Gold coating breakthrough for X-ray tomography


Rebecca Pool

Friday, May 10, 2019 - 13:15
Image: A thin layer of gold atoms significantly increases visualisation possibilities in X-ray tomography [Peter Ruehr, Markus Lambertz]
A new method to enhance surface contrast in X-ray micro-computed tomography makes even X-ray transparent samples, such as spider silk, visible during digital scans.
Akin to SEM sample preparation, the technique coats samples with a thin layer of gold to capture fine surface detail and internal anatomy with enhanced contrast.
As researcher Peter Ruehr, a doctoral student at the University of Cologne's Zoological Institute, points out: “Up to now, many delicate surface structures of our research objects could simply not be represented by means of computer tomographic analyses.”
“But by combining two well-established methods for the first time, we have... opened up a series of previously closed doors in the 3D evaluation of even the finest structures,” he adds.
To digitally reconstruct fine, low absorbance structures such as bristles or scales on the surface of an organism, Ruehr and colleagues from the Universities of Cologne and Bonn, used conventional and readily available sputter coaters to cover the entire sample with a thin layer of gold atoms.
They then went onto analyse a diverse array of animals and plants, and even spider silk, using X-ray micro-computed tomography. 
As Ruehr and colleagues detailed in the Journal of Anatomy, on average, they achieved a 14.48‐fold gain of surface contrast - ranging from 2.42‐fold to 86.93‐fold - compared with untreated specimens.
Before and after: The method is suited to a broad scientific application across biology and other sciences employing micro-computed tomography.
“This selective contrast‐enhancement, makes it possible to digitally reconstruct fine surface structures with low absorbance while the tissue‐dependent grey value resolution of the inner anatomy is maintained and remains fully visualisable,” highlights Ruehr. 
'The morphological details that can now be visualised can also be used for applications ranging from taxonomy and functional considerations to educational projects in museums,' adds Ruehr's colleague, Dr Markus Lambertz.
Research is published in the Journal of Anatomy.
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