Kristian Romlund Rix

A thesis for the degree of Doctor of Philosophy defended June 2019.

The PhD School of Science, Faculty of Science,  X-Ray and Neutron Science, Niels Bohr Institute, University of Copenhagen

Supervisors:
Prof. Robert Feidenhans’l
Prof. Brian Vinter
Assoc. Prof. Martin Bech

Applications of New X-ray Imaging Modalities in Food- and Medical Science

The general population will most likely recognize x-ray imaging as the radiographic images taken in hospitals to determine bone fractures. Fewer would know that a CT-scanner uses x-rays to make the tomography images, while only a fraction would associate phase contrast imaging with x-rays or anything meaningful. This is for good reason as only a few decades ago x-ray imaging was mainly used as a hospital diagnostic tool or applied by a few research groups at universities. This is no longer the case and the development within x-ray imaging has been considerable over the last two decades. Advanced micro tomographic scanners are increasingly industrialized which is also the case for Talbot interferometer three image modality systems. Today, this means that the use of x-ray imaging is widely spread within many research areas as well as industrial. The important knowledge that x-ray imaging provides also means that many industries is now paying for beam times at large scale synchrotron facilities.

This thesis starts with a brief introduction to x-ray imaging and the methods considered in this work. Here I will in short terms discuss the nature of x-rays, purely on a phenomenological level and explain were x-rays fit in, in the full electromagnetic spectrum. I will introduced the mechanisms which are exploited in x-ray imaging and from there introduced the techniques used in this work. This thesis contains three theory chapters. Chapter 2 contain some short introductions to the three main types of x-ray sources. These are the x-ray tube, the synchrotron and the newly developed free electron laser. Chapter 3 contains a thorough explanation of the important radiation matter interaction mechanisms where essential expressions are derived. This chapter also serves as a conceptual comparison between the optical light- and x-ray regimes of the electromagnetic spectrum.

As the chapter progresses I will try to highlight the derived concepts which are of interest, from an imaging point of view, and relate it to a specific technique. Chapter 6 is more general and touches on more topics compared to chapter 3. Due to this, most topics are only superficially discussed and many concepts will be stated with reference instead of a full derivation. Concepts and topics that are used in the publication are the main focus in this chapter. The subjects discussed is x-ray wave propagation, ifferent image formation and -enhancement techniques.