Optimization of region-of-interest imaging with penetrating radiation

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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.