[NHCOLL-L:1783] Scanning X-rays

[Andy Bentley]

Hi all

I was asked by various people to please post a summary of responses to my
query regarding scanning of x-rays.  A number of people responded and I also
came across a message string on the Biomechanics and Movement Science
Listserver to which a Virginia Ferguson gave a very good concise summary of
her findings.  All of the reponses I received are covered by this list and
so I post it here for the benefit of all:

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Here is a summary of the responses and Virginia's comments on each:

1) Try having a mirror cut to match the dimensions of your scanner.  Place
the x-ray on the scanner and then place the mirror over it.  The quality
isn't
absolute top notch, but it ain't bad and is certainly cheaper than buying a
scanner dedicated for x-rays!  This isn't difficult, any glass shop can do
it no problem and inexpensively.

*** We tried using a large mirror with several different HP scanners (HP
IIC, HP 5C, and an HP 5300C).  This did not work well.  In fact, several
responders told me that films are best scanned using transmitted light,
rather than reflected light.

2) Use the x-ray as a photo negative and print a contact print -
ie place the x-ray on some 10x8 photo paper, expose it to
white light, and develop the print as you would any photo. This print can
then be scanned in by a conventional scanner.

*** We tried this through our Universities publishing department - it
resulted in a high degree of variability on the contact prints when
processing the same x-ray more than once.  Also, it does not pick up areas
where bone is scarce (that can be seen on the x-ray) such as the ulna,
radius, and hand bones of a mouse.

3)  Take pictures with a high quality digital camera when they are on a
light board, etc.

*** A light board provides an uneven lightsource.  If using the images for
the purpose of publishing an x-ray, this works fine.  If you want to analyze
for intensity, this is not acceptable, in my opinion, as - once again - the
gradations in the light source cause some areas of the image to appear
artifically lighter.

4) Lay a lightbox on top of the x-ray on the scanner.

*** Same as #3.  Also, light boxes with flourescent lamps can form
diffraction patterns on the scanned image.

5)  One lab bought a $60 000 x-ray scanner that does the job

*** These are expensive medical image scanners that will probably do a much
better job than commercially available scanners + transparency adapters.  If
you need very high resolution and can afford it, this may be a good
solution.  There are many schools that have such equipment in radiology
departments.

6) Most people who responded to my query suggested using a transparency
adapter.  This is a special cover that works with your scanner to provide a
transmitted light source that tracks the scanning bar.

*** It turns out that I was able to obtain a scanner and transparency
adapter for free to test these suggestions.  It is an HP Scanjet 5300C with
a transparency adapter.  Thus far, it is working very well - excepting the
small area that the transparency adapter covers (5”x5”).  The scanned images
appear to be consistently “lit” - resulting in no lighter/darker spots on
the image.  And I can “normalize” all of my images by using a phantom - I
made an epoxy disk containing small sections of cortical bone with
thicknesses of 0.25, 0.5,...mm which I scan in on every image and use to set
a standard intensity when I analyze my images in Photoshop.  Thus far, this
seems to be the most cost effective result that yields good results.

If you do not have the resources to buy such a system (much less than
$1000), then you can pay a professional service to do this for you and some
universities have publishing departments that do this as well.

Hope that helps all who were interested

Andy

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Andy Bentley
Ichthyology Collection Manager
University of Kansas
Natural History Museum
Dyche Hall
1345 Jayhawk Boulevard
Lawrence, KS, 66045-7561
USA

Tel: (785) 864-3863
Fax: (785) 864-5335
Email: ABentley at ku.edu              :
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