Two-dimensional single grating phase contrast system

Jingzhu Xu, Louisiana State University
Joyoni Dey, Louisiana State University
Kyungmin Ham, Louisiana State University
Narayan Bhusal, Louisiana State University
Leslie G. Butler, Louisiana State University


Phase contrast X-ray not only provides attenuation of tissue, but two other modalities (phase and scatter) in same scan. Scatter (dark-field) images provided by the technology are far more sensitive to structural and density changes of tissue such as lungs and can identify lung disease where conventional X-ray fails. Other areas poised to benefit greatly are mammography and bone joint imaging (eg. imaging arthritis). Of the various interferometer techniques, the two at the forefront are: Far-field Interferometry (FFI) (Miao et al, Nat. Phy. 2015) and Talbot-Lau interferometry (TLI) (Momose JJAP 2005, Pfeiffer Nature 2006). While the TLI has already made clinical strides, the newer FFI has advantage of not requiring an absorption grating ("analyzer") and provides few-fold higher scatter sensitivity. In this work, a novel 2D single phase-grating (not requiring the analyzer), near-field phase contrast system was simulated using Sommerfeld- Rayleigh diffraction integrals. We observed 2D fringe patterns (pitch 800nm) at 50mm distance from the grating. Such a pattern period of 0.05mm, can be imaged by the LSU-interferometers with CT detector resolution (0.015mm) or Philips mammography detector resolution (0.05mm) making this practical system. Our design has a few advantages over Miao et al FFI system. We accomplish in one X-ray grating the functionality that requires 2-3 phase-grating in their design. And our design can also provide a compact system (source to detector distance < 1m) with control over the fringe pattern by fine tuning grating structure. We retain all the benefits of far-field systems - of not requiring analyzer and high scatter sensitivity over Talbot-Lau interferometers.