PET and Cancer

Lindsey

Positron Emission Tomography (PET) can provide comprehensive and accurate staging information for patients diagnosed with cancer by imaging the metabolic activity within various types of cancer. PET can also be utilized to detect recurrent disease and is used to follow patients after chemotherapy and radiation. PET images can demonstrate pathological changes in the human body before they are seen on the other imaging modalities such as CT and MRI. PET through the presence or absence of unusually high metabolic activity can show whether a tumor is benign or malignant.

One of the biochemical characteristics of malignant cells relates to the increased rate of glycolysis in tumor cells. PET uses the radioisotope Fluorine-18 Deoxyglucose (FDG) to detect cancer. FDG is rapidly transported across the cell membrane of metabolically active tumors and it accumulates over time.

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The FDG metabolism is faster in malignant tumors then in surrounding healthy tissue. If there are malignant cells, there will be a high concentrate of FDG in the tumors (the signals will be stronger) compared to the background (surrounding normal tissue) because cancer metabolizes more glucose. Intracellular activity varies with different types of cancer. Malignant cells tend to have a high concentration of FDG on PET images but not all tumors show significant metabolic activity. “PET exams are positive in about three-quarters of patients with known morphologically primary or residual tumor”.

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