Abstract
The treatment schedule for radiation therapy is often interrupted because of complicated skin reactions. Qualitative and quantitative information relating beam parameters and skin reactions will be helpful. Skin dose measured with ultra-thin TLDs (GR-200F) at some clinical setups was carried out in this work. The measurement of percent depth dose (PDD) values was performed for 6-15 MV photons and 6-21 MeV electrons under various situations of irradiation. The results were also verified with that of Monte Carlo simulation done by OMEGA/BEAM code. The topic of skin dose, which was measured by ultra-thin TLDs, in the treatment of breast cancer by tangential field technique is also presented. The effect of lead cutouts in skin dose in electron irradiation is included in this dissertation as well.PDD values measured by ultra-thin TLDs for 6, 10 and 15 MV photons are increased with increased field sizes and are decreased with increased photon energy. For electrons, the PDD values are increased with increased electron energy ranging from 6 to 21 MeV and are also increased with increased size. The values for 6 MV photons, and 10□10 cm2, 20□20 cm2, 30□30 cm2 fields are 16.1□0.7%, 25.9□0.5% and 34.9□0.5%, respectively. For 15 MV photons, these three values are 10.6□0.6%, 21.3□0.8% and 30.7□1.4%, respectively. The results of PDD values in Monte Carlo simulation for 6 MV photons and 10□10 cm2, 20□20 cm2, 30□30 cm2 fields are 13.7□0.2%, 23.1□0.4% and 29.8□0.5%, respectively. For 15 MV photons, the values are 8.7□0.1%, 18.8□0.1% and 27.1□0.3% respectively.The effect of physical and virtual wedges in skin dose that measured by ultra-thin TLDs was performed for the study of skin dose in the treatment of breast cancer by tangential field technique. The results show that larger skin dose in-field were found in the treatment with virtual wedge than that with physical wedge. The skin dose is decreased with the increased angle of wedge both in virtual and physical wedges owing to the beam hardening effect.PDD curves shift upstream in smaller fields caused by lead cutouts in electron irradiation result in larger skin dose was found in the study of the effect of lead cutouts in skin dose in electron irradiation. The larger electron energy, the more significant the effect of lead cutouts in skin dose. For 10□10 cm2 electron cone, 6-15% skin dose increment caused by lead cutouts was found in electrons ranging from 6-21 MeV. The size of electron cone to the variation of skin dose is not significant.