What Is the Typical PET Scan Procedure?

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  • Written By: Jessica Ellis
  • Edited By: Bronwyn Harris
  • Last Modified Date: 27 November 2019
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    Conjecture Corporation
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A positron emission tomography (PET) scan is a diagnostic test that can help identify abnormal chemical activity throughout the body. PET scan procedure is relatively simple for the patient, though it may change slightly based on the area of the body being examined. Patients may be required to make some alterations to diet or medications before undergoing the test.

Before the test, a patient needs to inform doctors if he or she is taking any medications for existing conditions. Depending on the medication, doctors may ask the patient to avoid taking the drug for a day or two before the PET scan procedure. Women also must inform doctors if they are pregnant or might be pregnant, as the radioactive material ingested for the test can harm fetuses. Doctors may also ask the patient to fast for several hours before the test; it may help to schedule the test first thing in the morning, so that the fasting hours coincide with sleeping hours.

At the medical facility, the PET scan procedure begins with the patient taking a dose of a mildly radioactive material. The radioactivity of the medication is very low-level, and is not considered a risk to human health. Depending on the type of scan being done, patients may be able to swallow the medication, breathe it in as gas, or have it injected into the body. Doctors may choose to opt for gas or injection methods if a patient has any difficulty swallowing.


After the medication is administered, the patient is generally required to rest quietly for 30 minutes to an hour. This waiting period allows the medication to reach the target area and begin absorption. Toward the end of the waiting period, the patient may be taken to the PET scan room. This room will contain a large, circular machine with a narrow table in the middle. Once the waiting period has lapsed, the patient will lie down on the table for the main PET scan procedure.

During the procedure, the patient must lie completely still. People who have difficulty lying still for long periods of time, or those who have claustrophobia, may be given a sedative before the test. If the patient moves, the images captured by the machine will be blurry and may disrupt diagnosis. The doctor or machine technician generally informs the patient when the test is starting, and may check in with him or her from time to time. The entire PET scan procedure usually takes about half an hour.

Following the test, most patients can resume normal activities. If a sedative has been used, doctors may require that patients bring a driver with them to the testing facility. Doctors will often recommend that patients increase water intake for a day or two following the test, in order to flush all remaining traces of the radioactive tracer. Results from the test need to be read and interpreted by a doctor, who will usually contact the patient with the findings within a few days.



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