宫颈癌调强放疗中膀胱解剖结构变化及对其吸收剂量影响研究

Bladder anatomical changes and dose variation during the course of intensity-modulated radiation therapy of cervical cancer

目的研究宫颈癌患者调强放疗中膀胱体积与位置变化及对其吸收剂量的影响。方法随机选取20例接受宫颈癌根治性调强放疗患者，采集分次治疗前锥形束CT（CBCT）图像，与原始治疗计划cT图像实施基于骨性解剖结构的刚体配准。由同一医师在CBCT图像上勾画膀胱轮廓，并映射回原始治疗计划CT图像，分析分次治疗间膀胱体积与位置及其吸收剂量变化。结果20例患者共采集451次CBCT图像进行分析。膀胱体积与位置变化较大，15例患者膀胱体积与V。无相关性（r=-0．225～0．473，P值均〉0．05），4例呈负相关性（r=-0．564，P〈0．05；r=-0．597，P〈0．01；r=-0．942，P〈0．01；r=-0．816，P〈0．01），1例呈正相关性（r=0．662，P〈0．01）；治疗中超出标准（V45≤50％）次数共64次（14．2％）。结论宫颈癌调强放疗中大部分患者通过适当充盈膀胱处理后膀胱体积与位置变化仍较大，但对其剂量影响在临床可接受范围，对个别临床靶体积较大患者应密切观察其退缩情况，必要时进行在线或离线分析及时修改治疗计划。

Objective To investigate bladder anatomical changes and dose variation in patients with cervical cancer. Methods We analyzed 20 patients, undergoing external beam radiotherapy scanning cone beam CT （CBCT） before each fraction. Bladder was contoured on each CBCT, was projected onto the planning CT and assesses anatomical changes and dose variation. Results A total 451 CBCT images, for 20 patients were collected for analysis, show more change in bladder volume and position. In 15 cases bladder volume and V45 had no significant correlation （ r = 0. 225 - 0. 473, all P 〉 0. 05 ）, 4 cases shows negative correlation （r = -0. 564,P 〈0. 05 ;r = -0. 597 ,P 〈0.01 ;r = -0. 942,P 〈0. 01 ;r = -0. 816 ,P 〈0. 01 ）, 1 case shows positive correlation （r = 0. 662 ,P 〈 0. 01 ）. Have more than the criteria （V45 ≤50% ） number is 64/451 （14. 2% ） in whole treatment. Conclusions For most patients by filling adequacy bladder, bladder dose variation is acceptable; CTV lager for individual patients should be closely observed its regression, implementation of the offline or online calibration.