Heart models 3D printed in Canada help surgeons treat pediatric heart defects

Surgeons rehearsing a procedure using a 3D printed replica model of a heart

Javelin customer 3D HOPE Medical is world leader

3D printed replicas of precious child-sized hearts, placed in the skilled hands of the top pediatric cardiac surgeons in the world – this is the vital work of Dr. Shi-Joon Yoo of 3D HOPE Medical.

Dr. Yoo is a cardiac radiologist who leads the Section of Cardiac Imaging, Department of Diagnostic Imaging at the Hospital for Sick Children in Toronto. He’s a specialist in imaging for congenital heart diseases in infants and young children and 3D prints models of human organs using the digital data obtained from MRI, CT, and ultrasound.

Although he hasn’t been counting, Dr. Yoo believes he has made physical representations of 300 different cases of heart defects, and has printed a total of about 1,000 tiny hearts.

Why 3D printing

Dr. Yoo says visualization in 2D is not as powerful as having a model you can touch, pull, push, or rotate; it does not allow you to make an incision to look inside an anatomical structure and examine hidden elements.

“Even seeing a 3D model on screen or on paper – it’s not really 3D, it’s still 2D. There is still room for misunderstanding. It’s different to hold a physical model in space. When the anatomy is unusual and complicated, I used to have to write two pages to explain a scan, or take 10 minutes to explain it. Now the fine detail is all in the model.”

Instead of having to assemble a picture in their minds, surgeons hold the 3D-printed replica, which represents the heart of an actual patient, and plan the procedure. Because of the knowledge and practice gained before stepping into the operating room, surgery is shorter and the patient spends less time under anaesthesia, leading to better outcomes. Sometimes a sterilized model even ends up in the operating room as a guide.

When operating on an infant or young child, it’s difficult for the assisting surgeon to see inside an opening that’s just a few centimetres long. Being able to see, touch, and practise on a model advances their competency and confidence and cuts down on years of learning. The operation can be rehearsed, and assistants can be as familiar with the defect as the primary surgeon.

It’s an enormous benefit, because at least 10 years of experience is needed before a surgeon is ready to perform delicate pediatric cardiac surgeries. The anatomy is complex, cases are varied, and the incidence is rare. At the Hospital for Sick Children, even with all affected Ontario children coming for treatment, individual surgeons might see only one or two rare cases a year.

Dr. Yoo presenting at Javelin (photo courtesy of The Oakville Beaver)

Dr. Yoo says before 3D printing, it was learning by doing, working on patients. True discovery happened while the child was open on the table.

Another benefit of having true-to-life physical models is easier communication with families. Using models of real cases that are similar, a surgeon can show parents before and after models and exactly what the surgery will do for their child.

Early adopter

Dr. Yoo has been working with Javelin Technologies since 2013, but he’s been working with 3D printing technologies since 2009. During that year, he met a German doctor who mentioned 3D printing in a lecture, and Dr. Yoo was immediately captivated.

“In two seconds – I am not exaggerating – I saw the potential in my field.”

He began 3D printing by providing model hearts to cardiologists and surgeons at the Hospital for Sick Children. He started with powder-based inkjet technology, which is primarily used to create rigid, ceramic-like models. These models enlightened education and treatment planning, but were limited because of the stiffness.

Investment in better technology

Dr. Yoo knew that a higher end printer could manufacture models that were pliable and varied in opacity, so he established his own business, 3D HOPE Medical, and with his own money purchased the Stratasys Objet260 Connex, sold and supported by Javelin Technologies.

Based on Polyjet technology, this printer uses photopolymer resin cured by UV light to build models that are similar in consistency and flexibility to human heart tissue.

3D printed heart models

The highest resolution medical imaging can give surgeons is 0.3 to 0.7 mm. The Stratasys Objet260 Connex delivers smooth surface finish and high resolution parts. The layer thickness can go down to 16 microns.

The realities of the process

“I always expose whatever I know about the process,” Dr. Yoo says. “People don’t catch on to the time it takes and all the meticulous steps involved. Printing is the easiest part of the job.”

He says his blueprint – diagnostic imaging – provides a sea of information that must be sorted and segmented for rapid prototyping. And later, after the model is printed, skilled people must carefully clean and dye the model. Because 3D printing technology is not suitable for replicating the valve structures within the heart, those parts must be made separately and manually. It’s labour-intensive, time consuming, and expensive. One new heart model can take 12 to 20 hours to produce, and Dr. Yoo estimates the value of each (modestly) at about $2,000.

Educating colleagues around the world

Dr. Yoo is a leader among his colleagues. He has two sets of educational models that he takes on the road to teach the medical community and has presented to members of the American Heart Association, the American Association of Thoracic Surgeons, and the Radiological Society of North America. In January 2016, Toronto’s Hospital for Sick Children hosted a training session for cardiac surgeons from around the world.

Looking ahead

Dr. Yoo hopes the software of the future will help simplify the segmentation work he does to get imaging files ready for printing and that printed material will be even more lifelike. He looks forward to one day printing in silicon, the best possible material for cutting and suturing. And because he’s funding his work out of his own pocket, he wishes for better financial support for people working in an academic medical environment like his.

“I’m always looking at new things,” Dr. Yoo says. “The process and materials are reasonably good, but we should never stop trying to improve.”

Watch the video below (no audio) to learn more about 3D printed heart models and how they are used.

Results:

The Stratasys Objet 260 Connex 3D printer sold and supported by Javelin Technologies offered radiologist Dr. Yoo the flexible materials he needed to replicate human heart tissue as closely as possible:

• The Stratasys Objet260 Connex can deliver 16-micron resolution, meeting or beating the top resolution available in digital imaging in the medical industry.
• Cardiac surgeons use the knowledge and experience gained through studying and rehearsing on 3D printed models to shorten surgeries and reduce the time the patient spends under anaesthesia, improving outcomes.
• Slight variations in congenital heart defects in infants and young children can be replicated in 3D models, exposing surgeons to a variety of real-life cases they wouldn’t otherwise see, touch, and practise on in 3D. This cuts years off their training time.
• Communication with families is improved when surgeons can explain conditions and surgeries using 3D printed models of actual cases.
• The 3D printed hearts are educating the world’s best physicians including pediatric cardiologists, cardiac surgeons, and radiologists, who are bringing new skills and techniques to their home countries.