Evaluation of m-([18F]fluoropropyl)benzylguanidine ([18F]FPBG) for myocardial imaging in rat

Objectives To investigate PET radiotracer for adrenergically innervated organ imaging as the heart, we have developed nca m-([¹⁸F]fluoropropyl)benzylguanidine ([¹⁸F]FPBG) as the potential myocardial imaging.

Methods [¹⁸F]FPBG was prepared in two steps: the labeling of F-18 and the deprotection. SD rats were injected with [¹⁸F]FPBG via tail vein, and the heart and bladder were collected at 30 and 60 min postinjection. The heart were homogenized and centrifuged, whereas urine samples were filtered through a membrane. The samples were analyzed by HPLC. Biodistribution were carried out using [¹⁸F]FPBG in normal SP rat. After simultaneous injection of [¹⁸F]FPBG, normal and reserpin treated model underwent dynamic PET imaging for 180 min respectively,

Results [¹⁸F]FPBG was prepared with radiochemical yields of 17-30% and purified by HPLC with high radiochemical purity (97%). In metabolism studies, only [¹⁸F]FPBG was observed in heart at 30, 60 min. In contrast, two identified metabolites and parent were appeared in urine. Tissue distribution of [¹⁸F]FPBG in rat showed high radioactivity accumulation in heart where high heart to blood uptake ratios were 19.5 and 10.5 at 60,180 min, respectively. The highest uptake was shown in adrenal gland where adrenal/blood ratios were 28.8 and 25.4 at 60, 180 min, respectively. Reserpin pretreatment reduced the ratio of heart to liver by 41 % at 20 min and continued by130 min.

Conclusions Our results demonstrated that [¹⁸F]FPBG may be useful for myocardial imaging and deserves further studies to evaluate its utility for PET imaging of adrenergically innervated organ imaging.