左侧乳腺癌保乳术后采用深吸气屏气放疗的心脏剂量学分析

目的 探究左侧乳腺癌保乳术后放疗患者采用深吸气屏气(DIBH)技术对心脏剂量的改善情况,分析可能影响心脏剂量的解剖因素。方法 前瞻性入组 15例左侧乳腺癌保乳术后行全乳放疗患者,符合呼吸控制要求。分别在自由呼吸(FB)和DIBH状态下进行2次模拟CT扫描,在DIBH图像上制定全乳放疗计划。比较FB和DIBH状态下心肺位置和体积变化以及心肺剂量差异,探究FB状态下各解剖因素与心脏剂量的相关性。对计数资料组间行非参数Wilcoxon秩和检验,双变量相关分析采用Pearson法。结果 DIBH与FB状态下心脏体积相似(P=0.773),而双肺体积明显增加(P=0.001)。心脏、冠脉左前降支、左心室、右心室和左肺 Dmean、Dmax和V5—V40均明显降低(P<0.05)。DIBH使肺体积增加越显著,心脏平均剂量下降幅度越大。FB状态下乳腺体积、心肺体积比、乳腺下界与心脏下界距离、最大心脏切缘距离分别与心脏剂量呈线性相关,其中心肺体积比、最大心脏切缘距离与心脏剂量具有独立相关性。结论 左侧乳腺癌保乳术后采用DIBH技术行全乳放疗较FB状态明显降低心肺剂量。肺体积的变化是改善心脏相对解剖位置的基础。心肺体积比、最大心脏切缘距离或许可以作为进行DIBH技术治疗的参考标准。

Cardiac dosimetry of deep inspiration breath-hold technique in whole breast irradiation for left breast cancer after breast-conserving surgery

Objective To study the effect of deep inspiration breath-hold (DIBH) technique on the heart dose in whole breast irradiation (WBI) for left breast cancer after breast-conserving surgery, and to investigate the anatomical factors for heart dose. Methods Fifteen patients with left breast cancer who received WBI after breast-conserving surgery and met breathing control requirements were prospectively enrolled as subjects. Simulated CT scans were performed during free breathing (FB) and DIBH. The WBI plans were optimized based on DIBH images. The position, volume, and radiation doses to the heart and lung were compared between the status of FB and DIBH. Correlation of heart dose with various anatomical factors was analyzed in FB status. Between-group comparison of categorical data was made by nonparametric Wilcoxon rank test. A two-variable correlation analysis was made by the Pearson method. Results There was no significant difference in heart volume between the status of FB and DIBH (P=0.773).The volume of both lungs was significantly larger in DIBH status than in FB status (P=0.001). The mean and maximum doses and V5-V40 for the heart, left anterior descending coronary artery,left ventricle, right ventricle, and left lung were significantly lower in DIBH status than in FB status (all P<0.05). The greater DIBH increased the lung volume, the greater the mean heart dose decreased. In FB status, the left breast volume, heart-to-lung volume ratio, distance between the inferior margins of breast and heart, and maximum heart margin distance showed a linear correlation with heart dose. Particularly, the heart-to-lung volume ratio and maximum heart margin distance were independently correlated with heart dose. Conclusions DIBH technique in WBI for left breast cancer after breast-conserving surgery significantly reduces heart and lung doses compared with FB. Changes in lung volume are the basis for improving the relative anatomical location of the heart. The heart-to-lung volume ratio and maximum heart margin distance may provide a reference for DIBH technique.