Published December 14, 2018
A UB team of biomedical engineers, neurosurgeons and cardiovascular interventionalists has developed a way to generate 3D prints of the human vascular system, giving surgeons pre-surgical, hands-on access to individual patients’ life-threatening vascular diseases in the heart and brain before any scalpels ever touch human skin.
Initiated by Ciprian “Chip” Ionita, assistant professor in the Department of Biomedical Engineering, and Adnan Siddiqui, professor of neurosurgery in the Jacobs School of Medicine and Biomedical Sciences, the method that creates 3D prints is already being used to better prepare doctors performing delicate surgeries to treat such conditions as stroke, aneurysms, cardiac arrest and congestive heart failure.
The 3D prints also are being used to train residents and medical students learning how to proceed with these delicate and often life-or-death procedures.
“The whole idea of these 3D-printed models is to not only mimic patient anatomy, but to also mimic some of their vascular mechanical properties,” says Ionita, whose Department of Biomedical Engineering is a joint department in the Jacobs School and the School of Engineering and Applied Sciences.
Before 3D printing, these lifelike models were costly, complicated to make and had to be shipped from Switzerland at a cost of more than $12,000 each. Now, each model costs about $100 and can be produced specifically for one patient. The number of models and their specifics suitable for 3D printing are endless — and can be custom-made to fit individual patients.
Ionita and Siddiqui began their 3D-printing research when the Clinical and Translational Research Center (CRTC), Gates Vascular Institute (GVI) and Jacobs Institute were created to place engineers, physicists and vascular surgeons all under one roof.
“We are now able to optimize our research by meeting every day and working together,” Ionita says.
He is also working with engineers at the Center of Excellence in Bioinformatics and Life Sciences to enhance the mechanics of the models, and make them even more lifelike.
The 3D-printed models are built to scale for a patient’s arteries, and are often referred to as “phantoms.” The models are warmed up during surgical practice sessions to simulate the gummy elasticity of arteries within a vascular system, and allow the devices, fabricated with shape memory alloys, to behave the same as human arteries.
“We are trying to help surgeons who have really difficult cases, and have doubts about the approach,” says Ionita. “They will then have us make a model, come to the lab for surgical planning and practicing, and make a decision.”
From the moment a patient arrives at the hospital to the analysis of post-surgery for research purposes, the entire team works together to correct the patient’s life-threatening vascular condition.
The models are also used to train residents and medical students. 3D prints are available at the Gates Vascular Institute for those in training to learn the proper methods for treating vascular conditions such as a stroke, aneurysm, cardiac arrest and congestive heart failure.
Ionita says students receive a better education by witnessing the decision-making process all the way from a patient scan to surgery.
“Without human interrelation between the researchers and the surgeons,” says Ionita, “the meaningful medical work can’t be done.”
The first phase of the process starts when a patient receives a diagnosis from a doctor, Ionita explains. “They give us problems,” he says, “then we try to solve them.”
Next, a scan of the diseased area is taken through 3D medical imaging.
A process called segmentation — or the selection and isolation of the structure of interest — is collected and analyzed. Once a specific segment is located, engineers create a 3D geometry and put it into a secondary software to manipulate before printing the model.
The model, or phantom, is then 3D-printed right in house. A model can take from 20 minutes to 20 hours to print, depending on how complex and precise the phantom needs to be, Ionita says. The printing time also depends on the different types of material being used. Materials can be combined for a single print to get the correct texture. Rubber silicone mimics blood vessels the best, and is used the most for prints, he says.
Depending on the patient, the print can be used to understand hemodynamics, validate medical software, test devices or create a surgical plan.
When treating a patient with a very high risk or novel procedure, a doctor and his team head to Ionita’s lab. This is where they practice on the patient-specific model to develop a customized surgical plan. How they want to approach the model will determine their steps. If it does not work on the model, Ionita says, they will then readjust the surgeon’s plan and keep track of the changes.
“There was a case where a surgeon made changes to 70 percent of the steps he was going to do originally,” says Ionita. The surgeon decided to use different devices and stiffer wire to better accommodate the patient during surgery, based on the outcome of practicing the surgical plan on the model.
In the final phase of the process, the surgical team starts surgery by using the approach they perfected on the patient-personalized model.
Soon there will be an extensive database of brain and heart vascular scans compiled in clinical trials. In addition to the models making it easier for doctors to decide what surgical tactics to take, this large database can speed up testing for a new device or a procedure used in the clinic.
“The whole idea is for us to understand more depth into a patient’s vascular structures’ interaction with the devices and blood flow, why a person would fully recover from an aneurysm after six months and why another patient would not,” says Ionita.
“At the end of the day, it’s about a patient’s specific geometry and vascular mechanics, or the difference between two patients.”
Lauren Shepard, Ionita’s student assistant, studies how to use the 3D prints to better understand the flow and pressure conditions within a patient’s diseased arteries. In one particular experiment, Shepard is trying to understand how different variants in the brain vasculature effect the pressure gradience, or flow.
At the bottom of the skull there is a vascular structure called the circle of Willis. This connects the anterior circulation to the posterior circulation, “almost like a safety vascular feature to make sure in case one of the arteries gets blocked, your brain still gets blood supply from the other arteries,” says Ionita.
Not all individuals have a full circle of Willis — only 28 percent of people have a full and complete structure that connects all of the vessels together, he says. People who have vascular stenosis — a narrowing of the vessel — can be asymptomatic and unaware they have a vascular disease, while others are severely symptomatic.
Ionita’s team of biomedical engineers is trying to understand how variants of the circle of Willis affects the blood in the vessels leading to the brain. The team also is trying to determine the metrics of patients’ risk level when they come into the hospital, which is extremely important for classifications.
In the cardiac equivalent of this study, conducted in collaboration with Vijay Iyer, clinical associate professor of medicine, and Michael Wilson, medical director for cardiac CT at Kaleida Health, researchers examined how catheter lab measurements of pressure gradients across coronary arteries correlate with measurements in the lab.
“This is the first clinical trial of its own where they’re trying to replicate a study in humans with 3D-printed, patient-specific benchtop models,” says Ionita. “We concluded this cardiovascular study because we found significant correlation between the measures of flow from the model to the measures of flow from patients.”
The success of this experiment led to the team’s next project. Ionita’s team is now moving toward the neuro-application of this study, and building off of what they learned in the coronary and cardiac application.
“There is no better tool than 3D printing to replicate patient anatomy,” says Ionita. He predicts that 3D printing will become standard in all medical fields in the near future. As of now, radiology departments across the country are adopting 3D printing as a new 3D medical imaging representation, he says. Due to increased acceptance, 3D printing will become a reimbursable tool as of June 2019, allowing doctors to use it as a patient service for better diagnosis and treatment planning for high risk patients.
Ionita explains the main goal of this 3D printing is to create major advancements in surgery through biomedical engineering and diligent teamwork.
“We as a team hope to achieve safer surgery with less complications,” he says, “and ultimately save lives.”