基于Halcyon加速器百分百图像引导模式下盆腔肿瘤CTV-PTV边界外放的研究

Research on CTV-PTV Margin for Pelvic Tumor Based on the Halcyon Accelerator’s Guided Mode with 100%Image Guidance

目的探讨基于Halcyon加速器百分百图像引导模式下盆腔肿瘤临床靶区-计划靶区(Clinical Target Volume,CTV)-(Planning Target Volume,PTV)边界外放的摆位误差。方法选取2023年1—5月在Halcyon加速器上行调强放射治疗的19例盆腔肿瘤患者为研究对象,采集每个患者分次间、纠正后、分次内300套共900个锥形束CT图像,与计划CT进行配准融合,得到三维方向上的矢量误差,用X(左右)方向、Y(头脚)方向、Z(腹背)方向表示。计算摆位误差及分布趋势,并根据纠正后及分次内的摆位误差计算CTV-PTV的外放边界。结果X方向上,分次间、纠正后、分次内的摆位绝对误差分别为(2.07±1.82)、(0.19±0.19)、(0.30±0.28)mm;Y方向上,分次间、纠正后、分次内的摆位绝对误差分别为(3.87±2.67)、(0.23±0.31)、(0.27±0.23)mm;Z方向上,分次间、纠正后、分次内的摆位绝对误差分别为(0.72±0.83)、(0.20±0.22)、(0.30±0.27)mm,差异均有统计学意义(P<0.05)。纠正后和分次内X、Y、Z 3个方向分别有97%和96.33%的摆位误差在1 mm以内。CTV-PTV外放边界从6.36 mm缩小到1.06 mm。结论从摆位误差角度来看,基于Halcyon加速器百分百图像引导模式下的盆腔肿瘤治疗,根据纠正后和分次内的摆位误差计算CTV-PTV外放边界为1.1 mm。通过Halcyon加速器治疗盆腔肿瘤患者可降低摆位误差,提高患者靶区和危及器官的安全精度,缩小CTV-PTV边界外放值,减少正常组织的累及体积。

Objective To explore setup errors of clinical target volume to planning target volume(CTV-PTV)margin in pelvic tumor based on Halcyon accelerator’s fully guided mode with 100%image guidance.Methods A total of 19 patients with pelvic tumors who underwent intensity modulated radiation therapy on the Halcyon accelerator from January to May 2023 were selected as the study subjects.A total of 900 cone beam CT images were collected,including 300 sets of inter-fractional,post-correction and intra-fractional images for each patient.These images were registered and fused with the planned CT to obtain the three-dimensional vector error,represented by X(left-right),Y(head-foot),and Z(anterior-posterior)directions.Then,the setup errors and their distribution trends were calculated,and the margin of CTV-PTV based on the corrected and intra-fractional setup errors were determined.Results In the X direction,the absolute setup errors between inter-fractional,corrected and intra-fractional were(2.07±1.82),(0.19±0.19),(0.30±0.28)mm respectively.In the Y direction,the absolute setup errors were(3.87±2.67),(0.23±0.31),(0.27±0.23)mm respectively.In the Z direction,the absolute setup errors were(0.72±0.83),(0.20±0.22),(0.30±0.27)mm respectively.All differences were statistically significant(P<0.05).There were 97%and 96.33%of corrected and intra-fractional set-up errors in the X,Y,Z directions within 1 mm.CTV-PTV margin had been reduced from 6.36 mm to 1.06 mm.Conclusion From the perspective of setup errors,for pelvic tumor treatment based on Halcyon accelerator(100%image guided mode),the CTV-PTV margin is calculated as 1.1 mm based on the corrected and intra-fractional setup errors.Treatment of pelvic tumor patients using the Halcyon accelerator can reduce setup errors,improve the safety and accuracy of targeting the tumor region and organs at risk,reduce the CTV-PTV margin,and minimize the volume of normal tissues involved.