(NCI) Developing an Intermediate Energy Linac for Robotic Radiotherapy

 描述(由申请人提供)：广泛使用非共面光束的机器人放射治疗已被证明有效地显著改善了放射治疗剂量学，从而改善了治疗结果。然而，目前由CyberKnife实施的这项技术效率低下，在剂量学上也不是最优的。这严重限制了有资格接受机器人放射治疗的患者数量和接受治疗的患者的可实现临床结果。为了克服这些局限性，我们建议开发一种新型的机器人放射治疗系统，该系统可以有效地充分利用非共面输送空间的潜力来治疗大多数放射治疗患者。创新点：所提出的系统在以下方面具有很高的创新性：1)集成了束流定向和注量优化。2)明显更紧凑的直线加速器，以允许后波束。3)灵活的字段大小 和MLC分辨率，可有效处理大多数目标大小。4)集成体成像系统。本课题旨在设计一种硬件平台，实现这种机器人放射治疗系统。为了减小机架尺寸，直线加速器的长度和源与MLC之间的距离都需要显著减小。我们建议设计一种新的2 mV光源，以缩短直线加速器的长度，并提供治疗所需的剂量率。物理MLC叶片厚度不能实质上小于1 mm。为了在治疗距离上获得高的MLC分辨率，在CyberKnife中，在初级准直器和MLC之间使用了间隔件，从而增加了机架尺寸。我们建议消除间隔区，但改变病灶到肿瘤的距离(FTD)，以达到所需的视野大小和MLC分辨率。这需要在巨大的解空间中进行优化，4P算法独一无二地证明了这一点。体积成像一直是现代放射治疗中不可或缺的组成部分，但不幸的是，现有的机器人系统缺少体积成像。拟议的新直线加速器将能够从相同的2 mV直线加速器提供千伏成像波束，与机架或沙发安装的成像器相结合，将允许进行体积成像，以实现更精确的肿瘤靶向。目标：1：产生2 mV X射线的加速器的原型设计2：结合成像系统的设计3：为整个临床系统开发概念设计影响：第一阶段项目的成功将导致第一个2 mV直线加速器的设计，该加速器能够在100厘米和千伏的成像光束下产生具有竞争力的高剂量率&GT；800cGymin，用于图像引导放射治疗。这为一种新的机器人放射治疗系统铺平了技术道路，该系统提供的放射计划的剂量一致性超过了现有的X射线平台。更重要的是，显著增加的场地大小、吞吐量和体积成像能力将使新的机器人系统能够争夺比CyberKnife目前占据的利基市场大得多的市场，包括传统直线加速器。

 DESCRIPTION (provided by applicant): Robotic radiotherapy using extensively non-coplanar beams has been shown effective to significantly improve radiation therapy dosimetry that leads to improved treatment outcome. However, current implementation of this technique by CyberKnife is inefficient and not optimal dosimetrically. This has severely limited both the number of patients eligible for robotic radiotherapy and the achievable clinical outcome for those who have been treated. In order to overcome these limitations, we propose to develop a novel robotic radiotherapy system that can efficiently utilize the full potential of the non-coplanar delivery space to treat the majority of radiotherapy patients. Innovation: The proposed system is highly innovative in the following aspect: 1) Integrated beam orientation and fluence optimization. 2) Significantly more compact linac to allow posterior beams. 3) Flexible field sizes and MLC resolution to efficiently treat most target sizes. 4) Integrated volumetric imaging system. This project is proposed to design a hardware platform materializing such robotic radiotherapy system. In order to reduce the gantry size, both the linac length and the distance between the source and the MLC need to be significantly reduced. We propose to design a new 2 MV source to reduce linac length and provide the required dose rate for treatment. The physical MLC leaf thickness cannot be substantially thinner than 1 mm. To achieve a high MLC resolution at the treatment distance, a spacer is used in CyberKnife between the primary collimator and the MLC, increasing the gantry dimension. We propose to eliminate the spacer but vary the focus-to-tumor distances (FTD) to achieve desired field size and MLC resolution. This requires optimization in an enormous solution space, a capacity uniquely demonstrated by the 4p algorithm. Volumetric imaging has been an indispensable component of modern radiotherapy but unfortunately missing from existing robotic systems. The proposed new linac will be able to deliver kV imaging beams from the same 2 MV linac, which in combination with gantry or couch mounted imagers will allow volumetric imaging for more precise tumor targeting. Aims: 1: Prototypical design of the accelerator to produce 2 MV X-rays 2: Design incorporated imaging system 3: Develop a conceptual design for the entire clinical system Impact: Success of the Phase I project would lead to the design of the first 2 MV linear accelerator capable of producing a competitively high dose rate of >800 cGy/min at 100 cm and kV imaging beams for image guided radiotherapy. This paves the technical path to a new robotic radiotherapy system delivering radiation plans with dose conformality surpassing existing X-ray platforms. More importantly, the significantly increased field size, throughput and the volumetric imaging capacity would allow the new robotic system to compete for a much larger market, including that for conventional linacs, than the niche market CyberKnife currently commands.