Volumetric High-Resolution X-Ray Phase-Contrast Virtual Histology of Breast Specimens With a Compact Laboratory System

Abstract

The assessment of margin involvement is a fundamental task in breast conserving surgery to prevent recurrences and reoperations. It is usually performed through histology, which makes the process time consuming and can prevent the complete volumetric analysis of large specimens. X-ray phase contrast tomography combines high resolution, sufficient penetration depth and high soft tissue contrast, and can therefore provide a potential solution to this problem. In this work, we used a highresolution implementation of the edge illumination X-ray phase contrast tomography based on "pixel-skipping" Xray masks and sample dithering, to provide high definition virtual slices of breast specimens. The scanner was originally designed for intra-operative applications in which short scanning times were prioritised over spatial resolution; however, thanks to the versatility of edge illumination, high-resolution capabilities can be obtained with the same system simply by swapping x-ray masks without this imposing a reduction in the available field of view. This This work is funded by the Wellcome Trust (grant 200137/Z/15/Z) and by EPSRC (grant EP/T005408/1). Alessandro Olivo is funded by the Royal Academy of Engineering under their "Chairs in Emerging Technologies" scheme. Charlotte K. Hagen and Marco Endrizzi are funded by the Royal Academy of Engineering under their "Research Fellowships" scheme. Peter R. T. Munro is funded by the Royal Society under their "University Research Fellowships" scheme. The authors wish to acknowledge the roles of the Breast Cancer Now Tissue Bank in collecting and making available the samples, and the patients who have generously donated their tissues which have been utilised in the generation of this publication.

Replacing the detector mask with a structured scintillator in edge-illumination x-ray phase contrast imaging

“…Two different EI setups have been used, a conventional one featuring two masks and a flat panel detector as used in previous work, and a single (sample) mask one using the CCD camera with the structured scintillator 18 . Both are "compact" setups which follow the design recently implemented for intra-operative specimen imaging 19,20 , resulting from the previous demonstration that reducing the system length at constant magnification does not negatively affect the (phase) signal-to-noise ratio if the exposure time is kept constant 21 . Schemes of these systems are shown in Fig.…”

“…different positions on the IC) 23 . The conventional setup used in this work employed a Rigaku 007 rotating anode Molybdenum source featuring a focal spot size of 70 µm and operated at 40 kVp, 30 mA, located at about 85 cm from the detector 19,20 . The molybdenum anode provides a relative narrow energy bandwidth due to the dominance of the main emission lines at 17.5 and 19.6 keV.…”

“…This mask design is usually referred to as a "skipped" configuration, since one every other pixel column is not illuminated. This greatly reduces the cross-talk between pixels, improving the intrinsic spatial resolution of the detector 20,24 . However, multiple images acquired while shifting the sample in sub-period steps (referred to as dithering steps) have to be acquired and digitally recombined to access such an improved level of resolution, which is ultimately limited by the aperture size 25 .…”

Augmenting a conventional x-ray scanner with edge illumination-based phase contrast imaging: how to design the gratings

“…3 As such, the applications of EI include non-destructive testing, 4 security 5 and (bio)medical imaging. 6 Rather than installing a dedicated XPCI system, our goal is to enable XPCI in a custom-built TESCAN UniTOM XL system (FleXCT) at the University of Antwerp, 7 a novel and highly flexible scanning system consisting of ten motorized axes, allowing a wide range of non-standard scans such as tiled and off-center scans, conveyor belt, laminography, dynamic zooming, and helical tomography. To this end, two gratings have to be incorporated in the existing system, enabling XPCI through the EI technique.…”

Joint reconstruction of attenuation, refraction and dark field x-ray phase contrasts using split Barzilai-Borwein steps

“…1 These signals have been shown to generate a higher contrast in soft tissue compared to attenuation contrast and allow to visualize sub-voxel structures in, for example, composite materials. 2 Applications for XPCI have broadened from biomedical studies [3][4][5][6] to non-destructive testing, 7 materials science 8,9 and security. 10,11 Edge illumination (EI) is an emerging XPCI technique, well-suited for use with lab-based X-ray sources with a large focal spot and polychromatic spectrum.…”