AN ANALYTICAL SOLUTION FOR THE DYNAMIC CONTROL OF MULTILEAF COLLIMATORS
AN ANALYTICAL SOLUTION FOR THE DYNAMIC CONTROL OF MULTILEAF COLLIMATORS
复制标题
DOI：
10.1088/0031-9155/39/1/003
复制
发表时间：
1994-01-01
影响因子：
3.5
通讯作者：
BRAHME, A
中科院分区：
文献类型：
--
作者：
SVENSSON, R;KALLMAN, P;BRAHME, A
目前放射治疗中的所有优化技术都得益于强非均匀辐射束的使用。在实时控制下产生这些场的最灵活的方式是通过基本光束扫描和/或动态多叶准直。在这项工作中，导出了在尽可能短的时间内使患者获得所需的能量通量分布或准直器开启密度所需的准直器叶片运动的一般解析表达式。通过对一般表达式的简化，导出了收缩场和窗帘快门技术的运动方程，并对相关的近似进行了明确的量化。考虑了有限速度和有限加速度对叶片运动的力学限制。结果表明，即使考虑速度和加速度的限制，也可以产生几乎任何期望的能量通量分布。窗帘技术的基本规律是，当叶片沿运动方向的能量通量梯度为正时，领先的叶片应以最大速度运动，落后的叶片应对场进行调制。在坡度为负的地区，落后的叶子应该全速移动，而领先的叶子应该调节磁场。然后，总体处理时间与连续极小值和极大值之间的能量通量或开口密度的总增量成正比。因此，对于具有多个高峰值的能量通量分布，治疗时间可能比传统的均匀剂量传输显著增加。然而，一般而言，与传统的统一治疗相比，治疗时间延长了约两倍。显然，这里开发的多叶准直器的方法也适用于简单的块准直器，因为它可以用于沿着准直器块的运动方向提供任意规则或不规则的动态楔形轮廓。
All current optimization techniques in radiation therapy benefit from the use of strongly non-uniform radiation beams. The most flexible way of generating these fields under real time control is by elementary beam scanning and/or dynamic multileaf collimation. In this work general analytical expressions are derived for the required motion of the collimator leaves to achieve a desired energy fluence distribution or collimator opening density in the patient in the shortest possible time. By simplification of the general expressions the equations of motion have been derived for both the shrinking field and the curtain shutter techniques with the associated approximations clearly quantified. The mechanical limitations on leaf motion, caused by the finite velocity and acceleration, are taken into account. It is shown that almost any desired energy fluence distribution can be created even when the limitations on velocity and acceleration are considered. The basic rule with the curtain shutter technique is that when the energy fluence gradient along the direction of motion of the leaves is positive, the leading leaf should move at maximum speed and the lagging leaf should modulate the field. In regions where the gradient is negative the lagging leaf should instead move at full speed and the leading leaf should modulate the field. The overall treatment time is then proportional to the total increment in energy fluence or opening density between consecutive minima and maxima. For energy fluence profiles with numerous high peaks the treatment time may therefore increase considerably over that for conventional uniform dose delivery. However, in general the treatment time is prolonged by a factor of about two compared to a traditional uniform treatment. Obviously the method developed here for multileaf collimators is also suitable for simple block collimators since it can be used to deliver arbitrary regular or irregular 'dynamic wedge' profiles along the direction of motion of the collimator blocks.