PC RAD · Towards a clinical implementation of phase contrast radiology

Final Activity Report Summary - PC RAD (Towards a clinical implementation of phase contrast radiology)

The project aimed at achieving some significant steps towards the clinical implementation of an innovative X-ray imaging technique, the so-called Phase contrast imaging (PCI). The first part of the project mostly focussed on modelling PCI with conventional X-ray sources, thus dealing with beam divergence and polychromaticity. A mathematical model based on the Fresnel / Kirchoff diffraction integrals was devised and a computer simulation was developed on this basis. This simulation accepted as inputs the source size, beam spectrum, detector resolution, source-to-sample and sample-to-detector distances and could thus be used to evaluate the PCI capabilities of any imaging system. Its reliability was experimentally demonstrated via the acquisition of images of different samples with different spectra, source size values, source-to-sample and sample-to-detector distances etc. and through the comparison of the experimental results to the corresponding simulation output. Optimal agreement was found in all cases. This work provided the extra result of demonstrating that, in most practical cases, polychromatic beams were capable of providing the same phase contrast image quality as their monochromatic counterpart. This was an important result, as any practical implementation of PCI would have to be based on the use of polychromatic beams to guarantee that a sufficient X-ray flux reached the detector. The second part of the project dealt with the development of a new technique capable of making PCI feasible with conventional X-ray sources and detectors. This was achieved through devising an innovative method based on the use of coded apertures. The concept was that two sets of coded apertures, one placed in contact with the detector and one placed upstream of the sample, allowed for the selection of those parts of the beam which fully contributed to the phase contrast signal, thus maximising it. The positive aspect of using coded apertures was that, unlike crystals, they could be used with polychromatic, diverging beams, therefore they allowed the beam provided by a conventional source to be exploited in full. Another advantage, particularly relevant in medical applications, was that the pre-sample set of coded-apertures prevented any unnecessary dose delivery. The new system was fully modelled and, on this basis, a simulation was written and successively verified through a proof-of-concept experiment. A prototype coded aperture system, covering a small fraction of the active area of a flat panel detector, was designed and fabricated. A range of images of different biological samples was then acquired using a near-standard mammography source, demonstrating that the technique also allowed for the acquisition of intense phase contrast signals in the cases in which conventional sources and detector were used. A United Kingdom patent application was filed to protect the IP and the future development would involve the realisation of a dedicated, full-scale imaging prototype. Alongside diagnostic radiology, applications in the field of security scans and non-destructive testing could be foreseen.

Data: CORDIS, © European Union