Cao Junsheng, Roeske John C, Chmura Steve J, Salama Joseph K, Shoushtari Asal N, Boyer Arthur L, Martel Mary K
Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL, USA.
Med Dosim. 2009 Summer;34(2):126-32. doi: 10.1016/j.meddos.2008.07.002. Epub 2008 Sep 4.
The standard treatment technique used for whole-breast irradiation can result in undesirable dose distributions in the treatment site, leading to skin reaction/fibrosis and pulmonary and cardiac toxicities. Hence, the technique has evolved from conventional wedged technique (CWT) to segment intensity-modulated radiation therapy (SIMRT) and beamlet IMRT (IMRT). However, these newer techniques feature more highly modulated dose distributions that may be affected by respiration. The purpose of this work was to conduct a simple study of the clinical impact of respiratory motion on breast radiotherapy dose distributions for the three treatment planning techniques. The ultimate goal was to determine which patients would benefit most from the use of motion management. Eight patients with early-stage breast cancer underwent a free-breathing (FB) computed tomography (CT) simulation, with medial and lateral markers placed on the skin. Two additional CT scans were obtained at the end of inspiration (EI) and the end of expiration (EE). The FB-CT scan was used to develop treatment plans using each technique. Each plan was then applied to EI and EE-CT scans. Compared with the FB CT scan, the medial markers moved up to 1.8 cm in the anterior-superior direction at the end of inspiration (EI-scan), and on average 8 mm. The CWT and SIMRT techniques were not "sensitive" to respiratory motion, because the % clinical target volume (CTV) receiving 95% of the prescription dose (V(95%)) remained constant for both techniques. For patients that had large respiratory motion indicated by marker movement >0.6 cm, differences in coverage of the CTV at the V100% between FB and EI for beamlet IMRT plans were on the order of >10% and up to 18%. A linear model was developed to relate the dosimetric coverage difference introduced by respiration with the motion information. With this model, the dosimetric coverage difference introduced by respiratory motion could be evaluated during patient CT simulation. An appropriate treatment method can be chosen after the simulation.
用于全乳照射的标准治疗技术可能会在治疗部位产生不理想的剂量分布，导致皮肤反应/纤维化以及肺部和心脏毒性。因此，该技术已从传统楔形技术（CWT）发展到分段调强放射治疗（SIMRT）和子野调强放射治疗（IMRT）。然而，这些较新的技术具有更高调制的剂量分布，可能会受到呼吸的影响。这项工作的目的是对呼吸运动对三种治疗计划技术的乳腺放射治疗剂量分布的临床影响进行一项简单研究。最终目标是确定哪些患者将从运动管理的使用中获益最大。八名早期乳腺癌患者接受了自由呼吸（FB）计算机断层扫描（CT）模拟，在皮肤上放置了内侧和外侧标记物。在吸气末（EI）和呼气末（EE）又获得了另外两次CT扫描。使用每种技术通过FB-CT扫描制定治疗计划。然后将每个计划应用于EI和EE-CT扫描。与FB CT扫描相比，内侧标记物在吸气末（EI扫描）时在前后上方向上移动了1.8 cm，平均移动了8 mm。CWT和SIMRT技术对呼吸运动不“敏感”，因为两种技术接受95%处方剂量（V(95%)）的临床靶体积（CTV）百分比保持不变。对于标记物移动>0.6 cm表明呼吸运动较大的患者，子野IMRT计划在FB和EI时CTV在V100%的覆盖差异约为>10%，最高可达18%。建立了一个线性模型，将呼吸引入的剂量学覆盖差异与运动信息相关联。利用该模型，可以在患者CT模拟期间评估呼吸运动引入的剂量学覆盖差异。模拟后可以选择合适的治疗方法。
