X-Message-Number: 5398
Date: Mon, 11 Dec 1995 01:22:49 -0800
From:  (Greg Stock)
Subject: Dendritic spines

>DE>: Scott Fraser et al. (at Cal Tech) have the record for MRI resolution
at 18 um
>DE>: cubed.  Optical coherence microscopy should be able to reach less than 10
>DE>: um, but only at depths less than 2 mm.
>
>DE>So, it would apprear that, for such tiny samples, it should be possible 
>DE>to obtain results very nearly as good as using optical techniques?

Brian Wowk replied --
>
>	The problem is that scan times for this resolution are extremely
>long (on the order of hours), whereas optical imaging is practically
>instaneous.  While MRI might return some useful information, I think
>imaging changes in dendritic spines over several hours is out of the question 
>with current MR microscopy technology.  New probe designs over the next
>decade might change that.

I don't think you appreciate the applications possible with optical
coherence microscopy.  With light microscopy you simply can't penetrate
deeply into a sample  -- 2mm is a VERY thick sample -- so you have to do
thin sectioning, which unfortunately destroys what you're looking at.
(Perhaps not important with cryonics, it depends what you have in mind.)
The important applications that people are looking at with the coherence
technique are things like following the development of an embryo and mapping
the movements and divisions of cells over time.  Here you can't afford to
destroy what you're observing.
  
As to your comment about scan times, I don't know enough to comment.

   
             Gregory Stock
, 


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