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Research
We are a multi-PI collaboration aiming to develop novel X-ray image formation techniques and to deploy them with the very latest developments in source and detector technology.
One of our key interests is x-ray phase contrast imaging (XPCI) 鈥� a revolutionary approach where variations in x-ray phase are exploited to generate image contrast, rather than attenuation, as has been the convention since x-ray imaging was first developed. XPCI has been shown to significantly enhance the visibility of all details in an x-ray image, and to enable the detection of features classically considered x-ray invisible 鈥� with applications in a variety of areas, from earlier detection of life-threatening diseases in medicine to improved detection of threat objects in security scans and of minute defects/blemishes in industrial inspections. Scientific applications are also wide ranging, spanning medicine, biology, energy, materials science, archeology, cultural heritage preservation and others.
As well as XPCI our research covers topics such as x-ray microscopy, novel x-ray detectors, new x-ray source technologies, methods for fast CT and micro-CT, resolution enhancement, dark-field and ultra-small angle scattering, dual and multiple-energy imaging and the development of theoretical models which underpin these techniques.
Key Advances
- XPCI with conventional, incoherent laboratory sources
Most XPCI methods are limited to very specialized facilities called synchrotrons, of which there are approximately only 50 in the world. This is because such methods require a source of high spatial coherence (i.e., all of the x-rays originate from a very small spot) in order to work. The only alternatives to synchrotron radiation are microfocal sources, or collimated conventional sources to artificially increase the source coherence 鈥� both of which limit the available x-ray flux leading to unfeasibly long exposure times. The AXIm group has developed a method that employs uncollimated conventional sources, i.e. x-ray tubes like those found widely in clinics throughout the world,听飞颈迟丑辞耻迟听filtering the x-ray beam in any way. This means that the full flux generated by the source is used in image formation, thus allowing clinically compatible image acquisition times.听
. More information can be found in the following links from听听补苍诲听. A summary of our tech-transfer activities was recently provided in an .听- Staging tumours with x-rays
Use of edge-illumination (EI) X-Ray Phase Contrast imaging (XPCI) CT on oesophageal specimens resected in oesophagectomy operations revealed muscle layers with exquisite definition. (T) staging of oesophageal tumours is based on the determination of how many layers the tumour has penetrated into: the ability to visualize the layers very clearly allowed doing this based on the x-ray images alone. Obtaining precise tumour staging already during surgery would prompt additional intervention if and where possible, provide a more precise prognosis and allow treatment planning and patient management already at that stage ().
T2 cancer example, with XPCI CT slide with lesion segmented by the radiologists (a) presented side-by-side with its histopathology counterpart (b), where two points where the tumor is invading into the muscle layers have been highlighted with red arrows by the pathologist.
- Femtosecond multimodal imaging听
Laser-driven x-ray sources can provide incredibly short x-ray pulses. This experiment combined their use with a single-mask implementation of our edge-illumination technology (鈥渂eam tracking鈥�, see 鈥淧revious Advances鈥�), which enables the simultaneous retrieval of attenuation, phase and dark-field images from a single frame. As a result, all three images were obtained from a single shot of 22 fs duration, which open new possibilities for e.g. pump-probe experiments. 听()
Multi-modal images (from left to right: attenuation, refraction, dark-field) of cell following electrochemical deposition, with the lithium stratification on the Li side most clearly visible in the dark-field image.听
- Direct measurement of scattering signals听
鈥淒ark-field鈥� (or Ultra-small angle scattering) measurements with the edge-illumination (EI) method are connected to the general theory of x-ray scattering, showing EI allows absolute measurement of the scattering signals with no influence from the characteristics of the imaging system (e.g. auto-correlation length). An additional contrast channel is also introduced 鈥� the variance of refraction 鈥� that plays an analogous role as dark field for sample features larger than the system鈥檚 spatial resolution ().
Modelling of the scattering distribution from an ensemble of microspheres, when multiple scattering is and is not negligible (left and right hand panels, respectively). The article shows how this model is compatible both with the classic theory of x-ray scattering and with the experimental measurements performed with EI
