放疗是肿瘤综合治疗体系的重要组成部分。在放疗中，多叶准直器（Multi-leaf Collimator，MLC）能够精确、迅速地形成期望的射野形状，相较于传统的挡块，大幅提升了放疗效率。MLC也广泛应用于调强放疗中，通过精确调控MLC叶片的运动轨迹，实现期望的剂量分布。MLC性能对放疗疗效有重要影响，目前主要的性能不足体现为：叶片间隙导致射线漏射；射野与靶区的适形程度有待提高；驱动模块的故障率偏高。为进一步提升MLC性能，本课题研制了新型单层MLC和新型双层MLC，完成了两型MLC的设计制造和性能测试。

与常规单层MLC不同，新型单层MLC的搭载了创新设计的固定部伸缩部叶片和电磁耦合式驱动模块。固定部伸缩部叶片通过叶片闭合时形成的交错结构，有效解决了叶片末端漏射和穿射问题。电磁耦合式驱动模块通过双电机协同驱动机制实现了对MLC全叶片组的同步控制，从根本上降低了驱动模块的故障率。设计完成后，委托国产MLC厂商完成加工制造。加工完成后进一步开发了配套控制算法，实现了叶片运动轨迹的精确闭环控制。

新型单层MLC外挂于医科达公司Versa HD加速器进行性能测试。剂量学测试表明，相对叶片间的漏射率显著降低，由常规MLC测量值48.41% 显著降至0.41%。同时，相邻叶片间漏射率控制在0.59%，在16 mm × 32 mm射野下的半影宽度为2.82 mm。临床脑转移病例计划应用结果显示，新型单层MLC在保证处方剂量达标的同时，降低了3.1% 的脑平均受照剂量，其它各危及器官受照剂量也有不同程度的下降，更好地保护了危及器官。这也证明其可以替代全部后备铅门，节省治疗空间并降低机头负载。机械测试显示，叶片运动速度最高达3 cm/s，重复到位精度为0.23 mm。可靠性分析显示，相较于同等叶片数量的常规MLC，新型单层MLC的故障率降低了60.94%。

与常规双层MLC不同，新型双层MLC搭载了创新设计的指形末端叶片，通过双层叶片的动态补偿机制实现靶区适形度的提升。此外，对新型双层MLC的电磁耦合式驱动模块进行结构优化，改进位置反馈单元，不仅进一步提升了叶片到位精度，还实现单侧两层MLC仅使用一台电机驱动。设计完成后，本课题委托国产加速器厂商完成新型双层MLC的加工。

新型双层MLC集成于沈阳东软智睿公司NeuRT Aurora加速器进行性能测试。机械性能测试显示，改进型电磁耦合式驱动模块将到位精度进一步提高至0.1 mm以内，最大重复到位误差仅为0.059 mm。基于MV影像校准后，等中心叶片投影到位平均误差为0.06 mm。剂量学测试表明，新型双层MLC在使用双层叶片时漏射率小于0.1%，指形末端叶片在20 mm × 20 mm射野下的半影宽度为3.75 mm，均达到与现有双层MLC相同水平。而其在等中心形成与常规MLC形状不同的指形投影，能够更好的拟合靶区。实验证明，最优的指形投影形状能够在适形放疗中提升31.2% 的射野适形度并在容积旋转调强放疗中提升14.5% 的强度调制精度。

本课题提出的两型MLC，通过创新设计显著提升了MLC的性能。其中固定部伸缩部叶片应用于新型单层MLC，降低了漏射率；指形末端叶片应用于新型双层MLC，提高了射野适形度和强度图分布适形度；电磁耦合式驱动模块应用于两型MLC，降低了故障率。两型MLC为放疗技术的进一步发展提供了重要支持，有望在临床应用中发挥重要作用，为患者提供更安全、更精准的放疗。

Radiotherapy is a crucial component of the comprehensive treatment system for tumors. In radiotherapy, the Multi-leaf Collimator (MLC) can precisely and rapidly form the desired radiation field shape, significantly improving the efficiency of radiotherapy compared to traditional blocks. MLC is also widely used in intensity-modulated radiotherapy, achieving the desired dose distribution by precisely controlling the movement trajectory of the MLC leaves. The performance of the MLC has a significant impact on the efficacy of radiotherapy. Current performance shortcomings mainly include: radiation leakage due to leaf gaps; the conformity between the radiation field and the target area needs improvement; and the failure rate of the drive module is relatively high. To further enhance the performance of the MLC, this project developed a new single-layer MLC and a new double-layer MLC, completing the design, manufacturing, and performance testing of both types.

