宫颈癌调强放疗中靶区变化与剂量分析

目的 通过螺旋断层放疗系统(TOMO)观察宫颈癌治疗过程中,肿瘤及邻近组织器官移动所导致的靶区受照剂量的改变。方法 选取2013年8月至2014年2月于本院行TOMO治疗的5例宫颈癌患者,每次治疗前行兆伏级CT(MVCT)扫描与计划CT图像配准后,重新计算剂量分布并勾画肿瘤及靶区。分析分次治疗间肿瘤与靶区体积、位移与受照剂量之间的关系。结果 5例患者外照射结束时宫颈肿物体积、最大径分别平均下降68.90%、26.91%(t=5.21、8.39,P<0.05)。肿瘤、子宫、临床靶区(CTV)质心左右、前后、头脚方向中位位移分别为-1.43、-7.72、0.02、0.40、-1.24、-6.51、-0.43、-1.68和-0.22 mm。CTV中位V_95%为99.40%(95.96%~100%),中位漏照体积为6.94 cm³(0~32.30 cm³)。结论 宫颈癌放疗中,肿瘤变化、位置的移动与生理运动等因素的影响,使靶区实际受照剂量与初始计划存在差异,部分靶区漏照,在图像引导放疗(IGRT)下,漏照体积较少。

Variation of organ position and dose for cervical cancer patients treated with helical tomotherapy

Objective To observe the interfractional variation and actual dose for cervical cancer patients treated with tomotherapy. Methods Five patients who received tomotherapy were chosen from Aug 2013 to Feb 2014. A megavohage computed tomography (MVCT) scan was performed before treatment and then registered with the planning CT images. Dose distributions were recalculated and targets were contoured on the MVCT images. The differences between the actual radiation and planning were analyzed. Results In the patients received external radiotherapy, the decline in cervix volume and maximum diameter was 68.90% and 26.91%, respectively (t=5.21, 8.39, P<0.05). Cervix, uterus and CTV movement in left-right, anteroposterior, superoinferior were 1.43, -7.72, 0.02, -0.40, -1.24, -6.51, -0.43, -1.68 and -0.22 mm. The median CTV V_95% was 99.40% (95.96%-100%), and missing volume was 6.94 cm³ (0-32.30 cm³). Conclusions During radiotherapy for cervical cancer patients, the volume, position and doses are different between initial plan and actual radiation. Based on image guided radiation therapy (IGRT), missing targets are limited.