Biodistribution and radiation dosimetry of (82)Rb at rest and during peak pharmacological stress in patients referred for myocardial perfusion imaging.

PURPOSE: (82)Rb is an ultra-short-lived positron emitter used for myocardial blood flow quantification with PET imaging. The aim of this study was to quantify the biodistribution and radiation dosimetry in patients with coronary disease and in healthy normal volunteers.

METHODS: A total of 30 subjects, 26 patients with known or suspected coronary artery disease (CAD) and four healthy volunteers were injected with (82)Rb chloride at 10 MBq/kg followed by a 10-min dynamic PET scan. Chest scans at rest were acquired in all subjects, as well as one additional biodistribution scan of the head, neck, abdomen, pelvis or thighs. Chest scans under stress were acquired in 25 of the CAD patients. (82)Rb time-integrated activity coefficients were determined in 22 source organs using volume of interest analysis, including corrections for partial-volume losses. The mean time-integrated activity coefficients were used to calculate the whole-body effective dose using tissue weighting factors from the International Commission on Radiological Protection (ICRP) Publications 60 and 103.

RESULTS: A total of 283 organ time-integrated activity coefficients were calculated, with a minimum of four values per source organ. The rest and stress mean effective dose was 0.8 mSv/GBq, according to the most recent ICRP definition. Using 10 MBq/kg for 3D PET imaging, the effective dose to a gender-averaged reference person (60 kg female and 73 kg male) is 1.1 mSv for a complete rest and stress perfusion study. For 2D PET using a typical injected activity of 1.1 to 2.2 GBq each for rest and stress, the effective dose for a complete study is 1.8 to 3.5 mSv.

CONCLUSION: The current effective dose estimate in CAD patients is four times lower than the values reported previously by the ICRP, and about 35% lower than previous in vivo studies in young healthy subjects.