左侧乳腺癌保乳术后不同调强放疗计划的剂量学研究

Dosimetry study on different intensity modulated radiotherapy plans for left side breast cancer patients after breast conservative surgery

目的比较左侧乳腺癌保乳术后不同调强放疗技术的剂量学差异。方法选取14例左侧乳腺癌保乳术后患者,分别设计4野静态调强(4F-IMRT)、混合调强(Hy-IMRT)和2个部分弧长容积旋转调强放疗(VMAT)计划,并比较3组计划的计划靶区(PTV)、危及器官和正常组织剂量参数以及治疗效率的差异。结果 3组计划PTV的最小剂量、平均剂量(Dmean)、适形度指数和V_(105)相差不大,但最大剂量、均匀性指数和V_(110)差异有统计学意义(P<0.05),其中4FIMRT的靶区剂量分布最优。不同计划患侧肺V_5、V_(10)、V_(15)、Dmean以及心脏的V_(10)、V20差异有统计学意义(P<0.05),HyIMRT患侧肺和心脏的剂量参数优于4F-IMRT和VMAT计划。Hy-IMRT靶区外正常组织的V_5、V_(10)明显优于其它两种计划(P<0.05)。4F-IMRT所需机器跳数(MU)最多,而VMAT的治疗时间最短。结论 4F-IMRT在降低计划靶区高剂量区体积和提高剂量均匀性等方面有明显的优势;HyIMRT对左肺、右肺、心脏等危及器官保护较好,治疗所需的MU也最少;VMAT可以缩短治疗时间,提高患者舒适性和放疗工作效率。

Objective To compare the dosimetric differences in four fields IMRT （4F-IMRT） , hybrid intensity mod- ulated radiation therapy（Hy-IMRT） and volumetric modulated arc therapy（VMAT） planning for the left side breast cancer after breast conserving surgery. Methods 14 patients with left sided breast cancer undergoing breast conser- ving therapy were selected. Three radiotherapy plans based on 4F-IMRT, Hy-IMRT and VMAT were developed re- spectively. All plans were optimized to meet the requirement of 95 % planning target volume （PTV） covered by pre- scribed dose. The dosimetric parameters of PTV and organ at risk （ OAR）, the monitor units （MU） and mean deliv- ery time were compared. Results In three groups of plans, The minimum dose, mean dose, conformity index（CI） and V105 of PTV were similar in three groups, but the difference of the PTV max dose, homogeneity index（HI） and V110 was statistically significant（ P 〈0. 05 ） , 4F-IMRT had a better dose distribution in PTV. The differences were statistically significant（P 〈0.05） in terms of V5, V10, V15, mean dose of the left lung and V10, V20 of the heart. Compared with 4F-IMRT and VMAT, The dosimetric parameters of the left lung and heart in Hy-IMRT had obvious advantages. The surrounding normal tissue V5 and V10 in Hy-IMRT were superior to those of the 4F-IMRT and VMAT（P 〈0.05）. The 4F-IMRT had the most MU, but the mean delivery time of the VMAT was the shortest. Conclusion 4F-IMRT have significant advantages in reducing the volume of high dose area and increasing the uni- formity of dose in planning target volume. Hy-IMRT have better protection to the left lung, right lung, heart and other OAR, VMAT can shorten the treatment time, improve patient comfort and radiotherapy efficiency.