PET CT in Clinical Practice

By Dr. Promila Pankaj in Nuclear Medicine

Nov 13 , 2020 | 2 min read

Positron emission tomography/computed tomography (PET/CT) is an advanced, non invasive, painless “state-of-the-art” molecular Imaging technology which is combination of two state of the art technology, PET and a High Resolution Multislice CT. PET acquire  functional images of the body and  CT acquire high resolution structural images, which are then co registered to detect disease at cellular level. Because PET CT detects disease at cellular level, it is able to detect diseases much before the patient experienced symptoms and signs of the disease. PET CT scanner affords unparalleled diagnostic capabilities, particularly in the fields of oncology, cardiology and neurology. PET CT can give all the information required for staging and management of diseases in a single test, rather than undergoing separate examination. Hence, it increases patient comfort and convenience by reducing the number of scanning sessions a patient must undergo and makes the PET CT very cost effective.
PET scan is done after injecting small doses of radioactive tracer into the body. Commonly used radioactive tracer FDG ( fluorodeoxyglucose ) is similar to glucose which is taken up by all body cells and more by abnormal cancer cells. The camera acquires 3 D images of the whole body and the cancer cells are seen more brightly as compared to normal cells.
After the initial diagnosis of cancer, PET CT scan is usually done for localizing the cancer and its spread in the body, assessing effectiveness of chemotherapy and checking for recurrence of cancer. PET CT is also useful to localize the site of primary tumor in cases where cancer has already spread in the body and the primary site of origin of the cancer is not known. PET CT scan is also useful in detection of the cause of pyrexia of unknown origin (PUO) and paraneoplstic syndrome and viable hibernating myocardium before undergoing major cardiac surgeries. Ga-68 DOTANOC PET/CT scan is done for staging of neuroendocrine tumors.
F-18 PSMA (Prostate-specific membrane antigen) is another tracer which is highly specific for prostate cells and routinely done to scan prostate cancer patient. The same PSMA tracer labeled with different radio nuclide is also used to treat prostate cancer patient
F-18 DOPA is another highly specific PET tracer used to scan patients of suspected Parkinson’s disease.
At Max Super Specialty Hospital, Shalimar Bagh, a high resolution 3-dimensional contrast enhanced CT scan is obtained in most cases and where necessary CT angiography is also performed in the same sitting. Acquiring 0.625 mm thick slices in all planes, using a volume acquisition on a 32 slice/second MDCT, obviates the need for a separate CT scan examination and makes the PET CT very cost effective imaging modality.

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