When 14-year-old Mia came down with a mysterious fever that lasted three weeks, her doctors ran test after test but couldn't figure out why. Stories like hers are more common than you might think. Fever of unknown origin — or FUO, as doctors call it — happens when a patient's temperature stays high for weeks without a clear cause. Now, a major new study offers hope that a special kind of scan can crack these medical mysteries much faster.
Researchers studied 929 patients with unexplained fevers across 12 medical centers around the world. They found that PET/CT scans — a type of molecular imaging that shows how organs and tissues are working inside the body — helped doctors diagnose the cause in roughly 75 percent of cases. The scan uses a tiny amount of radioactive sugar, called 18F-FDG, that lights up areas of inflammation or infection so doctors can see exactly where the problem is hiding.
Dr. Domenico Albano, a nuclear medicine physician at the University of Brescia in Italy who led the study, said the findings could change how hospitals approach mysterious fevers. Currently, these scans are usually ordered only after other tests come back empty. But the research suggests PET/CT could become one of the first tools doctors reach for, rather than a last resort.
The study also found that the scans didn't just help with diagnosis — they actually changed how patients were treated. In about three out of four patients, the PET/CT results led doctors to start new treatments, adjust existing ones, or decide whether a patient needed surgery or a biopsy. That means fewer wasted weeks on the wrong medications and fewer unnecessary procedures for patients.
Researchers also identified clues that make a PET/CT more likely to show something useful. Patients with higher levels of a protein called C-reactive protein — a sign of inflammation — were more likely to have positive scan results. The same was true for patients who hadn't been on antibiotics for long before their scan.
Dr. Albano said combining these warning signs with PET/CT imaging could help hospitals diagnose FUO faster and get patients the right treatment sooner. The study was published in the Journal of Nuclear Medicine.