Digitizing X-radiographs

Rachel Danzing <rachel.danzing [at] brooklynmuseum__org> writes

>We are interested if anyone has digitized their x-radiographs and
>what their experiences were.  Were any equipment or special
>techniques found to be useful?

We have been digitizing film radiographs at the Department of
Archaeological Sciences, University of Bradford, for several years.
We started by using a dedicated medical X-ray scanner but found that
this equipment could not cope with the high optical densities formed
by industrial film.  The darkest parts of the image formed on
medical film typically have a Dmax just over 3 where as industrial
film can form much higher densities--up to a Dmax of about 4.7.  The
document scanners with built in lights for digitising photo
transparencies have also been used to try and capture radiographic
images but these often have an even lower Dmax than the medical
X-ray scanner and certainly too narrow a dynamic range to capture
all information in an X-ray image.

In the end we purchased a dedicated industrial X-ray scanner which
copes with all the film sizes we use (up to 14 inch width) and
captures 16 bit images at a resolution of 512 dpi.  This gives a
pixel size of 50 micron which gives excellent results, even when
digitising very high definition images of textiles. This has
revolutionised our ability to explore, interpret, publish and
archive films.  By applying DIP to the images we can frequently
reveal information not visible by inspection of the radiograph on a
light box.

We did experiment with a range of other capture systems before our
purchase. We tried using cameras and flatbed documents scanners,
none of which gave us the quality of result which was needed to
explore the radiographs fully. This work is reported in

    O'Connor, S. and Maher, J. 2001.
    The digitisation of X-radiographs for dissemination, archiving
    and improved image interpretation, in The Conservator, 25,
    pp3-15

and

    O'Connor, S., Maher, J. and Janaway, R. 2002.
    Towards a replacement for Xeroradiography. The Conservator, 26:
    100-114.

More recently I have done some work in collaboration with Andy
Chopping, Head of Photography at the Museum of London Archaeological
Service, using a higher quality studio camera and document scanner,
but the results from the industrial X-ray scanner are still
superior.  The results of this work will be published in the
forthcoming book by Sonia O'Connor and Mary M Brooks, entitled
X-Radiography of Textiles, Dress and Related Objects which will be
published by Elsevier under the Butterworth Heinemann imprint in
their conservation 'black book' series.

Our scanner is an Agfa FS50 B (since bought out by GE Inspection
Technologies).  Fuji market the identical machine but with their own
capture software.  These machines are expensive to buy but as a
shared facility (we do digitisation for a number of museums,
archaeological units and other university departments) the unit cost
per film is quite cheap.

Sonia O'Connor
Research Fellow in Conservation
Department of Archaeological Sciences
University of Bradford
Bradford
West Yorkshire BD7 1DP
+44 1274 236498 (office)
+44 1274 235210 (lab)
Fax: +44 1274 235190


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                  Conservation DistList Instance 19:47
                 Distributed: Wednesday, March 29, 2006
                       Message Id: cdl-19-47-006
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