Dr. Sunil Singhal at the Philadelphia hospital told the Associated Press that using glowing dyes is a big aid during surgery. “We can be sure we're not taking too much [tissue] or too little,” he said. The new dyes are experimental. There are several long-term studies that are aimed at getting the approval of the Food and Drug Administration. The drug company Johnson & Johnson recently invested $40 million in a method that uses one of the dyes. Money from the federal government also has supported some of the work. Paula Jacobs, an imaging expert with the National Cancer Institute, said the new dyes will improve patients’ lives. She predicts that many dyes will be available within five years.