早期乳腺癌保乳术后放疗相邻野衔接处的剂量观察

Dosimetric Observation of the Field Junction in Early-stage Breast Cancer Patients after Breast-Conserving Surgery

目的探讨保乳术后放疗相邻野衔接处的剂量分布情况,为临床治疗提供剂量学参考。方法选取5例早期乳腺癌保乳手术后放疗患者,将金属氧化物半导体场效应管(MOSFET)5个剂量探头布置于相邻野衔接线的垂直线上,探头间隔2mm,多次测量后获取各个探头读数,比较其剂量差异。结果照射野衔接线处单次测量剂量变化大,总的平均剂量与上下探头比较在同一平滑线上,两野衔接良好;胸壁和乳腺皮肤表面剂量分别为3669.75cGy和3887.5cGy。结论照射野衔接处总的照射剂量稳定可靠,但单次剂量变化显著,可能影响该处的放射生物学效应;乳腺表浅组织受照剂量不足,可通过加用填充物来提高表浅剂量。

Objective To study the dosage distribution across field junction in early-stage breast cancer patients after breast-conserving surgery,and provide some advices for radiotherapy in clinical practice. Mehtods Five early-stage breast cancer patients after breast-conserving surgery were included into our observation. Metal oxide-sillicon semiconductor field effect transistor （ MOSFET） probes were laid on the line with vertical field junction line and interval of 2 mm. After many measuerments,the readings were obtained. We were able to study the difference of readings. Results The dose variation of the third probe was significant in a single measurment of the field junction,but the total average dose was reliable and stable,conpared with the upper and lower probes which were on a smooth line; the skin doses for the chest wall and the breast were 3 669. 75 cGy and 3 887. 5 cGy respectively. Conclusion It is stable and reliable for the dose on the field junction,however,big bias appear at the bondary in a single measurment. This may have potentially impact on biological effects of radiation; the skin dose of the breast and the chest wall is lower than the planned value. It is necessary to take measures to improve the skin dose value in those areas.