June 21, 2001
MEDIA CONTACT: Gary Stephenson
New Machine Fuses Positron Emission Tomography (PET), Computerized Tomography (CT) Into a Single Unit To Enhance Cancer Diagnosis
Hailed by some experts as an important advance in cancer detection, the first commercially available combination PET/CT scanner to be installed in a U.S. hospital will go to the Johns Hopkins Medicine’s Department of Nuclear Medicine this month.
The installation will mark the first time the new technology will be used for patients in a regular clinical setting, and Hopkins experts say they hope to have the unit up and running some time in early summer.
What’s unique about the PET/CT scanner, made by General Electric, is its ability to simultaneously produce images of metabolic processes in the body and images of the body’s internal anatomy – processes and features that reveal important, sometimes critical information to physicians, such as the presence of minute malignant tumors.
"The unique combination of CT technology, which provides great anatomical detail, and that of PET, which provides information on the activity of tumors, makes a PET/CT scanner superior to either technology alone," says Elias Zerhouni, M.D., chairman and Martin Donner Professor of Radiology at Hopkins.
While singly, both CT and PET scanners provide diagnostic images, the two modalities operate on widely different principles. In the case of CT, x-rays are sent through the body and then measured by detectors in the CT scanner. A computer with a special algorithm then processes those measurements to produce pictures of the body’s internal structures. With PET, images are obtained by injecting patients with a solution of sugar that has been "tagged" with a radioactive chemical isotope. Sugar is used by all metabolically active organs or tumors. When the tagged sugar is taken up by organs or tumors, it starts to decay, emitting positrons. These positrons then collide with electrons, giving off gamma rays, which the PET unit converts into images. These images indicate metabolic "hot spots," often indicative of rapidly growing tumors.
Combining these two technologies into a single unit gives clinicians a powerful tool for assessing a variety of diseases, according to Richard Wahl, M.D., director of nuclear medicine at Hopkins and vice chairman for technology and business development in Hopkins’ department of radiology. He is the first person in the United States to recognize and apply PET imaging using glucose to a broad array of human cancers, demonstrating that PET could accurately diagnose primary and metastatic breast cancer, metastatic melanoma and ovarian cancer, as well as accurately stage lung cancer. Wahl was one of the pioneers who helped develop and apply computer methods to join images from separate PET and CT scanners together to form "fusion" images of cancer in the early 1990s. The PET/CT scanner will now allow such fusion images to be obtained routinely, according to Wahl.
"When we began performing PET images of cancer patients in the 1980s, it was apparent that PET could find very small cancers, but it was hard to tell precisely where they were located because PET displayed little anatomy," Wahl notes. "This problem led us to develop fusion imaging, using computer software to combine the anatomic information from CT with the unique functional imaging from PET. I think that the fusing of these two technologies represents the future of cancer imaging."