RERC is one of the pioneering research groups that has been on
the cutting edge of using 3-D laser technology to rapidly scan and
generate accurate 3-D models of limbs, feet, & torso for use
in CAD/CAM software to produce better fitting prosthetics and orthotics.
Casting vs. Scanning
The standard method of casting human limbs, feet, etc. has many
drawbacks. It is very subjective. How tightly the plaster wraps
are wound varies between prosthetists and from one cast to another.
This affects volume and shape of the resulting model. Prosthetists
will often modify the cast while it is drying on the patient by
pressing on the cast in certain areas. This is also very subjective
and variable. Prosthetists will often attempt to transfer landmarks
to the cast by marking the patient with a pen. Movement during casting
can shift these landmarks. It is very time consuming for both the
prosthetist and the patient. Wrapping and drying can easily take
one hour. Then the prosthetist has to cut off the cast to remove
it and attempt to bring the seam back together without altering
the shape or volume. He then must pour plaster into the cast and
wait for it to harden, then cut the cast off (destroying the ability
to make another copy).
Scanning is fast (from 3.5 to 10 secs), reliable, and repeatable.
Anatomical landmarks placed on the skin are read by the scanner
and precisely attached to the resulting electronic 3-D model of
the subject. This model is easily stored and can be retrieved at
any time in the future for use in a CAD/CAM socket design modification
with leading optical scanning manufacturers such as Cyberware, RERC
has developed high accuracy scanners for use in the field of prosthetics
& orthotics. The BelowKnee
Prosthetic Optical Digitizer was specifically developed by Cyberware
for the RERC to quickly and accurately scan the residual limbs of
below knee amputees. RERC developed custom operator software to
easily scan, detect and identify landmarks, and save the resulting
electronic 3-D model to a file that can be read into leading Socket
Design CAD/CAM application packages. A number of BK scanners are
currently being field tested at VA stations across the country.
Digitizer has the same advantages as the BK scanner but was
designed for patients with amputations above the knee. To properly
design an AK socket the lateral hip and the area between the legs
on the amputated side must be accurately characterized. The Lower
Limbs digitizer's unique head design with tilted viewing angles
allows these areas to be scanned. The extended travel of the heads
also allows for the scanning of an entire leg for the design of
braces and orthoses.
Optical Digitizer is a unique scanner that creates accurate
3-D models of the whole foot and ankle. The scanner can mimic current
foot casting practices in that it can scan while the foot is on
platforms with various heel heights as well as on a flat surface.
Imbedded force transducers measure the total weight as well as the
relative position of the weight distribution. This information is
displayed in real time to the subject. Goal weights and positions
can be set so that the patient can dynamically control the amount
of body weight and relative positioning during the foot scan. Small
landmarks are also easily transferred to electronic 3-D models.
This file can be input into RERC's custom Pedorthic
CAD/CAM system to design lasts, insoles, and shoe upper patterns
used to manufacture of footwear.
Whole Body Optical
Digitizer uses four optical scan heads with a custom made system
of uprights and servo motors to control scan head movement. The
digitizer is capable of scanning the whole body in one scan and
can be used for custom body braces, equipment fitting and possible
applications to clothing and uniform fitting.