From: Andy Christensen (
Date: Fri Jan 17 1997 - 13:43:06 EET

Steve Deak wrote:
> I have approached Hasbro's upper management concerning this particular
> issue. I will build the skull model FREE OF CHARGE if this will be of
> medical benefit.
> I will need an STL file, so I challenge someone to convert the CT images
> to an STL file and send them to me.
> Let's do it!!

Dear Steve,

        Your efforts for Lynda Hurley's colleague are commendable. Having been
in this business for two years, we feel it is our duty to add a little
bit on input. There are a few points that I would like to make on this
same matter.

1) Industrial parts (ie: toys, boats, airplanes) are not equal to
anatomical parts, even though they can be produced on the same
equipment. The trick here lies in the processing of data from a CT
scan. The value added by a medical bureau in this situation is the
"cleanup" of the CT scan. Often when a CT scan is done, the patient
will have teeth fillings or other implants which have the effect of
scattering the radiation from a scan. The biomedical engineer's job is
to decide what portion of the scan is "scatter" and what portion is
bone. The post-processing step is also very important for retaining
small features of bony anatomy.

2) Although the STL format (even though there are conflicting original
meanings on what this is :-)) is the industry standard for rapid
prototyping, it is not what medical bureaus use. A format more suited
toward 2 1/2 dimensional data (stacked 2D slices) is the .slc format.
This format maintains the integrity of the data from start to finish.
On occasion we will utilize the .sli format for modeling.

3) Just as industrial parts have a potential to make money, so do
anatomical parts. If the boy's father (and ultimately the surgeon) wish
to proceed with a model that will be used to evaluate the child's
anatomical situation, I think that this should be handled start to
finish by a respected medical bureau.

        I would be glad to speak with the surgeon on this case and discuss the
re-imbursement possibilities. Oh, and by the way, a full skull .stl
file would be somewhere in the neighborhood of 35MB and would tie up an
SLA-250 for better than 2 days. Not to come down hard here, but these
models are being used for very serious purposes and there are
specialists who do this kind of work every day of the week.

Andy Christensen

Andy Christensen
Sales & Marketing
Medical Modeling Corporation
17301 W. Colfax Ave., Ste. 300
Golden, CO 80401 USA
303/277-9472 fax

"SLA Anatomical Models . . . The Ultimate Analysis Tool."

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