Surgeons, radiologists, and 3D imagers at Walter Reed Army Medical Center collaborate to improve outcomes for troops, veterans, and their families.

Tucked in a small office near the main radiology department, Walter Reed Army Medical Center’s (WRAMC) 3D Medical Applications Center (3D MedApps) is adorned with the lifelike models of spines, skulls, and joints—all of which originated from multislice CT scans.

Led by director Stephen Rouse, DDS, the 3D MedApps team spends its days pairing CT images with the advanced computer technology and 3D modeling fabrication systems to create a hands-on answer to a question surgeons have asked for years: Exactly what is happening within the body?

“If a doctor is looking at an ankle fracture, for example, and it is on a bone deep inside, it is very difficult to determine the best course of treatment using just standard radiology,” Rouse said. “But with our technology, we can separate out the damaged bone to show them exactly where the fracture is, what the best route of ingress is, what direction they should come from, and how long a screw they can use.”

Requests for the 3D models come in from all areas of the hospital, including neurosurgery, orthopedics, plastic surgery, and maxillofacial surgery, but because the technology is relatively new, only about 1,500 have been requested since the technology was installed in late 2003. Still, those who do take advantage of the service are ardent supporters.

“This is an amazing tool. When working with patients who have head, neck, or facial defects, being able to create models from three-dimensional imaging is invaluable,” said Maj Christopher R. Cote, MD, MC, the chief of Facial Plastic and Reconstructive Surgery, Otolaryngology-Head and Neck Surgery Service at WRAMC, located in Washington, DC. Surgeons find the models most helpful for patients with cancer or for those recovering from some type of trauma, he adds. “Traditionally, we have relied on our own ability and knowledge of anatomy to re-create parts of the face and body that just don’t exist anymore. Now we have a tool that can be objective and act as a guide to repairing those defects,” Cote said.

Benefits You Can Touch

With roots in the industrial field, the 3D technology in use at WRAMC was initially purchased by two Air Force dentists hoping to speed the process of creating crowns and bridges.

“They soon discovered it really didn’t do what they wanted it to do, but it worked very well for other medical applications,” Rouse said. Today, the technology is used predominantly for craniofacial and complex orthopedic injuries, giving surgeons insight into which pieces of bone can be saved. “We create a 3D, solid model, with those pieces held in their current anatomic position.”

Each model starts with images from thin-slice CT scans. The 3D MedApps staff then uses image processing and editing software to create virtual, 3D models. Those graphic files are sent to machines capable of generating solid, resin models of the 3D image. (For a step-by-step look at how the models are made, see the sidebar on the next page.)

“We can either create a template for a surgeon to use in creating a custom fixation or we can actually create a custom appliance for them,” Rouse said. Clinicians use the resin models not only to rehearse the surgery, but also to provide a guide for bending fixation bars prior to entering the OR. These templates can even be sterilized for use during the surgery.

Also available to surgeons is the option to have titanium structures created using the same process that manufactures the models. Detailed CT images are converted into 3D graphics, then they are fed into a system that crafts a 3D titanium mesh plate that is put in place to support the brain and provides natural contouring for the patient while allowing tissue to grow into it.

“As a result, there are fewer problems with postoperative infection and epidural or subdural hematomas,” Rouse said. “The titanium is about 5 mm thick and will not interfere with the readability of future MRI or CT scans.”

Building a Team

Putting all the pieces in place for an image to be successfully transformed into a 3D model has created a collaborative environment among the surgeons, radiologists, and 3D imagers at WRAMC.

“I wouldn’t say the impact on radiology is negligible, because it was a whole new addition to our department, but it doesn’t in any way impede our workflow,” said Col Michael P Brazaitis, MD, chief of radiology. “We simply take patients who are going to be receiving CT scans and acquire a fine-cut CT so we render more detail of the area involved, as those images are required by the 3D lab.”

Radiologists are also serving as consultants for surgeons looking to make use of the modeling technology rather than simply handing off images.

