About Your FDG PET-MRI

Time to Read: About 11 minutes

This information will help you get ready for your magnetic resonance imaging (MRI) with positron emission tomography (PET) scan.

Metal and electronic devices can disrupt the MRI scanner’s magnetic field. If you have metal or electronic devices or objects in your body, tell the person doing your MRI. It may not be safe for you to have an MRI. If an MRI isn’t safe for you, your doctor will order a different imaging test.

If you have any of the devices listed below, call 646-227-2323.

  • Pacemaker.
  • Automatic implantable cardioverter-defibrillator (AICD).
  • Breast tissue expander.
  • Aneurysm clip.

If an MRI isn’t safe for you, your doctor will order a different test. If you have any other questions about your MRI, call your doctor’s office.


About PET-MRI scans

A PET-MRI scan is an imaging procedure that is used to:

  • Find cancer cells.
  • Plan your treatment.
  • See how your treatment is working.

You will have MRI images taken at the same time as your PET scan. MRI is an imaging procedure that uses strong magnetic fields to take pictures of the inside of your body. The MRI pictures are combined with your PET scan to create pictures of your soft tissues and bones.

Most PET scans are done to study your body’s use of glucose (a type of sugar). This is because cancerous cells take in glucose faster than normal tissue. Glucose comes from many foods and drinks, so it’s important to follow certain eating and drinking guidelines. These are listed in “What to do the day of your PET-MRI” section of this resource.

The PET-MRI table is on a track that slides into the machine. The machine is like a long tunnel that is open at both ends. Most PET-MRI scans take about 30 to 45 minutes.

You’ll need to lay still inside the PET-MRI machine during your scan. The machine will make loud noises during your scan. Talk with your healthcare provider if this may make you uncomfortable, anxious, cause pain, or if you have claustrophobia. They can help plan ways to help you feel more comfortable during your PET-MRI.

You can also use breathing exercises before or during your scan to help you feel more comfortable. Read the “Exercises to Help You Relax for Your PET-MRI” section of this resource for more information.

Things you may get the day of your PET-MRI


Before your PET-MRI, you’ll get a radioactive medication called a tracer. The tracer is attached to a substance that your cells and tissues use. Cancer cells use the substance differently than non-cancer cells. The radioactive part of the tracer lets your healthcare provider see how your cells are using the substance. This helps them find any usage that is not normal.

Your PET-MRI will use FDG as the tracer. You will get the tracer through a catheter (thin, flexible tube). The catheter may be an intravenous (IV) line in your arm, hand, or central venous catheter (CVC), if you have one.

The tracer is used by your cells and doesn’t stay in your body long. It leaves your body mainly through your urine.


You may need to get contrast the day of your MRI. Contrast is a special dye that helps make the images from your scan clearer. For MRI scans, contrast goes into your bloodstream.

If you’re getting contrast, you’ll get it through a catheter in your vein. Your nurse will place the IV line in one of your veins, usually in your arm or hand. Talk to your nurse if you have a CVC.

Tell your healthcare provider if you have had a reaction to MRI contrast before. You may get medication to lower your risk of having another allergic reaction. If you do, you’ll get a resource called /node/20513.

Contrast will leave your body through your urine (pee) within 1 to 2 days.


If you are having an PET-MRI with anesthesia, read the “For People Getting Anesthesia” section of this resource. This has information about how to get ready for your MRI with anesthesia.

Getting ready for your PET-MRI

Take devices off your skin

If you wear any of these devices on your skin, you may need to take it off before your PET-MRI:

  • Most medication patches
  • Continuous glucose monitor (CGM)
  • Insulin pump

If you change your device, talk with your healthcare provider about scheduling your appointment closer to the date you need to change it. Make sure you have an extra device or medication patch with you to put on after your PET-MRI.

If you have a medical implant or device, ask the healthcare provider who put it in for the exact name and manufacturer. If you don’t have this information, you may need to reschedule your PET-MRI.

Diabetes care

If you have diabetes, talk to your doctor who ordered your test. They will tell you how to manage your medication before your PET-MRI.

Breastfeeding and pregnancy

Your healthcare provider will ask you if you’re pregnant or think you may be pregnant. If you are pregnant, your doctor may choose not to give you contrast. If you think you may be pregnant, we will do a urine pregnancy test before your PET-MRI with contrast.

It’s safe to continue breastfeeding after getting PET-MRI contrast. A very small amount of contrast will end up in your breastmilk if you are breastfeeding. This may change the taste of breastmilk slightly for a short time. If you have any concerns, you can choose not to breastfeed for 12 to 24 hours after your scan.

If you plan to pause breastfeeding after your PET-MRI, express (pump) milk and save it before your MRI. For 12 to 24 hours after your PET-MRI, continue to express milk and throw it away. After 12 to 24 hours, you can start breastfeeding again on your normal schedule.

If you have questions, talk to your doctor about your options. You can also talk to the radiologist on the day of your PET-MRI.

What to do the day before your PET-MRI

If you are having anesthesia (medication to make you sleepy) during your MRI, your healthcare provider will go over specific instructions. Read the “For People Getting Anesthesia” section of this resource for more information.

