München 2004 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

ST: Strahlenphysik und Strahlenwirkung

ST 7: Strahlenwirkungen - Strahlentherapie III

ST 7.7: Fachvortrag

Thursday, March 25, 2004, 18:00–18:15, HS 129

The effective total body dose and doses to various critical organs from secondary neutrons produced in patients during therapy with C-ions- Are there any risk? — •Anwar Chaudhri — Inst. f. Medizinische Physik, Klinikum-Nuernberg

By making use of the experimental neutron production data from different elements, under bombardment with carbon ions of 100 to 400 MeV/n energies, we have stimated the flux and energy distribution of secondary neutrons produced in patients during therapy with C-ions. Our results indicate that at least 4 neutrons, with energies greater than 5 MeV, are produced for every C-ion of 400 MeV/n energy incident on tissue.This number reduces to 3, 1.4 and 0.3 respectively at incident C-ion energies of 300, 200 and 100 MeV/n. This energy range of C-ions corresponds to that being actually used in C-therapy. For a typical therapy C-ion dose of 20 Gy (physical), the effective whole body dose due to the secondary neutrons is estimated to be about 1 Sv, that is about 5 C-ion dose. The doses to 22 Critical Organs (as defined by the ICRP/ICRU)from these neutrons have also been estimated and ranges between 200-250 mGY at an incident C-ion energy of 400 MeV/n. These figures could be higher if neutrons with energies less than 5 MeV, about which we do not have any experimental data, were also included. In our opinion these neutron doses are large enough to potentially cause secondary primary cancers and induce other harmful effects into patients. Therefore, this matter of secondary neutrons from patients during therapy with C-ions must be even more thoroughly investigated before continuing therapy with C-ions.