简化手工调强在乳腺切线照射中的应用研究

目的 通过简化手工调强照射与标准切线照射的计划比较研究,为其临床应用提供依据。方法 64例乳腺癌保乳术后患者,每例均行简化手工调强计划和标准切线计划。简化手工调强计划是在内和(或)外侧切线开野方向,复制出遮挡高剂量区的附加野,通过调整附加野和开野之间的权重来减少高剂量区范围。为了优选出简化调强计划,将大于103%、105%及107%高剂量区作为遮挡范围,分别做3套计划来筛选最优计划,同样标准切线计划也进行了楔形板优选,2种优选计划对于靶区覆盖和靶区剂量均匀度和危及器官受量进行了比较。结果 当剂量归一为95%CTV体积100%时,85%优选简化调强计划的遮挡区为大于103%的高剂量区,94%简化调强计划的靶区充分覆盖,基于乳腺CTV体积的分组研究显示,简化调强在大乳腺组不但能显著减少高剂量区和降低最高点剂量,而且也提高剂量均匀指数,但这种效应在小乳腺组不明显。另外,也同时减少了周围危及器官受量。结论 简化手工调强技术在大乳腺病例中可以替代标准切线技术来改善靶区剂量均匀度。

Application of simplified manual intensity modulated technique in breast tangential irradiation

Objective To compare the planning systems of the simplified manual intensity modulated (SMIM) irradiation and standard tangential (ST) irradiation, in order to explore the application of SMIM technique in clinic. Methods In 64 cases of breast cancers after breast conserving surgery, each underwent both SMIM and ST planning systems. SMIM planning was designed by copying additional fields for shielding the high dose areas from internal or lateral tangential field. The high dose areas were reduced by adjusting the size of the additional field and open tangential field. To optimize the SMIM planning, 3 high dose areas (>103%,>105% and >107%) were shielded and 3 protocols carried out. The wedges were also optimized in ST plan. The target coverage and dose homogeneity and dose of organ at risk were compared between SMIM and ST planning systems. Results When the dose was normalized to cover the volume of 95% CTV,85% of the shielded areas in optimal SMIM planning were that of >103% high dose area,and 94% of target area was covered. The study on the volume of breast CTV showed that, in the large breast group, SMIM could not only significantly reduce the high dose areas, and the maximum dose as well as the dose of organ at risk, but also enhance the dose homogeneity index. However, no such effect was not significant in the small breast group. Conclusions The simplified manual intensity modulated technique can improve target dose homogeneity in the large breast cases instead of the standard tangential technique.