Positron emission tomography (PET) and computerized tomography (CT) are both state-of-the-art imaging tools that allow physicians to pinpoint the location of cancer within the body before making treatment plan. The highly sensitive PET scan images detects the biological (physiological) disorders at the molecular level, while the CT scan provides a detailed picture of the body's internal anatomy. The PET/CT scan combines the strengths of these two well-established imaging modalities into a single scan.
A CT scan is able to detect and localize changes in the body structure or anatomy, such as the size, shape and exact location of an abnormal growth, a sizeable tumour or a musculoskeletal injury. A PET scan is very different from an ultrasound, X-ray, MRI, or CT scan. A PET scan allows the physician to distinguish between living and dead tissue or between benign and malignant disorders. Since a PET scan images the biology of disorders at the molecular level, as it can help the physician detect abnormalities in cellular activity at a very early stage, generally before anatomic changes are visible
The majority of PET/CT scans are performed for oncologic applications. Physicians utilize PET/CT scans for diagnosing, staging and evaluating treatments for their cancer patients. A PET scan helps the physician distinguish between living and dead tissue or between benign and malignant disorders. PET imaging provides the physician with additional information about cellular activity which guides the characterization of a questionable abnormality as malignant or benign.
Positron Emitters Fluorine F-18 decays by positron (β+) emission and has a half-life of 110 minutes (less than 2 hours). The principal photons useful for diagnostic imaging are the 511 keV gamma photons, resulting from the interaction of the emitted positron with an electron. C-11 N-13 O-15 F-18
F-18 FDG - Fluorodeoxyglucose FDG is the most common Positron-Emitting Radiopharmaceutical used in 95% of PET scan procedures. Simply stated, FDG is radioactive glucose and is useful in determining abnormal metabolic processes within the body. FDG is of tremendous value in the early detection of critical disease using PET technology.
F-18 flurodeoxyglucose FDG Is acyclotron produced, which is a glucose analog. This agent has utility as a tumour- imaging agent because of an increased demand for glucose by tumours with an advanced state of malignancy. Not only can F-18 flurodeoxyglucoselocate and differentiate tumours but it can also help distinguish between recurrent tumour and radiation necrosis in patients receiving radiation therapy
FDG concentrates in metabolically active cells, where it is phosphorylated but does not undergo subsequent metabolism because of the replacement of the hydroxyl group in the 2 position with a fluorine atom. It is metabolically trapped for a sufficient time to allow imaging. Administration and dosage. IV, 15 mCi
Cyclotron A medical cyclotron is necessary to manufacture the most common radiopharmaceuticals used for PET scanning. The cyclotron is a circular particle accelerator that makes use of magnetic force to propel atomic particles (negative hydrogen ions) in a circular pattern. These accelerated particles are stripped of their electrons resulting in positively charged particles (protons) that are then targeted onto a specially enriched form of water. This bombardment results in the formation of radioactive material, which is then transported to the radiopharmacy or “hot lab”, where it is purified and finally incorporated into an FDG molecule.
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