鼻咽癌放疗不规则低熔点铅挡块的制作及质量保证

目的：检测鼻咽癌放疗不规则低熔点铅挡块的制作是否符合临床治疗计划要求,分析挡块产生偏差的原因,完善放射治疗的质量保证和质量控制方法。方法：患者在模拟定位机下面罩固定定位并拍摄模拟定位片,物理师根据医生勾画的形状制作不规则低熔点铅挡块,而后把固定好的铅档块在模拟机下拍摄模拟验证片。通过与定位片的对比,观察挡铅的范围与医生所勾画的挡铅轮廓是否一致,并找出两者之间的偏差。结果：随机选取252块挡块进行分析,通过模拟定位机验证,有220块合格,合格率达87.3%;另有32块挡块不合格,偏差率为12.7%。结论：用低熔点铅制作的不规则挡块方便、准确、偏差率较低,能提高挡块的质量。它不仅符合临床治疗计划设计要求,而且提高了放射治疗的精确性,是一种目前鼻咽癌常规放疗中行之有效的好方法。

Block of irregular low melting point of lead production and quality assurance on radiotherapy of nasopharyngeal carcinoma

Objective：To study whether the make of the irregular low melting-point lend block on radiotherapy of nasopharyngeal carcinoma coincides with the request of clinic treatment plan,analyze the reasons of the block error.Methods： Patients were fixed with face mask and to take photograph of simulated positioning films,low melting point block of lead was fabricate by physics engineer after doctor wake off the outline,to take photography of simulated verification films and to check out blocked range,then to compare with simulated positioning films and to find out deviations.Results： The error of 252 lead blocks were measured on simulator and 220 blocks were qualified and others unqualified.Conclusion： Low melting-point lead block as a blind is convenient and accurate and with low deviations,it＇s an effective method,which not only meets the requirement of designed proposal but also promotes the accuracy of radiotherapy.