Types of PET/CT Scans
There are several different types of PET/CT scans, each using a different isotope that is coded to detect a specific type of cancer. These isotopes come in the form of a liquid, which is injected before the scan. The "tracer" cells in this liquid enter the body and attach to the specified cancer cells, causing them to "light up" on the PET/CT so doctors can see where they are located in the body.
Following are the isotopes currently in use at the Harold Leever Cancer Center.
How it works: FDG (fluorodeoxyglucose) is a tracer molecule that is used to identify cells that are rapidly multiplying. Cancer cells are three times more active than the normal cells in the body, and therefore can show up in the image distinctively.
What it's for: FDG is used to diagnose and monitor various types of cancer, including lung, brain, and colorectal cancer cells, as well as lymphoma and melanoma.
Test preparation: Patients must fast for six hours before this test, and have a blood glucose level of less than 200. (The technologist will conduct a test using a glucometer.) After the injection, the patient must rest quietly for one hour, and will be asked to empty their bladder immediately before the scan, which will take between 15 and 25 minutes.
How it works: F18 PSMA (prostate-specific membrane antigen) attaches to prostate tumor cells and flags their presence in the body.
What it's for: This test can be used for patients with known prostate cancer and a rising PSA level or for initial staging of prostate cancer. A PSMA PET scan is able to detect prostate cancer cells that can be missed by other imaging types.
Test preparation: There is no fasting requirement for this test. There is a one-hour rest period following the injection, followed by emptying the bladder. The imaging period is 20 to 30 minutes.
How it works: Cerianna (fluoroestradiol F18) can detect estrogen receptor positive (ER+) breast cancer by attaching itself to ER+ cancer cells.
What it's for: Cerianna may be used for patients who have had a biopsy that shows ER+ cells. Cerianna can be used to identify any ER+ cells elsewhere in the body other than the biopsy site.
Test preparation: There is no fasting requirement for this test. Patients must not be taking specific hormone blocking medications, for which the technologist will screen prior to the test. Patients are required to rest quietly for 80 minutes after the injection, followed by 20 to 30 minutes imaging time.
NetSpot (Gallium Ga 68 Dotatate)
How it works: NetSpot binds to the somatostatin receptors found in neuroendocrine tumors.
What it's for: Neuroendocrine tumors are a rare, hormone-producing type of tumor that can occur anywhere in the body but are most commonly found in the lungs, stomach, intestines, and pancreas.
Test preparation: There is no fasting requirement for this test. Patients must not be taking somatostatin medications, for which the technologist will screen prior to the test. Patients are required to rest quietly for 40 minutes after the injection, followed by 25 to 30 minutes imaging time.