不同照射条件下脊柱内固定系统对脊柱肿瘤放射治疗的影响

Influence of internal fixation systems on radiation therapy for spinal tumor under different radiation conditions

目的 观察脊柱内固定系统对脊柱肿瘤放射治疗的影响.方法 拟通过选取新鲜冷冻家猪腰椎骨作为脊柱内固定模型的载体,同时选取临床常用的钛合金材料内固定系统,构建前路钛网骨水泥＋前路钛合金钉板系统模型.在不同照射条件下（能量为6 mV,照射剂量为300、600、1 200 mGy）照射内固定模型,探测不同部位、不同类型脊柱内固定、脊柱椎体、脊髓局部照射剂量的改变及其规律,并与放射治疗计划系统（TPS）组进行比较研究.结果 脊柱内固定物对脊柱肿瘤放射剂量影响明显,放射剂量值均成约1倍的差值增加,增加百分比分别为95.03％、105.63％、101.00％、96.96％、97.84％、101.78％、98.20％、101.88％、94.67％、106.31％.3种不同的照射剂量下差异有统计学意义（P＜0.01）.结论 对于骨转移瘤患者,进行金属内植物固定后,应综合考虑射线的衰减以及散射作用,然后选择修正后的TPS进行评估,避免或减少放射线剂量的影响.

Objective To study the influences of internal fixation system on the radiation therapy for spinal tumor.Methods According to the common method of internal fixation after the resection of spinal tumor,different models of spinal internal fixation were constructed by using the lumbar vertebra of freshly frozen domestic pigs and titanium alloy as an internal fixation system.The variations of radiation dose in the vertebral body and partial spinal cord in different types of internal fixation were studied under the different radiation conditions （6 mV,and 300,600,1 200 mGy） in the same fixation model （anterior bone cemnent with titanium mesh ＋ anterior screw-plate）,which were also compared with those in treatment planning system （TPS） group.Results The spinal internal fixation materials had great impact on the radiation dose absorbed by spinal tumors,and radiation dose values approximately increased by one time,of which the increased percentage was 95.03％,105.63％,101.00％,96.96％,97.84％,101.78％,98.20％,101.88％,94.67％,106.31％,respectively.Under the different radiation conditions,there was statistically significant difference among three different radiation doses （P ＜ 0.01）.Conclusion The X-ray attenuation and scattering should be considered for the patients with bone metastasis after receiving the fixation of metal implants.The modified TPS should be evaluated,so as to avoid or reduce the side effects from the radiation dose.