Grating based laboratory 5.41 keV X-ray phase contrast microscopy with zone-plate: design, instrumentation and validation.

BackgroundIt has been demonstrated that grating interferometers can be utilized to enhance the X-ray imaging contrast of low-density and weakly absorbing objects.ObjectiveIn this study, the design, instrumentation and validation of a grating based laboratory 5.41 keV X-ray phase-contrast microscope with zone-plate are reported.MethodsThis dedicated microscope was carefully designed by coupling the zone-plate imaging method and the grating interferometer imaging method. Specially fabricated X-ray optics were integrated along with a certain X-ray tube source illumination module, motion stages and X-ray detection module. The system's spatial resolution was characterized with the modulation transfer function (MTF) analysis and the power spectral density (PSD) analysis. The absorption-contrast and phase-contrast images were extracted from the acquired phase stepping dataset. The splitting and superposition behavior of the phase-contrast signal was evaluated by comparing the experimental results with the numerical simulation. CT projections of a mitochondria-targeted, antibody-stained Jurkat T cell were pre-processed by geometric registration before performing the standard filtered back-projection (FBP) reconstruction.ResultsThe absorption imaging results of the Siemens star phantom demonstrated that this microscope achieved a spatial resolution of 35.0 nm based on MTF analysis, while the minimum detectable structure size was 28.5 nm based on PSD analysis. The phase-contrast imaging of a 5.00μm diameter polystyrene microsphere demonstrated the splitting phenomenon (8.54μm on the sample plane) of the ±1st order components, and both the splitting distance and line profiles agreed well with the theoretical imaging model. In the reconstructed phase-contrast CT images, the mitochondria could be clearly identified.ConclusionsThis study reported the development of a grating based laboratory 5.41 keV X-ray phase-contrast microscope with zone-plate. Results showed that it could significantly enhance the imaging performance of low-density objects such as polystyrene microsphere and biological cells.