Microdosimetry of Auger and conversion electrons of Tl-201, Cr-51, Fe-55, Tc-99m, and beta-rays of Tl-204 at the cellular level

V International Conference on Application of Physics in Medicine and Biology (Trieste Medical Physics 96) / IX Congresso AIFB / EFOMP Medical Physics 96 / EUTECH 96 -- SEP 02-06, 1996 -- TRIESTE, ITALYWOS: 000074057200048Auger nuclides have the particular importance in nuclear medicine because of their radiotoxicities experimentally observed on the living sytems. The radiotoxicity of an Auger emitter is a result of the local absorption of Auger electrons in a small volume of absorbing medium. Conventional dosimetry ignores low-energy electrons. So, it is inadequate for determination of biological effects. For this reason, the microdosimetric approach chould be considered for evaluation of biological effects associated with the low-energy electrons and further experimental or theoretical studies should be carried out. In this study, a new microdosimetric approach has been presented for calculations of stopping powers, LET values, ranges, and energy depositions of Auger and conversion electrons emitted from Ti-204, Fe-55, Cr-51, Tc-99m radionuclides which are currently used in nuclear medicine. For these calculations, the approximative elemental composition of cell nucleus and Bethe's modified stopping power equation were used. A qbasic computer program coded as UNAKNUC that was earlier developed for Auger electrons of I-125 was similarly used for Auger and conversion electrons, and beta-rays of Tl-204.Int Ctr Theoret Phys, Ist Nazl Fis Nucl, Univ Studi Trieste, Assoc Italiana Fis Biomed, European Federat Org Med Phys, CNR, Regione Autonoma Friuli Venezia Giulia, Comune Trieste, Provincia Triest