配合度较差鼻咽癌患者VMAT摆位误差及靶区外扩距离的研究

Volumetric modulated are therapy for nasopharyngeal carcinoma patients with poor compliance： setup error and expansion margin of target volume

目的应用KV—CBCT统计配合度较差鼻咽癌患者的摆位误差，并计算其CTV→PTV外扩边界。方法统计2013-2015年间45例鼻咽癌患者的摆位误差，计算出随机误差95％CI-1并制定PTV-1值。在此基础上，收集自2015年根据前5次验证数据得到配合度较差特殊患者（随机误差不在95％CI-1内）16例，统计其摆位误差。计算出随机误差95％CI-2并制定PTV-2值。对该16例特殊患者选取PTV-1，制定计划-1；选取PTV-1结合PTv-2，制定计划-2。比较计划-1与计划-2的剂量学差异。结果PTV-1和PTV-2均在Y方向最大，引入摆位误差后计划-1的CTV不能满足处方剂量要求。计划-2的CTV的V95%、D95比计划-1分别提高6．26％、4．43％。只有脊髓D01在2个计划中不同（P=0．005），但能满足临床剂量要求。结论选取PTV-1结合PTv．2为外扩边界可以有效提高配合度较差患者靶区剂量。同时不会对正常组织造成损害。

Objective To investigate the setup error for nasopharyngeal carcinoma （NPC） patients with poor compliance using kV cone-beam computed tomography, and to calculate the expansion margin from the clinical target volume （CTV） to planning target volume （PTV）. Methods In 45 NPC patients from 2013 to 2015, the setup error, 95% confidence interval （CI）-1 for random error, and PTV-1 value were calculated. Moreover, in 16 NPC patients with poor compliance based on five verifications （ random error not within 95% CI-1）, the setup error, 95% CI-2 for random error, and PTV-2 value were calculated. For the 16 special patients, PTV-1 and PTV-1 combined with PTV-2 were used to develop the plan-1 and plan-2, respectively. The dosimetric difference between plan-1 and plan-2 was evaluated. Results Both PTV-1 and PTV-2 had the largest expansion margin in the y direction. The CTV of plan-1 could not meet the requirement of the prescription dose after the setup error was introduced. Compared with plan-l, the V95~ and D95 values for the CTV of plan-2 were increased by 6. 26% and 4. 43%, respectively. The D0i value was significantly larger in plan - 2 than in plan - 1 （ P= 0. 005 ） , which , however, met the clinical requirement. Conclusions In patients with poor compliance, the dose to target volume can be effectively elevated and the normal tissue can be spared from damage when PTV-1 combined with PTV-2 is selected as expansion margin.