Re: 3D medical modelling

Date: Sun Mar 10 2002 - 17:53:25 EET

I usually just read this list but couldn't resist putting my 2 cents worth in
on the application of r-p in medicine. In my opinion, there is no question
that the technology is available to transform the way we diagnosis and treat
patients but the problem is more complex than just the technology. I would
like to use a simple example that most of you can relate to. If your son or
daughter went to the orthodontist to have his or her teeth straightened or
face changed with skeletal surgery some very specific evaluations would be
preformed. The following information is generally needed: photos of the face,
two large x-rays of the head, models of the teeth and records of the way the
TMJ (joints ) relate the jaws and teeth to each other. None of this
information is digital (except possibly the photo) much of the process of
making a diagnosis is done with a pencil on a sheet of acetate over the
x-rays. This is a very scientific process and used by virtually all surgeons
and orthodontists. Tracings are made of the bones of the face and teeth and
their spatial relationship to each other measured and compared to known
standards. Other measurements are made of the models and if jaw surgery is
needed, acetate templates are cut of the tracings to rotate and move the
teeth and bone in 2D (on the desk top) to determine the final result. If a
surgeon is planning to move the jaws by cutting them and repositioning them
in a new relationship, he usually mounts the models in an metal instrument
that is like the jaws and cuts the plaster models to make the planned moves
to see the final result before surgery. If the result is acceptable,
autopolymerizing acrylic resin templates are made of the teeth to relate them
together during surgery. This is accomplished using the TMJ (joints) as an
axis of rotation and recording the number of degrees of rotation or opening
to precisely position the cut jaw before plating it in place with titanium
plates and screws.

This is only a part of the process but I think it helps illustrate the
present state of affairs. Now as you all know we could get a CT scan of the
patient and have better information about the real soft and hard tissue
anatomy of the patient, and we could scan the teeth or models of the teeth
many ways and relate that scan date to the CT data. We could also record jaw
movement digitally and allow for the scan data of the teeth and bones to be
moved in CAD to the new desired position and we could make the surgical
templates for positioning the teeth with r-p. None of these processes is a
big deal and can be done easily. So why isn't everyone doing it?

The answer to that question is the critical point. Oral and maxillofacial
surgeons, orthodontists, plastic surgeons, neurosurgeons and a host of other
people would love to have scanning, CAD and r-p do the jobs they presently do
by hand but it will not happen until software is developed that does what
they need easily and in a fashion that is similar to the present process.
That will only happen when we create inter-relationships that allow
engineers, surgeons, clinicians, researchers and marketing people to work
together to develop the software we need.

Generally, just providing conventional CAD and scanning equipment will not
work. Most medical people are very busy, they do not have the time to learn
Pro-e, they need someone else to do that for them.

For more information about the rp-ml, see

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