RESUMO
Objective To evaluate the effect of stainless steel applicator on dose distribution in GZP 60 Co brachytherapy source and to obtain the dosimetric parameters of the 60 Co source with stainless steel applicator. Methods Geant4 was employed to obtain the mean adsorption dose of the 60 Co brachytherapy source in the range of 0-10 cm, and the dosimetric parameters were calculated according to the formula proposed by AAPM reports TG43 and TG43U1. The 60 Co source was located in the center of a sphere water phantom with a radius of 30 cm. Results For channel 1 and 2 of GZP 60 Co source, the results of Λ with stainless steel applicator were 1. 014 cGyh-1 U-1( with a difference of 0. 5％ compared with non-applicator) , the results of Λ with stainless steel applicator for channel 3 were 0. 998 cGyh-1 U-1 ( with a difference of 0. 1％ compared with non-applicator) . The radial dose function in the range of 0. 5-10. 0 cm in a longitudinal direction was calculated and the fitting formula for the function was obtained. The polynomial function for the radial dose function and the anisotropy function with a of 0°-175° and an r of 0. 5-10. 0 cm were obtained. Conclusion The dosimetric parameters of the 60 Co source with stainless steel applicator are obtained, which provide more accurate reference data for clinical application. In clinical practice, the effect of stainless steel applicator on dose distribution should be considered.
RESUMO
Objective To study the effect of 60 Co radiotherapy on the gene expession of fibronectin (FN) and matrix metalloproteinase-2 (MMP-2) in the cultured rat vascular smooth muscle cells (VSMCs). Methods Rat VSMCs were cultured in DMEM containing 10% FBS, and were radiated by 60 Co at the doses of 0,7,14 and 28Gy, respectively. mRNA level of FN and MMP-2 was measured by RT-PCR. Results The expression level of MMP-2 mRNA decreased from 82.52?6.50 to 64.25?3.81 and 42.17?3.16 in VSMCs with 14,25Gy radiation, respectively(P