Possibilities of energy-resolved X-ray radiography for the investigation of paintings |
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Authors: | Ana E Cabal Rodríguez Diana Leyva Pernía Olivier Schalm Pierre J M Van Espen |
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Institution: | (1) CEADEN, Calle 30 #502 esq. 5ta ave, Playa, La Habana, Cuba;(2) Dept. of Chemistry, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium;(3) Artesis University College of Antwerp, Conservation Studies, Blindestraat 9, 2000 Antwerp, Belgium; |
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Abstract: | X-ray radiographic images of paintings often show little or no contrast. In order to increase the contrast in radiographic
images we measured the X-ray spectrum of a low power X-ray tube, after passing through the painting, with a high energy-resolution
SDD detector. To obtain images, the detector is collimated with a 400 μm diameter pinhole and the painting was moved through
the beam in the x and y-direction using a dwell time of a few seconds per pixel. The data obtained consists of a data cube of, typically, 200 × 200
pixels and a 512-channel X-ray spectrum for each pixel, spanning the energy range from 0 to 40 keV. Having the absorbance
spectrum available for each pixel, we are able, a posteriori, to produce images by edge subtraction for any given element.
In this way high contrast, element-specific, images can be obtained. Because of the high energy-resolution a much simpler
edge subtraction algorithm can be applied. We also used principal-component imaging to obtain, in a more automated way, images
with high contrast. Some of these images can easily be attributed to specific elements. It turns out that preprocessing of
the spectral data is crucial for the success of the multivariate image processing. |
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