CT Alone
Its strengths: A primary tool of oncology imaging for several decades, Computed Tomography (CT) scanning is unrivaled in its ability to indicate the precise anatomy of structures within the body,
including tumors.
Its limitations: As accurate as it is for showing internal anatomy, the anatomy doesn't always tell the whole story. Many times, residual live tumor cannot be distinguished from dead tumor or scar tissue arising from previous disease and treatment. Often, CT scanning cannot even differentiate tumor tissue from normal tissue.
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PET Alone
Its strengths: Positron Emission Tomography (PET) images physiological and biochemical processes rather than anatomy. With PET, the patient receives a substance containing radioactive atoms known as "positron emitters" attached to biologically active molecules. During scanning, multiple rings of PET detectors encircle the body, recording the emission of small amounts of radiation from these emitters to, in turn, create "tomographic" images (slices) of the body.
Its limitations: While it provides critical metabolic information, PET images lack the high-resolution quality of CT scans. PET scans also don't outline anatomical structures very well. So while a PET scan may be better able to detect an abnormality suspicious for cancer, it may be unable to identify its exact location.
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PET/CT Together
The best of both worlds: The PET/CT approach incorporates both scanners in a single gantry. Precise calibration of the system produces CT and PET images that are aligned almost perfectly, allowing for a small amount of inevitable patient motion during scanning. Images are obtained sequentially on the same scanner.
Together, these two technologies provide extraordinary opportunities for detecting cancer early, determining the extent of cancer present and assessing treatment success. PET alone is highly accurate, but the data set produced by the combined technologies has been proven valuable in interpreting PET images.
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