低熔点铅在Graves眼病放疗中的剂量学优势分析  

Dosimetric superiority of low melting-point lead in the radiotherapy of Graves’ophthalmopathy

作　　者：赵卫东[1] 宁健[1] 赵水喜[2] 杨书明[1] 郑子薇[1] 穆晓峰[1] 

机构地区：[1]武警总医院肿瘤放疗中心,北京100039 [2]武警总医院肿瘤一科,北京100039

出　　处：《解放军医学杂志》2013年第2期133-136,共4页Medical Journal of Chinese People's Liberation Army

摘　　要：目的对低熔点铅(LML)和多叶光栅(MLC)两种照射野成形方法在眼眶放疗中的剂量学差异进行比较,以便使用晶体剂量更低的技术用于临床Graves眼病的治疗。方法选择适于放疗的单、双侧Graves眼病患者各10例,采用相同的靶区勾画原则,计划靶区(PTV)处方剂量为2000cGy/10次,单侧组布野方法为3野(2个X线平野+1个电子线野),双侧组为4野(2个X线平野+2个电子线野),分别采用LML和MLC形成照射野。比较两种照射野成形方法的靶区适形指数(CI)和剂量体积直方图(DVH);采用免冲洗胶片和剂量分析软件分析两种方法形成半野照射野的有效半影区大小及其对晶体受量的影响。结果 MLC单侧组患侧晶体剂量为582±34cGy,健侧晶体剂量为160±22cGy,CI为0.69;双侧组左右晶体剂量分别为591±47cGy和585±52cGy,CI为0.67。LML单侧组患侧晶体剂量为252±45cGy,健侧晶体剂量为148±19cGy,CI为0.71;双侧组左右晶体剂量分别247±44、256±42cGy,CI为0.68。在X线能量设定为4MV和8MV时,半野照射野5cm×5cm,深度4cm,LML的有效半影区与MLC比较小约3mm。结论用LML来形成小面积照射野可能更加适形,并可减小照射野半影,显著降低患者患侧晶体的受量。Objective To compare the dosimetric difference between the two beams formed by low meltingpoint lead （LML） and multileaf collimator （MLC） in orbit radiotherapy, so as to select the one with a lower lens dose for treatment of Graves＇ ophthalmopathy. Methods Patients with unilateral and bilateral Graves＇ ophthalmopathy （10 cases each） suitable for radiotherapy were selected for dosimetric comparison. The identical sketching principle of target volume was employed, and the prescribed dose of planning target volume （PTV） was 2000 cGy/10 times. The distribution of radiation field in unilateral group was 3 fields （2 X-ray fields ＋ 1 electron field）, and in bilateral group was 4 fields （2 X-ray fields ＋ 2 electron fields）, and LML and MLC were employed to form the radiation field. The conformity index （CI） and dose volume histogram （DVH） were compared between the two formation methods of radiation field; the effective penumbra area of the half radiation field formed by the two methods and its influence on the lens dose were analyzed with flushing-free film and dose analysis software. Results The average dose of the affected side lens in MLC unilateral group was 582 ＋ 34cGy, and of the lens of uninjured side was 160 -＋ 22cGy, the CI of target volume was 0.69; the average dose of the left and right lens in MLC bilateral group was 591 ＋ 47cGy and 585 ＋ 52cGy, respectively, and the CI was 0.67. The average dose of the affected side lens in LML unilateral group was 252 -＋ 45cGy, and that of the uninjured side lens was 148 _＋ 19cGy, and the CI was 0.71; the average dose of the left and right lens in LML bilateral group was 247 -＋ 44cGy and 256 -＋ 42cGy, respectively, and the CI was 0.68. When the X-ray energy was setup at 4MV and 8MV, the half radiation field was 5cm 5cm with a depth of 4cmj and the effective penumbra area of LML was 3ram smaller than that of MLC. Conclusion A small radiation area formed by LML may be more appropriate, and it may not only diminish the pe

关 键 词：GRAVES眼病 放射疗法 多叶光栅 低熔点铅 放射治疗计划 计算机辅助 

分 类 号：R581.11[医药卫生—内分泌]