辐射防护及医用体内辐射剂量.pptVIP

Radiation Protection and Medical Internal Dosimetry 輻射防護及醫用體內輻射劑量 高雄醫學大學附設中和紀念醫院 核子醫學科 陳 毓 雯 主任 Pattern of Radiation Effect Exposure Contamination Units of Radiation Dose Activity (A) Bq Radiation exposure C/kg Air kerama Absorbed dose (D) gray Equivalent dose (H) sievert LET (linear energy transfer) Effective dose (E) Conversions of Units Threshold Doses for Determininstic Effects in The More Radiosensitive Tissues and Organs Biological Effects of Exposure Nonstochastic effects Stochastic effects Probability of Risk of Fatal Cancer between Age and Sex Dose in Medical Imaging Annual Effective Dose Distribution in The World Internal Dosimetry The method of calculating absorbed dose delivered internally has been developed over many years by the Medical Internal Radiation Dose (MIRD) committee of the American Society of Nuclear Medicine. The aim of committee was to develop a dosimetry system (MIRD schema) for diagnostic nuclear medicine. However, the methods have also been applied in radionuclide therapy and in internal contamination. MIRD Schema Source Organs vs Target Organs Dt s = A s St s Cumulated activity, As the total number of radioactive disintegrations which occur in the sourve organ, and depends on: the activity administered; the uptake of , retention by, and excretion from the organ; and thte physical decay of the radionuclide. S-factors have been tabulated for a variety of radionuclides and for different source/target configurations in both standard man and children. Cumulated Activity Flow Chart of MIRD Methology S- Factors St s = 1/ mi ? Δi ?i Δi equilibrium absorbed dose constant ?i absorbed fraction specific absorbed fraction (Monte Carlo calculations) Example Calculated the absorbed dose to