Master's Thesis : Tomosynthesis Imaging: Principles, Simulations and Practical Performance

Abstract

Among the wide range of possible nondestructive testing (NDT) methods in the industry, today X-ray imaging technologies are a powerful solution. With the recent advances in technology, it has indeed become possible to acquire digital images of X-ray projections very efficiently. Such fast, two-dimensional visualization of inner structures of opaque objects naturally led to the problem of reconstructing entirely any object based on their X-ray projections. This problem is known as Computed Tomography (CT). In some cases a full reconstruction of the object is wanted but practically infeasible, either because of time restrictions or simply because projections can not be acquired all around the object. Examples include the 3D inspection of an airplane wing or the demining operation of an unidentified object. In such scenarios, tomosynthesis can be a useful alternative. This thesis aims at providing theoretical, numerical and practical insights about tomosynthesis imaging as a new X-RIS solution for NDT. To this end, the work is divided in three main parts. The first part focuses on building a theoretical background about X-ray physics and the reconstruction problem is addressed. The second part contains a simulation study of the tomosynthesis prototype built by X-RIS, which allows to understand the artefacts caused by the reconstruction algorithms regardless of practical complications. Finally, the last part provides examples of real reconstructions and discusses the practical feasibility of tomosynthesis for quasi real-time (less than 30 seconds) inspection of industrial parts. The results of the numerical and practical experiments carried out in this work show that despite the presence of heavy artefacts in the reconstructions, the X-RIS tomosynthesis prototype is able to retrieve accurate depth information about inner structures of objects --- and in a decent amount of time.