University at Buffalo - The State University of New York

Published: January 6, 2005

By ELLEN GOLDBAUM
Contributing Editor

The threading of slender catheters and stents through arteries to deliver treatments to the heart, the brain and elsewhere in the body has produced nothing short of a medical revolution.

But these delicate procedures require that patients be exposed to continuous radiation that can last up to an hour or more, sometimes causing skin injuries that in rare cases develop necrosis (tissue death), requiring skin grafts.

A new system tracks a patient’s X-ray radiation exposure, with risk levels color-coded from blue, which is acceptable, to red, which is unacceptable.

Now UB researchers, working with an Amherst startup company called Esensors, have developed a unique, real-time patient dose-tracking system that lets physicians know when the accumulated radiation dose is approaching a dangerous threshold.

The system is designed to be used either as a retrofit with existing fluoroscopy machines or to be included in the design of new machines.

Funded by grants totaling $814,000 from the U.S. Food and Drug Administration under the Small Business Innovation and Research program, the team of researchers is completing a prototype that will be clinically site-tested prior to commercialization.

"Our system provides complete tracking of actual radiation levels on the skin, providing both instantaneous dose rate, as well as cumulative exposure," explained Daniel Bednarek, project director, researcher at UB's Toshiba Stroke Research Center, professor of radiology and research associate professor of neurosurgery and biophysics in the School of Medicine and Biomedical Sciences.

Development of the system was spurred by a growing concern among physicians and by advisories issued by the FDA's Center for Devices and Radiological Health warning of occasional but severe radiation-induced skin injuries during prolonged, fluoroscopically guided invasive procedures.

"It can take a long time to insert a catheter into the brain and perform a complicated endovascular treatment, for example," explained Bednarek, also an adjunct professor in the Department of Physics in the College of Arts and Sciences. "Patients undergoing such procedures sometimes develop erythema—redness—hair loss or even skin necrosis in the exposed area."

These effects can result whenever long fluoroscopic times are used during interventional procedures, such as coronary angioplasty, stent placement, radiofrequency cardiac ablation and vascular embolization.

"With the equipment that currently is being used, the physician can minimize the chance for burns by moving the X-ray source instead of keeping the intensity on one spot," explained Darold Wobschall, UB professor emeritus of electrical engineering and president of Esensors. "The problem is that the physician is concentrating on the surgery and with X-rays coming in, he or she would have to be keeping mental track of where the dose is occurring at the same time.

"Our system solves that problem," said Wobschall.

Through electronic sensors, the system tracks the position of the X-ray gantry and patient table, and thus the location of the X-ray relative to the patient to determine the radiation exposure at the patient's skin, he explained.

"The computer tracks the beam's location and intensity, presenting the beam and the cumulative distribution of dose on the patient's skin as a color-coded graphic on a display screen," he said.

As the dose accumulates, the color on the display changes from green, which is acceptable, through yellow to red, which is a signal that the patient could be receiving too much radiation.

This visualization of the X-ray beam and its location with reference to a graphic model of the patient presents the physician with real-time visual feedback, allowing him or her to make the appropriate adjustments.

An added feature under development includes a visualization of the distribution and amount of X-ray scatter throughout the room, providing a way to gauge exposure for the physician and other health-care personnel who may be present.

The development effort for the computer graphic display was led by co-investigator Kevin Chugh, formerly a research scientist in UB's New York State Center for Engineering Design and Industrial Innovation (NYSCEDII).

Petru M. Dinu, a doctoral candidate in the Department of Physics, played a major role in developing the system at the Toshiba Stroke Research Center.