多叶准直器的结构设计

多叶准直器是加速器上用于射野适形的主要装置,具有简单有效的特点。现已广泛应用于适形、调强等放射治疗技术。为了安全有效地使用多叶准直器,有必要了解不同类型的多叶准直器,了解各种多叶准直器的结构特点及剂量学特征。本文旨在综述MLC的基本结构设计,介绍多叶准直器在加速器上的安装位置选择及影响,综述叶片纵截面和端面的设计方案和单、双聚焦特点,总结各厂家生产的多叶准直器的叶片宽度选择和实现叶片位置控制的各种机制。另外,文中介绍了双层多叶准直器等几种新型设计方案。     

医用直线加速器多叶准直器（MLC）的日常维护与故障检修

多叶准直器（MLC）现已成为医用加速器的标准配置，主要用于适形放疗中，也可部分取代普通放疗的挡铅。由于多叶准直器（MLC）在放疗过程的突出作用，根据我们的工作经验对其工作原理及日常维护做个介绍。多叶准直器分手动和电动两类，现在各医用加速器生产厂家都采用电动多叶准直器，我们主要讨论该类多叶准直器。     

基于DICOM RT标准的射野数据传输

介绍了1种基于DICOM RT标准的射野数据生成和传输方法,用于调强放射治疗中治疗机器（加速器）的标准或多叶准直器的控制.文中首先介绍了系统模块的实现方法,然后分别对静态多叶准直器（SMLC）和动态多叶准直器（DMLC）2种调强实现方法进行详细地描述,最后结合实例来验证系统的有效性.     

多叶准直器射野和独立准直器射野剂量学比较

目的探讨多叶准直器射野和独立准直器射野剂量学数据对放射治疗计划系统建模的影响。方法在Varianunique型直线加速器上对多叶准直器和独立准直器射野的百分深度剂量、射野离轴量以及总散射因子进行比较。结果两种射野的百分深度剂量差别不大,但射野离轴量以及射野总散射因子差别较大。多叶准直器形成的射野均比独立准直器形成的射野要大;随射野变小,两者总散射因子的差异越来越显著。结论在计划系统的建模过程中必须关注不同射野的剂量学数据差异,建议在调强计划系统建模过程中采用多叶准直器射野进行数据采集。     

KB1800直线加速器DMLC电子多叶准直器的安装

介绍DMLC电子多叶准直器的安装过程以及注意事项。阐述医用直线加速器安装多叶准直器(MLC)的必要性,详细分解KB1800直线加速器安装DMLC电子多叶准直器的安装步骤,解释每个步骤的意义,并提出各步骤需要注意的问题。展示了KB1800直线加速器安装电子多叶准直器的过程和早期生产的加速器开展三维适形放疗、调强放疗等精确放疗技术的可行性。早期生产的直线加速器可以通过安装独立的电子多叶准直器,实现开展三维适形放疗、调强放疗等精确放疗技术。     

医用电子直线加速器多叶准直器(MLC)性能比较

通过分析介绍世界三大放疗设备厂家医用电子直线加速器多叶准直器的结构特点,比较了各厂家多叶准直器的优缺点。     

宫颈癌多固定野三维适形放疗铅挡块与多叶准直器应用的比较

目的 介绍宫颈癌多固定野三维适形放疗铅挡块与多叶准直器的方法。方法 将宫颈癌多固定野三维适形放疗铅挡块与多叶准直器的应用进行比较。结果 宫颈癌多固定野三维适形放疗铅挡块与多叶准直器对肿瘤组织和危及器官的实际受照剂量的影响不同。结论 在多固定野三维适形放射治疗中,应根据肿瘤组织的放射致死剂量、危及器官的放射耐受剂量等科学、准确、有效地使用铅挡块和多叶准直器。     

铅挡块与多叶准直器挡野技术分析

目的 探讨铅挡块与多叶准直器挡野技术。方法 对铅挡块、多叶准直器漏射剂量、不规则靶区边缘1cm处剂量、物理半影区等进行测量。结果 铅挡块优于多叶准直器。结论 根据实际的治疗情况、技术要求等选择性应用。     

