arXiv subjects

Carlos Navarrete-León

Publications and source records attributed to Carlos Navarrete-León.

3 recordsLinked to original sources

arXiv2026

Spatial resolution of X-ray beam-tracking microscopy

X-ray beam-tracking is a phase-contrast imaging technique capable of simultaneously retrieving transmission, phase, and dark-field images. Although the spatial resolution in beam-tracking is largely considered to be 'aperture driven', no model yet exists to describe this in full. The dark-field channel is of particular interest, due to previous observations of anomalously high sharpness compared to transmission and phase channels. We derive a full optical transfer function model for each contrast channel using the Fokker-Planck equation for near-field imaging. Experimental validation using both synchrotron-based and laboratory-based setups, with 15 um circular and 10 um rectangular apertures, reveals a limiting resolution of at least 3 um, much smaller than the apertures themselves. Together, the model and the supporting experiments offer a full description of spatial resolution in beam-tracking, and formally confirm the greater spatial resolution in the dark-field channel. These findings open new possibilities in system design and experimental protocols to exploit these capabilities.

physics.optics↗

arXiv2025

Offset geometry for extended field-of-view in multi-contrast and multi-scale X-ray microtomography of lung cancer lobectomy specimens

X-ray microtomography is a powerful non-destructive technique allowing 3D virtual histology of resected human tissue. The achievable imaging field-of-view, is however limited by the fixed number of detector elements, enforcing the requirement to sacrifice spatial resolution in order to image larger samples. In applications such as soft-tissue imaging, phase-contrast methods are often employed to enhance image contrast. Some of these methods, especially those suited to laboratory sources, rely on optical elements, the dimensions of which can impose a further limitation on the field-of-view. We describe an efficient method to double the maximum field-of-view of a cone-beam X-ray microtomography system, without sacrificing on spatial resolution, and including multi-contrast capabilities. We demonstrate an experimental realisation of the method, achieving exemplary reconstructions of a resected human lung sample, with a cubic voxel of 10.5 $μ$m linear dimensions, across a horizontal field-of-view of 4.3 cm. The same concepts are applied to free-space propagation imaging of a 2.7 mm segment of the same sample, achieving a cubic voxel of 450 nm linear dimensions. We show that the methodology can be applied at a range of different length-scales and geometries, and that it is directly compatible with complementary implementations of X-ray phase-contrast imaging.

physics.med-ph↗

arXiv2023

Direct x-ray scattering signal measurements in edge-illumination/beam-tracking imaging and their interplay with the variance of the refraction signals

X-ray dark-field or ultra-small angle scatter imaging has become increasingly important since the introduction of phase-based x-ray imaging and is having transformative impact in fields such as in vivo lung imaging and explosives detection. Here we show that dark-field images acquired with the edge-illumination method (either in its traditional double mask or simplified single mask implementation) provide a direct measurement of the scattering function, which is unaffected by system-specific parameters such as the autocorrelation length. We show that this is a consequence both of the specific measurement setup and of the mathematical approach followed to retrieve the dark-field images. We show agreement with theoretical models for datasets acquired both with synchrotron and laboratory x-ray sources. We also introduce a new contrast mechanism, the variance of refraction, which is extracted from the same dataset and provides a direct link with the size of the scattering centres. We show that this can also be described by the same theoretical models. We study the behaviour of both signals vs. key parameters such as x-ray energy and scatterer radius. We find this allows quantitative, direct, multi-scale scattering measurements during imaging, with implications in all fields where dark-field imaging is used.

physics.optics↗