Proton imaging is a promising technology for proton radiotherapy as it can be used for: (1) direct sampling of the tissue stopping power, (2) input information for multi-modality RSP reconstruction, (3) gold-standard calibration against concurrent techniques, (4) tracking motion and (5) pre-treatment positioning. However, no end-to-end characterization of the image quality (signal-to-noise ratio and spatial resolution, blurring uncertainty) against the dose has been done. This work aims to establish a model relating these characteristics and to describe their relationship with proton energy and object size. The imaging noise originates from two processes: the Coulomb scattering with the nucleus, producing a path deviation, and the energy loss straggling with electrons. The noise is found to increases with thickness crossed and, independently, decreases with decreasing energy. The scattering noise is dominant around high-gradient edge whereas the straggling noise is maximal in homogeneous regions. Image quality metrics are found to behave oppositely against energy: lower energy minimizes both the noise and the spatial resolution, with the optimal energy choice depending on the application and location in the imaged object. In conclusion, the model presented will help define an optimal usage of proton imaging to reach the promised application of this technology and establish a fair comparison with other imaging techniques.

中文翻译：

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质子成像的统计局限性。


质子成像是质子放射治疗的一项有前景的技术，因为它可用于：(1) 组织停止能力的直接采样，(2) 用于多模态 RSP 重建的输入信息，(3) 针对并发技术的金标准校准， (4) 跟踪运动和 (5) 治疗前定位。然而，尚未针对剂量进行图像质量（信噪比和空间分辨率、模糊不确定性）的端到端表征。这项工作旨在建立一个与这些特征相关的模型，并描述它们与质子能量和物体尺寸的关系。成像噪声源自两个过程：原子核的库仑散射，产生路径偏差，以及电子散乱的能量损失。发现噪声随着厚度的交叉而增加，并且独立地随着能量的减少而减少。散射噪声在高梯度边缘周围占主导地位，而散乱噪声在均匀区域中最大。研究发现图像质量指标与能量相反：较低的能量可以最大限度地减少噪声和空间分辨率，最佳能量选择取决于成像对象中的应用和位置。总之，所提出的模型将有助于定义质子成像的最佳使用，以实现该技术的预期应用，并与其他成像技术进行公平的比较。