Neilson Christopher E, Yartsev Slav
London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.
J Med Phys. 2012 Apr;37(2):97-101. doi: 10.4103/0971-6203.94744.
Helical tomotherapy's ability to provide daily megavoltage (MV) computed tomography (CT) images for patient set-up verification allows for the creation of adapted plans. As plans become more complex by introducing sharper dose gradients in an effort to spare healthy tissue, inter-fraction changes of organ position with respect to plan become a limiting factor in the correct dose delivery to the target. Tomotherapy's planned adaptive option provides the possibility to evaluate the dose distribution for each fraction and subsequently adapt the original plan to the current anatomy. In this study, 30 adapted plans were created using new contours based on the daily MVCT studies of a bladder cancer patient with considerable anatomical variations. Dose to the rectum and two planning target volumes (PTVs) were compared between the original plan, the dose that was actually delivered to the patient, and the theoretical dose from the 30 adapted plans. The adaptation simulation displayed a lower dose to 35% and 50% of the rectum compared to no adaptation at all, while maintaining an equivalent dose to the PTVs. Although online adaptation is currently too time-consuming, it has the potential to improve the effectiveness of radiotherapy.
螺旋断层放射治疗能够提供每日兆伏级（MV）计算机断层扫描（CT）图像用于患者摆位验证，从而能够制定适形计划。随着计划通过引入更锐利的剂量梯度变得更加复杂，以努力保护健康组织，器官位置相对于计划的分次间变化成为向靶区正确输送剂量的限制因素。断层放射治疗的计划自适应选项提供了评估每个分次剂量分布并随后使原始计划适应当前解剖结构的可能性。在本研究中，基于一名膀胱癌患者每日MVCT研究的新轮廓创建了30个适形计划，该患者存在显著的解剖学变化。比较了原始计划、实际输送给患者的剂量以及30个适形计划的理论剂量对直肠和两个计划靶体积（PTV）的剂量。与完全不进行自适应相比，自适应模拟显示直肠35%和50%的剂量更低，同时保持PTV的剂量相当。尽管在线自适应目前耗时过长，但它有提高放射治疗有效性的潜力。
