乳腺癌根治术后三种放疗技术在模体中的剂量监测分析

The Dose Monitoring Analysis about Three Kinds of Radiotherapy Technologies in Die Bodies of Breast Cancer after Radical Mastectomy

目的观察分析乳腺癌术后临床常用技术的剂量分布特点，为临床治疗提供剂量学依据。方法使用高仿真非均质等效拟人体模型，模拟典型成年女子左侧乳腺癌术后患者，对患侧胸壁感兴趣区域的代表测量点及其不同深度测量点进行标记后按放疗体位行CT模拟定位。在TPS上分别为模体设计三种技术的方案．并在模体上进行模拟照射。使用金属氧化物半导体场效应管（MOSFET）对各点进行实时测量，并与TPS上各标记点计算值进行比对分析。结果三种计划方法中各深度测量点的实际测量值与TPS中的相应各点的计算值相比较发现，在皮肤表面和浅层计划值与实测值相差较大，而随着深度的增加，在lem深度测量点时计划值与实测值接近；除表皮外，三种方法照射的靶区实测剂量基本能满足l}缶床剂量学要求；IMRT照射在靶区剂量均匀性方面要好于3D．CRT和7MeV电子线照射；7MeV电子线照射时．曲面胸壁的测量点中出现低于处方剂量16％的欠剂量区。结论1．乳腺癌术后胸壁放疗时，各种方案在不加组织补偿的情况下皮肤剂量均不足，将导致胸壁复发率提高，在临床治疗中应根据不同方案选用适当厚度的补偿膜。2．电子线照射在曲面靶区的胸壁深处容易形成剂量不足区，在实际临床中应选择胸壁平坦而薄的患者进行电子线治疗。3．IMRT技术在控制靶区剂量高量、靶区剂量均匀性以及减少肺高剂量体积等方面均优于3D-CRT技术。但是由于胸壁受呼吸运动的影响较大，在逆向IMRT时．其不能考虑呼吸运动对靶区剂量范围的影响。

Objective To observe and analyze the dose distribution characteristics of the clinical technology commonly used in postoperative breast cancer, and provide dose basis for clinical treatment.Methods We used high simulation of inhomogeneous equivalent to human body model,to simulate the typical adult woman patient after the operation of left breast cancer, after marking the representative points and its different points on behalf of depth to the region of interest with side of the chest wall.We did CT simulation positioning according to the radiation position.Separately design three schemes on the TPS for die bodies,simulate the irradiation in the die bodies,and did real time measurement to each point with metal oxide semiconductors field-effect transistors（MOSFET）,and compared and analyzed with the TPS marked calculated value.Results By comparison between practical measurement value of its different points on behalf of depth and the corresponding calculated value of each point in TPS,we found that in the skin surface and shallow, difference between planned value and the measured value is large,but along with the increase of depth,the planned value is close to the measured value when mearsuring in lcm depth of points;In addition to the epidermis,three methods of measured dose radiation target areas could basically meet clinical dose learning requirements;IMRT is better than 3D-CRT and 7Mev electronic line irradiation in the target dose tmiformity;When using 7Mev electronic line irradiation,dose lack area less than 16% of the prescribed dose appears in the measuring point of chest wall surface.Conclusions 1.When radiation to the chest wall for postoperative breast cancer patients,various schemes do not add organization compensation. The skin dose is deficient,which will improve the chest wall recurrence rate.Clinical treatment should choose proper thickness of the compensation membrane according to different schemes.2.Electronic line irradiation deep in the chest wall of surface target is easy to form underdosed area, in actual clinical treatment should choose plain chest wall and thin patients for electronic line therapy.3.IMRT techniques is better than 3D-CRT technology in controlling the target high dose,dose uniformity of target,and in reducing the high dose volume of lung etc.But because of the influence of the chest wall breathing movement is bigger, in reverse IMRT, it can not consider the influence of breathing exercise on the target area dose.