多叶准直器位置系统误差对不同T分期鼻咽癌容积旋转调强放疗计划的剂量影响研究  

Comparison of dosimetric impacts of the systematic errors of a multi-leaf collimator on volumetric modulated arc therapy plans for different T stages of nasopharyngeal carcinoma

作　　者：朱志鹏 黎桂华 李相德[1] 覃文[2] 郑莲容 Zhu Zhipeng;Li Guihua;Li Xiangde;Qin Wen;Zheng Lianrong(Department of Radiation Oncology,Second Affiliated Hospital of Guangxi Medical University,Nanning 530000,China;Department of Radiation Oncology,Frist Affiliated Hospital of Guangxi Medical University,Nanning 530012,China)

机构地区：[1]广西医科大学第二附属医院放疗科,南宁530000 [2]广西医科大学第一附属医院放疗科,南宁530012

出　　处：《中华放射医学与防护杂志》2024年第11期953-959,共7页Chinese Journal of Radiological Medicine and Protection

基　　金：广西壮族自治区卫建委自筹课题(Z-A20230603,Z-A20230606)。

摘　　要：目的研究多叶准直器(MLC)叶片位置系统误差对不同T分期鼻咽癌容积旋转调强放疗(VMAT)的剂量学影响。方法选取44例T1~4N1M0鼻咽癌患者,在Pinnacle计划系统设计VMAT计划并作为初始计划,其中T1和T2期患者的计划原发肿瘤靶区(PGTV)处方剂量为68~70 Gy/33次,T3和T4期患者PGTV处方剂量为71 Gy/33次,其余计划靶区处方剂量相同。初始计划文件中,每个MLC叶片位置分别引入±0.2~±1 mm系统误差,使子野面积增大或减少,模拟VMAT治疗中MLC位置可能出现的误差计划。剂量评价指标分为靶区和危及器官,靶区为PGTV和PGTVnd的D98%,危及器官为脑干、脊髓和视交叉的D0.1 cm3。结果引入MLC位置系统误差后计划各剂量指标敏感度范围为(3.87%~9.87%)/mm(R2=0.932~0.998,P<0.01)。T4期PGTVD98%敏感度大于T1、T2和T3期(Z=-3.12、-2.86、-2.59,P<0.05),T3期视交叉D0.1 cm3敏感度小于T1和T2期(Z=-2.92、-2.72,P<0.05),T4期视交叉D0.1 cm3敏感度小于T1和T2期(Z=-3.51、-3.25,P<0.05)。跳数与单次PGTV处方剂量比(MU/Gy)和PGTVD98%敏感度两者关系式为:y=-3.020+0.025x(r=0.80,P<0.05)。结论随着鼻咽癌T分期增大,计划的MU/Gy也随之增大,PGTVD98%受MLC位置系统误差影响更大。T4期鼻咽癌VMAT计划引入MLC位置系统误差后剂量变化普遍大于其他T期患者,需对T4期鼻咽癌患者进行更严格的叶片位置质量控制,建议叶片系统误差小于0.42 mm。ObjectiveTo investigate the differences in dosimetric impacts of the systematic errors induced by the leaf positions of a multi-leaf collimator(MLC)on the volumetric modulated arc therapy(VMAT)for patients with different T stages of nasopharyngeal carcinoma(NPC).MethodsA total of 44 patients with T 1-4N 1M 0 NPC were selected to design the VMAT plans using the Pinnacle planning system as the initial plans.The prescribed doses to the primary gross tumor volume(PGTV)were 68-70 Gy in 33 fractions for patients with T 1 and T 2 stage NPC and 71 Gy in 33 fractions for patients with T 3 and T 4 stage NPC.The prescribed doses to other target volumes were identical.In the initial plan files,a systematic error ranging from±0.2 to±1 mm was introduced to the position of each MLC leaf,leading to an increase or decrease in the subfield area.Then,potential error plans at the positions of MLC leaves during VMAT treatment were simulated.Dose evaluation indices involved target volumes and organs at risk(OARs).The indices related to target volumes consisted of the D98%of PGTV and PGTVnd,while those concerning OARs included the D 0.1 cm 3 of the brainstem,spinal cord,and optic chiasm.ResultsAfter the systematic errors induced by the positions of MLC leaves were introduced,the sensitivity range of each dose index range was(3.87%-9.87%)/mm(R 2=0.932-0.998,P<0.01).Specifically,patients with stage T 4 NPC displayed higher sensitivity to the D 98%of PGTV than those with stage T 1,T 2 and T 3 NPC(Z=-3.12,-2.86,-2.59,P<0.05),patients with stage T 3 NPC exhibited lower sensitivity to the D 0.1 cm 3 of optic chiasm than those with stage T 1 and T 2 NPC(Z=-2.92,-2.72,P<0.05),and patients with stage T 4 NPC manifested lower sensitivity to the D 0.1 cm 3 of chiasma than those with stage T 1 and T 2 NPC(Z=-3.51,-3.25,P<0.05).The relationship between the sensitivity of MU/Gy and PGTV D 98%was y=-3.020+0.025 x(r=0.80,P<0.05).ConclusionThe MU/Gy in the plans increased with the T stage of NPC,and the D 98%of PGTV was more significantly affected by

关 键 词：鼻咽癌 容积旋转调强 叶片位置异向系统误差 剂量学 

分 类 号：R739.63[医药卫生—肿瘤] R730.55[医药卫生—临床医学]