剂量验证在宫颈癌全盆调强放疗中的应用

目的 探讨电离室法和胶片法评价宫颈癌全盆调强放射治疗的剂量准确性.方法 采用Pinnacle 7.0逆向调强计划系统对宫颈癌患者设计全盆调强计划,并将该治疗计划移植至模体,采用指形电离室测量预先设定的空间点的绝对剂量,然后将各照射野机架角置于0°,用胶片分别测量各射野在模体表面下2cm实际的注量图,将实测的剂量和注量图与治疗计划系统给出的结果 相比对.结果 各有效测量点绝对剂量与实测剂量的偏差均低于5%,而实际照射注量图与计划输出注量图的比对结果 基本一致.结论 采用电离室法和胶片法验证宫颈癌全盆调强切实可行,测量结果 符合临床要求.

Application of dosimetric verification in intensity-modulated pan-pelvis radiation therapy for cervix cancer

Objective To evaluate the intensity-modulated radiation therapy(IMRT)for the whole pelvis in the treatment for cervix cancer with the method of ionization chamber verification and fluence map verification.Methods IMRT plan was designed with Pinnacle 7.0 inversed treatment planning system,and the planning parameter was copied to the solid water phantom.The dose of the reference points in the phantom was calibrated with ionization chamber,and compared with those in IMRT plan.Then the gantry angle was set as 0 degree.The solid water phantom was irradiated with film,and the actual fluence maps were obtained 2cm below the phantom surface,and then the delivered films were compared with those fluence maps in plan.Results The error percentage at 4 points was less than 3% in absolute dose calibration,at 2 points was less than 5%,at another 2 points was less than 5%,at 1 point was over 10%,and at another 1 point was over 15%.It was found that the last two calibrated points were set in a region with a high dose gradient,resulting in high error.In fact they were impertinent.So another two points were chosen in uniformity area of dose distribution.The percentage of error were both less than 3%.The fluence maps between films and plan were consistent.Conclusion It is feasible to evaluate IMRT plan for whole pelvis in the treatment of cervix cancer with the method of ionization chamber verification and fluence map verification.The results can meet the clinical requirement.