ElektaPrecise直线加速器新型全碳素纤维治疗床床板对放疗剂量的影响

Effect of the new carbon fiber bed board of Elekta Precise linear accelerator on the radiation dose

目的探讨ElektaPrecise直线加速器新型全碳素纤维治疗床床板对放疗剂量的影响。方法应用等中心技术（SAD）测量，设2组射野，均为等中心对穿野（-组穿过床板，另-组不穿过床板），用PTw剂量仪0．6cm3。Farmer电离室比对测量，计算出治疗床主床板、体部延长板、头颈肩延长板不同位置及其衔接处对放疗剂量的衰减。结果6MV能量时，治疗床主床板对剂量的衰减为1．4％～7．2％，主床板衔接头1、4、7和8cm处对剂量的衰减分别为2．8％-38．7％、1．4％-30．1％、1．5％-20．8％和1．4％-11．2％；体部延长板对剂量的衰减为0．5％～5．0％，体部延长板衔接头1cm位置对剂量的衰减为4．7％～15．4％；头颈肩延长板颈部位置对剂量的衰减在0．5％-3．3％，头颈肩延长板肩部位置对剂量的衰减在5．3％-16．7％；延长板和主床板衔接处对剂量的衰减在6．8％～30．4％。结论新型全碳素纤维治疗床床板不同部位对剂量衰减不同，床板衔接部位标记区域对剂量衰减比较大。

Objective To investigate the dosimetric influence of pure carbon fiber treatment tabletop of Elekta Precise new linear accelerator in radiotherapy. Methods Surface-axis distance （SAD） technology was employed for the measurement. Two groups of fields were set and both of them were SAD opposed portals （one of them went through the tabletop, while the other did not）. A PTW electrometer and a O. 6 cm3 Farmer ionization chamber were utilized for comparison measurement. Then dose attenuation of the main table board, extended body board, the extended board for head, neck and shoulders, and the joints of these boards were calculated. Results Under the energy of 6 MV, the dose attenuations of the following locations were： 1.4% - 7.2% at the main treatment table board; 2. 8% - 38.7% , 1.4% - 30.1% , 1.5 % -20.8% and 1.4% - 11.2% , respectively at distances of 1,4, ？ and 8 cm from the joint of the main table board ;0. 5% - 5.0% at the extended body board; 4. 7% - 15.4% at distance of lcm from the joint of the extended body board; 0. 5% - 3.3% at the neck position of the extended board for head, neck and shoulders; 5.3% - 16.7% at the shoulder positions; and 6.8% - 30. 4% at the joint between the extended boards and the main table board. Conclusions The dose attenuations of the new linear accelerator pure carbon fiber treatment tabletop vary at different locations. Considerable higher attenuations are observed at the table board joints than other locations.