Optimization of region-of-interest imaging with penetrating radiation

具有穿透辐射的成像是现代社会的共同特征。X射线成像的医疗和安全用途是众所周知的，而工业射线照相广泛用于金属部件和焊缝的检查。此外，计算机断层扫描（CT）现在是医疗诊断中的一种可行工具，并在一些机场用作爆炸物检测装置。这种技术依赖于对暴露于辐射（X射线、伽马射线或中子）的对象的整个部分（在CT的情况下为横截面）进行成像。 这样的“整体”成像过程虽然有用，但以在可能特别感兴趣的一些位置处降低更精细细节的定义为代价。试图增强图像清晰度需要在整个图像中的任何地方增加图像分辨率;这反过来又需要增加辐射曝光，并且通常伴随着更高水平的噪声和波动。因此，需要一种“感兴趣区域”成像过程，其可以“聚焦”在对象的特定部分上，以在空间分辨率和/或材料对比度方面获得更精细的细节。这样的成像过程也可以用作整体成像的后续，以提供例如高应力区域、乘客行李中的可疑材料或身体中的肿瘤处的更精细的细节。拟议的工作的目的是优化成像系统，以提高图像质量在某些地区的利益，在一个实用和灵活的方式，使现场应用与常用的设备。据作者所知，还没有系统的方法来实现最佳的感兴趣区域成像。将对已开发的安排进行实验验证。这项工作将涉及辐射输运计算，数学优化，逆问题的解决方案，成像系统的设计和成像概念的实验验证。这些技能对于培养非破坏性检查和成像系统工程方面的高素质人员非常有益。

Imaging with penetrating radiation is a common feature of modern day society. Medical and security uses of x-ray imaging are well known, while industrial radiography is widely employed for inspection of metal parts and welds. Moreover, computed tomography (CT) is nowadays a viable tool in medical diagnostics, and is used at some airports as an explosive detection device. Such techniques rely on imaging the entire portion (a cross section in the case of CT) of the object exposed to radiation (x-ray, gamma-rays, or neutrons).  Such an "overall" imaging process though useful, comes at the expense of reduced definition of finer details at some locations that may be of particular interest. Attempting to enhance image definition requires increasing the image resolution everywhere in the overall image; which necessitates in turn increased radiation exposure, and is typically accompanied by a higher level of noise and fluctuations. There is therefore a need for a "region-of-interest" imaging process that can "focus" on a particular portion of an object to obtain finer details in terms of spatial resolution and/or material contrast. Such imaging process can also be utilized as a follow-up to overall imaging to provide finer details at, for example, an area of high stress, a suspect material in a passenger luggage, or a tumor in a body. The objective of the proposed work is to optimize imaging systems to enhance image quality at certain regions of interest, in a practical and flexible manner that enables field application with commonly available equipment. To the author's knowledge, no systematic approach has been undertaken to achieve best region-of-interest imaging. Experimental validation of developed arrangements will be performed. This work will involve radiation transport calculations, mathematical optimization, inverse problem solution, imaging system design and experimental validation of imaging concepts. Such skills are quite beneficial for the training of highly qualified personnel in the engineering of non-destructive examination and imaging systems.