Kurichiyanil Neeraj, Pinto Marco, Parodi Katia
Department for Medical Physics, Ludwig-Maximilians-Universität München, Am Coulombwall 1, 85748 Garching, Germany.
Phys Med Biol. 2025 Jul 10;70(14). doi: 10.1088/1361-6560/adea08.
Preclinical small animal proton beam irradiation systems are increasingly in demand. However, the absence of dedicated systems comparable in precision to those in clinical settings presents a considerable hurdle to investigations in this field. To address this need, the SIRMIO project has developed a novel compact beam transport system configured to degrade and focus clinical proton beams. The beamline, about 1 m long, housed in an environment to minimize scatter, includes degraders, collimators, and a permanent magnet quadrupole triplet to focus protons degraded from clinical energies. It is tailored to transport focused proton beams within the energy range of 20 to 50 MeV, ideal for small animal preclinical studies. The flexibility of this beamline design allows achieving beam-spot sizes of 1 mm sigma at the isocenter for all focused energies, with the particle fluence and spot sizes being variable through dynamic adjustment of the collimator and magnetic lattice. 3D scanning of the target volume is possible due to lateral beam scanning integrated into this design, without the use of additional scanning dipole magnets.The beamline was optimized using an accelerator beam optics code, followed by a Monte Carlo (MC) model to account for beam-matter interactions. Using an experimentally validated clinical proton beam phase space as input, degraded beams are transported through the MC model. Outcomes are assessed for beam characteristics and dosimetric properties.Beams transported by our proposed beamline design are shown to result in dosimetric properties suitable for preclinical studies, while also emulating realistic clinically relevant beam delivery scenarios like pencil beam scanning. Compared to a similar-sized collimator-only beamline, this design enhances transmission and reduces secondary dose at the target due to absence of scattering elements nearby.The portable SIRMIO beamline offers a flexible, precise alternative to passive methods for adapting clinical proton beams for small animal irradiation, enhancing preclinical research with clinically relevant beam delivery and enabling experiments in conditions more closely matching clinical practice.
临床前小动物质子束辐照系统的需求日益增加。然而，缺乏在精度上可与临床环境中的系统相媲美的专用系统，给该领域的研究带来了相当大的障碍。为满足这一需求，SIRMIO项目开发了一种新型紧凑型束流传输系统，该系统可对临床质子束进行能量降解和聚焦。这条约1米长的束流线安置在一个能将散射降至最低的环境中，包括能量降解器、准直器和一个用于聚焦从临床能量降解后的质子的永磁四极三联体。它经过专门设计，可传输能量范围在20至50兆电子伏之间的聚焦质子束，这对于小动物临床前研究来说是理想的。这种束流线设计的灵活性使得在等中心处，对于所有聚焦能量都能实现1毫米标准差的束斑尺寸，通过动态调整准直器和磁晶格，粒子注量和束斑尺寸可以变化。由于该设计集成了横向束流扫描功能，无需使用额外的扫描偶极磁体，因此可以对目标体积进行三维扫描。使用加速器束流光学代码对束流线进行了优化，随后使用蒙特卡罗（MC）模型来考虑束流与物质的相互作用。以经过实验验证的临床质子束相空间作为输入，将降解后的束流通过MC模型进行传输。对束流特性和剂量学特性进行结果评估。我们提出的束流线设计所传输的束流显示出具有适合临床前研究的剂量学特性，同时还能模拟如笔形束扫描等现实的临床相关束流输送场景。与类似尺寸的仅含准直器的束流线相比，这种设计提高了传输率，并由于附近没有散射元件而降低了目标处的二次剂量。便携式SIRMIO束流线为将临床质子束适配用于小动物辐照的被动方法提供了一种灵活、精确的替代方案，通过临床相关的束流输送增强了临床前研究，并能够在更接近临床实践的条件下进行实验。
