Charlotte Hagen

Prof Charlotte Hagen graduated with a Diploma in Mathematics from the University of Hamburg (Germany) in 2010 and subsequently with a PhD in Medical Physics from UCL in 2014. During her PhD research, Charlotte co-developed one of the first x-ray phase contrast micro computed tomography (micro-CT) scanners operating with laboratory x-ray sources. Her subsequent postdoc years (2014-2018), which she also spent at UCL, were focused on advancing the technology and its applications. In 2018, Charlotte was awarded a Research Fellowship by the Royal Academy of Engineering and, in the same year, was offered a proleptic Lectureship in Radiation Physics in the UCL Department of Medical Physics and Biomedical Engineering, marking the beginning of her independent research. Charlotte’s work is overarchingly focused on the development of new imaging methods and systems with an emphasis on x-ray micro-CT. She has been teaching a module on medical imaging with ionising radiation since 2020, both at undergraduate and postgraduate level.

Abstract:
Intra-operative imaging with phase-based micro-CT: status, challenges, and how novel detectors may solve them

Phase contrast techniques have transformed x-ray micro-CT, making the technology suitable to the intra-operative imaging of excised tissues. Promising results in this domain were achieved with phase-based micro-CT systems that operate with amplitude-modulated beams. These systems create arrays of spatially distinct beamlets, which enables both x-ray phase contrast imaging and fine-tuned control over spatial resolution. The phase contrast offers enhanced visualization of soft tissues, while adjustable spatial resolution allows imaging at levels exceeding traditional limits set by x-ray source and detector characteristics. This presentation will review the latest results achieved with such systems. It will focus on the advantages they bring to intra-operative imaging, but also highlight a challenges, such as long scan times for high-resolution scans, which are a direct consequence of using opaque modulators in these systems. It will focus specifically on the role of the detector, highlighting how its properties (specifically its point spread function (PSF)) are intricately linked with the modulator design, and therefore have an impact on scan time. Novel detectors, especially photon counters which offer a PSF confined to a single pixel, bear huge potential in this regard, and their usage could lead to notable scan time reductions. The presentation will conclude with a brief introduction to ongoing work in our labs that explores the specific opportunities provided by photon counting detectors. Among these is self-supervised, machine learning based denoising of the acquired images, potentially permitting the use of shorter exposures and thereby accelerating scans. This is expected to benefit all applications of the phase-based micro-CT but intra-operative imaging in particular, as scans need to be completed within tight clinical timeframes.