Re: MRI and dino eggs, etc. Murdoch

[Crpntr@ix.netcom.com (Kenneth Carpenter)]

You wrote: 

>
>
>With regard to the use of magnetic resonance imaging (MRI)
>in the study of dinosaur eggs ...
>
>It HAS been investigated, notably by Neil Clark (a frequent 
>contributor to this forum) and co-workers from Glasgow.  They
>report that "the images show a shell structure distinct from
>the rest of the egg.  By acquiring a projection of the entire
>egg, the water content of the shell was measured ...." (M.
>McJury, N.D.L. Clark, J. Liston, and B. Condon, Proceedings
>of the Society of Magnetic Resonance, Second Meeting, August,
>1994, p. 706).
>
>These results reflect a major limitation of conventional MRI:
>only comparatively mobile hydrogen nuclei can be detected, such
>as those from soft tissue, lipids, various bodily fluids ...
>and adsorbed water on or in egg shells.  (The same mobility limitation
>applies when other MR-active nuclei, such as phosphorus-31 and
>carbon-13, are examined.  In the absence of motion, the little
>nuclear magnets interact with each other, completely washing out the
>spatial encoding necessary for imaging.  A more painful and
>protracted explanation can be provided, if so desired ....)
>
>A more thoroughly pursued and successful "geo-application" of MRI is
>the analysis of oil well cores.  What is imaged is the liquid-like
>oil and/or water in the sandstone pores.  The images provide 
>information about oil/water distribution, efficiency of enhanced oil 
>recovery, diffusion rates, pore size and connectivity, etc.  Therefore,
>by analogy, perhaps some fossils in certain matrices could be MR imaged
>by the presence or absence of pore fluids.  The content of
>paramagnetic ions (such as iron) must be low, however -- otherwise, 
>the unpaired electrons mess things up.
>
>Finally, it IS possible to image some rigid solids (such as P-31
>in bone) directly, but at present, these are difficult experiments on
>very small samples.
>
>Now back to dinos ....
>
>Jim Murdoch
>Picker International (a medical imaging company -- surprise, surprise)
>Highland Heights, Ohio
>
>
>



As I stated before, all of the techniques have not been successful at 
demonstrating EMBRYOS within eggs.  I am aware that the shell shows up 
nicely in CT, X-ray, MRI, etc., but that was not the point I was 
discussing.  The calcite of the shell is usually the original shell, so 
has a different density than the surrounding and infilled matrix. This 
morning Karl Hirsh told me of yet another experiment of his using CT of 
a fossil egg known to have bones (seen on the broken edge).  The results 
were again negative.  The egg was small, about 5 cm wide, 1 cm thick so 
there was no difficulty with penetration by the X-rays.