Scientists at the Naval Research
Laboratory (NRL) recently created a model of the human spine
that may prove to be a helpful study tool for doctors at the
National Naval Medical Center (NNMC). Dr. James Thomas and Mr.
Roy Rayne from NRL's Multifunctional Materials Branch used NRL's
Helisys Laminated Object Manufacturing System (LOMS) to create
a full-scale model of a human spine. Doctors at the NNMC are
interested in the NRL modeling capability because the equipment
available at NNMC can only create anatomical models less than
10 inches in length.
NRL scientists used the LOMS
process to create a
very detailed anatomical model of a human
spine with severe
scoliosis from CT-scan digital data, explains
Dr. Thomas.
Models made using solid freeform fabrication techniques,
of
which LOMS is one, are used in medicine today for visualization
and planning of complex surgical procedures. Doctors at the National
Navy Medical Center made several fractional-scale models of this
particular patient's spine. However, because of the extreme
curvature
of the deformed spine, the doctors wanted a
full-scale model.
NRL's LOM facility is capable of fabricating
the full-scale,
17.5-inch-long model of the spine. In addition,
the LOMS model
had the added advantages of providing
outstanding contrast on
the detailed skeletal features and an
appearance and texture
that is closer to actual bone.
The LOMS fabrication process starts by computationally slicing
a computer representation of the spine (CT-scan) into thin contour
layers about the horizontal plane. The physical model is created
by bonding together multiple layers of paper, each with a unique
laser-cut outline corresponding to the spinal material boundary.
The paper layers are bonded together using an adhesive that is
activated by a heated pressure roller. The paper regions outside
of the spinal material boundaries are laser-cut in a crosshatch
pattern to aid in the removal of the excess material.
The spine model was fabricated
by the LOMS machine as a solid block 18 x 7 x 5 inches in dimension,
using approximately 1070 layers of paper stacked in the 5-inch
dimension. The spine was embedded in this rectangular block and
had to be "dug-out" by removing (decubing) the extraneous
material. The fabrication process took over 70 hours, because
of the many fine-scale features in the model, and decubing took
approximately 30 hours spread out over several weeks.
In July, Dr. Thomas and Dr. Peter
Matic, head of the Multifunctional Materials Branch, met with
doctors at NNMC to show them the model of the spine. NRL had
become involved in this project because of a casual conversation
between Dr. Matic and CAPT Charles Richardson, of the NNMC Radiology
Department, which took place several months earlier. The doctors
at NNMC were pleased upon seeing the model at the July meeting.
CDR Ross R. Moquin, a neurosurgeon at NNMC and Walter Reed Army
Medical Center (WRAMC), said that he would be using the
NRL-developed
model as a "a surgical planning tool,
teaching tool, and
a patient education tool." NRL
researchers and NNMC/WRAMC
doctors agreed to follow-up this
effort with a meeting to explore
the possibility of joint
research in which NRL would use their
scientific modeling
expertise to aid NNMC doctors in their neurological
related
research. Dr. Matic explains that he hopes that NRL can
develop
unique techniques and applications, using the LOMS process.
If
the NNMC/WRAMC doctors decide there is a regular and continuing
need for LOMS-based anatomical models, NRL will help them identify
commercial sources capable of doing this work on a production
basis.
Currently
NRL uses the LOM facility
for materials related research and
functional prototyping of
ceramic and other material devices
enabling rapid design verification
and model development. Some
recently fabricated prototypes include:
a novel telescoping
ceramic actuator, low-weight ceramic ring
actuators that can
only be formed by this technique, an instrumentation
case mold,
and patterns and molds for fabricating multifunctional
structure-battery components for an unmanned air vehicle.
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 85 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
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