Quantitative phase nano-imaging with a laboratory source

TL;DR

This work demonstrates quantitative X-ray Far-Field Ptychography (X-FFP) in a compact laboratory setting using a liquid-metal-jet source, achieving nanoscale spatial resolution around $300\ \,nm$ with quantitative phase maps at $9.25$ keV. The authors establish a stable, pinhole-based illumination platform, validate quantitative phase reconstruction with a Siemens star, and image a brain-tissue phantom to illustrate biomedical relevance. Key contributions include establishing lab-based quantitative phase imaging capabilities, detailed stability characterization, and a discussion of practical improvements (multi-beam or single-shot ptychography, higher flux sources) to enable faster acquisition and 3D imaging. This work paves the way for broad adoption of high-resolution, quantitative X-ray phase imaging at laboratory facilities, expanding access beyond large-scale synchrotrons.

Abstract

Investigating the structure of matter at the nanoscale non destructively is a key capability enabled by X-ray imaging. One of the most powerful nano-imaging methods is X-ray ptychography, a coherent diffraction imaging technique that has become the go-to method at synchrotron facilities for applications ranging from brain imaging to battery materials. However, the requirements in terms of X-ray beam quality have limited its use to large synchrotron facilities and, to date, only one attempt has been made to translate the technique to a small-scale laboratory. To unleash the power of this technique to the broad user community of laboratory X-ray sources, there are outstanding questions to answer including whether the quantitativeness of the information is preserved in a laboratory despite the drastic decrease in X-ray flux of several orders of magnitude, with respect to synchrotron instruments. In this study not only we demonstrate that the quantitativeness of X-ray ptychography is preserved in a laboratory setting, but we also apply the method to the imaging of a brain tissue phantom. Finally, we describe the current challenges and limitations, and we set the basis for further development and future directions of quantitative nano-imaging with laboratory X-ray sources.

Figures (5)

• Figure 1: X-FFP setup. The radiation is produced by high-brilliance microfocus LMJ source. A coherent beamlet is isolated by a pinhole and used to scan the sample. Diffraction patterns are detected in the far-field.
• Figure 2: Stability of the X-ray source over just less than four days. Horizontal (a) and vertical (b) pointing stability and associated standard deviations, measured from the time evolution of the centroid of the beam. (c) Scatter plot of the measured beam centroids, with respect to the centroid of the median beam, as recorded by the detector. (d) Integrated beam intensity, as a function of time, normalized by the median and associated standard deviation.
• Figure 3: Linearity of the Andor Ikon M-SY CCD detector. See the Characterization section in the Methods for details on the protocol used.
• Figure 4: Quantitative phase reconstruction of a Siemens star test sample. (a) Phase image reconstructed by 20000 iterations of the extended ptychographic engine algorithm (ePIE) Maiden_2009, The scale bar corresponds to 5. (b) average phase shift of the star (Au) compared to the surrounding protective polymer. It was calculated as the relative phase of ten couples of ROIs. The mean value, with uncertainty band is shown in blue and compared to the expected value. (c) azimuthal profile of the phase corresponding to the red line in (a). The radial distance $\rho$, as well as the minimum spoke width (res, i.e. resolved feature), is reported.
• Figure 5: Ptychographic scan of a polymer used as brain phantom for diffusion magnetic resonance imaging. (a) High resolution scan acquired at the Diamond Light Source, adapted from Erin_2025. (b) Detail from (a). (c) Lower resolution scan acquired with the laboratory-based ptychography setup. (b) and (c) have the same spatial extent but do not correspond to the same region. The scale bar corresponds to 5 in all images.