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ST: Strahlen- und Medizinphysik

ST 7: Strahlentherapie mit schnellen Ionen II

ST 7.10: Talk

Tuesday, March 14, 2006, 13:00–13:10, D

Production of secondary from patients during therapy with C-ions; their dose contributions and potential risks — •Anwar Chaudhri — Inst. of Medical Physics, Klinikum-Nuernberg & PCSIR, Lahore, Pakistan

During therapy with C-ions a large number of neutrons are produced in patients* tissues which have the potential to induce new cancers. There is no information in the literature on the fluence, energy distributions and doses due to these neutrons. By using neutron out-put data from different elements we have shown that for every C-ion 4,3,1.4 and 0.3 neutrons are produced from patients at incident energies of 400, 300, 200 and 100 MeV / u, respectively. For a physical treatment C-ion dose of 20 Gy in the Bragg Peak, the total number of secondary neutrons produced in patients are 1.6 x 10 9 / cm 2, 7.3 x 10 8 / cm 2, 2.5 x 10 8 / cm 2 and 4,1 x 10 7 / cm 2 respectively at carbon-ions energies of 400,. 300, 200 and 100 MeV/u. These approximately correspond to effective whole body doses of around 950, 120 and 19 mSv cm 2 respectively at C-ions energies of 400, 200 and 100 MeV/u, and doses to various organs which could be as much as over 200 mGy cm 2 at 400 MeV/u energies of C-ions. In our opinion the large number of secondary neutrons produced from patients during therapy with C-ions, and their corresponding doses, indicate they could have real potential to cause new primary cancers and cause other harmful side-effects in patients. It is therefore strongly recommended that serious and careful considerations should be given before deciding to treat patients with C-ions, especially children, younger people and those who still have many years to live.