6 MeV电子线和铱192治疗瘢痕疙瘩的剂量学比较

Dosimetric Comparison of 6 MeV Electron Beam and Iridium 192 in the Treatment of Keloid

目的比较6 MeV电子线和铱192(^(192)Ir)高剂量率(HDR)三维后装近距离敷贴两种放射治疗技术在瘢痕疙瘩术后平整表面靶区、曲面靶区、超长靶区(长度>25 cm)模体中的剂量学差异。方法在胸部仿真模体上,采用激光灯标记拟照射瘢痕疙瘩术后位置(包括平整表面和曲面),固体水模体模拟超长靶区,分别获取电子线放射治疗CT图像、三维后装近距离敷贴放射治疗CT图像、超长靶区CT图像,图像导入计划系统完成计划设计后进行剂量分布比较。结果平整表面靶区6 MeV电子线和^(192)Ir HDR后装敷贴两种放射治疗技术的剂量分布一致,均匀性无明显差异。曲面靶区6 MeV电子线的照射剂量分布随着表面曲度变化,上下各层面的有效治疗深度变化明显;^(192)Ir HDR三维后装近距离敷贴的照射剂量随切口曲度变化,剂量分布较为一致。超长靶区两种放射治疗技术的照射剂量分布比较,6 MeV电子线照射需要行分野照射,衔接处皮下0.8 cm左右处会产生>115%的高剂量区,^(192)Ir HDR三维后装近距离敷贴照射无需射野衔接,剂量分布均匀一致。结论瘢痕疙瘩术后放射治疗在平整表面靶区采用6 MeV电子线照射和^(192)Ir HDR三维后装近距离敷贴治疗的剂量学变化无差异,在曲面靶区和超长靶区^(192)Ir HDR三维后装近距离敷贴的照射剂量分布优于6 MeV电子线。

Objective The dosimetric differences of 6 MeV electron beam and iridium 192(^(192)Ir)high dose rate(HDR)three-dimensional post-loading brachytherapy in the flat surface target area,curved surface target area and ultra-long target area(longer than 25 cm)phantom after keloid surgery were compared.Methods On the chest simulation phantom,the postoperative positions of keloid,including flat surface and curved surface,were marked by the laser,and the solid water phantom was used to simulate the ultra-long target area.The electron beam radiotherapy CT image,three-dimensional post-loading brachytherapy CT image and ultra-long target area CT image were obtained respectively,and the images were imported into the planning system to complete the planning design and then compare the dose distribution.Results The dose distribution in the flat surface target area of 6 MeV electron beam and ^(192)Ir HDR post-loading brachytherapy were consistent,and there was no significant difference in uniformity.The irradiation dose distribution of 6 MeV electron beam in the curved target area changed with the change of surface curvature,and the effective treatment depth of upper and lower layers changed significantly;While the irradiation dose distribution of ^(192)Ir HDR post-loading brachytherapy changed with the curvature of the incision,and the dose distribution was consistent.When the irradiation dose distributions in the ultra-long target area between the two radiotherapy methods were compared,6 MeV electron beam irradiation required split-field irradiation,and a high dose area of more than 115%was produced at the junction(almost 0.8 cm subcutaneous).^(192)Ir HDR post-loading brachytherapy irradiation didn't require field connection,and the dose distribution was uniform.Conclusions There is no difference in the dosimetric change of flat target area between 6 MeV electron beam irradiation and ^(192)Ir HDR post-loading brachytherapy in keloid postoperative radiotherapy.The dose distribution of ^(192)Ir HDR post-loading brachytherapy is better than that of 6 MeV electron irradiation in the curved target area and ultra-long target area.