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[目的]通过对比传统真空垫固定法与腘窝固定法在宫颈癌外照射放疗中摆位误差的优劣,探索一种简单有效的体位固定方法。[方法]两组宫颈癌患者分别采用传统真空垫固定法(传统组)和腘窝固定法(改进组),通过Varian TrueBeam治疗系统的锥形束CT(CBCT)在治疗过程中定期采集摆位误差数据用于比较分析,并依据Van Herk外扩边界计算公式计算两种固定法的计划靶体积(PTV)外扩值。分别以两种外扩值建立新的PTV并计算危及器官照射体积。[结果]传统组与改进组X/Y/Z轴向上PTV外扩值分别为0.63cm、0.65cm、0.76cm和0.61cm、061cm、0.58cm。依据改进组外扩值建立靶区可以显著减少PTV及膀胱、直肠、小肠、骨盆的照射体积(P值均为0.000)。改进组降低了Y轴上误差的倾向性(P值为0.029),缩小了向左,向头、向腹部及向背部的误差大小,传统组及改进组在上述4个方向上的误差分别为:(0.29±0.20)cm、(0.25±0.23)cm、(0.27±0.18)cm、(0.30±0.26)cm和(0.22±0.16)cm、(0.17±0.13)cm、(0.18±0.17)cm、(0.23±0.17)cm,P值分别为0.001、0.000、0.001和0.001。[结论 ]腘窝固定法缩小了宫颈癌外照射放疗所需PTV外扩值,减少了PTV及正常器官照射体积,是一种有效的体位固定方法。
[Objective] To compare the advantages and disadvantages of traditional vacuum pad fixation and popliteal fixation in radiotherapy of cervical cancer with external irradiation, and to explore a simple and effective method of position fixation. [Methods] Cervical cancer patients in two groups were treated with conventional vacuum pad fixation (traditional group) and popliteal fossa fixation group (modified group) respectively. Conical beam CT (CBCT) by Varian TrueBeam system was used to collect the position The error data were used for comparative analysis and the planned target volume (PTV) re-spread of the two fixation methods was calculated based on the Van Herk expansion boundary calculation formula. New PTVs were established with two extrinsic extensions, respectively, and the volume of organs at risk of exposure was calculated. [Results] The PTV echocardiographic values of X / Y / Z axis in the traditional group and the improved group were 0.63cm, 0.65cm, 0.76cm and 0.61cm, 061cm and 0.58cm respectively. The establishment of target zone based on the improved extra-group expansion could significantly reduce the volume of PTV and bladder, rectum, small intestine and pelvis irradiation (P = 0.000). The improvement group reduced the error of the Y-axis (P = 0.029), and reduced the error to the left, to the head, to the abdomen and to the back. The errors of the traditional group and the improved group in the above four directions were (0.29 ± 0.20) cm, (0.27 ± 0.13) cm, (0.27 ± 0.18) cm, (0.30 ± 0.26) cm and (0.23 ± 0.17) cm, P values were 0.001, 0.000, 0.001 and 0.001, respectively. [Conclusion] The popliteal fossa fixation method reduces the PTV value needed for radiotherapy of cervical cancer outside radiotherapy and reduces the volume of PTV and normal organs irradiation, which is an effective method of immobilization.