图像引导放疗二维电子射野影像系统验证模式和三维锥形束验证模式对鼻咽癌调强放疗摆位误差的影响

Effects of image-guided radiotherapy two-dimensional electron field imaging system and three-dimensional cone-beam CT verification modes on the positioning errors of intensity modulated radiotherapy for nasopharyngeal carcinoma

目的:探讨图像引导放疗(IGRT)二维电子射野影像系统(EPID)验证模式和三维锥形束CT(CBCT)验证模式对鼻咽癌调强放疗(IMRT)摆位误差的影响。方法:选择2018年10月—2021年10月行IMRT的鼻咽癌患者30例,根据使用的IGRT方式随机分为EPID组(n=15)和CBCT组(n=15)。比较两组患者影像采集和配准时间,图像配准后记录并分析左右(Lat)、头脚(Long)、前后(Vert)三个方向的摆位误差及验证效果。计算靶区外扩边界(MPTV):临床靶区(CTV)到计划靶区(PTV)的外扩范围。采用视觉模拟评分法(VAS)评估患者疼痛情况。比较两组危及器官的辐照剂量。结果:EPID组患者Lat,Long和Vert三个方向的摆位误差与CBCT组比较,差异均无统计学意义(P>0.05)。CBCT组图像采集、配准时间显著大于EPID组,VAS疼痛评分低于EPID组,差异均有统计学意义(P<0.05)。EPID组Lat,Long和Vert三个方向的MPTV均大于CBCT组,且均大于6 mm,差异有统计学意义(P<0.05)。CBCT组患者危及非肿瘤区域内耳、脊髓、啮合关节、视神经的平均受照剂量均小于EPID组,差异有统计学意义(P<0.05)。结论:采用三维CBCT模式进行放射治疗鼻咽癌,摆位误差较小,可降低危及组织的受照剂量和患者的疼痛指数,提高放射治疗的精准性。

Objective:To investigate the effect of image-guided radiotherapy(IGRT)two-dimensional electron field imaging system(EPID)verification mode and three dimensional cone-beam CT(CBCT)verification mode on the positioning error of intensity modulated radiotherapy(IMRT)for nasopharyngeal carcinoma.Methods:The study subjects were 30 patients with nasopharyngeal carcinoma treated with IMRT in hospital from October 2018 to October 2021,who were divided into EPID group(n=15)and CBCT group(n=15)according to IGRT methods used.The time of image collection and registration was compared between the two groups.After image registration,the positioning errors in left-right(Lat),head-foot(Long)and front-to-back(Vert)directions were recorded and analyzed and the verification effect was obtained.The expansion range from clinical target(CTV)to planned target(PTV)was calculated,and the planned target expansion boundary(MPTV).Visual analogue scale(VAS)was used to assess pain.The irradiation doses of other organs at risk were compared between the two groups.Results:There were no significant difference in the positioning errors in Lat,Long and Vert directions between EPID group and CBCT group(P>0.05).The time of image acquisition and registration in CBCT group was significantly longer than that in EPID group,and the VAS pain score was lower than that in EPID group,with statistical significance(P<0.05).The MPTV in Lat,Long and Vert directions of patients in CBCT group were all greater than those in EPID group,and all were greater than 6 mm,with statistical significance(P<0.05).The average dose of the inner ear,spinal cord,meshing joint and optic nerve in non-tumor areas in CBCT group was smaller than that in EPID group,with statistical significance(P<0.05).Conclusion:Using Three-dimensional CBCT model for radiotherapy of nasopharyngeal carcinoma,the positioning error is small,can reduce the radiation dose of tissue at risk and pain index of patients,improve the accuracy of radiotherapy.