NRL Scientists Create Unique Model of Human Spine for National Naval Medical Center

9/26/2001 - 29-01r
Contact: Public Affairs Office, (202) 767-2541

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.

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The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 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 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.

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