胸部肿瘤患者放疗旋转摆位误差分析

目的 分析量化胸部肿瘤患者放疗旋转摆位误差以及单纯调整平移摆位误差前、后旋转误差的变化.方法 回顾性分析在我院参加"千伏锥形束cT(KVCBCT)在线引导放疗剩余摆位误差研究"患者的锥形束cT图像.选择20例患者入组研究,其中肺癌16例、食管癌2例、胸腺瘤2例,中位年龄61岁(19～80岁).每例患者治疗期间每周行KVCBCT引导放疗分析1次,共分析6次.将20例患者的224幅KVCBCT图像和计划设计CT图像进行离线配准,获取患者旋转摆位误差.患者左右方向的旋转误差为俯仰误差(P_1),头脚方向的为滚动误差(R_1),前后方向的为偏斜误差(Y_1).分析患者单纯调整平移摆位误差前(P_1、R_1、Y_1)与后(P_2、R_2、Y_2)的旋转摆位误差差异以及相关性.结果 胸部肿瘤患者的P_1、R_1、Y_1分别为-0.28°±1.52°、0.21°±0.91°、0.27°±0.78°,其中P_1与R_1、P_1与Y_1均相似(t=-1.44,P=0.158;t=1.44,P=0.158),R_2与Y_2不同(t=2.73,P=0.010).P_2、R_2、Y_2分别为-0.39°±1.40°、0.23°±0.78°、0.22°±0.87°,其中P2与R_2、P_2与Y_2、R_1与Y_1均相似(t=1.73,P=0.092;t=1.66,P=0.106;t=1.72,P=0.093).单纯调整平移摆位误差前后P_1与P_2、R_1与R_2、Y_1与Y_2均相似(t=0.24,P=0.813;t=1.11,P=0.910;t=0.19,P=0.849).无论是单纯调整平移误差前还是后,3个方向间的旋转摆位误差均无相关性(r_1=-0.11,P=0.270;r_2=-0.09,P=0.332).结论 3个方向间的旋转摆位误差均无相关性,单纯调整平移摆位误差前、后旋转误差无变化,但俯仰和偏斜旋转误差的校正需得到重视.

Evaluation of rotational set-up errors in patients with thoracic neoplasms

Objective To assess the rotational set-up errors in patients with thoracic neoplasms. Methods 224 kilovohage cone-beam computed tomography (KVCBCT) scans from 20 thoracic tumor pa-tients were evaluated retrospectively. All these patients were involved in the research of " Evaluation of the residual set-up error for online kilovohage cone-beam CT guided thoracic tumor radiation". Rotational set-up errors, including pitch, roll and yaw, were calculated by 'aligning the KVCBCT with the planning CT, using the semi-automatic alignment method. Results The average rotational set-up errors were -0.28°±1.52°, 0.21°± 0.91° and 0.27°± 0. 78° in the left-fight, superior-inferior and anterior-posterior axis, respective-ly. The maximal rotational errors of pitch, roll and yaw were 3.5°, 2.7° and 2.2°, respectively. After cor-rection for translational set-up errors, no statistically significant changes in rotational error were observed. Conclusions The rotational set-up errors in patients with thoracic neoplasms were all small in magnitude. Rotational errors may not change after the correction for translational set-up errors alone, which should be e-valuated in a larger sample future.