Speaker
Description
X-ray microscopy offers a unique combination of penetration depth, non-destructive volumetric imaging, and high spatial resolution, enabling three-dimensional characterization of material structure and tissue morphology. Laboratory implementations of such systems have benefited from recent developments in nano-focus X-ray sources and high-resolution detectors, enabling sub-micron spatial resolution through high geometric magnification [1].
Here, we present a laboratory-based nano-tomography system combining a nanofocus transmission target source (Nanotune N2, Excillum) with a large-area, high-resolution direct conversion detector based on amorphous selenium (BrillianSe, KA Imaging). The system features focal spot sizes down to 0.3 µm and a 4096 × 4096 pixel detector with 8 µm pitch, enabling sub-micron spatial resolution over a comparatively large field of view (0.5-2 mm). This allows nano-resolution imaging (~400 nm, Figure 1) while preserving sample context, which we look to exploit for biological applications requiring sub-cellular tissue characterization at the Francis Crick Institute.
The BrillianSe detector provides efficient X-ray detection due to its direct-conversion architecture and fine pixel pitch [2]. However, the amorphous selenium sensor exhibits temporal effects such as residual signal (lag) and exposure-history-dependent variations in response (ghosting), arising from charge trapping and release processes. These effects manifest as transient overshoot and slow signal relaxation (Figure 2) following irradiation and sample imaging, which can degrade image quality and introduce artefacts in tomographic reconstructions.
In this work, we investigate these temporal effects and characterize their dependence on acquisition parameters, including exposure time, tube voltage, and sample contrast. We examine their impact on image quality in both model systems and experimental nanoCT datasets. Finally, we present strategies to mitigate these effects through both acquisition design and image processing, improving the robustness of nanoCT imaging with amorphous selenium detectors.
[1] C. Fella et al. Microscopy and Microanalysis, 2018 Aug, 24, S2, 234–235.
[2] A. Pil-Ali et al. Sensors (Basel). 2022 Aug 7;22(15):5890.
This work is supported by the Wellcome Trust 221367/Z/20/Z; and by the Francis Crick Institute, which receives its core funding from Cancer Research UK (CC0103), the UK Medical Research Council (CC0103), and the Wellcome Trust (CC0103).