Feasibility of myocardial PET imaging using a benzylguanidine analog: meta-(3-[ 18 F]fluoropropyl)benzylguanidine ([ 18 F]mFPBG).

INTRODUCTION: Global and regional sympathetic activity in the heart can be evaluated using [123 I]meta-iodobenzylguanidine ([123 I]mIBG) imaging. However, [123 I]mIBG is associated with low image spatial resolution and sensitivity in cardiac imaging. We investigated the capability of an F-18-labeled mIBG derivative, meta-(3-[18 F]fluoropropyl)benzylguanidine ([18 F]mFPBG), for identifying ischemic and viable myocardium in a rat model of myocardial infarction.

MATERIALS AND METHODS: The ex vivo biodistribution and in vivo metabolic stability of [18 F]mFPBG were investigated in Sprague-Dawley rats. Selective cardiac adrenergic activation was confirmed via a blocking experiment involving pretreatment with desipramine (2 mg kg-1 ), followed by the administration of [18 F]mFPBG. Imaging properties of [18 F]mFPBG were compared with those of traditional cardiac imaging radiotracers ([123 I]mIBG and [99m Tc]MIBI) in a rat model of myocardial infarction. Non-invasive image-based measurements of infarct sizes were then compared with histological findings by using Bland-Altman analysis.

RESULTS: The differences in infarct sizes determined using histological analysis and [18 F]mFPBG PET were -2.55 ± 4.99% (range: -12.33 to 7.22), -2.35 ± 3.32% (range: -8.87 to 4.16), and -3.15 ± 6.16% (range: -15.24 to 8.93) at 5, 20, and 40 min, respectively. Furthermore, [18 F]mFPBG PET was superior to traditional imaging methods in assessing the degree of ischemia in areas of myocardial infarction, as well as the actual infarct size.

CONCLUSION: Compared to [123 I]mIBG, [18 F]mFPBG showed improved spatial resolution and sensitivity in a rat model of myocardial infarction. This result suggested that [18 F]mFPBG is a promising cardiac PET imaging agent for potential diagnostic application in PET cardiology.