摘要目的 研究用金属氧化物半导体场效应晶体管(MOSFET)探测器测量接受高能X射线半束照射的乳腺癌患者的照射剂量。方法 采用MOSFET探测器首先在人体模型上测量,研究在6MV X射线半束照射中相邻半野剂量的分布情况和加速器相关因子的影响,然后实时测量10例乳腺癌患者腋锁野与胸壁切线野6MVX射线半束照射时匹配线上、腋锁野内和胸壁切线野内皮肤的实际吸收剂量。结果 人体模型的剂量测定显示6 MVX射线照射两相邻半野匹配线上剂量与给定剂量差异极小(均3％内),照射野内剂量差异也较小(均1.5％内)。准直器角度在270°和90°时匹配线剂量值与准直器角度在0°时匹配线剂量值不同。患者的剂量测量显示胸壁皮肤实际测量剂量与计划剂量偏差最大达- 30.39％,最小也达- 18.85％,平均偏差为- 24.76％;保乳术患者胸壁实际受照剂量与计划剂量偏差较根治术患者大,两者相比不同(t=2.40,P＜0.05);腋锁野皮肤剂量最大和最小剂量差值为6.04 cGy,保乳术患者腋锁野剂量与根治术患者相比相似(t=1.30,P＞0.05)。在不同分次照射中两相邻野交界处的单次剂量测定有显著地变化,但在15个分次照射中穿过交界处的平均剂量数值较稳定。结论 MOSFET探测器适用于乳腺癌放疗中相邻野交界处剂量测定;乳腺癌患者放疗中有必要进行全程剂量监测,随时调整剂量、纠正误差以提高靶区吸收剂量准确性。

abstractsObjective The purpose of the study was to observe and analysis the actual dosage of patients with breast cancer using metal oxide semiconductor field effect transistor (MOSFET) detector.Methods First, Phantom measurements were performed to investigate dose distribution in the area of the junction in a half-field matching method and the influence of factors related to the accelerator. In vivo dose measurements were performed for patients with breast cancer to investigate the skin dose and the junction of supraclavicular-axillary field and tangential field in 6 MV X-ray beams. Results Phantom measurements showed that the relative deviation in the junction were within + 3％, and the dose distributions in the junction area depended on the matching field direction (x or y). In vivo measurement of tangential region for patients showed that, the maximum dose deviation between measurement and calculation was -30. 39％,the minimum deviation was - 18. 85％, the average dose deviation was -24. 76％. The dose deviation of tangential fields for patients with breast-conserving surgery was larger than that patients with radical surgery (t =2. 40 ,P＜0. 05), while dose deviation of supraclavicular-axillary fields was not significantly different. The average values of 15 fraction in the junction area showed more stable than one individual measurement.Conclusions It is important to real-time, in vivo measurement of radiation dose during radiotherapy in patients with breast cancer, and change treatment plan in time, to ensure the accuracy of target dose.