3-D printed models aid surgical planning and preparation
By Jennifer Salopek Summer 2016
About a year ago, Michael W. Itagaki, MD, an interventional radiologist at Swedish Medical Center in Seattle, published a post on his blog titled, “Saving a spleen with 3-D printing: Presurgical planning with medical models makes ‘impossible’ surgeries possible.” In the blog post, Dr. Itagaki detailed his treatment of a patient with multiple aneurysms in her splenic artery. She was solidly opposed to the standard procedures—surgical splenectomy or splenic artery embolization—because both would lead to the loss of the spleen and put her at risk of future infections. Challenged by the patient to ﬁnd another way, Dr. Itagaki identiﬁed the treatment of brain aneurysms, which preserves blood ﬂow in the parent artery, as a promising alternative. But, having never conducted such a procedure, he was uncertain whether it would work. He told her, “The only way to know if the equipment would work would be to try it during an actual procedure.” She gave him a puzzled look and asked, “Well, isn’t there a way for you to practice?”
Using third-party providers, Dr. Itagaki had a replica of the patient’s splenic artery produced from her CT scan via 3-D printing and used it to practice the procedure until he identiﬁed the optimal combination of catheters and wires. “I was able to get all of the trial and error done in the model, something that otherwise would have taken place during the actual procedure,” he writes.
Medical professionals from a wide variety of specialties are recognizing the potential of 3-D printing for education, surgical planning and practice. One of its ﬁrst uses in medicine was as a surgical planning tool for the separation of conjoined twins, says Gregory Elfering, vice president of sales, medical and simulation products, at Colorado-based 3D Systems. He notes that his company’s product lines cover a lot of disciplines, including orthopedics and dentistry, and interest from interventional radiologists and interventional cardiologists is growing fast.
“IRs can use 3-D models to plan their surgeries,” he says. “Most are using them for catheter-based angio procedures and aneurysm repair. The models allow the doctors to take measurements and even to see calciﬁcation. They can think through deployment, seating, leak minimization—really get their minds around the patient’s visual anatomy.”
One IR who sees real potential for the technology is Barry T. Katzen, MD, FSIR, founder and chief medical executive of Miami Cardiac and Vascular Institute. “The state of the art is moving rapidly, and the potential is to understand patient-speciﬁc anatomy,” he says. “By doing a rehearsal through modeling and simulators, everyone knows exactly what they’re going to do and when they’re going to do it.” Dr. Katzen notes that Baptist Health, the system in which he works, is moving toward creating its own 3-D lab.
The process used to create customized 3-D models begins with an image: a CT or PET scan or an MRI. Specialized software segments the scan into very thin horizontal slices, which the 3-D printing hardware then converts into a physical object in an additive manufacturing process via stereolithography, a process in which layers of liquid resin are laid down and subsequently harden. Specialized machines produce 3-D prints in rubber, titanium and steel.
Over the past decade, the cost of 3-D printers has been coming down, making the technology much more accessible to practitioners and patients. Elfering notes that a life-sized model of a vascular target area costs around $1,500. In his blog post, Dr. Itagaki notes that he paid for the models out of pocket.
Multiple third-party companies provide this service, including Axial3D, based in Belfast, Northern Ireland. According to CEO Daniel Crawford, Axial3D has just launched an online ordering service that takes only minutes and produces customized anatomical models in just days. Crawford, who has a background in radiology and anatomy, wrote his master’s thesis on 3-D printing.
“I was making 3-D models to teach anatomy when I realized that the technology could be effective for preoperative planning,” he says. Axial3D clients upload 2D scans via an online portal, which can integrate with the hospital’s picture archiving communications system. The information is then rendered by proprietary software into a fully interactive 3-D visualization. Although most current Axial3D clients are working in orthopedics, the company is planning a study on atrial and mitral valve replacements in patients with complex aortic deformities.
“The 3-D model enables IRs and interventional cardiologists to measure and prepare,” Crawford says. “It allows doctors to take exactly what they need, reducing guesswork to a minimum.”
Software is the crucial interface between CT and PET scans or MRIs and the 3-D printer. Although 3-D printers are becoming more affordable, the software is less so, typically because professional engineering software has been used. In his workshop at the SIR annual meeting in Vancouver in April, Dr. Itagaki discussed the freeware software he has developed. Called Embodi3D, the application allows users to convert an imaging study to an STL ﬁle that can be sent to a 3-D printer. Free tutorials and 3-D printable ﬁles are available at embodi3d.com.
“I’ve been trying to make 3-D printing more accessible to everybody because I think it’s a very powerful technology,” Dr. Itagaki says. “Almost every month it seems there is a newer, cheaper and better option available.”
3-D models can also be used to take education and training to a new level, notes Elfering. Dr. Itagaki agrees: “By designing 3-D advanced training models for things like IVC ﬁlter deployment, we give trainees a chance to practice a procedure multiple times in a safe environment. This will greatly enhance training for all kinds of procedures.”
The 3-D printers also can be used for device design and prototyping, says Gideon Balloch, products manager at Massachusetts-based Formlabs, which distributes its products to more than 40 countries.
“The declining cost of 3-D printing means that we can iterate on designs more quickly,” he says. “We can print clinically relevant scenarios on a desktop 3-D printer that is high-resolution, high- detail and accurate.”
Agile MV, a Formlabs customer, is a medical device development and strategic consulting ﬁrm based in Montreal. Co-founder and managing director Étienne Lagacé explains that his clients are venture-backed medical device and pharmaceutical companies, as well as clinicians who want to test their ideas.
“3-D printing has evolved rapidly over the past few years, especially in the medical arena. We see it used for early prototyping of minimally invasive, catheter-based products where the process can go from idea to computer- aided design to physical components in hours or days,” he says. He notes that 3-D prototyping is ideal for more complex devices with many moving parts.
The ﬁrst international conference on 3-D printing in medicine was held in April in Mainz, Germany. Session topics ranged from craniofacial surgery and mandibular reconstruction to bioprinting, the process through which pioneers hope to produce human organs via 3-D printing and are already producing extracellular matrices. Lagacé notes special potential in pediatric applications, in which devices may become bioabsorbable as patients grow.
“If 3-D printing can help medical practitioners feel conﬁdent to do advanced or complicated cases that might be on the edge of their ability, then that could have a dramatic impact on all of medicine,” Dr. Itagaki says.
Dr. Katzen certainly thinks so. “This is about making what we do better,” he says, “about making patient care better, about making outcomes better. Technology is moving at a rapid rate, and everyone should keep their eyes on it. It is an exciting future.”
Photos courtesy embodi3d.com.
Jennifer J. Salopek is a freelance writer in McLean, Virginia. She can be reached at firstname.lastname@example.org.