射线能量对子宫内膜癌调强放疗计划质量的影响

目的 研究射线能量对子宫内膜癌术后全盆腔调强放射治疗计划质量的影响。方法 选择10例子宫内膜癌术后患者,对每例患者分别设计6和18 MV的全盆腔调强放射治疗计划。所有计划均使用相同的布野方案和剂量体积约束。比较两组计划的靶区、危及器官和正常组织的剂量分布。结果 6和18 MV计划的平均PTV₁₀₀分别是95.6%和95.3% (检验值P=0.26), D_mean分别是52.55 Gy和52.60 Gy(P=0.54),适形指数分别是0.87 和 0.88 (P=0.03),均匀性指数均为1.10 (P=0.38)。18 MV计划较6 MV计划正常组织的平均积分剂量下降了2.4% (P=0.001),小肠和结肠的平均V₃₀和V₅₀分别下降了4.2% (P=0.006)和3.3% (P=0.046),其他危及器官的剂量分布间差异无统计学意义。结论 对于子宫内膜癌的术后全盆腔调强放射治疗,18 MV计划比6 MV计划剂量分布的适形度更好,能够更好地保护正常组织、小肠和结肠。两组计划靶区的覆盖度和剂量分布的均匀性,以及直肠、膀胱和盆腔骨的保护相当。

Effect of beam energy on quality of IMRT plans for endometrial cancer

Objective To investigate the effect of beam energy on the quality of postoperative whole pelvic IMRT plans for endometrial cancer. Methods Computed Tomography (CT) image sets of ten postoperative endometrial cancer patients were acquired and two whole pelvic IMRT plans were created for each patient, one with 6 MV and the other with 18 MV photons. Beam arrangements and optimization constraints were the same for two plans. The dose distribution of the targets, organs at risk and normal tissue was analyzed and compared for plans generated with both energies. Results The mean PTV₁₀₀ were 95.6% and 95.3% (P=0.26), the D_mean were 52.55 Gy and 52.60 Gy (P=0.54) for the plans with 6- and 18- MV photons, respectively. The mean conformity index were 0.87 and 0.88 (P=0.03). The mean homogeneity index were both 1.10 (P=0.38). The mean integral dose to normal tissue was 2.4% lower with 18 MV plans (P=0.00), the mean V₃₀ and V₅₀ of small intestine and colon were also reduced by 4.2% (P=0.006) and 3.3% (P=0.046),respectively. No statistically significant difference was found for the dose distribution to the other organs at risk between the plans with 6- and 18- MV photons. Conclusions Compared with 6 MV IMRT plans, 18 MV IMRT plans resulted in more conformal dose distribution, better sparing of small intestine and colon, and normal tissue, with comparable PTV coverage and sparing of rectum, bladder, and pelvic bones.