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What is a PET/CT?

What is a PET/CT?

PET/CT is a state of the art imaging tool most often used to assist physicians in staging and re-staging cancer patients but also can be used in the diagnosis of Alzheimer’s disease, for cardiac perfusion imaging, cardiac viability and bone scanning.

PET/CT combines the anatomical benefits of a CT scan with the highly sensitive ability of the PET scan to detect changes in cellular activity. Combining the two into one imaging modality uses the best qualities of each to increase the overall sensitivity of the exam.

A CT scan is a series of x-rays taken sequentially to produce images that resemble cross-sections of organs and other structures. CT images give sharp views of anatomical features and differentiate between types of soft tissue, bone and blood vessels.

PET scans focus on the physiology of structures. They detect changes at the molecular level. In oncology studies we use a radioactive glucose, fluorodeoxyglucose (FDG), to track the high rate in which cancer cells metabolize glucose in the body. PET scans have the ability to distinguish between scar tissue and active cancer and assist in detecting new and reoccurring cancers at the earliest stage so treatment can be made as soon as possible.

It’s the combination of the two types of imaging, each contributing differently, that make PET/CT so useful. For instance, a regular CT scan may show that a lymph node is a normal size but a PET scan might show that normal-sized lymph node is actually made up of cells that are behaving abnormally. The CT scan gives the radiologist the best possible anatomical image and location of the node and the PET portion of the scan adds the cellular activity indicating that despite the normal size there is abnormal cellular activity.

PET/CT is not an exam used as a screening tool to diagnose cancer but is used after a cancer diagnosis to help determine the exact size and location of the tumor(s), identify any metastatic disease that may be present and establish the best course of treatment for the patient. The test is also used following chemotherapy and/or radiation to check whether the cancer has responded to treatment.

Because cancer treatment is so specialized and individualized for each patient, these studies are critical. PET/CT is used by the Tumor Board at Sonora Regional Medical Center as oncologists, radiologists, pathologists, and other care providers collaborate on each patient’s specific care plan.


How does PET/CT work?

PET/CT is a very easy exam. When imaging for oncology, patients must fast for six hours. One hour before the images are taken, patients are injected with a very small amount of fluorodeoxyglucose (FDG). Patients then rest quietly while the FDG distributes throughout the body. When cancer cells are present, they will rapidly consume the FDG in higher proportion than other cells in the body. This allows the radiologist to identify the abnormal areas on the images.

During the exam, patients lie on a flat surface which is moved into the scanner. The scanner is shaped like a donut with openings on each end. We make accommodations for comfort using blankets and pillows and patients wear their normal clothing. Although the entire exam takes about two hours the imaging itself only takes approximately 25 minutes and there are no special instructions following the exam.

What happens after a PET/CT?

A specially-trained radiologist will read the images and prepare a detailed report. Results are typically provided to the patient by their oncologist or other referring physician.

Does insurance cover PET/CT?

There are some rules regarding how many PET/CT scans a patient can receive and how far apart they must be spaced. They cannot be used for screening. As with many advanced imaging studies private insurance usually requires prior authorization. Medicare covers PET/CT for use in initial treatment strategy and subsequent treatment strategy for most types of cancer. It is important to discuss these options with your physician to make the best utilization of these tests throughout your cancer treatment.

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