Positron Emission Tomography–Computed Tomography (PET-CT)
PET-CT is an imaging technique consisting of a combination of positron emission tomography and computed tomography. PET provides a three-dimensional view of physiological and functional processes in the body. A small amount of radioactive material is administered intravenously during the PET scan and distributed throughout the body via the bloodstream.
This means that changes in the human body can be observed at a cellular level. The radioactive substance administered is fluorodeoxyglucose (FDG), a kind of sugar molecule. This molecule accumulates in cells that grow rapidly in the body, such as cancer cells. Data from PET alone is not enough to make a thorough assessment. In conjunction with computed tomography, which provides cross-sectional images, changes can be detected much earlier and in greater detail, increasing accuracy. The amount of radiation released during PET scans is very low. When PET-CT or CT is prescribed, patients may react, thinking they are harmful. But even in nature there is some radiation, and life without radiation is not possible.
Anyone for whom a PET-CT scan is planned will be asked whether they have other health problems, especially diabetes. The image quality may not be very good in patients with diabetes. In these patients, the sugar inside the body competes with the sugar molecules injected from outside. They can continue to take medication other than insulin or diabetes medication taken orally. Patients are also advised not to eat or drink anything six hours before the scan. One hour after the intravenous administration of the radioactive substance, the patient is given time to urinate, after which they are asked to remain motionless in the PET-CT device . PET-CT is the preferred imaging method for patients with suspected or diagnosed cancer. It is used to diagnose cancer, determine its stage, and assess response to treatment. It contributes to the correct planning of radiotherapy. It plays a role in distinguishing changes to the tissue after treatments such as radiation or surgery on actual tumors. PET-CT is very useful in terms of determining the right treatment for cancer patients and avoiding unnecessary surgery. Studies show that a PET-CT scan changes the disease stage at a rate of 25–60% and that patient treatment is made more accurate. A PET-CT scan can be used for almost all cancer types. It can provide almost 100% accurate diagnostic results, especially for lung cancer and lymphomas. The accuracy rate for breast cancer, pancreatic cancer, head and neck cancer, as well as cancers of the digestive system, such as stomach and esophageal cancer, is also very high. About 95% of the adenosine triphosphate (ATP) required for brain function is provided by glucose metabolism. Therefore, under physiological conditions, the use of FDG in brain tumors is not preferred because the brain retains too much FDG. Markers such as methionine, choline, thymidine, and fluoromisonidazole are preferable.