFBG SUV and V-T and 0.80 between MFBG PET-derived V-T and MIBG SPECT-derived heart-to-mediastinum activity concentration ratio. Conclusion MFBG is a promising PET radiotracer for the assessment of myocardial sympathetic innervation.