Abstract
BACKGROUND: We have set out to develop a catheter-based theranostic system that: (a) identifies diseased and at-risk myocardium via endocardial detection of systemically delivered β-emitting radiotracers and (b) utilizes molecular signals to guide delivery of therapeutics to appropriate tissue via direct intramyocardial injection. METHODS: Our prototype device consists of a miniature β-radiation detector contained within the tip of a flexible intravascular catheter. The catheter can be adapted to incorporate an injection port and retractable needle for therapeutic delivery. The performance of the β-detection catheter was assessed in vitro with various β-emitting radionuclides and ex vivo in hearts of pigs following systemic injection of (18)F-fluorodeoxyglucose ((18)F-FDG) at 1-week post-myocardial infarction. Regional catheter-based endocardial measurements of (18)F activity were compared to regional tissue activity from PET/CT images and gamma counting. RESULTS: The β-detection catheter demonstrated sensitive in vitro detection of β-radiation from (22)Na (β(+)), (18)F (β(+)), and (204)Tl (β(-)), with minimal sensitivity to γ-radiation. For (18)F, the catheter demonstrated a sensitivity of 4067 counts/s/μCi in contact and a spatial resolution of 1.1 mm FWHM. Ex vivo measurements of endocardial (18)F activity with the β-detection catheter in the chronic pig infarct model demonstrated good qualitative and quantitative correlation with regional tissue activity from PET/CT images and gamma counting. CONCLUSION: The prototype β-detection catheter demonstrates sensitive and selective detection of β(-) and β(+) emissions over a wide range of energies and enables high-fidelity ex vivo characterization of endocardial activity from systemically delivered (18)F-FDG.