Agazaryan Nzhde, Solberg Timothy D
Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-6951, USA.
Med Phys. 2003 Jul;30(7):1758-67. doi: 10.1118/1.1578791.
A leaf sequencing algorithm has been implemented to deliver segmental and dynamic multileaf collimated intensity-modulated radiotherapy (SMLC-IMRT and DMLC-IMRT, respectively) using a linear accelerator equipped with a micro-multileaf collimator (mMLC). The implementation extends a previously published algorithm for the SMLC-IMRT to include the dynamic MLC-IMRT method and several dosimetric considerations. The algorithm has been extended to account for the transmitted radiation and minimize the leakage between opposing and neighboring leaves. The underdosage problem associated with the tongue-and-groove design of the MLC is significantly reduced by synchronizing the MLC leaf movements. The workings of the leaf sequencing parameters have been investigated and the results of the planar dosimetric investigations show that the sequencing parameters affect the measured dose distributions as intended. Investigations of clinical cases suggest that SMLC and DMLC delivery methods produce comparable results with leaf sequences obtained by root-mean-square (RMS) errors specification of 1.5% and lower, approximately corresponding to 20 or more segments. For SMLC-IMRT, there is little to be gained by using an RMS error specification smaller than 2%, approximately corresponding to 15 segments; however, more segments directly translate to longer treatment time and more strain on the MLC. The implemented leaf synchronization method does not increase the required monitor units while it reduces the measured TG underdoses from a maximum of 12% to a maximum of 3% observed with single field measurements of representative clinical cases studied.
已经实现了一种叶片排序算法，以使用配备有微型多叶准直器（mMLC）的直线加速器进行分段和动态多叶准直调强放射治疗（分别为SMLC-IMRT和DMLC-IMRT）。该实现将先前发表的用于SMLC-IMRT的算法扩展到包括动态MLC-IMRT方法和几个剂量学考虑因素。该算法已扩展以考虑透射辐射，并使相对和相邻叶片之间的泄漏最小化。通过同步MLC叶片运动，与MLC的舌槽设计相关的剂量不足问题得到了显著减少。已经研究了叶片排序参数的作用，平面剂量学研究结果表明，排序参数按预期影响测量的剂量分布。临床病例研究表明，SMLC和DMLC递送方法在均方根（RMS）误差规格为1.5%及更低（大约对应于20个或更多段）的叶片序列下产生可比的结果。对于SMLC-IMRT，使用小于2%的RMS误差规格（大约对应于15段）几乎没有什么好处；然而，更多的段直接转化为更长的治疗时间和对MLC更大的压力。所实施的叶片同步方法不会增加所需的监测单位，同时它将测量的舌槽剂量不足从代表性临床病例单野测量中观察到的最高12%降低到最高3%。
