Development of an ultra-high dose rate rotational linac for FLASH Radiotherapy

摘要 放射治疗用于治疗60%的癌症患者和40%的治愈病例。然而，正常组织 尽管几十年来，放射治疗的毒性仍然使许多患者无法获得更有效的肿瘤控制 调强放射治疗和图像引导放射治疗的技术发展。超 高剂量率，也就是，FLASH放射治疗最近重新成为一种潜在的方法， 在物理剂量适形性的基础上提高辐射生物剂量适形性。虽然现有的X- 射线直线加速器和质子系统可以被修改以提供FLASH剂量率，它们受限于任一场尺寸， 深度穿透或剂量适形性，以用于治疗大多数人类肿瘤。概念系统，如 由于非常高的能量电子和相位器将需要克服重大和危险的技术障碍， 临床实践。在这个学术-工业伙伴关系项目中，我们建议开发一种高剂量率 X射线放射治疗系统是现有临床FLASH放射治疗技术的放大。有 实现X射线闪光剂量率的三大技术挑战。首先是直线加速器 能够产生如此高的剂量率。对于这项挑战，我们假设12 MV X射线 束>300戈伊/s的非准直剂量率可以使用已经证明的 加速器技术。第二个挑战是良好的X射线剂量测定的良好分离的光束角度。 第三个挑战是适形剂量分布的强度调制。紧密相关的第二和第三 挑战是由于普通C形臂台架的缓慢机械运动和MLC叶速度。到 克服这两个挑战，我们建议开发一个旋转环机架FLASH IMRT平台， 准静态MLC。快速旋转的环形机架系统将在一个非常短的时间内以弧形提供整个治疗。 短时间通过使用具有大量MLC的解耦MLC环来实现强度调制 每一排预成形用于旋转IMRT的孔径。该系统将能够实现高度 适形剂量分布可与最先进的VMAT相媲美，同时利用 FLASH放射生物学。我们提出以下目标：目标1。高剂量率直线加速器的研制;目标2。 旋转直接孔径优化与去耦（ROAD）MLC环的发展;目的3。 使用台式系统演示旋转FLASH。

Abstract Radiotherapy is used to treat 60% of the cancer patients and 40% of curative cases. However, normal tissue toxicities still prevent radiotherapy from achieving more effective tumor control in many patients despite decades of technological development in intensity-modulated radiation therapy and image-guided radiation therapy. Ultra- high dose rate, a.k.a., FLASH radiotherapy has recently re-emerged as a potential method to significantly improve the radiation biological dose conformality on top of the physical dose conformality. Although existing X- ray linac and proton systems can be modified to deliver the FLASH dose rate, they are limited in either field size, depth penetration, or dose conformality to be useful for treating most human tumors. Conceptual systems such as very high energy electron and PHASER will need to overcome significant and risky technological barriers to be clinically practical. In this Academic-Industrial Partnerships project, we propose to develop a high dose rate X-ray radiotherapy system that is a scale-up of existing technologies for clinical FLASH radiotherapy. There are three major technical challenges in achieving the FLASH dose rate with X-rays. The first is the linear accelerator that is capable to produce such a high dose rate. For this challenge, we hypothesize that a 12 MV X-ray beam >300 Gy/s uncollimated dose rate can be achieved using a combination of already-demonstrated accelerator technologies. The second challenge is the well-separated beam angles for good X-ray dosimetry. The third challenge is intensity modulation for conformal dose distribution. The tightly correlated second and third challenges are due to the slow mechanical movement of the common C-arm gantry and the MLC leaf speed. To overcome these two challenges, we propose to develop a rotational ring-gantry FLASH IMRT platform with many quasi-static MLCs. The fast-spinning ring-gantry system would deliver the entire treatment in an arc within a very short time. The intensity modulation is achieved by using a decoupled MLC ring with a large number of MLC banks each pre-shaping the aperture for rotational IMRT. The system would then be able to achieve highly conformal dose distribution comparable to state of the art VMAT, and at the same time take advantage of the FLASH radiobiology. We propose the following aims: Aim 1. High dose rate linac development; Aim 2. Development of ROtational direct Aperture optimization with a Decoupled (ROAD) MLC ring; Aim 3. Demonstration of rotational FLASH using a benchtop system.