FLUORINE-18-FLUOROMISONIDAZOLE RADIATION-DOSIMETRY IN IMAGING STUDIES

Fluoromisonidazole (FMISO), labeled with the positron emitter F-18, is a useful hypoxia imaging agent for PET studies, with potential applic ations in patients with tumors, cardiovascular disease and stroke. Met hods: Radiation doses were calculated in patients undergoing imaging s tudies to help define the radiation risk of FMISO-PET imaging. Time-de pendent concentrations of radioactivity were determined in blood sampl es and PET images of patients following intravenous injection of [F-18 ]FMISO. Radiation absorbed doses were calculated using the procedures of the Medical Internal Radiation Dose (MIRD) committee, taking into a ccount the variation in dose based on the distribution of activities o bserved in the individual patients. As part of this study we also calc ulated an S value for brain to eye. Effective dose equivalent was calc ulated using ICRP 60 weights. Results: Effective dose equivalent was 0 .013 mSv/MBq in men and 0.014 mSv/MBq in women. Individual organ doses for women were not different from men. Assuming bladder voiding at 2- or 4-hr intervals, the critical organ that received the highest dose was the urinary bladder wall (0.021 mGy/MBq with 2-hr voiding interval s or 0.029 mGy/MBq with 4-hr voiding intervals). Conclusion: The organ doses for [F-18]FMISO are comparable to those associated with other c ommonly performed nuclear medicine tests and indicate that potential r adiation risks associated with this study are within generally accepte d limits.