“It has fostered a lot of multidisciplinary cooperation. We find that different plastic surgeons are working with each other and they are working with radiologists and other imaging specialists on these cases, and that is the type of environment where the quality of medicine goes way up,” Cote said. “The ability to use this tool is exciting, because it is bringing together multiple disciplines, and hopefully, it will advance the work we are doing.”

Investing in the Future

Such advancement doesn’t come without a price. The software, manpower, and systems required to create the 3D models are expensive, and WRAMC is like any health care organization in that finding room in the budget for a burgeoning technology sometimes proves to be a challenge.

“We are an expense, there is no doubt about it. But we have data showing that in every case where the models have been used—either preoperatively or intraoperatively—it has shaved between 1 and 6 hours off the surgical procedure,” Rouse said.

That time savings translates to additional surgeries, and income, for the medical center, providing an obvious benefit for soldiers returning from areas of combat where blast injuries from improvised explosive devices often demand lengthy and multiple surgeries.

It also is proving beneficial to the other patients treated in the facility. Like the majority of military health care installations, WRAMC also treats the families of service members.

“Freeing up that OR space, which is in short supply for us, means elective, dependent, and noncombat procedures that would have to be stalled off or sent to an outside facility could actually be done in-house,” Rouse said.

Cote routinely finds the models to be time-saving devices. “Using them as guides actually saves us a lot of time and ultimately the hospital a lot of money,” he said, giving the example of a jaw reconstruction. The procedure, during which the patient’s fibular bone is used to replace missing facial structures, typically takes between 12 and 14 hours. “Now we are using three-dimensional models of the jaw and of the leg to take measurements to create the reconstructive plates, as well as determine where the bone cuts need to be and how the plates need to be mounted, the night before surgery. It saves us about an hour and a half in the operating room.”

Such dramatically shorter surgeries improve patient outcomes, according to Brazaitis. “Having the ability to study the internal structures and predesign the necessary supports before the surgery is tremendous,” he said. “There is less anesthesia time, less chance of hemorrhaging and infection, and a quicker recovery.”

Technology with a Human Touch

In addition to the benefits enjoyed by surgeons and other clinicians, the 3D models of individual medical conditions has proven to be an effective tool in explaining to patients and their families the exact nature of their injuries, as well as the specifics of efforts taken to treat them.

“They are able to converse with the patient and the family regarding the difficulty of what they’re going to do, as well as exactly what is involved and why paralysis or death could be a possibility,” Rouse said. “It becomes part of the preop protocol.”

Because 3D MedApps works primarily on the most severe cases, physicians are also seeing its ability to help rebuild the spirits of those with extensive craniofacial disfigurement due to injury or disease.

“These patients may function reasonably well, neurologically speaking, but they often have a tremendous physical deformity that is very obvious; in those cases, this technology is profoundly important,” said Brazaitis, who is also the radiology consultant for the Army’s North Atlantic Regional Medical Command. “If you can repair their anatomy, it is a huge step in helping them re-establish their own identity. They feel much more confident about themselves; they feel like they are whole again.”

Neurosurgeons at WRAMC also note that such repairs have improvements beyond the aesthetic, often improving the patient’s neurological function. “It establishes a more normal internal environment for the brain so the hemodynamic and cerebral spinal fluid pressures and the venous and arterial pressures of the brain start to become more normalized,” Brazaitis said.

Looking Forward

The cost of technology isn’t the only thing keeping 3D modeling out of hospitals around the globe, according to Brazaitis, who believes the future of this service lies in regional availability.

“Any one hospital is probably not going to have a substantial need for this sort of program,” he said. “But access to a program like this is going to be important for those who are doing craniofacial reconstructions and complex pelvic and spine fracture work.”

As such, WRAMC’s approach to delivering the 3D technology could serve as a model as the service expands throughout medicine. Located on the nation’s mid-Atlantic coast, the three-man team at 3D MedApps supports cases for every branch of service through all Department of Defense installations, as well as many facilities operated by the Department of Veterans Affairs.

