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vsjserge39
01-06-1993, 12:25 AM
Dear Biomch-L readers,

I would like to know your opinion about the following problem:

I am currently working NMR ( or MRI ) pictures on PC's
and want to start 3d reconstruction using finite elements. Of
course I need to juxtapose each slide with its neighbours in
order to get coherent voxels.
Here is my questions:
1) Do you think that the placing of fiducial
reference elements (inside the coil) is really necessary
( like the techniques used in
microscopy where a linear reference system is embalmed and cut
with the specimen) ?
2) Is the following supposition right or not ?
The elements of the 3d-matrix (e.g. 256*256*25),
obtained by superposing each slide, are automatically in line
with each other (except if computational errors occur !). So
we can consider one column as an alignment of "fiducial"
points (here pixels). e.g., the alignment of the pixels 2,2,1
trough 2,2,25 is directly correct and does not need to use an
external reference system.

The placing of a reference system inside the coil
can give some problems:
- It increases the size of both the coil and the
field of view, leading to a loss of resolution.
- We have not find a matter giving a signal close to
the signal of anatomical structures. So the histogram of the
pixels intensity is wider than if no fiducial points were
used. Consequently, certain possibilities of pictures
manipulation are reduced.
- The system of reference must rigourously be
perpendicular to the plane of the slides. And this is not
practical if several orientations are necessary without a
movement of the patient or volunteer.

So, it would be very nice if external markers are not
necessary !

Thank you for any answer and happy new year !


Serge

******************************************
* Serge Van Sint Jan *
* Department for Functional anatomy *
* University of Brussels (ULB) *
* Electronic mail: sintjans@ulb.ac.be *
* Tel: int + 32 2 555 63 25 *
* int + 32 2 555 63 76 *
* Fax: int + 32 2 555 63 78 *
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