How Long After PET Scan Are You Radioactive (And Why)?

How Long After PET Scan Are You Radioactive (And Why)?

Exact Answer: 6-12 Hours

PET scan stands for Positron emission tomography. It is one of the functional imagining techniques. It helps measure and visualize the change in metabolic processes, various other physiological activities such as blood flow, absorption, and regional chemical composition. It is widely popular in all parts of the world.

The procedure involves the use of radiotracers that are radioactive substances helpful in treating various health issues. Different tracers can be used in the process, and the exact tracer is decided after determining the target area of the body. However, the scan is very costly, and not every individual can afford the benefits of this treatment.

How Long After PET Scan Are You Radioactive

How Long After PET Scan Are You Radioactive?

PET falls under the category of medical scintigraphy technique and is used in nuclear medicine. A radiopharmaceutical, termed a radioisotope, is attached to the drug. The drug is then used as a tracer after it gets attached to our body. After this, it emits gamma rays that are detected by gamma cameras. Gamma cameras form a three-dimensional image of the target area of our body. The image capturing is very similar to that of an X-ray image capturing.

There are various tracers used, such as 18F-FDG, to detect cancer, oxygen-15 helps measure the blood flow, and NaF-F18 is popularly used to detect bone formation in the body. Modern PET scanners now come with a CT scanner already incorporated inside them and are called PET-CT scanners. PET scan images can also be reconstructed with the help of the CT scan done using one scanner in the same session.

Type Of Radiation Used In The ScanTime For Which The Person Is Radioactive
High power gamma raysApproximately twelve hours
Low power gamma raysApproximately six hours

Medical experts have identified that a person becomes radioactive for some time after undergoing a PET Scan. If the patient is treated with high power gamma rays, then the person remains radioactive for approximately twelve hours. In contrast, if gamma rays’ power is low, then the person is observed to be radioactive for around six hours.

Why Does It Take That Long After PET Scan To Remain Radioactive?

PET is a medical and research tool and is widely used in both clinical and pre-clinical settings. Medical experts use it heavily for the imaging of various tumors inside the human body. It is also used in the search for metastases in various fields of clinical oncology. It is also famous for the treatment of diagnosis of many brain diseases. PET scan also helps enhance the knowledge about the average human brain, supports drug movement and heart functioning. PET scans are also widely used to study various tumors in the animal’s body.

Heavy radiation exposure can prove harmful, but the amount of radiation faced in a PET scan is not scary. As the scan involves gamma rays, the body becomes radioactive for some time, and the radiation goes away slowly as time passes by. The doctors provide all the required guidelines to be followed after completing a PET scan, and it is the patient’s responsibility to adhere to all the instructions provided.

It is advised to maintain distance from newborn babies, children, and pregnant women after completing a PET scan. The radiation coming out from the patient can be harmful to the people around. It is also recommended to drink high quantities of fluids because it helps the kidneys remove any contrast material present inside our body. The doctors also check the radiation levels of the patient after the scan and inform whether everything is good or not.


Overall, it can be concluded that a PET scan helps treat various cancer issues and is also valuable for identifying different types of tumors inside the body. The scans are also performed on many animals to study several health issues in them. The scan is very costly and is done only by an authorized medical expert.

On average, a person remains radioactive for approximately six to twelve hours after the scan. The doctor measures the radiation level of the patient and decides whether it is safe for the person to go close to other individuals. The scan is also widely used for treating many brain diseases.


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28 thoughts on “How Long After PET Scan Are You Radioactive (And Why)?”

  1. This article was really informative and gave a clear understanding of the PET scan process and radioactive effects. Thank you for sharing with us.

  2. The radioactive effects of PET scans are definitely something to consider. This article explains it well.

  3. The article was very enlightening regarding the radioactive effects of PET scans and their importance in diagnosing health issues.

    1. I agree, understanding these processes is crucial for the medical field and for the well-being of patients.

  4. The article provided a comprehensive explanation of PET scans, their uses, and the radioactive effects. It was a very interesting read.

  5. The article has shed light on the radioactive nature of PET scans and the safety precautions involved. Very informative and interesting.

  6. I found the explanation of the radioactive effects after a PET scan quite intriguing. It’s a fascinating field of study.

  7. Avatar of Christian Moore
    Christian Moore

    The article has opened my eyes to the importance of understanding the radioactive aspects of PET scans. A very enlightening read.

  8. The article wonderfully explained the process and safety precautions related to PET scans. Very well done.

  9. Learning about the radioactive effects of PET scans was very interesting. This article provided a lot of valuable information.

  10. I didn’t know much about PET scans before reading this article, but now I feel much more informed. Thanks for the insights.

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