PET scans are pictures of the actual biological functioning of the human body. PET scans on the other hand, show the actual metabolic functioning of the organs. Because PET scans are pictures of the body's chemistry, many diseases can be seen with PET, often at their earliest stages. Using cancer as an example, CT or MRI can pinpoint a lesion, but these procedures often cannot say whether its benign or malignant. With PET scanning, doctors can determine with a high degree of accuracy if it is, or is not, cancer.
Cancer spreads silently in the body.
By the time symptoms appear, it is often too late for effective treatment. Using a glucose probe, PET can effectively scan for cancer. Staging of cancer is linked to the survival rate. PET is the also very helpful in the early detection of Alzheimer's disease. CT and MRI scanning are generally not helpful in diagnosing Alzheimer's disease, because they will only show atrophy, which is also apparent in normal aging.