Senior Staff Writer
CHICAGO — Researchers are using CT and 3-D printing technology to recreate life-sized models of patients' heads to assist in face transplantation surgery, according to a study presented this week at the annual meeting of the Radiological Society of North America (Oak Brook, Illinois) in Chicago.
Doctors at Brigham and Women's Hospital (Boston) performed the country's first full-face transplantation in 2011 and have subsequently completed four additional face transplants. The procedure is performed on patients who have lost some or all of their face as a result of injury or disease.
In the study, researchers assessed the clinical impact of using 3-D printed models of the recipient's head in the planning of face transplantation surgery. The team was led by Frank Rybicki, a radiologist and director of the hospital's Applied Imaging Science Laboratory; Bohdan Pomahac, lead face transplantation surgeon; and Amire Imanzadeh, a research fellow.
"This is a complex surgery and its success is dependent on surgical planning," Rybicki said. "Our study demonstrated that if you use this model and hold the skull in your hand, there is no better way to plan the procedure."
Rybicki told reporters during an RSNA press conference that, because the model is based on the CT scan, the data is the same that the physicians would have by either looking at the CT images or by doing 3-D visualization. "The data is the same, but the difference is that you can actually hold the 3-D printed model in your hand and understand the relationships between the anatomy and the topology and how things fit in much more sophisticated way than you can with just 3-D visualization because that's on a 2-D screen and now we have the model, so-called, in your hands," he said.
Each of the transplant recipients underwent preoperative CT with 3-D visualization. To build each life-size skull model, the CT images of the transplant recipient's head were segmented and processed using customized software, creating specialized data files that were input into a 3-D printer.
"In some patients, we need to modify the recipient's facial bones prior to transplantation," Imanzadeh said. "The 3-D printed model helps us to prepare the facial structures so when the actual transplantation occurs, the surgery goes more smoothly."
Although the entire transplant procedure lasts as long as 25 hours, the actual vascular connections from the donor face to the recipient typically takes about an hour, during which time the patient's blood flow must be stopped.
"If there are absent or missing bony structures needed for reconstruction, we can make modifications based on the 3-D printed model prior to the actual transplantation, instead of taking the time to do alterations during ischemia time," Rybicki said. "The 3-D model is important for making the transplant cosmetically appealing."
The researchers said they also used the models in the operating room to increase the surgeons' understanding of the anatomy of the recipient's face during the procedure.
"You can spin, rotate and scroll through as many CT images as you want but there's no substitute for having the real thing in your hand," Rybicki said. "The ability to work with the model gives you an unprecedented level of reassurance and confidence in the procedure."
Senior surgeons and radiologists involved in the five face transplantations agreed that the 3-D printed models provided superior pre-operative data and allowed complex anatomy and bony defects to be better appreciated, reducing total procedure time.
"Less time spent in the operating room is better for overall patient outcomes," Pomahac said.
Based on the results of this study, 3-D printing is now routinely used for surgical planning for face transplantation procedures at Brigham and Women's Hospital, and 3-D printed models may be implemented in other complex surgeries.
Rybicki explained during the press conference that in theory, 3-D printed models could be made from an MRI scan or even 3-D ultrasound images. "Typically, because of the complexity in the face transplant surgeries, we need to see the vessels and so we need to do the CT for the angiogram and CT is really the best way of looking at the bone so we typically use CT to do these models and it's a very important and elegant way to get the data," he said, while holding in his hands a 3-D printed bone model of a patient's face. "In the soft tissue models, where we actually take the soft tissues and we want to study those soft tissues in relationship with the face ... we definitely want to use another modality, like MRI, because CT involves radiation, and we can take a photograph anytime we want. So if we really want to study longitudinal tissue changes, it would probably be better in the future to make our soft tissue models off of MRI scans. To date, we haven't done that, but it's an interesting thing to explore."
Today there are many medical and surgical uses for 3-D printed models, Rybicki said, the most common use being surgical planning. However, he said 3-D printing is also very important in patient care because many different plates and implantable devices are also being done with 3-D printing now. "If someone has a catastrophic injury and they need a piece of bone or something that is made, that thing can be 3-D printed in titanium and implanted in the patient," he said.
But one of the most futuristic and exciting areas of 3-D printing, according to Rybicki, is bioprinting. "Actually making living tissue and 3-D printing that living tissue so that it can then be part of the medical care," he said. "That's one of the major steps that's going to happen in the future of 3-D printing to help patients." //