整合呼吸因素后三维适形及调强放疗计划在胃癌术后放疗中的剂量学研究

目的 比较整合呼吸移动因素后胃癌术后三维适形、调强放疗计划的靶区及部分正常组织剂量学差异,为临床计划设计时参考.方法 10例胃癌术后患者在平静自由呼吸状态下进行常规CT定位,设计三维适形(3DCRT)及调强放疗(IMRT)计划.根据患者呼吸时相情况生成概率分布函数(PDF),将所得PDF与三维静态剂量进行三维剂量卷积计算,得到自由呼吸状态下整合后的3DCRT与IMRT计划.比较呼吸移动因素整合后3DCRT与IMRT计划在靶区剂量分布和部分正常组织受量差异,如CTV接受100%处方剂量45 Gy的体积占靶体积百分比(V45)、肝脏接受40 Gy的体积(V40)和双侧肾脏V15、V18等.结果 整合呼吸移动因素后靶区剂量覆盖率和均匀性的IMRT计划优于3DCRT计划,其中V45为98%:87%(t=-3.35,P=0.010)、平均剂量为(46.81±0.75)Gy:(45.99±1.12)Gy(t=-0.31,P=0.030).正常组织中肝脏V40的IMRT计划明显低于3DCRT计划(12%:16%;t=3.75,P=0.010),左肾脏V15和V18的IMRT计划也明显低于3DCRT计划34%∶50%(t=2.17,P=0.050)和27%∶46%(t=3.11,P=0.020)],右肾V15和V18的3DCRT计划略优于IMRT计划15%∶21%(t=-2.42,P=0.040)和11%∶15%(t=-2.71,P=0.030)].结论 整合呼吸移动因素后,IMRT较3DCRT计划有更好靶区覆盖率和较低肝脏及左侧肾脏受量.

Comparison of dosimetry distribution between three-dimension conformal and intensity modulated plan integrated with breath motion in postoperative radiation of gastric cancer

Objective To compare the dose distribution of the target and normal tissues in gastric cancers between three-dimension conformal radiation therapy (3DCRT) and intensity modulated radiation therapy (IMRT) plan when respiratory motion factors integrated in the plan. Methods From January 2005to November 2006, 10 patients with post-operatively radiation of gastric cancer were enrolled in this study.Planning CT were acquired conventionally with free-breath mode and the static treatment plans of the 3DCRT and IMRT were designed respectively. Probability distribution functions (PDF) were generated and convoluted with the static dose distributions from 3DCRT and IMRT plans to obtain the integrated plans. The dose distributions of the target and normal tissues were compared between 3DCRT and IMRT integration treatment plans, such as V45 of clinical target volume, V4o of liver and V15, V18 of left and right kidney.Results In the respiratory integrated treatment planning, the target volume coverage and homogeneity with IMRT are superior to those with 3DCRT ( ( V45 98%∶ 87% (t = -3. 35 ,P =0. 010) ,mean dose 46. 81 Gy ±0. 75 Gy∶45.99 Gy ± 1.12 Gy (t = -0. 31 ,P=0. 020) ). The V40 of teh liver in IMRT are smaller than those in 3DCRT ( 12%∶ 16% ;t=3.75,P=0.010). For the left kidney, the V15 and V18 in IMRT are smaller than those in 3DCRT ( (34%∶ 50% (t = 2. 17 ,P = 0. 050) and 27%∶46% (t = 3. 11 ,P = 0. 020) ),but for the right kidney, V15 and V18 in 3DCRT are smaller than those in IMRT ( ( 15%∶ 21% (t = - 2. 42,P=0.040) and 11%∶15% (t= -2.71,P=0.030)). Conclusions When respiratory motion factor integrated in the treatment plan, IMRT showed advantage both in target coverage and normal tissue sparing in the high dose region of liver and left kidney.