西门子多叶准直器及其质量保证

通过介绍西门子多叶准直器（multileaf collimator,MLC）叶片的结构特性以及质量保证的具体方法,具体分析西门子各种不同型号多叶准直器叶片的结构特点以及各项机械参数,并详细研究应用胶片法对多叶准直器叶片的运行精度进行验证的实验方法。胶片法成像测量结果及利用实验软件得出的实验数据表明,质量保证措施的正确执行是保证系统治疗精度准确的基础。     

多叶准直器的设计与临床应用评价

多叶准直器是医用直线加速器中遮挡射线的装置，在放射治疗中调节射野形状和剂量分布，直接影响靶区与危及器官受量。目前，多叶准直器在结构上呈现出多样化，各类多叶准直器的剂量学对比也同步推进。本文按多叶准直器的基本构成将其分类，分别介绍各主流加速器厂商产品的硬件结构与设计特点（包括瓦里安Millennium MLC、HD120MLC、Halcyon；医科达MLCi/i2、Agility；安科瑞InCise 2 MLC、TomoTherapy二元气动光栅）；在临床应用评价方面，以鼻咽癌放疗计划为主，综述多叶准直器剂量学表现的对比研究，以及相关条件设置对剂量分布的影响。本文综述的多叶准直器的设计与临床应用评价，为更具创新性设计方案的提出、临床个体化治疗中加速器的选择与参数设定提供参考。     

多叶光栅的校准

本文提出移动位置标定方法和移动速度标定方法,对多叶光栅进行校准。     

外置电动多叶光栅维修四例

对德国 Leibinger多叶光栅存在的四类故障进行现象描述、原因分析和排除,为多叶光栅的维修提供了有效的分析思路和解决方法.     

整体挡铅适形治疗的方法及剂量验证

本文介绍了利用模拟定位机和挡铅技术实现适形放疗的方法,通过采用透明人形头模和半导体剂量仪对照射野进行剂量验证,证明这一方法的有效性和可靠性,其目的是在未配备MLC(多叶准直器)的中小规模放疗单位中推广开展适形放射治疗。     

An economic framework for evaluating a multileaf collimator

OBJECTIVES: As health care budgets continue to face close scrutiny, any new acquisition must be evaluated for both costs and outcomes. This study was undertaken to demonstrate the application of an economic framework for the evaluation of a multileaf collimator as an example of a new technology that can have both quantifiable and nonquantifiable benefits for patients, staff, and cancer care institutions. METHODS: Using financial data from the Northeastern Ontario Regional Cancer Centre (NEORCC) and a recognized staffing model, a commercial spreadsheet, developed to economically characterize the principal radiotherapy processes has been used to determine the net incremental annual cost of a multileaf collimator (MLC). RESULTS: The incremental annual cost of purchasing an MLC is estimated at approximately $85,000 (1997 CDN $). Without increasing patient throughput, this increases the average cost of a course of radiotherapy by approximately CDN $200. Savings can be accrued by decreasing mold room activity, increasing the hourly patient capacity on each treatment machine, and decreasing sick time due to strain injuries. CONCLUSIONS: Although the clinical outcome of techniques facilitated by MLCs, such as intensity-modulated radiation therapy, are unknown at this time, an economic context within which to objectively evaluate this technology is presented. The framework presented suggests a method of quantifying outcome-justified expenditures, such as improved patient outcome and greater treatment flexibility, which, when offset against the incremental annual equipment cost, may be used to help justify the acquisition of multileaf technology.     

