In two studies presented during today's poster session at the Society of Nuclear Medicine in Los Angeles, Todd Blodgett, M.D., a fellow in the department of radiology, University of Pittsburgh School of Medicine, found the advanced scanners identified additional lesions in 80 percent of a group of patients with ovarian carcinoma and in 45 percent of a group of patients with cervical carcinoma. Those lesions did not show on scans of the same patients taken with conventional CT or ultrasound, the tools used at most hospitals to follow patients with these types of cancers.
"We found the combined PET/CT is a very important machine for staging and re-staging patients with these types of cancers. These cancers are notoriously difficult to pinpoint in the body because they are in relatively small areas packed with many different types of tissue," said Dr. Blodgett. "It is difficult, using conventional CT or ultrasound, to find all the lesions or to identify their precise locations."
CT and ultrasound are the most frequently used imaging methods for these cancers, but do not provide images with the necessary combination of clear structural definition and metabolic activity that is achieved with the PET/CT, said Dr. Blodgett.
The PET/CT, developed jointly by David Townsend, Ph.D., senior PET physicist, and professor of radiology at the University of Pittsburgh School of Medicine and Ronald Nutt, Ph.D., president, CPS Innovations, Knoxville, Tenn., works by combining PET (positron emission tomography) technology, in which the scanner maps cellular metabolism of glucose, and CT, which builds a clear cross section of tissue structures using x-rays.
In areas of the body where tissue is dense, organs and bone make it difficult to separate cancerous tissue from normal. Images from the combined PET/CT scanner are particularly useful in allowing a radiologist to see cancerous activity at a metabolic level and pinpoint its exact location in the tissue so a biopsy can be performed and proper treatment begun.
"These results, though gained from a relatively small sample, are significant because they show the current standard of using CT or ultrasound as the primary method for finding lesions may not be the best," said Dr. Townsend. "The tools most doctors rely on for this very important function may be missing a significant number of lesions."
In the first study, Dr. Blodgett and his colleagues examined 15 women with ovarian carcinoma using both CT and PET/CT. In 12 of 15 cases, or 80 percent, PET/CT identified lesions that CT did not. In 11 of the 12 cases where additional lesions were uncovered, the revelation changed the way doctors managed the illness.
In the second study, Dr. Blodgett and his colleagues studied 11 patients with cervical carcinoma. Of those 11, five had additional lesions identified by PET/CT and all five had their treatment changed to reflect the new information.
The results, though a very promising development for those with difficult-to-track cancers, such as ovarian, cervical, head and neck and lung, most likely will not lead to an immediate change in current diagnostic standards, said Dr. Townsend, because the scanners are not as widely-available as CT or ultrasound equipment. Combined PET/CT scanners have been available commercially for just over a year, and at present are located in about 70 hospitals in the United States, Europe and Asia.
The PET/CT was co-invented by Dr. Townsend and Dr. Nutt and the first prototype of the machine was tested at the University of Pittsburgh Medical Center from 1998 to 2001. During that time, over 300 patients were scanned. Results from the Pittsburgh trials led the U.S. Food and Drug Administration to approve the PET/CT as a diagnostic tool for cancer in October 2000. The medical center became the first in the nation to install the PET/CT scanner manufactured by CPS Innovations in Knoxville, Tenn. and distributed by Siemens as the biograph.
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