stereo x-rays

[telscope@xxxxxxxxxx (Peter Abrahams)]

>Paul Evens from Nottingham Trent University (UK) spoke about the
stereoscopic >X-Ray systems they have been developing for use in Airports
(to scan people's >baggage).    [SPIE Conference 2/96]
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>In regard to stereo X-rays, I do that all the time ....  Stuff works great!
>Clifford J. Mugnier  (cjmce@xxxxxxx)
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Last year, I enrolled in Computer Science classes at the local Community
College (that's what it takes to decipher the Postscript files in the Photo 3d
archives, I'm in my second term of Unix & still can't get it right--but I'm 
ability-deficient that way.)  I made the acquaintance of a radiology student, 
and he mentioned that stereo x-rays were a standard technique; for locating 
bullets, tumors, whatever they look for.
The great Elihu Thomson is cited as the first to propose and expose stereo
radiographs.  He is quoted, "The effect is very curious...two heavily insulated 
wires twisted together...the wires alone are seen, standing apart in space." 
 He also suggested stereo fluoroscopy (motion pictures,) a technique that
might never have been executed (any volunteers??)  
This 1896 article was immediately followed by French and English reports. 
The heart and GI tract were poorly imaged, "they appeared
as disks rather than three dimensional and their movements resulted in 
undesirable parallax...modern cross-sectional imaging effectively marked the
end of the stereoscopic era in diagnostic radiology." (Ronald Eisenberg,
Radiology, an Illustrated History, 1992.)  This book has stereo pairs of
Roentgen & his wife, taken by him -- photographic, not radiographic.

I had x-rays of seashells on my mind, and we decided that stereos of shells
would be a worthwhile project.  William Conklin, a radiologist in South
Carolina,
has done hundreds of x-rays of shells, but does not know of any radiologic
stereos of shells, according to a phone conversation with my radiology
student.  
X-rays of seashells are very beautiful, and show delicate spirals and detail
with great contrast--if correctly exposed, an art in itself, involving a balance
between kilovolts of power and quantities of 'mass'.  
The very first stereo we took was a true delight, the inner layers of shell
could be seen to arch up from the film surface, each layer demarcated from
the next, a truly complex and inspiring construction.  I am active in the local
seashell club, and the generosity of members has resulted in 50 pairs of
radiographs.  
The problem is...they are hard to view.  Maybe some readers can free view
8 x 10 inch transparencies, if so, I would like to know about this gift of
divergence.  I own a few viewers used by radiologists, one is a prism viewer 
with two large rhomboid prisms, a very unusual item I would like to know more
about (hint to experts out there.)  The others use mirrors and work nicely, but
the radiographs still have to be lit from behind--I bought large sheets of white
frosted mylar, which works, but requires a lot of light to illuminate 10 pairs.

These x-rays will be shown at the next meeting of the Cascade Stereoscopic
Society, which meets outside Portland, Oregon, on March 30.  Those of you 
who are too lazy to jet in for the event have my sincere sympathy; I will be
making photographs of the radiographs to submit to Stereo World, but the
delicate contrast of the originals will be lost.

We will be making more of these stereos as lab time is available.  There are
other objects suitable for this technique, but what of them is more beautiful
than a sea shell?
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telscope@xxxxxxxxxx (Peter Abrahams)          
the history of the telescope, 
     the prism binocular, and the microscope


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