Pugachev A, Li J G, Boyer A L, Hancock S L, Le Q T, Donaldson S S, Xing L
Department of Radiation Oncology, Stanford University School of Medicine, CA 94305-5304, USA.
Int J Radiat Oncol Biol Phys. 2001 Jun 1;50(2):551-60. doi: 10.1016/s0360-3016(01)01502-4.
To investigate the role of beam orientation optimization in intensity-modulated radiation therapy (IMRT) and to examine the potential benefits of noncoplanar intensity-modulated beams.
A beam orientation optimization algorithm was implemented. For this purpose, system variables were divided into two groups: beam position (gantry and table angles) and beam profile (beamlet weights). Simulated annealing was used for beam orientation optimization and the simultaneous iterative inverse treatment planning algorithm (SIITP) for beam intensity profile optimization. Three clinical cases were studied: a localized prostate cancer, a nasopharyngeal cancer, and a paraspinal tumor. Nine fields were used for all treatments. For each case, 3 types of treatment plan optimization were performed: (1) beam intensity profiles were optimized for 9 equiangular spaced coplanar beams; (2) orientations and intensity profiles were optimized for 9 coplanar beams; (3) orientations and intensity profiles were optimized for 9 noncoplanar beams.
For the localized prostate case, all 3 types of optimization described above resulted in dose distributions of a similar quality. For the nasopharynx case, optimized noncoplanar beams provided a significant gain in the gross tumor volume coverage. For the paraspinal case, orientation optimization using noncoplanar beams resulted in better kidney sparing and improved gross tumor volume coverage.
The sensitivity of an IMRT treatment plan with respect to the selection of beam orientations varies from site to site. For some cases, the choice of beam orientations is important even when the number of beams is as large as 9. Noncoplanar beams provide an additional degree of freedom for IMRT treatment optimization and may allow for notable improvement in the quality of some complicated plans.
研究射束方向优化在调强放射治疗（IMRT）中的作用，并探讨非共面调强射束的潜在益处。
实施了一种射束方向优化算法。为此，将系统变量分为两组：射束位置（机架和治疗床角度）和射束轮廓（子野权重）。使用模拟退火进行射束方向优化，使用同步迭代逆向治疗计划算法（SIITP）进行射束强度轮廓优化。研究了三个临床病例：局限性前列腺癌、鼻咽癌和脊柱旁肿瘤。所有治疗均使用九个射野。对于每个病例，进行了三种类型的治疗计划优化：（1）针对九个等角间隔的共面射束优化射束强度轮廓；（2）针对九个共面射束优化方向和强度轮廓；（3）针对九个非共面射束优化方向和强度轮廓。
对于局限性前列腺病例，上述所有三种优化类型均产生了质量相似的剂量分布。对于鼻咽癌病例，优化后的非共面射束在大体肿瘤体积覆盖方面有显著提高。对于脊柱旁病例，使用非共面射束进行方向优化可更好地保护肾脏并改善大体肿瘤体积覆盖。
IMRT治疗计划对射束方向选择的敏感性因部位而异。对于某些病例，即使射束数量多达九个，射束方向的选择也很重要。非共面射束为IMRT治疗优化提供了额外的自由度，并可能使一些复杂计划的质量得到显著改善。
