Taking the Art Out
A crucial step in making tissue welding widely applicable is building easy-to-use laser systems that are safe and reliable in many surgeons’ hands, not just in those of the highly skilled researchers who are developing the systems. Though Poppas and other surgeons have earned reputations as excellent welders, their technique is still in some ways an art form. Judging when to turn the laser off, for one thing, is tricky; if the tissue gets too hot it will burn, if it doesn’t get hot enough the weld will be weak.
Poppas, who uses protein solders when he welds, explains that eyeballing the endpoint of a weld leaves a lot of room for error. “The only way to do it is by looking at visual changes that occur in the solder-when you see it harden, when you see it glisten over, when you see it bubble, when you see it turn opaque. Those are extremely subjective parameters, and every surgeon is going to have a different opinion on what a weld looks like.”
To make the process consistently reproducible for the average surgeon, Poppas is working with Danvers, Mass.-based Abiomed to test a “smarter” welding system. The Abiomed approach employs an infrared detector, similar to those used in ear thermometers, to measure the temperature of a spot as the laser heats it. The signal from the thermometer feeds into a microprocessor, which adjusts the laser’s output to maintain the temperature within a few degrees. The system, according to Robert Stewart, a principal staff scientist at Abiomed, “takes the art out” of welding. “Anybody can set a temperature and weld and it will work.”
In some of the delicate operations targeted by tissue welders-for example those involving newborns and even fetuses prior to birth-such reliability could be a matter of life and death. While these high-risk applications give laser tissue welding a chance to shine (sutures would tear through fragile fetal tissues), they also highlight the stakes involved in keeping the laser in check. To perform the operations safely, researchers from Lawrence Livermore National Laboratory in Berkeley, Calif., have invented a feedback-controlled welding system, and, working with Conversion Energy Enterprises of Spring Valley, N.Y., the team is testing the feasibility of using it to seal and join together newborn and fetal blood vessels.