X-Message-Number: 798
Date: 04 May 92 02:20:47 EDT
From: Brian Wowk <>
Subject: brain scanning

To: >INTERNET: 
 
David Stodolsky: 
 
>X-ray holography would, if it worked, allow examination of internal  
>structure in the storage media, just as internal structure can be recovered  
>from a brain by electron microscope. That is, you adjust the focal depth to  
>see a certain distance inside the specimen. 
 
        I presume you are suggesting viewing the brain hologram with some  
device which has a one-micron depth of focus at a distance of 10cm.  While  
this is interesting, I suspect it is mathematically equivalent to a computed  
tomography reconstruction, the constraints of which I have already discussed. 
 
        Getting down to nitty-gritty details, 50 keV x-rays have a wavelength  
 that is about 1/10th of an atomic diameter.  How are you going to record the  
 interference patterns of such waves?  Also, how do you produce coherent x- 
 rays without an atomic bomb? 
 
        If one is hell bent on imaging a brain with external x-rays, CT (as  
enormously impractical as it is) is the only way to do it.  X-ray holography  
has no advantages, and has the distinct disadvantage of being physically  
impossible. 
          
        There are far better ways to ascertain the microscopic structure of a  
brain than by frying it with x-rays.  One near-term method (proposed by Ralph  
Merkle and others) is simple sectioning and electron microscopy.  In the long  
term, invasive (but not necessarily injurious) nanoscopic probing will be the  
way to do it.  Micromachines and nanomachines equipped with MRI  
gradient/receive coils could do the job nicely, with capabilities for in-situ  
molecular analysis as well. 
 
        What, though, is the point of this discussion?  Are you suggesting  
that capabilities for recovering patient identity (and perhaps uploading)  
will be available before the capability of actual revival from cryonic  
suspension?  This I seriously doubt. 
 
                                               --- Brian Wowk 

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