中文摘要：

目的提出一种用于双层多叶准直器（MLC）的指形叶片的设计方案。方法首先建立描述优化MLC叶片端面形状的数学模型。优化确定MLC指形叶片的端面设计参数，比较指形叶片设计和传统的直线形叶片端面设计的适形性能。使用的优化方法有单纯形法和模拟退火法。优化计算基于634个从临床病例中采集的靶区。这些靶区的面积为20．0—602．7cm^2，平均面积为（125．7±70．0）cm^2。结果通过优化计算，确定指形叶片的端面在加速器等中心的投影为半圆形。与传统的直线形叶片端面的MLC相比，指形叶片设计能使MLC射野与靶区之间不一致区域的面积（TAD）下降32．3％。结论指形叶片设计显著提高了MLC射野与靶区之间的适性度。

英文摘要：

Objective To introduce a finger leaf design that is applied to dual layer MLCs. Methods An optimization model was firstly constructed to describe the problem of determining leaf end shapes, and the corresponding problems were then solved by the simplex search method or the simulated annealing technique. Optimal parameters for arc shapes of leaf end projections were obtained, and a comparison was done between optimized MLCs and conventional MLCs in terms of field conformity. The optimization process was based on 634 target fields selected from the patient data base of a treatment planning system. Areas of these fields ranged from 20. 0 to 602.7 cm^2 with a mean and its standard deviation of （ 125.7 ± 70. 0） cm^2. Results The optimized leaf end shapes projected to the isocenter plane were semicircles. With the finger leaf design, the total area of discrepancy regions between MLC fields and target fields was reduced by 32.3%. Conclusions The finger leaf design improves the conformity of the MLC shaped fields to the desired target fields.