What to Expect When You’re Going for Your First PET Scan


What is a PET-CT Scan?

A PET-CT scan (Positron Emission Tomography and Computed Tomography) is a 3D imaging investigation used to detect the presence of cancer or tumors in the bones, tissues, and organs. It is a functional imaging modality done to analyze the status and functioning of your organs and tissue, diagnose cancer or any other non-cancerous tumors, plan radiation treatment, and follow up with patients during and after the course of treatment. A PET-CT scan is also used for accurately determining the spread of cancer inside a patient’s body. It is an important investigation to check whether your cancer is under control or has recurred. In a PET scan, a special dye containing radiotracers (mildly radioactive agents) is injected into a patient’s body to see how well their organs and tissues are working. The areas of disease, where cells are more active than normal, show up as bright spots on the PET scanner.


How it Works

PET scans are to assess the body’s regulation of glucose as cancer cells metabolize it faster than other tissues. It is important to follow the dietary guidelines as advised by your hospital.


Preparing for your PET-CT scan

The first PET-CT scan can be scary and intimidating for many people mainly due to its large footprint and associated anxiety on the likely outcome. Here are a few things you need to prepare and take care of before your first PET-CT scan:

Daily Medication & Allergies

Inform your doctor about any medications that you may take, including your daily vitamin supplements. Your doctor will inform you whether it is okay/safe to take them before the PET-CT scan.

You must also inform your doctor about any allergies. If required, the doctor will make necessary arrangements beforehand.


Some special arrangements need to be made for PET-CT scans for diabetic patients. Doctors usually recommend that you take your medication at least 4 hours before the scan. Just make sure your doctor is well-informed about your medical history before the examination.


If you have claustrophobia or are generally afraid of being in closed spaces, you must inform your doctor before your PET-CT scan. Sometimes the hospital allows you to take a guest with you in the screening room for moral support.

Pregnancy and breast-feeding guidelines

It is not usually advised for pregnant women or nursing mothers to take a PET-CT scan unless necessary. Your doctor will be able to guide you based on your situation.

Diet and Water Fast

You are supposed to do at least a 6-hour water fast before going for your PET-CT scan. Doctors also recommend that you switch to a low-carb diet 24 hours prior. Moreover, it is also advised to increase your water intake right before the scan. In some cases, your doctor may ask you to drink a glass of oral contrast before your CT scan. Oral contrast is a liquid containing a chemical, either barium or Gastrografin, that helps the doctor get better images of your scan. You will be asked to wait at least 60 or 90 minutes after taking the contrast for it to pass through your body. Some people are allergic to barium, iodine, or any type of contrast dye, so make sure you inform your doctor beforehand. Your doctor might also ask you to have IV (intravenous) contrast dye before your scan. IV dyes are usually iodine-based, so make sure you inform your doctor if you have had any past allergic reactions to iodine. Note that modern IV contrast dyes are less likely to cause an allergic reaction, so you can still have your CT scan done in most cases.

Request for music

If you are feeling scared or nervous about your first PET-CT scan, music acts as a great relaxant to calm your nerves. You can request your doctor to make arrangements for you if you wish to listen to music during your PET-CT scan.

Remove metal accessories

Metal accessories can interfere with the testing equipment. Make sure you are not wearing any metal accessories when coming for your scan, for instance, jewelry, watch, spectacles, etc. Even clothes with metallic buttons or undergarments with metallic hooks are supposed to be removed before the exam. Medical devices like pacemakers and prostheses do not affect your PET-CT scan results. Wearing an insulin pump or glucose monitor does not impede CT scans, but devices should be removed whenever possible.


What to Expect During a PET-CT scan?

A PET-CT scan is usually 30 minutes to 1 hour long but can go up to 2 hours in some cases. During the procedure, patients are supposed to lie completely still on the machine bed. In some cases, they will be asked to hold their breath from time to time during the scan. Once inside, patients are allowed to talk to the technologist, who is monitoring them from a nearby window.

preventative measure

After the PET-CT scan

One thing recommended after your first PET-CT scan is to drink lots of water; about 5-6 glasses are ideal. For nursing mothers, it is recommended to wait for at least 24 hours before recommencing breastfeeding. Some people might experience a few post-scan symptoms such as nasal congestion, irritation, dizziness, nausea, pain, or tremors. In such cases, please immediately consult your doctor. Please note: During a PET-CT scan investigation performed judiciously using low doses of radiation, your risk of developing radiation ill effects and cancer is very minimal. The American College of Radiologists guidelines recommends no imaging investigation should be done until there is a clear medical need.