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/CT captures images of changes in the body's metabolism caused by actively growing cancer cells and provides a detailed picture of the body's internal anatomy that reveals the size, shape and exact location of the abnormal cancerous growths.
The PET/CT scan begins with 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/CT scanner. The CT portion of the exam sends X-rays through the body which are then measured by detectors in the CT scanner. A computer algorithm then processes those measurements to produce images of the body's internal structures.
The PET 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 PET and CT images are produced.
The CT and PET images 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 surrounding tissue, since more of the radiopharmaceutical will be absorbed in those areas. Each imaging modality can be viewed independently of the other without compromise, or used in concert for complementary functional and anatomic diagnosis. PET/CT is a highly sensitive procedure that aids in the detection of small cancerous tumors and 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