早期原发胃淋巴瘤三维适形放疗剂量优化研究

分析早期原发胃淋巴瘤不同三维适形放疗技术（3DCRT）的剂量分布特征，为临床优化应用提供参考。方法:选取9例早期原发胃淋巴瘤患者，在空腹状态下做模拟定位CT，并在CT图像上勾画出胃肿瘤和受累淋巴结、临床靶区（CTV）、计划靶区（PTV），以及邻近危及器官（OARs）。每例设计2种放疗计划:四野3DCRT及上下半束六野的优化3DCRT，用剂量体积关系图分析剂量学结果。结果:四野及优化3DCRT的适形指数分别为0.67±0.06及0.64±0.05；剂量不均匀性指数分别为1.10±0.02及1.11±0.03。左、右肾V15在四野3DCRT及优化3DCRT中分别为（47±30）%、（33±18）%和（24±18）%、（12±12）%。优化3DCRT的肝脏V20较四野3DCRT减少24%。结论:3DCRT能够给予肿瘤靶区均匀的剂量分布，而采用优化六野3DCRT可以更好的保护肾脏、肝脏等危及器官。 

Dosimetric Optimization of Three-dimensional Conformal Radiotherapy for Early Stage Primary Gastric Lymphoma Treatment

To evaluate the dosimetric characters of different three-dimensional conformal radiation therapy ( 3DCRT ) techniques for early stage primary gastric lymphoma treatment and provide a reference for its optimized clinical application. Methods: Nine patients with early stage primary gastric lymphoma were enrolled for the current research. A simulated CT position was made in the fasting state. Gastric tumors with invaded lymph nodes, clinical target volume, and planning target volume ( PTV ) were contoured on each computed tomography scan. Organs at risk ( OARs ), such as each kidney, the liver, and the spinal cord were also contoured. Treatment planning for the ordinary four-field 3DCRT and optimized six-field 3DCRT was conducted for each patient. The prescribed PTV dose was 36 Gy. The dose distribution of PTVs and OARs were compared using the dose-volume relationship line graph. Results: The conformal indices for the ordinary four-field 3DCRT and optimized six-field 3DCRT were 0.67 ± 0.06 and 0.64 ± 0.05, respectively, whereas the inhomogeneity indices were 1.10 ± 0.02 and 1.11 ± 0.03, respectively. The V15 ( ratio of the kidney volume accepted higher than 15 Gy irradiation ) values for the left and right kidneys in the ordinary four-field 3DCRT and optimized six-field 3DCRT were 47% ± 30%, 33% ± 18%, and 24% ± 18%, and 12% ± 12%, respectively. The V20 ( ratio of the liver volume accepted higher than 20 Gy irradiation ) values for the liver in the optimized six-field 3DCRT decreased by 24% compared with those of the ordinary four-field 3DCRT. Conclusion: 3DCRT can successfully achieve the ideal dose distribution and coverage over the target volume, and the optimized six-field 3DCRT can better protect the kidneys, liver, and other OARs.