X-Message-Number: 4756
From:  (David Stodolsky)
Subject: Electron Holography for brain scan?
Date: Thu, 10 Aug 95 13:36:04 +0200 (CET DST)

Tonomura, A. (1990, April).
Electron Holography: A new view of the microscopic.
_Physics Today_, pp. 22 - 29.

This is a report on some beautiful work.
See .5 Angstrom height difference imaged clearly.
See a single magnetic flux quanta.
See curvature of space on the desktop.

Holograms are made with a 'camera', which at any time has a single
electron in it. The question is how you get wave interference when there
is no simultaneous reference beam? The electron 'knows' how it would
have been affected, if it had taken the other path, quantum mechanically
speaking.

When making the hologram, several different effects can be used to
generate 24X magnification. The recorded object can then be imaged
using laser light. There are lots of magnification options here.

This is a brain backup method cryonicists can love ;-).
Don't have to worry about brain heating, since the rate of energy
input can be easily controlled. A problem is keeping the material
fixed in location long enough to put an electron in each voxal. This
would appear to require cryonic suspension.

A potential problem is penetration of the brain by electrons, but
I remember someone saying that this form of radiation might be useful
for sterilizing patients infected with Ebola (or was that x-rays?)

The major limitation seems to be the coherence of the electron beam.
This article claims only 3,000 interference fringes, which is much to
low for a brain scan. But could this be improved? I'll leave it to
people more familiar with imaging technology to tell us.

dss
 

David S. Stodolsky      Euromath Center     University of Copenhagen
   Tel.: +45 38 33 03 30   Fax: +45 38 33 88 80 (C)


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