PROCEEDINGS ARTICLE | March 19, 2014
Proc. SPIE. 9033, Medical Imaging 2014: Physics of Medical Imaging
KEYWORDS: Sensors, X-rays, Phase contrast, X-ray imaging, Scattering, X-ray sources, Photons, Breast, Phase measurement, Detection and tracking algorithms
We present a development of the laboratory-based implementation of edge-illumination (EI) x-ray phase contrast
imaging (XPCI) that simultaneously enables low-dose and high sensitivity. Lab-based EI-XPCI simplifies the set-up
with respect to other methods, as it only requires two optical elements, the large pitch of which relaxes the alignment
requirements. Albeit in the past it was erroneously assumed that this would reduce the sensitivity, we demonstrate
quantitatively that this is not the case.
We discuss a system where the pre-sample mask open fraction is smaller than 50%, and a large fraction of the created
beamlets hits the apertures in the detector mask. This ensures that the majority of photons traversing the sample are
detected i.e. used for image formation, optimizing dose delivery. We show that the sensitivity depends on the dimension
of the part of each beamlet hitting the detector apertures, optimized in the system design. We also show that the aperture
pitch does not influence the sensitivity. Compared to previous implementations, we only reduced the beamlet fraction
hitting the absorbing septa on the detector mask, not the one falling inside the apertures: the same number of x-rays per
second is thus detected, i.e. the dose is reduced, but not at the expense of exposure time.
We also present an extension of our phase-retrieval algorithm enabling the extraction of ultra-small-angle scattering by
means of only one additional frame, with all three frames acquired within dose limits imposed by e.g. clinical
mammography, and easy adaptation to lab-based phase-contrast x-ray microscopy implementations.
