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

Background It has been demonstrated that grating interferometers can be utilized to enhance the X-ray imaging contrast of low-density and weakly absorbing objects. Objective In 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. Methods This 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. Results The 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mn>5.00</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> diameter polystyrene microsphere demonstrated the splitting phenomenon ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mn>8.54</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> on the sample plane) of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mo>±</mml:mo> <mml:msup> <mml:mn>1</mml:mn> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">st</mml:mi> </mml:mrow> </mml:mrow> </mml:msup> </mml:math> 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. Conclusions This 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.