BALTIMORE, Md., Dec. 4 -- Johns Hopkins radiologists say a combination of positron emission tomography (PET) and computed tomography (CT) detects the spread of cancer better than PET alone. In a study to be presented at the Radiological Society of North America tomorrow, researchers reported that overall, PET-CT improves the ability to distinguish cancerous from normal tissue and to locate metastases, or where they have spread. The study used a scanner that fuses CT technology, which provides anatomical detail, with PET images, which detect metabolic activity of tumors. "PET-CT was very specific, as it was able to distinguish cancer from noncancer 100 percent of the time (10 of 10), while PET alone was specific for cancer only 50 percent of the time (two of four)," said Richard L. Wahl, M.D., director of the division of nuclear medicine at Johns Hopkins. Routine contrast-enhanced CT was able to find disease in three of the five false negatives produced by PET-CT. "The CT portion of combined PET-CT scanners is very helpful at locating disease, but it could miss some lesions that can be found with contrast-enhanced CT," says Elliot K. Fishman, M.D., director of diagnostic imaging and body CT for the Kimmel Cancer Center at Johns Hopkins. The researchers said more studies are needed to determine the value of combined PET/CT over PET alone and over CT. A second study by Wahl and Fishman being presented at the meeting shows how whole-body CT provides a 19 percent improvement over combined PET-CT in detecting colorectal cancer recurrence. For more information, visit: www.jhu.edu