Catheters are an invaluable way of delivering life-saving drugs and nutrition directly to the blood vessels near the heart, but guiding the devices through veins can be tricky. A doctor in Boston is developing a catheter fitted with a light that's visible outside the body so that it's easier for medical professionals to get it in place.

Farhad Imam, a newborn-intensive-care physician at Children's Hospital Boston, says that his transilluminating catheter could be useful in outpatient, wilderness, and military settings, where there isn't the luxury of using fluoroscopy or ultrasound to track the device's movement.

More generally, the transilluminating catheter could reduce the need for reinsertions and repeated x-rays to check the instrument's positioning, Imam says.

"That would make our lives a little bit easier," says Mary Haygood, clinical manager for the vascular access team at Cincinnati Children's Hospital Medical Center, who was not involved in the work.

Imam designed his catheter with babies in mind, knowing that it would be relatively easy for light to shine through their thin skin. However, he thinks that it will also work in adults.

Imam has tested the catheter in rabbits and patented it, and he's now gearing up for human trials, which he expects to begin in 2009. He's working with a catheter manufacturer and an optics company to produce a variety of prototypes.

"The reason why we're so excited about this technology is, it's simple, it's intuitive in the sense that you can see it with your own eyes, and you don't need an extra pair of hands to hold something," Imam says.

Central venous catheters, which feed into the sizeable veins leading to the heart, are commonly used in intensive care and during cancer treatment. They're needed to administer potent drugs like chemotherapeutic agents that have to be diluted in the rush of blood flowing through a large vein; to treat patients whose peripheral veins have collapsed and can't be accessed with an intravenous line; and to administer long courses of antibiotics, pain relievers, and nutrition, which can't be given through peripheral intravenous lines that must be replaced every few days and are easily dislodged.

Some central catheters are inserted directly into the chest during a surgical procedure, but increasingly, variants called peripherally inserted central catheters (PICCs) are being used. They consist of a long, flexible tube that's inserted in a small vein in the arm or ankle, then carefully threaded up into the chest until it reaches the large vessels that deliver torrents of blood to the heart.

PICCs can be guided into place using fluoroscopy or ultrasound to trace the path of the catheter in real time, but that requires pricey equipment and specially trained personnel, and, in the case of fluoroscopy, it exposes the patient to radiation. Magnetic probes have also been developed, but they require calibration and an extra hand. Such methods "all make it harder to do something that's already hard to do on its own," Imam says.

A simpler, although not as accurate, method that can be performed at the bedside is to first measure the distance the PICC will travel using external landmarks like the shoulder and clavicle, then insert a PICC to that predetermined length and check its positioning with an x-ray.