Unlike conventional single-layer MLCs, the new single-layer MLC is equipped with innovatively designed fixed and movable leaves and an electromagnetic coupling drive module. The fixed and movable leaves effectively solve the problem of radiation leakage and transmission at the leaf ends through an interlocking structure formed when the leaves are closed. The electromagnetic coupling drive module achieves synchronous control of the entire leaf group of the MLC through a dual-motor cooperative drive mechanism, fundamentally reducing the failure rate of the drive module. After the design is completed, domestic MLC manufacturers were commissioned to complete the processing and manufacturing. Following the manufacturing, supporting control algorithms were developed to achieve precise closed-loop control of the leaf movement trajectory.

The new single-layer MLC was externally mounted on Elekta's Versa HD accelerator for performance testing. Dosimetric tests show that the relative inter-leaf leakage rate is significantly reduced, dropping from 48.41% with traditional MLCs to 0.41%. Meanwhile, the leakage rate between adjacent leaves is controlled at 0.59%, and the penumbra width under a 16 mm × 32 mm radiation field is 2.82 mm. Clinical application results for brain metastasis cases show that the new single-layer MLC ensured the prescription dose was met while reducing the average brain dose by 3.1%, and the doses to other organs at risk were also reduced to varying degrees, better protecting the organs at risk. Mechanical tests show that the maximum leaf movement speed reached 3 cm/s, with a repeat positioning accuracy of 0.23 mm. Reliability analysis indicates that the failure rate of the new single-layer MLC is reduced by 60.94% compared to conventional MLCs with the same number of leaves.

Unlike conventional double-layer MLCs, the new double-layer MLC is equipped with innovatively designed finger-end leaves, improving target conformity through a dynamic compensation mechanism of the double-layer leaves. Additionally, the electromagnetic coupling drive module of the new double-layer MLC was structurally optimized, improving the position feedback unit, which not only further enhanced the leaf positioning accuracy but also allowed a single motor to drive one side of the two-layer MLC. After the design is completed, domestic accelerator manufacturers are commissioned to complete the processing of the new double-layer MLC.

The new double-layer MLC is integrated into Neusoft NeuRT Aurora accelerator for performance testing. Mechanical performance tests shows that the improved electromagnetic coupling drive module further increases the positioning accuracy to within 0.1 mm, with a maximum repeat positioning error of only 0.059 mm. After calibration based on MV imaging, the average positioning error of the isocentric leaf projection is 0.06 mm. Dosimetry testing shows that the leakage rate of the new dual-layer MLC is less than 0.1% when using double-layer leaves, and the penumbra width of the tongue-shaped leaf tip under a 20 mm × 20 mm field is 3.75 mm, which is comparable to the performance of the existing dual-layer MLCs, while forming a finger-shaped projection at the isocenter different from conventional MLCs, better fitting the target area. Experiments proves that the optimal finger-shaped projection could improve field conformity by 31.2% in conformal radiotherapy and intensity modulation accuracy by 14.5% in volumetric modulated arc therapy.

The two types of MLCs proposed in this project significantly enhance MLC performance through innovative designs. The fixed and movable leaves applied in the new single-layer MLC reduce leakage rates; the finger-end leaves applied in the new double-layer MLC improve field conformity and intensity map distribution conformity; and the electromagnetic coupling drive module applied in both types of MLCs reduces failure rates. These two types of MLCs provide important support for the further development of radiotherapy technology and are expected to play a significant role in clinical applications, offering patients safer and more precise radiotherapy.