When disease strikes, the biochemistry of cells and tissue changes. In cancer, for example, cells begin to grow at a much faster rate. In one continuous whole-body scan, PET captures images of changes in the body's metabolism caused by actively growing cancer cells.
The PET scan begins with an injection of a glucose-based radiopharmaceutical, which travels through the body, eventually collecting in the organs and tissues targeted for examination.
The patient lies flat on a table that moves incrementally through the PET scanner. The scanner has cameras that detect the gamma rays emitted from the patient, and turns those into electrical signals. These are processed by a computer to generate the images. The table moves slowly through the scanner and many sets of images are produced.
The acquired electrical signals are assembled by the computer into a 3-D image of the patient's body. If an area is cancerous, the signals will be stronger there than in the surrounding tissue, since more of the radiopharmaceutical will be absorbed in those areas.
PET is a highly sensitive procedure that aids in the detection of small cancerous tumors, and also subtle changes in the brain and heart. This enables physicians to identify and treat these diseases earlier and more accurately.
Image courtesy of University of Tennessee Medical Center, Knoxville, TN, USA