3-D printed models may soon guide one-of-a-kind pediatric heart operations

Photo credit: Bryce Vickmark, MIT News
Photo credit: Bryce Vickmark, MIT News

No two hearts are alike. It sounds like poetry, but this adage takes on a special meaning for pediatric cardiac surgeons.

Children born with congenital heart disease have unique cardiac anatomies. To correct them, surgeons need a nuanced understanding of each structure and chamber of the heart, and for decades have relied on (increasingly sophisticated) imaging technology.

Soon, though, they will be able to touch, turn and view replicas of their patients’ hearts up close. Researchers at Boston Children’s Hospital and MIT have jointly designed a computer program that can convert MRI scans of a patient’s heart into 3-D physical models.

Andrew Powell, MD, senior associate in Cardiac Imaging at the Boston Children’s Heart Center and one of the project leaders, explains that constructing a 3-D heart model involves three steps:

Step 1: Obtain the 3-D image data. This can be done with MRI, CT and 3-D echocardiography.

Step 2: Identify the borders of the important heart structures (“segmentation”). This step requires a physician to view the images and separate out the myocardium, blood pool and great vessels.

Step 3: Render a virtual heart model and build it using a 3-D printer.

While the medical research community has been using 3-D printing for some time now, adapting this technology for heart surgeries has proven quite complicated. At first, just the segmentation process took up to ten hours—an unacceptable timeline when a patient’s life may be in jeopardy. Doctors wanted to be able to perform an imaging study one day and have a 3-D printed model available the next.

So the team sought to decrease the time a cardiologist spent manually segmenting and labeling heart structures, using an algorithm to help identify the boundaries between them based on standard heart measurements. There was a problem, however: patients with congenital heart disease need surgery precisely because their hearts are anatomically abnormal.

Surgeon vs. machine

The group decided to test a hybrid approach in which the cardiologist manually segments a small percentage of the anatomic abnormalities and the algorithm does the rest. They found that when a cardiologist steps in to work on just 14 of 200 sections of the heart, the algorithm can complete the picture with 90 percent accuracy.

The whole process—from imaging to physical model—now takes between three and five hours.

Once implemented, the technology is expected to decrease the risks involved in heart operations as well as shorten their length by allowing surgeons to choose their strategy and instruments before a patient even enters the operating room. “Eventually, we want to be able to do this on a rapid and routine basis,” says Powell.

Sitiram Emani, MD, a cardiac surgeon at Boston Children’s not involved in the research, is enthusiastic about this new technology. “We have used this type of model in a few patients, and in fact performed ‘virtual surgery’ on the heart to simulate real conditions,” he said in a recent interview with MIT News. “Doing this really helped with the real surgery in terms of reducing the amount of time spent examining the heart and performing the repair.”

Learn more about Cardiology Research at the Boston Children’s Heart Center