Gauer T, Albers D, Cremers F, Harmansa R, Pellegrini R, Schmidt R
Department of Radiotherapy and Radio-Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Phys Med Biol. 2006 Dec 7;51(23):5987-6003. doi: 10.1088/0031-9155/51/23/003. Epub 2006 Oct 30.
A multileaf collimator for electrons (eMLC) has been designed that fulfils the technical requirements for providing advanced irradiation techniques with electrons. In the present work, the basic design parameters of leaf material, leaf height, leaf width and number of leaves as well as leaf overtravel and leaf shape were determined such that an eMLC with motorized leaves can be manufactured by a company specialized in MLC technology. For this purpose, a manually driven eMLC with variable source-to-collimator distance (SCD) was used to evaluate the chosen leaf specification and investigate the impact of the SCD on the off-axis dose distribution. In order to select the final SCD of the eMLC, a compromise had to be found between maximum field size, minimum beam penumbra and necessary distance between eMLC and isocentre to eliminate patient realignments during gantry rotation. As a result, the eMLC is placed according to the target position at 72 and 84 cm SCD, respectively. This feature will be achieved by interchangeable distance holders. At these SCDs, the corresponding maximum field sizes at 100 cm source-to-isocentre distance are 20 x 20 cm and 17 x 17 cm, respectively. Finally, the off-axis dose distribution at the maximum opening of the eMLC was improved by fine-tuning the settings of the accelerator jaws and introducing trimmer bars above the eMLC. Following this optimization, a prototype eMLC consisting of 2 x 24 computer-controlled brass leaves is manufactured by 3D Line Medical Systems.
已经设计了一种用于电子的多叶准直器（eMLC），它满足了提供先进电子照射技术的技术要求。在本工作中，确定了叶片材料、叶片高度、叶片宽度、叶片数量以及叶片超程和叶片形状等基本设计参数，以便一家专门从事MLC技术的公司能够制造出具有电动叶片的eMLC。为此，使用了一种源到准直器距离（SCD）可变的手动驱动eMLC来评估所选的叶片规格，并研究SCD对离轴剂量分布的影响。为了选择eMLC的最终SCD，必须在最大射野尺寸、最小射束半影以及eMLC与等中心之间的必要距离之间找到折衷方案，以消除机架旋转期间患者的重新定位。结果，根据目标位置，eMLC分别放置在SCD为72 cm和84 cm处。这一特性将通过可互换的距离固定器来实现。在这些SCD下，在源到等中心距离为100 cm时，相应的最大射野尺寸分别为20×20 cm和17×17 cm。最后，通过微调加速器准直器的设置并在eMLC上方引入微调棒，改善了eMLC最大开口处的离轴剂量分布。经过这种优化，由3D Line Medical Systems制造了一个由2×24个计算机控制的黄铜叶片组成的eMLC原型。
