Speaker: Alessandro Olivo 

(Dept. of Medical Physics & Biomedical Engineering, University College London) 

X-Ray imaging is 130 years old. However, despite significant innovation in detector development and CT scanners, the underpinning physical principle has not changed since Röntgen’s discovery: features are detected based on their x-ray attenuation difference against the background they’re immersed in. This is the key limitation of x-ray imaging and e.g. the reason why it is considered to have “limited soft tissue sensitivity”, an area where MRI is used instead. The same limitation affects many other application areas, in a sense defining where x-rays can and cannot be used.

However, all x-rays undergo very tiny (microradian) deviations upon traversing a sample, the only exception being those extremely rare samples that are completely homogeneous on the microscopic scale. Conventional x-ray imaging systems are insensitive to this phenomenon: x-rays that have deviated by a few microradians are simply considered “primaries”, i.e. x-rays that have not interacted with the sample. Instead, if properly analysed, these “micro-deviated” x-rays can reveal a lot of information on the sample they have traversed. This allows the detection of features classically considered “x-ray invisible”, redefining x-rays’ areas of applicability.

In this seminar, I will discuss how lab systems can be built that are sensitive to these microscopic deviations and present a series of applications in medicine, security, biology and materials science.