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However, “using external landmarks is never necessarily a completely accurate reflection of what the body looks like,” says David Rodeberg, a surgeon in the Division of Pediatric General and Thoracic Surgery at Children’s Hospital of Pittsburgh of UPMC, who wasn’t involved in Imam’s work.

The process often needs to be repeated because PICCs can get stuck or flip around and end up directed toward the head rather than the heart. Imam says that between a third and half of PICCs that are placed without the help of ultrasound or fluoroscopy need to be readjusted or reinserted. Misdirected catheters can damage veins and allow toxic drugs to leak into the surrounding tissue. In rare cases, if a catheter is pushed too far into the heart, it can trigger an irregular heartbeat or other serious problems.

Imam came up with the idea of a light-guided catheter five years ago, when he was an intern at Children’s Hospital Boston, where PICCs are commonly used in babies, and he “saw a few of these end up in the wrong place.

For his first prototype, Imam attached the light from a laser pointer to the tip of a PICC. He is now investigating different wavelengths of visible light, focusing on red, which penetrates tissue well, and green, which is easy to see, and he’s considering using a flashing light to make the catheter even more visible. One of the prototypes that’s being developed is outfitted with lights all along the catheter line so that when it’s inserted, “you can see essentially a dashed line moving forward.” Tests on rabbits indicate that the glow shows the catheter’s position to within millimeters. The realm of accuracy needed for a catheter insertion, Imam says, is about a centimeter.

A three-to-five-milliwatt light in a vein less than a centimeter under the skin was easily seen outside the body during Imam’s tests in a dimly lit room. PICCs often get stuck or are misdirected in these shallow veins.Imam says that he’s now working on solutions to that problem. Ideally, the catheter will still be visible as it travels deeper within the chest, toward the heart.

“If it will actually show you where it is when you go up into the chest, that’s a fascinating idea,” says David Gaieski, an attending physician in the emergency department at the Hospital of the University of Pennsylvania, who was not involved in the work.

Amy Kyes, manager for the Infusion Clinic and Vascular Access Team at Froedtert Hospital, in Wisconsin, says that while light would be useful to more accurately track the path of a catheter, she thinks that x-ray checks will still be necessary to confirm placement because “not everybody is built the same. I can only imagine that we’ll still have the radiology piece because of people’s different anatomy.”

Imam hopes that he can develop a catheter that’s visible throughout its journey toward the heart, but “there’s certainly nothing wrong with using this technology in combination with other probe technology,” he says.

At the very least, Imam says, a transilluminating catheter could be inserted without the need for fluoroscopy or ultrasound, make bedside placements more accurate, and cut down on the number of x-rays required.

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Credit: Patrick Bibbins / Children's Hospital Boston

Tagged: Biomedicine, optics, medicine

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