X-Message-Number: 28547
From: 
Date: Tue, 3 Oct 2006 16:21:05 EDT
Subject:  Uploading technology (1.iii.3) MRI Brain Reader 3 

Uploading technology (1.iii.3) MRI Brain Reader  3



In messages .#27635 and #27639 I had  given a first look at an MRI brain 
reader. Here I would show a specificity of  such a machine. It can't be on the 
track of current medical systems. There is no  hope it will be built as the 
technology evolves, it is another branch of the  tree.

Assume that the depolarization time T1 is one millisecond in  ice, this is an 
order of magnitude smaller than for the liquid phase. The  recovered signal 

will be stronger than with liquid state T1 on the order of the  second or more.
This is a good thing because all the energy is releaser in a  short time 

giving off more power and so a better signal over noise ratio. When  there is a
microscopic imaging, a difficulty arises.

Assume the  signal has the maximum duration, that is, it is equal to T1 and 
is one  millisecond long. We can think of it as  a monochromatic frequency  
modulated with all frequencies between zero and one kilo Hertz ( 1 kHz has a  
cycle duration of one millisecond). If He3 is used, its Larmor precession  

frequency is 3.26 kHz/gauss. So, to discriminate from one pixel to the next,  
nearly 
.3 gauss are called for, so that the frequencies are more than one kHz  

appart. If the resolving power is 100 nanometers, the magnetic field gradient is
.3g/100nm or, for a 4 inches picture line : 300 000 gauss or 30 Teslas. The  
continuous field must be at least 3 times larger, so the homogeneous field is  
100 T. This is at least 3 times the best laboratory  limit.


Most of the grey matter in the brain  containing  neurons are in a shallow 

coating no more than 2 to 3  millimeters thick. Even without surgery, this could
be reached with one  centimeter gradient. We are down to 10 T for the 

continuous field and 3 T for  the gradient. This is the technological limit for 
small 
volumes. We could  picture a rodent brain, no more. Rodents have a small 
brain and few convolutions  without of the reach parts. Man is another story.

The NMR is so not  up to the job. But the title is about Magnetics Resonance 
Imaging, not Nuclear  Resonance Imaging. MRI includes both, nuclear and 
electronics magnetics  resonance. Electrons are 2000 times lighter than hadron 

(protons, neutrons) in  the nucleus. So, they are swinging on the order of 2000

times faster. The Larmor  frequency is now in the MHz range per gauss. Assume it
is 10 MHz/gauss for a  given electron. A 100 nm resolution needs always 1 
kHz/pixel, but that  translates into .0001 gauss/pixel or one gauss/mm. If the 
resolving power is  pushed to 10 nm and the picture is one feet wide, the 

gradient field is only  3,000 gauss. The continuous field must be at least x3 
larger 
or near one Tesla.  This is perfectly in the range of present day technology. 
For such a field,  there is no need for exotic technologies as superconductor 
in liquid helium or  the like. Electron Resonance Imaging is the  solution.

YB.



 Content-Type: text/html; charset="US-ASCII"

[ AUTOMATICALLY SKIPPING HTML ENCODING! ] 

Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=28547