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hvoosterwyck48
05-07-1998, 07:19 PM
Dear all,

I' m working on finite element modelling of the upper and lower jaw for
patients with implant-supported oral prostheses. Because the FE models
have to be patient-dependent they are based on CT: both the anatomy as the
bone density (elastic modulus) must be implemented correctly. By means of
the FE results we want to have an idea whether observed bone density
changes around the implants in the patient's jaw can be correlated to the
calculated stress or strain distribution in the bone.

For the evaluation of bone density changes we want to take two CT scans of
the patient's jaw and compare the Hounsfield values: one preoperatively and
one postoperatively (after 9-12 months of function). I was wondering if
this sounds like a good idea to do. Does anyone of you have experience
with the use of CT scans for this purpose? Because maybe the resolution of
CT is too low to see anything of interest. The CTs for dental applications
are taken with a slice interval of 0.5 mm and have a resolution (pixel
size) of 0.25 mm.

Another problem might be that the presence of the titanium implants on the
postoperative CT will bias the Hounsfield value of bone in the immediate
vicinity of the implants so that these value will not be reliable. Has
this effect already been documented in literature? And are there solutions
to solve that problem?

Last but not least the preoperative and postoperative CT have to be
matched. Because the patient's position will not be identical during the
preop and postop scan reslicing has to be performed in order to match the
images. Does anyone know where I can find the necessary software (maybe as
shareware) to perform this matching? Or can I find information in
literature on matching algorithms?

All information on these topics will be very helpful. Thanks in advance
for your help.


Hans

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