What is 3D Printing?
LaPrincess C Brewer, MD: I am Dr LaPrincess Brewer, cardiology fellow at Mayo Clinic. Today on theheart.org, we will be discussing the role of 3D printing in congenital heart disease. I am joined by Dr Thomas Foley, assistant professor of radiology, who specializes in multimodality imaging.
3D printing is a compelling new technology that has the potential to revolutionize cardiac interventions. We are eager to hear how this innovative technology will enhance our knowledge and understanding of structural heart disease. To start, what is 3D printing?
Thomas A Foley, MD: 3D printing, which also goes by the names of "additive manufacturing" and "rapid prototyping," is a technology that uses a machine called a 3D printer to build three-dimensional models one layer at a time. It lays down one thin layer of material, which bonds with another thin layer of material. Over time, a model is built up from the bottom. The model is based on a computer-aided design. The model is designed with a computer program, sent to the printer, and the printer prints it over time. There are several technologies for doing this. The models that we have here were made on a printer that uses a liquid resin that solidifies when exposed to a UV light of a certain frequency.
It is bonded together at the same time. Other printers use gypsum powder, which can be bonded with a supergluelike material. There are printers that print with metal that is melted together with a laser. Other printers use a plastic, which is melted together with heat. Some printers even use such products as chocolate, so you can make edible prints.
Dr Brewer: What is the process for creating a 3D model of the heart or valves?
Dr Foley: To create a model of the heart or any body part, you start with an imaging modality. In most cases, this is either CT or MRI. A patient has a CT of the heart, and we need a volumetric data set. A data set has a stack of images that can be put together without any gaps in the anatomy. After that is acquired, we select what we want to print, and that process can take anywhere from a few minutes to a few hours. After the anatomy has been segmented out of the images, it is sent to another program to be processed. In this step, any noise that was in the model would be smoothed out. If the model is supposed to be hollow, we can hollow it out. If you want to make a cut, that can be done at this time. And if the parts of the model are not physically connected, you can place pegs to connect them so the model doesn't fall apart.
Dr Brewer: It gives you a true spatial relationship to allow you tangible manipulation of the cardiac structures.
Dr Foley: Yes, and when that portion is done, you overlay it onto the images that were initially acquired, so you can verify that the model corresponds to the patient's anatomy. Then you send it to the printer and it is printed. Our printer takes approximately 4 hours to print a small model and up to 12 hours to print a larger model of the heart. Some anatomic models have taken several days to print.
Do 3D Models Improve Outcomes of Care?
Dr Brewer: Have any studies been done to compare 3D models with traditional cardiovascular imaging techniques?
Dr Foley: A few studies[1,2] and reports of individual cases or some small case series have looked at this, but those are mostly anecdotal reports of a single surgeon's experience. They usually say that it helps improve the safety of the technique or reduce the time.
No controlled trials have looked at outcomes to see whether they have improved or whether there are cost savings with 3D printing. We still think this is a good technique. The studies will come in time; some are planned. If a surgeon tells us that this is beneficial and it makes them feel more confident in the surgery, we will make the model. It's also helpful for patients, when you are obtaining informed consent, because they can better understand the surgical procedure. So we have found that patients really like this technology.
Dr Brewer: You just touched on the cost savings. Are there any cost savings in using 3D models, and are they covered by insurance?
Dr Foley: No controlled studies have yet shown cost savings, but we believe that there are, because the costs of operating time and anesthesia are so high, even a small cost savings from a surgeon knowing the anatomy before entering the chest would pay for the models right there. If they improve safety outcomes or prevent complications, that would cover the cost of the models, too.
Right now, insurance companies and Medicare do not cover the cost of the models. Most of our models are made using development funds. In some places surgeons are paying for them out of the operating costs.
The Future of 3D Printing in Cardiology
Dr Brewer: What is the future of 3D printing? What do you foresee?
Dr Foley: There is a vast future for this technology. In the near term, the main uses of 3D models will still be for surgical planning. We used a model for a 6-year-old patient who had a ventricular septal defect and pulmonary atresia with multiple collateral arteries coming off the aorta and going to the lungs. The model was used to determine where the collaterals were, because some of them had to be reconnected to the main pulmonary artery and some had to be ligated, and the surgeon felt that this was very helpful in planning the procedure and knowing exactly what he needed to do.
Surgical planning will be one of the primary uses in the near future. Another use is for planning interventional procedures, such as placing percutaneous valves. We have done a few cases where we test-deploy a valve on the benchtop to see how it will fit and whether we think the procedure would be successful.
Moving beyond that, I think that we will start to print implantable devices, such as cardiac valves that will be custom-sized to the patient, or conduits, and these have the potential to be printed with biological material that could grow with the patient. If placed in a young child, the child may not need another valve replacement or it may prolong the time before needing another valve replacement. Some researchers have said that they will be able to 3D print a functional beating heart. That is on the horizon. I don't think it will happen any time soon, but we may see it.
Dr Brewer: The opportunities seem limitless, but right now, access is fairly limited. What types of centers have 3D printing for patients and surgeons and cardiologists to take advantage of?
Dr Foley: I know of several centers in the congenital heart disease world that do this. We do it. Several universities, such as Arizona State in partnership with Phoenix Children's Hospital, are doing it. The University of Toronto has a large program for 3D printing, as well as the University of Pennsylvania. I know there are others. There are several centers in Europe and Asia. But even some smaller centers are doing this; and if they don't have a 3D printer, several companies will make the models for them. They send the data to the company, and tell them what they want, and the company will make the model. If you are a surgeon, they will send you a preliminary digital model to see whether it incorporates all the anatomy that you want, and then they will print it. There are companies that will do just the printing, so you can actually make the model yourself on the computer and send it to be printed somewhere else. So there are several centers around the world that are doing it in-house, but there are also other options for doing it by contracting it out to other businesses.
Dr Brewer: This is wonderful information. Thanks, Dr. Foley, for these very great insights on this innovative tool that will be used to enhance patient-centered care. And thanks to our viewers. We hope you will continue to check out future content on Mayo Clinic's page at theheart.org on Medscape Cardiology.
Cite this: 3D Printing in Cardiovascular Medicine - Medscape - Apr 20, 2015.