VOA常速英语:3D Printers Help Heart Surgeons

WASHINGTON — 3D printers are slowly entering everyday life and they are increasingly being used in medicine. Doctors at Washington's Children's National Medical Center say the life-size tri-dimensional prints of their patients' hearts helps them in planning and executing surgeries.

Magnetic resonance imaging, computer tomography and ultrasound already give pretty good images of patients' internal organs, but doctors at the Children's National Medical Center say nothing beats holding a life-size model of a heart in your hand prior to the surgery. They can study it, plan the procedure and even practice the access to the damaged area.

Pediatric cardiologist Laura Olivieri says many of their young patients were born with hearts that did not form as they should have, but surgeons can correct that.

"Seeing the heart defect in three dimensions can really help the interventionist or the surgeon plan the best procedure," she said.

The hospital acquired the $250,000 printer about 18 months ago and the team is still expanding and finding new areas to print.

The procedure always starts with taking a set of three-dimensional images with magnetic resonance imager, computer tomography scanner and ultrasound machine. Highly trained pediatric cardiologists manipulate those images and separate the organ from the noise in the picture. In order to save time in printing they sometimes also cut away parts of the image irrelevant to the planned procedure.

"It takes us now about an average I would say about two hours of manual work on the computer to manipulate the data in to generate the 3D model and the printer takes about, for a full size heart like this, it takes about 12 hours," said mechanical engineer Alex Krieger, the principal investigator for pediatric surgical innovation at the Children's National Medical Center. "A smaller heart maybe five, six hours."

Krieger says in one instance his team printed a model of the heart of a patient with stenosis, or narrowing of the passage between two heart chambers. The interventional cardiologist wanted to see exactly what kind of stent he should use, the size and length of it, and also the access path.

"So this model allowed him to really look at that in depth and plan, and prepare for the procedure better," he said.

The machine prints by spraying layers of plastic, one on top of the other, while the ultraviolet light immediately cures it before the next layer is sprayed. Krieger says the printer can be loaded with two different materials. Precise control of their ratio allows the printed model to feel very natural, with both hard and soft tissues.

Cardiologist Olivieri says doctors still have to learn a lot about the new procedure.

"It's a brand new field. These have only been possible for a wery little amount of time and I don't think we even know the full capability of what we're going to be... what they're going to be used for," she said. "We're kind of talking about a technology that went going from feasible to kind of usable and we're right in that middle ground right now."

There is also hope that someday hospitals will be able to print even replacement parts for damaged organs.

"There's eventually some organ printing, you know, that's the ultimate goal, but I think there are a few steps between that we will reach in the next few years, on the way to full organ printing that I'm very excited about," said Krieger.