No abstract

X-ray dark-field imaging is used to visualise the ultra-small angle x-ray scattering signal that originates from sub-resolution density fluctuations within the sample microstructure. Dark-field tomography using the edgeillumination x-ray imaging system is presented as a tool for measuring this scattering signal in a sample in three dimensions. Its applicability to different fields is shown through example images of a multi-material phantom, a tissue-engineered oesophagus, a pouch cell battery and a short-fibre reinforced composite material. The multichannel contrast available in edge-illumination helps with material identification, with high contrast at boundaries enhancing dark-field reconstructions.

X-ray Phase-Contrast Computed Tomography (PC-CT) increases contrast in weakly attenuating samples, such as soft tissues. In Edge-Illumination (EI) PC-CT, phase effects are accessed from amplitude modulation of the x-ray beam using alternating transmitting and attenuating masks placed prior to the sample and detector. A large field of view PC-CT scanner using this technique was applied to two areas of cancer assessment, namely excised breast and esophageal tissue. For the breast tissue, Wide Local Excisions (WLEs) were studied intra-operatively using PC-CT for the evaluation of tumor removal in breast conservation surgery. Images were acquired in 10 minutes without compromising on image quality, showing this can be used in a clinical setting. Longer, higher resolution PC-CT images were also taken, with analysis showing previously undetected thinning of tumor strands. This would allow a second use of the system for "virtual histopathology", outside of surgery. For the esophagus samples, tissues were taken from esophagectomy surgery, where the lower part of the esophagus is removed, and the stomach relocated. For the assessment of ongoing therapy, accurate staging of tumors in the removed esophagus is essential, with the current gold standard provided by histopathology. PC-CT images were acquired on several samples and compare well with histopathology, with both modalities showing similar features. Examples are shown where staging of tumor penetration is possible with PC-CT images alone, which is hoped will be an important step in performing the imaging and staging intra-operatively.

The study of rigid body dynamics in soft tissue is an essential part of orthopaedic imaging. Our focus is the foot and ankle structure, which consists of 28 bones surrounded by a variety of soft tissue such as 30 muscles, numerous ligaments, bursae and nerves. The importance of understanding the involved dynamics is evident by the frequent need to find functional joint replacements to fight diseases such as hindfoot arthritis. We study a simplified problem by constructing a phantom with two "bones" submerged in silicone and a remotely controlled LEGO robot that moves one of the two bones.We perform motion registration by manipulating the bone segmented from an initial static scan and matching its digitally reconstructed radiographs to a sequence of scanned X-ray projections. The registration of the 3D volume to 2D projections requires the right combination of optimization and interpolation to achieve an optimal result. We test four different approaches with the help of the Flexible Algorithms for Image Registration (FAIR) toolbox.

Edge illumination is an X-ray phase contrast imaging technique that allows for the recovery of differential phase and dark-field (also known as scattering) contrast, in addition to conventional attenuation based contrast. These signals are retrieved by analysing the illumination profile of a series of beamlets across a detector. This can provide a wealth of information about the sample, especially biological tissues which produce little contrast using conventional attenuation radiography. To perform signal retrieval, Gaussian curves can be fit to the illumination profiles using a variety of methods. In this work, we compare the most prominent of these methods in terms of their contrast to noise ratio as well as computational times to investigate their effect on the retrieved projection data as well as the final reconstructions.