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Friday, November 28, 2014

Modeling the heart

ASU graduate student Justin Ryan creates 3D heart models that give cardiac surgeons at Phoenix Children's Hospital more precise imaging prior to surgery. Photo by Daniel Friedman.

Doctors gather as much information as possible when preparing to correct heart defects in pediatric patients. They read images from CT scans on computers. They may even use software to study abnormalities in three dimensions, moving a picture of the heart around on a computer screen to analyze and plan a surgical strategy.

But what if they could take the process one step further? What if they could simply press “print” to create a perfect, color-coded, three-dimensional plastic model of a child’s heart before the surgical procedure even begins?

At the Children’s Heart Center at Phoenix Children’s Hospital, Justin Ryan, a biomedical engineering graduate research associate at Arizona State University, is doing just that.
Ryan, who has a background in animation studies, uses those same technical skills to change the two-dimensional images from CT scans to a three-dimensional object.

“It’s very similar to what you might see in a CGI (computer-generated images) in a movie, or in a video game character,” he says. After the image is created on his laptop, Ryan sends it to a three-dimensional printer that creates the model.

The printer, about the size of a pastry case at a coffee shop, contains a cinderblock-sized chunk of Super Glue combined with gypsum, a common material used in drywall construction. Ink jets slowly spray super-thin layers of color on the powdery block, forming the model according to the precise specifications of the data. Ryan equates it to building a house, from the bottom up, brick by brick.

The printing process itself takes about three hours. When it is finished, Ryan brushes the excess powdery material away to reveal the model. “From there, we do a bit of post-processing, but in another hour after that, we can hand it off to the doctor. They can view it, and make their decisions on surgery.”

Using a heart model to prepare for surgery is like finding your way with a GPS instead of a paper map, says Daniel Velez, M.D., a congenital heart surgeon at PCH. With the models, a surgeon can see, and touch, the actual size of the structure before surgery even begins. “To be able to tell the parents more precisely what I’m going to do, and what I’m going to encounter—even though I do tell them about variations and variabilities to the plan—I’m more at ease and more certain,” he says.

Each part of the heart, from chambers to vessels, is assigned a different color. Studies show that color coding helps medical teams better understand the tiny anatomical structures they will work with during surgery, says John Nigro, M.D., director of cardiothoracic surgery and co-director of the heart center. In babies, he adds, the heart is about the size of a walnut. As a child grows, it is about the size of their fist. “You can imagine the size of a child’s fist is pretty small,” says Nigro.

The technology is so new that it is almost too early to know what kind of impact it will have, says Stephen G. Pophal, M.D., division chief of pediatric cardiology at PCH. Pophal, who specializes in pediatric cardiac catheterization procedures, says it could change medicine.

Pophal teamed up with ASU engineering professor David Frakes to start the project at PCH. Frakes says is a “first of its kind” application for modeling congenital heart disease. “We hope that very soon any doctor who is doing an operation here is going to be carrying one of these models into the operating room—and being better prepared to perform because of it.”

Prophal hopes that using models will give doctors a head start in correcting defects. Knowing more in advance could also cut down on the number of images needed as procedures are performed, lowering radiation exposure. The tough job of visualizing a defect in three dimensions based on a two-dimensional image—sort of like imagining what a house will look like based on architectural plans—would be eliminated, says Pophal. “If I had the model in my hand, I would save half the time, and have half of the worries.”

Learning that a child has a heart defect can be overwhelming for parents, says pediatric nurse practitioner Courtney Howell, CPNP. “I think that is the hard part for some families to understand. They have this beautiful baby, and they expected all the things to go perfectly. Now they have this huge diagnosis.”

Howell says that the heart models help parents understand their child’s defect—it offers complex medical terminology in a context they can understand. And if everyone on the team understands the nature of the defect, patients are likely to do better, Pophal says. “The major impact is that we will be able to teach people more about their heart problems. This makes it very simple.”

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Vicki Louk Balint

Multimedia journalist Vicki Louk Balint writes about health topics for RAISING ARIZONA KIDS magazine.

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