RADIATION-DOSIMETRY FOR BOLUS ADMINISTRATION OF OXYGEN-15-WATER

We describe the development of a biokinetic model which permits an est imation of organ activities and the dosimetry of a bolus of O-15-water . The aim of this study was to estimate time-activity functions and de duce the cumulated activities in different organs so that the radiatio n absorbed dose values can be estimated. Methods: The model we used in cludes the right heart chambers, lungs, left heart chambers, brain, li ver, kidneys, muscles, gastrointestinal tract and the remainder of the body. Activity in an organ will decay by physical decay with the deca y constant, lambda, and can diffuse in the organ. An exception is the heart, where blood is ejected from the heart chambers. Depending on th e location of the organ in relation to the blood sampling point, organ activities can be calculated by convolution or deconvolution. Results : The radiation absorbed dose values were estimated and an effective d ose equivalent H-E of 1.16 mu Sv/MBq (4.32 mrem/mCi) as well as an eff ective dose E of 1.15 mu SV/MBq (4.25 mrem/mCi) were calculated. The c umulated activities in select organs measured by PET gave good agreeme nt with the values calculated by this model. Conclusion: The values of effective dose equivalent and effective dose for bolus administration of O-15-water calculated from the absorbed doses estimated by the pro posed kinetic model are almost three times higher than those previousl y published. A total of 8700 MBq (235 mCi) of O-15-water can be admini stered if an effective dose of 10 mSv (1 rem) is accepted.