Biodistribution and radiodosimetry of a novel myocardial perfusion tracer (123)I-CMICE-013 in healthy rats

BACKGROUND: (123)I-CMICE-013 is a novel radiotracer previously reported to have promising characteristics for single-photon emission computed tomography (SPECT) myocardial perfusion imaging. We evaluated the biokinetics and radiodosimetry of this rotenone-like (123)I-labeled tracer in a microSPECT imaging-based study. METHODS: 37 to 111 MBq of (123)I-CMICE-013 was synthesized and administered intravenously to 14 healthy rats. Images were acquired with a microSPECT/CT camera at various time intervals and reconstructed to allow activity quantification in the tissues of interest. Radiation dosage resulted from the injection of (123)I-CMICE-013 was estimated base on the biodistribution data. Tissue uptake values from image analysis were verified by gamma-counting dissected organs ex vivo. RESULTS: The heart/stomach and heart/intestine uptake ratios peaked shortly after the injection of (123)I-CMICE-013, meanwhile the heart/liver ratio reached 2 as early as at 23 min post-injection. Little activity was observed in the lung and overnight clearance was significant in most of the measured tissues. The radiation dosimetry analysis based on the time-activity curves provided an estimate of the effective human dose of 6.99E-03 mSv/MBq using ICRP 60 and 7.15E-03 mSv/MBq using ICRP 103, which is comparable to the popular myocardium perfusion imaging (MPI) agents such as (99m)Tc-tetrofosmin and (99m)Tc-sestamibi, as well as other (123)I-based radiotracers. CONCLUSIONS: (123)I-CMICE-013 demonstrated desirable characteristics in its biokinetic and radiodosimetric profiles, supporting its potential application as a novel myocardial perfusion imaging agent.