乳腺癌改良根治术后CT模拟胸壁切线野照射剂量学分析

The Analysis of Irradiation Dosiology with Tangential Chest Wall Field Using CT Simulation after Modified Radical Mastectomy on Breast Carcinoma

目的:评价胸壁切线野照射CT模拟定位的价值。方法:28例有胸壁照射适应症的乳腺癌改良根治术后患者,进行CT模拟定位,三维治疗计划系统将CT图象进行数字化重建,勾画胸壁CTV及心、肺等危及器官,胸壁处方剂量为5000cGy,计算胸壁及其心、肺受照体积和受照剂量。结果:右肺体积为1403±234cm3,左肺为1133±186cm3,切线野中心肺厚度(CLD)平均为2.4±0.5cm。百分受照体积(PIV)右肺为(13.12±3.26)%,左肺为(12.72±3.58)%,心脏为(2.47±1.87)%,建立一元回归方程,肺PIV=-1.308+6.226CLD(r=0.727,P<0.001)。胸壁体积为441±142cm3,Dmean为4831±352cGy,胸壁V95%、V105%和V110%分别为(95.4±5.3)%、(18.7±15.4)%和(5.3±7.5)%。不加组织补偿胸壁Dmean和Dmin低于胸壁加组织补偿照射(P<0.05)。加300和450楔形板照射后胸壁受照剂量均匀性优于无楔形板和加150楔形板照射,统计学差异接近显著性意义。结论:乳腺癌改良根治术后胸壁切线野照射采用CT模拟定位可准确获得靶区和危及器官的剂量和体积信息,有助于评估心、肺并发症的发生。

Objective： To appraise the value of tangential chest wall irradiation with CT simulation. Methods： CT simulation was conducted for 28 breast cancer patients having received tangential chest wall irradiation after modified radical mastectomy, and digitizing reconstitution of the image pictures from spiral CT equipment and outlining of those organs at risk, such as cervical and thoracic vertebrae （CTV）, heart and lung, etc., were done by the 3D treatment planning system （TPS）. The prescribed dose for chest wall was e 5000cGy and irradiated volume and exposure dose for the chest wall, heart and lung were counted. Results： CT data showed that the mean volume of right and left lung was 1403±234 cm^3 and 1133±186 cm^3 respectively. The mean central lung distance （CLD） in the tangential field was 2.4±0.5cm. The percentage irradiated volume （PIV） of right and left lung were 13.12±3.26% and 12.72±3.58%, respectively. The PIV of heart was 2.47±1.87%. The simple regression line was as followed： lung PIV= -1.308＋6.226CLD （r=0.727, P〈0.001）. The mean volume of chest wall was 441±142cm^3. The mean dose （D mean） of the chest wall was 4831±352 cGy. The percentage of target volume receiving 95% isodose, 105% isodose and 110% isodose were 95.4±5.3%,18.7±15.4% and 5.3±7.5%. The 300 Boost and 450 wedge-shapedplate irradiation were added to meet the requirement of the target coverage and the uniform dose distributions. Dmean and Dmin of the chest wall without bolus were lower than those with boost（P〈0.05）,After the 30° and 45° wedges were added,the homogeneity of the dose was superior to that in the non-wedges and 15° wedges groups.The difference among the groups approached to statistical significance.Conclusions：CT simulation is a feasible means for the postmodified radical mastectomy breast cancer patients undergoing tangential chest wall radiotherapy.It allows a precise target defimition and an optimal target coverage and helps to evaluate the dose to critical structures.crucial