stereo x-rays at NSA

[P3D Peter Abrahams <telscope@xxxxxxxxxx>]

Concerning the stereo x-rays at NSA,

>The images had a relatively high percentage of areas that weren't expressed
>equally in both left and right views.

Yes, if I get a chance to do these again, I will decrease the disparity
between R & L.  The x-ray techs tilt the gun maybe 5 degrees to the R of
vertical and 5 to the left to make a stereo pair, a really radical amount,
the subject is only about two feet away.  Probably this is because they are
trying to locate the z axis placement of some tumor or bullet, and will
strain their eyes a little to do this if necessary.  It's particularly
noticeable because you're seeing the front & the back surfaces.  The
simpler shells, with a clean spiral form, needed this 
disparity, but the images of the complex shells had lots of areas that were
white on one side and black on the other, creating a rivalry.    If the
right side has an area of exposure (black) & the left is white, then the
thickness of the shell that the x rays passed through is different by that
amount, thin on the right and thick on the left.

_______________________________________
Peter Abrahams   telscope@xxxxxxxxxx
the history of the telescope, the microscope,
    and the prism binocular


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