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What it is: Positron emission tomography/computed tomography (PET/CT) scanning is a relatively new technique that provides physicians with a powerful system that can help to detect and diagnose conditions such as cancer earlier and more accurately. It combines the strengths of PET — which shows metabolism and function of cells — with CT, which has the ability to capture detailed anatomy. 

How it works: The PET/CT scan allows for highly defined, three-dimensional images of the inside of the human body, helping in the treatment of conditions such as cancer and heart disease. 

Why it is used: The PET scanner provides information about the metabolic function of cancer cells and can detect very small tumors (although it cannot indicate their exact location), while CT provides the anatomic information necessary for an accurate diagnosis.