A Winning Combination

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    If there is a metabolically active tumor in the region being scanned, says Meltzer, "you can see an area where there has been sugar uptake. But it looks like a blob and it's difficult, especially in some parts of the body, to tell exactly where it is." Dr. Steven Larson, director of the PET program at Manhattan's Sloan-Kettering, has his own description of the blob: "It's a little like lighting a match in the blackness of a vast cavern. We detect the match, but the location is imprecise."

    In designing the PET/CT to remedy this imprecision, says Townsend, one of the problems that he and Nutt faced was the engineering of the scanner tunnel into which the patient is rolled. "You don't want a very long tunnel that's frightening to patients," he explains. To further minimize the claustrophobic effects, they increased the diameter of the PET/CT tunnel to 28 in., making it far more spacious than the familiar typical magnetic resonance imaging (MRI) tunnels. "For the patient, it's very comfortable and convenient," says Townsend. "They arrive, they have a single scan, and then we have all the information."

    A far greater problem came in writing the code to run PET/CT's computer. "We needed and finally created software to control two different imaging systems from one computer console," says Townsend, "something that hadn't ever been done before."

    Now, given the go-ahead by the FDA, CTI will soon be producing an advanced version of the Pittsburgh prototype. Larson, who has ordered a machine for Sloan-Kettering's pet center, predicts that the PET/CT will "improve clinical management of patients and cut the overall time of their imaging in half, from about one hour for a whole body survey to about a half hour."

    Even apart, PET and CT scanners are triumphs of technology, devices that have saved countless lives, prolonged others, and often made many exploratory operations unnecessary. Yet each has limitations that can lead to uncertainties in diagnosis. By successfully combining the two technologies, Ronald Nutt and David Townsend have eliminated those uncertainties and provided medicine with a powerful new diagnostic tool.

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