Cote believes the positive effects of the 3D modeling will help the technology sell itself.

“The more we start using it, the more we will show these are going to be mainstream technologies and not just cutting-edge,” he said, using the example of PET imaging, which was considered to be fairly experimental not too long ago. “Academic tertiary medical centers are now finding there is a real value in PET. I think we are quite a bit earlier with the three-dimensional imaging, but it’s one of these technologies that makes total sense, and I think the more we use it, the more we are going to find ways to increase savings and improve the quality of care.”

Which, for Rouse, is the bottom line. “Patient outcomes are the be-all, end-all to me,” he said. Currently, he is awaiting approval for new machines capable of creating custom-made appliances in a variety of alloys, including titanium and cobalt chrome, which would give surgeons even more options in patient care. “We’re not yet prepared to do that, but you have to think big—and because of this type of imaging, it is not an impossible task.”

Turning CT Scans Into 3D Models

By Dana Hinesly

For the last 5 years, Stephen Rouse, DDS, and his team in the 3D Medical Applications Center at Walter Reed Army Medical Center (WRAMC) in Washington, DC, have converted imaging files into structures for use in preoperative preparation and patient reconstruction using a process known as “rapid prototyping,” or RP.

The first step in the process is obtaining clear, usable images.

“Everything we work with here starts with radiography,” Rouse said. As is the case at many large medical centers, many imaging studies are ordered by selecting from predetermined, drop-down menus or lists. For RP, more detail is usually required. The CT scan must be performed using soft-tissue protocols, with the thickness determined by the area in question.

“We ask for 1.25-mm slices on areas like the scapula, sinus, or the floor of an optical orbit,” Rouse said. “Bone in those areas is so thin that even at 1.25 mm, you’re not going to get it all, because the curvature of the bone can fall entirely within one slice.”

Images are then pulled from the hospital’s PACS system and manipulated using Mimics, a 3D image-processing and editing software program created by Belgium-based Materialise. Once all artifact has been removed and the desired area is isolated in the computer model, that data is transferred to machines capable of creating thin, horizontal cross-sections in physical space. Two such units in use at WRAMC are the SLA® 500 and the SLA 7000, both developed by 3D Systems.

“The two systems are the exact same technology, a couple of generations apart. Both house a vat of resin, and the 3D image we send from the computer actually prints on the surface of the resin,” Rouse said. “Each time the system runs across the liquid resin with a laser, it solidifies the surface. To account for the developing model, the platform on which it is being created drops a fraction of a millimeter—allowing the laser to continue to print on the surface.”

When the process is complete, the platform rises to the top to reveal a solid form of the 3D graphic file, which must then be painstakingly cleaned, removing all support structures.

Effective for large, solid structures—such as bones in arms and legs—the SLA units are not the first choice when models of delicate structures are required.

To create models of vascular structures or heterotopic ossification, Rouse turns to the InVision®, another modeler manufactured by 3D Systems that works much like an inkjet printer, or a ZCorp 450.

“It prints with plastic resin that solidifies right after it is printed, so the model actually rises as it is built,” Rouse said. “When you are printing on the surface of the liquid in an SLA, if you want what you are printing to stay in one spot—it has to be connected to something else. The SLA builds support for all of those pieces of anatomy that exceed 30° from the vertical.

“When you are building all of those blood vessels, anything that could possibly come loose or come off has a support on it,” Rouse continued, noting that all of those plastic supports must be removed from the fragile blood vessels before the model is useful to the clinician. “The supports in the InVision are built from wax—so all we have to do is warm the model; the wax will melt away, and then it’s ready.” As a result, a model of an aneurysm in the brain, for example, can be completed with less postproduction work.

Photos courtesy of Craig Coleman, Walter Reed Public Affairs.

Dana Hinesly is a contributing writer for Medical Imaging. For more information, contact .