It may sound like something out of science fiction, but doctors at Children’s National Medical Center are making hearts. Not actual hearts, but three-
dimensional synthetic models churned out by what looks like an ordinary printer.
The only one of its kind at a Washington area hospital, the printer uses data from individual patients to replicate the organs of those individuals, reflecting their particular intricacies and deformities. The device synthesizes images from CT scans or ultrasounds, translating that information into thin layers of plastic that are stacked until they form a three-dimensional object.
The technology, pediatric cardiologist Laura Olivieri says, “is amazing.”
Olivieri says that holding the replica of a heart enables her to make connections that she could not when looking at the actual organ on a computer screen.
“Because you’ve got a three-
dimensional problem,” she says. “What we’re all trying to do is reconstruct how far away X and Y are. But now you can just take [the model], and hold it, and look at it, and say, ‘Oh, they’re that far away.’ ”
In one recent case, Olivieri used a 3-D printer-produced model that she could take apart before the patient’s surgery.
“The cardiac anatomy of this patient is very rare,” said Olivieri. “And it’s not like there’s an FDA-designed device that will solve it.” The model allowed her to “look at the anatomy in 3-D and do some practice runs where the patient isn’t involved.”
To help prep a surgeon who needed to close the hole in an infant’s heart, Axel Krieger, a biomedical robotic expert at the center’s Sheikh Zayed Institute for Pediatric Surgical Innovation, created a model that used a mix of hard and soft plastics so the replica would feel like a real heart.
“We found the perfect combination of materials that actually allows you to place a suture through it or stick a needle through it,” Krieger said. “It feels similar to tissue. You can make a valve soft but the surrounding tissue hard, and then the bone really hard. So you can have different levels of the mechanical properties.”
He and his colleagues also modeled a dislocated spine by printing hard plastic vertebrae with softer, jellylike disks in between, so that it moved realistically, enabling doctors to better understand the injury.
Children’s hopes to use the printer to create models for patients with rare or complicated conditions, and for those who need corrective procedures on complex congenital defects.
“Congenital heart disease is so structural,” Olivieri said. “On some level, you can predict what a physiology is by looking at [a patient’s] anatomy. So a picture can predict how sick or how well a patient can be. That makes congenital heart disease one of the perfect applications for 3-D printing.”
Once used primarily by industrial companies for creating prototypes of such things as cars and jewelry, three-dimensional printing has expanded into much wider use in recent years. People are printing guitars, airplane parts — even guns. One man has used a 3-D printer to make more 3-D printers. Last week, Staples announced that customers will soon be able to print 3-D objects in its stores.
In medicine, 3-D printing is rapidly gaining a reputation as the next great promise. Bioengineers at Cornell recently printed an artificial ear — injected with cells from a cow’s ear — that looks and acts like a real ear. While not yet ready for clinical use, scientists say this kind of replica could help patients who lose ears in accidents or from disease, as well as those born with disfigured or missing ears. Doctors in Britain recently used a 3-D printer to create a partial prosthetic face for a man who had been disfigured by cancer. In February, the Food and Drug Administration approved a skull implant created by a 3-D printer.
Children’s National Medical Center isn’t yet making tissue with its 3-D printer; its plans for doing so are in the “early stages,” according to Peter Kim, vice president of the institute. But the hospital is expanding the scope of work it is doing with the machine. Children’s, which has had its printer for about a year, has used the device to create a robotic scope designed to reduce human involvement in endoscopic procedures; it has also designed forceps built to rotate a needle so it’s oriented properly when a doctor is stitching up a patient. The hospital is partnering with the University of Maryland to print medical devices that would break down in the body over time rather than requiring a follow-up removal procedure.
The machine at Children’s looks unremarkable, not much different than an industrial copier. It hums and whirs like a home printer. Peer through the printer’s glass surface while it’s running and you can see a bloblike model taking shape.
Depending on how complex a job is, it can take anywhere from a few hours to an entire day to produce a model. Instead of ink, the printer uses liquid plastics, which cost about 40 cents a gram. The tiniest heart might use about $30 of material; the plastic for a larger heart could run closer to $100. The models are built from bottom to top, each layer a thin plastic shaving on top of the one before.
“You have UV lights on both sides of the printer head,” Krieger said. “While it’s printing, it cures the level that is below. So it really builds it up stack by stack and cures it, so it solidifies and becomes hard.”
(And, no, printer jams aren’t just limited to the machines that spit out paper. “Absolutely, that happens with this printer,” Krieger said.)
Because of the high temperature during the process, models are surrounded with a soft filler material so that they don’t collapse on themselves as they’re being printed. This means that when a job is complete, the finished product looks at first like a warm, gelatinous blob.
“A solid mass, you wouldn’t recognize it at all,” said Kevin Cleary, technical director of the institute’s bioengineering initiative. “It’s like a diamond before you polish it up. Then you put it in a bath or in a power-washing machine to scrub it out.”
After the cleaning process, the model is complete.
The team at Children’s is making models in all colors, sizes and textures. The beige model of an infant’s heart is walnut-size and hard as a clamshell, while a much larger heart model — representing a 24-year-old patient — is jet-black and rubbery. Sometimes doctors choose different colors and textures so they can better examine distinct anatomic qualities. In other cases, the choices are purely aesthetic.
“You can print with different colors, different materials,” said Kim. “Some of them are transparent and see-through. You can use different materials from hard to soft to silicon.”
Though the possibilities of 3-D printing are enormous, the technology is still new, and it’s expensive. The printer at Children’s cost about $250,000. A high-end ultrasound machine can cost about $270,000, and a portable CT unit is about $550,000, according to Laurie Hogan, the director of radiology services at Children’s.
Making 3-D models is also time-consuming. Just prepping ultrasound images for the printer can take many hours.
“The very first one I did was not even recognizable as a heart, and it probably took me like 25 hours to do,” Olivieri said.
Although Johns Hopkins Hospital uses 3-D printing to make models of skull plates to prep for reconstructive surgeries, it doesn’t have a printer on-site, instead partnering with medical modeling companies. Other area hospitals, such as MedStar Georgetown University Hospital and George Washington University Hospital, don’t use 3-D printing at all.
But doctors at Children’s believe the investment — in time and money — is worth it.
“Complex congenital heart disease, thank goodness, is fairly rare,” Olivieri said. But “this is something that’s going to really help us take care of them.”
For Olivieri, there’s also the thrill of being on the cutting edge.
“Not that long ago, people with congenital heart disease didn’t even survive,” she said. With new surgical techniques, and now 3-D printing, “I don’t even think we now realize what it’s going to be, what impact that will have.”
LaFrance is a writer based in Washington and New York. Her husband is a pediatric cardiology fellow at Children’s, but he is not involved in the 3-D printing project.