Radioactive cancer patients attending this weekend's Super Bowl in Miami could be in for an alarming experience when they pass through radiation detectors designed to signal the presence of dirty bombs. Such cancer patients -- who have received treatment using radioisotopes and still may have tiny amounts of radioactive material in their bodies -- may want to come armed with letters from their doctors explaining their precarious set of circumstances.

The use of radioisotopes in medicine is growing -- and so is the use of radiation detectors in our security-conscious nation, which means patients are triggering alarms when they are not even aware they are being scanned, doctors and security officials say.

Nearly 60,000 people a day in the United States undergo treatment or tests that leave traces of radioactive material in their bodies, according to the Society of Nuclear Medicine. These traces are not enough to hurt anyone, but they are enough to trigger radiation alarms for up to three months.

Radioisotopes are commonly used to diagnose and treat certain cancers and thyroid disorders, to analyze heart function, and to scan bones and lungs. And many doctors already know to equip their patients with travel cards because of the problems they can encounter in public places.

Nearly 20 million nuclear medical procedures were performed in the United States in 2005 -- up 15 percent from 2001. Clearly, the number of people who could be mistaken for terrorists is quite large. So if you are one of these people -- with the power to create a buzz in a public setting -- get your papers in order so you can quickly confirm your identity as nothing more than a cancer patient.