RESUMEN
Objective To explore the shielding effects of 1-4 layers of lead aprons (LPs) and body shielding devices (BSDs) against stray radiation (SR) outside the electron beam field of 6-15 MeV.Methods JR-115B LiF TLDs were used to measure the stray radiation doses (SRDs) to the patient undergoing treatment,before and after being shielding,for different distances,different energies,different applicators,variable layers of LPs,and different thickness of body shielding devices (BSDs),respectively,along long calculating and comparing the shielding ratios of LPs and BSDs against SR.Results When the applicator (10 cm × 10 cm) is unchanged,the shielding ratio increased with the increased distance from measuring point (r =0.717,P ＜ 0.05) and decreased with the increased electron energy (r =-0.678,P ＜ 0.05);when the energy was constant,there was no correlation between the shielding ratio and the size of applicator (P ＞ 0.05);For lower energy electron beam of 6 and 9 MeV,the shielding ratio for 1 mm Pb-BSD was slightly higher than that for 2 layers of LA (t =2.519,2 662,P ＜ 0.05),ranging from 81.5％ to 95.3％ and 55.4％ to 84.6％,respectively.For 12 and 15 MeV higher energy electron beam,the shielding ratio for 2 mm Pb-BSD was slightly higher than that for 4 layers of LA (t=3.768,7.934,P＜0.05),ranging from 64.6％ to 93.4％ and 51.1％ to 92.4％,respectively.Conclusions LAs or BSDs are availavle for effectively reducing the doses from stray radiation,and may help reduce the secondary risks from stray radiation.BSDs have more obvious advantages than LPs with regard to shielding effect.
RESUMEN
Objective To study the dose distribution of the radioactive 125Ⅰ seeds sources in the treatment of prostate cancer and also to explore the more effective method for improving treatment planning system (TPS).Methods Choose the designated TPS and use TLDs dosimeter based on a prostate cancer model.Finally stimulated measurement was focused on dose distribution in prostate cancer.The number of 125Ⅰ seed sources implanted was 89, each with 1.37 × 107 ( ± 5% ) Bq.Results Maximum dose of every layer ranged from 151 to 241 Gy, by 4.1% to 66.0% higher than the prescribed dose (145 Gy).The Minimum dose of every layer ranged from 101 to 128 Gy, by 12% to 30% higher than the prescribed dose.The maximum dose of normal tissue at 10 mm from the edge of model ranged from 46 to 91 Gy.The deviation was 44% -63% compared with the prescribed dose.Conclusions The designated TPS shows that it could be used as a practical guide for treatment of prostate cancer with the radioactive 125Ⅰ seed sources.The research methods offered by the study can provide evaluation of the TPS.