浇铸方法对低熔点铅挡块透射率影响的研究

Research of Casting Method of Low Melting-point Lead Block Transmittivity

目的:通过比较不同浇铸方法制作的低熔点铅(LML)挡块的透射率,研究浇铸方法对LML挡块透射率的影响。方法:制作LML挡块32块,其中一次浇铸成型(以下称浇铸方法1)8块,两次浇铸成型24块,所有LML挡块厚度均为8 cm。24块两次浇铸成型的挡块中,第一次浇铸厚度至4 cm、6 cm、7 cm各8块(以下依次称浇铸方法2、3、4)。在挡块固定有机板上粘贴牢固后插入治疗机托架,出束测量并计算挡块透射率。结果:浇铸方法1至4制作的LML挡块透射率分别为(3.044±0.014)%、(2.908±0.017)%、(2.899±0.020)%和(2.886±0.021)%。一次浇铸成型的LML挡块和两次浇铸成型的LML挡块相比较,其透射率均有显著性差异(P<0.05);两次浇铸成型的LML挡块的透射率相互比较,随第一次浇铸的厚度的增加虽有降低的趋势,但除了浇铸方法2、4之间略有差异外(P<0.05),其余均没有统计学意义(P>0.05)。结论:无论采用哪种浇铸方法,只要达到LML全挡要求的厚度,制作出的LML挡块均能满足临床二维或三维适形治疗的基本要求,但浇铸LML挡块最优方法是分两次浇铸。

Objective： We can study the influence of different casting methods of low melting-point lead （LML） to the block transmittivity. Methods： Totally 32 pieces of LML blocks were made. Eight pieces of those LML block were made in single cast forming, 24 pieces in double cast forming that the thickness of the every 8 of these is 4 cm, 6 em, and 7 cm respectively. After making the pasted LML block adhere to the organic board, it was inserted into the therapy apparatus＇s bracket. Beam on, we can measure and calculate block transmittivity. Results： There are statistically differences of transmissivity between single and double cast forming （P 〈 0.05）; Except slight difference between thickness of 4em and 6 era （P 〈 0.05） there aren＇t significant differences of transmissivity between the differrent cast thicknesses （P 〉 0.05） in double east forming. Conclusions： In the casting LML block double east forming is an optimized method; whatever method is performed, the LML block can satisfy the treatment demand in the two-dimensional or three-dimensional conformal therapy, as long as it＇s thickness reaches or over 7.9cm.