The tracer will collect in areas of higher chemical activity, which is helpful because certain tissues of the body, and certain diseases, have a higher level of chemical activity. These areas of disease will show up as bright spots on the PET scan. A PET scan is typically an outpatient procedure.
This means you can go about your day after the test is finished. Your doctor may order a PET scan to inspect your blood flow , your oxygen intake, or the metabolism of your organs and tissues. PET scans show problems at the cellular level, giving your doctor the best view of complex systemic diseases. Cancer cells have a higher metabolic rate than noncancerous cells. Because of this high level of chemical activity, cancer cells show up as bright spots on PET scans. For this reason, PET scans are useful both for detecting cancer and for:.
PET scans reveal areas of decreased blood flow in the heart. This is because healthy heart tissue will take in more of the tracer than unhealthy tissue or tissue that has decreased blood flow. Different colors and degrees of brightness on the scan will indicate different levels of tissue function, helping you and your doctor decide how best to move forward. Learn more about the heart PET scan. Glucose is the main fuel of the brain.
By detecting radioactive glucose, the PET scan is able to detect which areas of the brain are utilizing glucose at the highest rates. Your doctor will look at the scan to see how the brain is working and to check for any abnormalities. Learn more about the brain PET scan. PET scans are used to help diagnose and manage many central nervous system CNS disorders, including:.
PET scans show metabolic changes occurring at the cellular level in an organ or tissue. This is important because disease often begins at the cellular level. PET scans can detect very early changes in your cells. CT scans and MRIs can only detect changes later, as a disease alters the structure of your organs or tissues. Detection of illness at the cellular level gives your doctor the best view of complex systemic diseases, such as:. A computer combines the images from the two scans to create a three-dimensional image, which provides more information and allows for a more precise diagnosis.
Gallium scans are similar to PET scans in that they involve the injection of gallium citrate, a radioactive tracer. The PET scan involves radioactive tracers, but the exposure to harmful radiation is minimal.
According to the Mayo Clinic, the amount of radiation in the tracer is small, so the risks to your body are low. The risks of the test are also minimal in comparison to how beneficial the results can be in diagnosing serious medical conditions. The tracer is essentially glucose with the radioactive component attached. This makes it very easy for your body to eliminate the tracers, even if you have a history of kidney disease or diabetes.
People who are allergic to iodine , aspartame, or saccharin should alert their doctor. Make sure all of your doctors know how many imaging scans you have had, including the number and type.
This information can help them decide which scans to use in the future to help reduce your risk. If you are concerned about your radiation exposure, talk with your doctor, including asking whether you can have another type of test that uses less radiation instead.
After the test is done, a doctor who specializes in looking at the test results will look at your scan. This person is a nuclear medicine specialist or a radiologist. They will decide what the results mean. Be sure to follow their instructions carefully to avoid affecting your scan results. Talk with the staff about the following topics, and ask questions about any information that is unclear or concerning to you.
What to eat. You may be told to drink only clear liquids after midnight the night before the scan. Depending on what part of your body will be scanned, you may need to stop all eating and drinking 4 hours before the scan. For some scans, you can eat and drink normally. Your medications and health history. Ask whether you should take your usual medications or supplements on the day of the test.
Also, let them know if you have diabetes or other medical conditions. In particular, diabetes can alter your test results and the radioactive tracer can impact your blood sugar. If you are breastfeeding or could be pregnant, tell the staff.
These scans can put the baby at risk. Let the staff know about any drug or food allergies you have, including any allergic reactions to iodine you may have had in the past. What to avoid. Don't do any heavy exercise like running, jogging, or weightlifting 24 hours before your exam.
Exercise can make your scans less accurate. What to wear. Wear loose, comfortable clothing without metal zippers or buttons. You will need to remove any clothing that includes metal because metal can affect the scan. This includes belts, earrings, shirts with snaps or zippers, bras, and glasses. If your clothing cannot be worn during the scan, you can wear a hospital gown.
You will be asked to remove any jewelry, so you may want to leave it at home the day of your exam. Insurance, costs, and consent. If you are concerned about the cost of your PET-CT scan, find out what your insurance provider will cover before the scan.
Ask how much of the cost you will have to pay. Once you get to the doctor's office or hospital, the staff will ask you to sign a consent form. This form states that you understand the benefits and risks of the scan and agree to have it.
A staff member will put an IV into one of your veins. This is a thin tube with a needle attached. The IV feels like a pinprick. Once the IV is in place, you will get the radioactive substance for the scan.
You will not feel anything from the radioactive substance. After the substance has been injected, you must limit your movement and avoid activity, but you can sit in a chair comfortably. Moving too much can make the substance move into areas that are not being studied. This makes it harder for doctors to read the scan. The radioactive substance takes 30 to 90 minutes to reach the body parts that will be scanned. You may also be asked to drink a contrast liquid. You might also get contrast liquid through your IV.
Sixty-one A total of scans were performed as the seventh follow-up scan or later. Of the follow-up scans, 54 Recurrence or metastasis was ruled out in New treatment was initiated in Treatment course was changed in 5. In some cases, the follow-up scans confirmed recurrence despite lack of symptoms, and, in others, the scans found no recurrence despite indications that the tumor may have returned.
The extra scans proved their worth when they found that some patients who appeared to have recurrence did not and that some patients who had no obvious signs of recurrence did, she says.
Compare that amount to the thousands of dollars for radiation or chemotherapy the patients are given and it makes no sense not to perform an additional scan if it can help make treatment decisions and eliminate costly treatments that are not necessary, Subramaniam says. CMS made its decision with "no science behind it," he says. Subramaniam says the three-scan limit applies to any tumor type, not just lung, and he and his investigators are researching whether additional scans have value in other cancers, including colorectal and breast cancers.
So it seems CMS is making an arbitrary rule that isn't cost-effective.
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