适形断层调强放疗光栅系统（YPSUN4000金雀系统）

适形断层调强放射治疗是最前沿的一种调强技术，采用类似CT的模式，分层沿环形对肿瘤进行照射治疗。适形断层调强光栅（MLC）是其关键设备。断层调强光栅直接外挂在各类加速器上，装拆方便，配合治疗床的旋转及移动．实现调强放疗。     

Single-arc volumetric modulated arc therapy planning for left breast cancer and regional nodes

We have successfully created a single arc volumetric modulated arc therapy (VMAT) plan for treating post-surgical left breast/chest wall and regional nodes using Elekta multileaf collimator (MLC). Dose volume histograms (DVHs) were compared between the VMAT plans and conventional tangential beam plans using a field-in-field technique, leading to significant DVH advantages in the VMAT plans. The difference between Elekta VMAT and Varian RapidArc due to different MLC designs was discussed in terms of the number of arcs required to cover a large target, highlighting a single arc capability of Elekta VMAT for a large target volume which may be less sensitive to unexpected organ motion during dose delivery.     

An experimental study on using a diagnostic computed radiography system as a quality assurance tool in radiotherapy

The advent of improved digital imaging modalities in diagnostic and therapy is fast making conventional films a nonexistent entity. However, several radiotherapy centers still persist with film for performing quality assurance (QA) tests. This paper investigates the feasibility of using a diagnostic computed radiography (CR) system as a QA tool in radiotherapy. QA tests such as light field congruence, field size verification, determination of radiation isocentre size, multileaf collimator (MLC) check and determination of isocentric shift for stereotactic radiosurgery (SRS) were performed and compared with film. The maximum variation observed between CR and film was 0.4 mm for field size verification, −0.13 mm for the radiation isocentre size check, 0.77 for MLC check and −0.1 mm for isocentric shift using the Winston Lutz test tool for SRS QA. From these results obtained with the CR it is concluded that a diagnostic CR system can be an excellent cost-effective digital alternative to therapy film as a tool for QA in radiotherapy.     

Depth scaling of solid phantom for intensity modulated radiotherapy beams

To reduce the uncertainty of absorbed dose for high energy photon beams, water has been chosen as a reference material by the dosimetry protocols. However, solid phantoms are used as media for absolute dose verification of intensity modulated radiotherapy (IMRT). For the absorbed dose measurement, the fluence scaling factor is used for converting an ionization chamber reading in a solid phantom to absorbed dose to water. Furthermore the depth scaling factor is indispensable in determining the fluence scaling factor. For IMRT beams, a photon energy spectrum is varied by transmitting through a multileaf collimator and attenuating in media. However, the effects of spectral variations on depth scaling have not been clarified yet. In this study, variations of photon energy spectra were determined using the EGS Monte Carlo simulation. The depth scaling factors for commercially available solid phantoms were determined from effective mass attenuation coefficients using photon energy spectra. The results clarified the effect of spectral variation on the depth scaling and produced an accurate scaling method for IMRT beams.     

An open source solution for an in-house built dynamic platform for the validation of stereotactic ablative body radiotherapy for VMAT and IMRT

An in-house solution for the verification of dose delivered to a moving phantom as required for the clinical implementation of lung stereotactic ablative body radiation therapy was developed. The superior–inferior movement required to simulate tumour motion during a normal breathing cycle was achieved via the novel use of an Arduino Uno?, a low-cost open-source microcontroller board connected to a high torque servo motor. Slow CT imaging was used to acquire the image set and a 4D cone beam CT (4D-CBCT) verified the efficacy of contoured margins before treatment on the moving phantom. Treatment fields were delivered to a section of a CIRS? anthropomorphic phantom. Dose verification to the dynamic phantom with Gafchromic EBT3 film using 3 %-1 mm gamma analysis acceptance criteria registered an absolute dose pass rate for IMRT and VMAT of 98 and 96.6 %, respectively. It was verified that 100 % of the PTV received the prescribed dose of 12 Gy per fraction using the dynamic phantom, and no major discrepancy between planned and measured results due to interplay between multileaf collimator sequences and target motion was observed. This study confirmed that the use of an in-house solution using open source hardware and software with existing quality assurance equipment was appropriate in validating a new treatment technique.