Avoid high-energy and repetitive activities

Avoid high-energy activity and repetitive motions for 24 hours before your scan. This includes running, jogging, or cycling. These activities can lower the quality of the images that we get from your PET-MRI.

Stay warm

It’s important that you stay warm the day before and the day of your scan. If you get cold, a special type of fat becomes active. This can make it hard for your radiologist (doctor who specializes in reading scans) to read your PET-CT. Staying warm will keep the fat from becoming active and make the pictures from your scan clearer.


Follow these instructions:

  • Avoid areas where you may become too cold.
  • Keep your hands and feet warm at all times.
  • In the winter, dress extra warmly. Wear hats, scarves, gloves, and extra layers.
  • In the summer, avoid turning on your air conditioner to very high.
  • Bring a sweater with you to your appointment.

What to do the day of your PET-MRI

Continue to avoid high-energy and repetitive activities until after your scan.

If you are not getting anesthesia, follow the instructions below. You may not be able to have your PET-CT if you do not follow these instructions before your procedure.

For 6 hours before you arrive for your scan:

  • Do not eat anything.
  • Do not chew gum or suck on hard candy, mints, or cough drops.
  • You may drink only water.
  • If you take medications, take them with water only.

Things to remember

  • Know the time and location of your MRI. You can check the patient portal or call your doctor’s office to confirm. Please note the arrival time for your appointment on the patient portal.
  • If you wear a medication patch on your skin, bring an extra one with you.
  • Leave any valuables at home if they are not needed. This includes credit cards and jewelry.
  • Eat a meal before your MRI.
  • You may be taking medication for anxiety or to help you relax during your MRI. If you are, take the medication 30 to 60 minutes before your MRI.

What to expect when you arrive

Many staff members will ask you to say and spell your name and birth date. This is for your safety. People with the same or similar names may be having a procedure on the same day. Once you’re in the department, you’ll fill out a brief questionnaire.

Your care team will prick your finger or draw blood from your arm to measure your blood glucose (sugar). Your blood sugar level needs to be between 70 milligrams per deciliter (mg/dL) and 199 mg/dL.

If your blood sugar level is 200 mg/dL or above, you may need to get insulin. Your scan may need to be rescheduled if your blood sugar level is above 200 mg/dL or below 70 mg/dL.

Your care team will inject the tracer into your vein. You’ll wait about 60 minutes for your body to absorb the tracer. How long this takes will depend on the area of your body being scanned. You will also get contrast to drink at this time.

Try to relax and limit your movement during this time. You can sleep, read, listen to music, or watch videos while you’re waiting. Ask for a blanket if you feel cold.

Your care team will ask you to urinate (pee) just before your scan.

Going into the MRI scan room

When it’s time for your PET-MRI, you’ll remove your hearing aids, glasses, and dentures, if you have them. You’ll either walk into the procedure room or a staff member will bring you there on a stretcher.

Inside the MRI scan room

A member of your care team will help you onto the MRI table. The technologist will place a frame or padded covering over the part of your body that is being scanned. It has coils that capture images of your body during your scan. Your healthcare provider will use these images to plan your care.

The machine makes loud noises during the scan. Your technologist will give you earplugs or headphones to listen to music to protect your ears. You can ask for both if you are very sensitive to noise. If you wear a device on your skin, you’ll need to remove it if you haven’t already been removed.

Once you’re comfortable on the MRI table, your technologist will slide it into the magnetic part of the machine. They will begin the scan. Most of your body will be inside the tunnel during the scan. You’ll be able to speak with your technologist during the entire scan.

It is important that you lay still and breathe normally during your scan. You can use the conscious breathing exercises to help you relax. Remember, do not use deep breathing during the scan. It can cause your body to move too much.

Most MRI scans will take 30 to 45 minutes.

What to do after your PET-MRI

When your PET-MRI is finished, you’ll be helped off the table. You can leave after you get your belongings. There are no restrictions after your PET-MRI. No special care is needed.

You may leave as soon as your scan is done, unless you have other tests or procedures scheduled. You’ll get a card stating that you had a test done with a radioactive tracer and your test date. Keep this card with you because some security equipment can find radioactivity until it leaves your body. This should take less than a day.


It’s important that you limit close contact with babies or pregnant people as much as possible for 12 hours after your scan. Otherwise, you can go about your day as usual, including having visits with your healthcare providers.

If you’re breastfeeding, stop for 12 hours after your scan. During this time, you can continue to pump milk and either throw it away or store it for 12 hours. After 24 hours, you can feed it to your baby. You can restart breastfeeding 12 hours after your scan.

Remember to stay hydrated after your scan. Drink water and other fluids throughout the rest of the day to help remove the tracer from your body. You can go back to your normal diet right away, unless you’re given other instructions.

If you had contrast, it will leave your body through your urine within 24 hours.

Getting your PET-MRI results

A radiologist will read your scan and send your results to your doctor. If your PET-MRI was done to find cancer cells, your doctor should have your results in 2 business days. Ask your doctor how they will share your results with you. If your PET-MRI was done to plan your treatment, your doctor will use the images to plan your care.


For People Getting Anesthesia

If you are getting anesthesia (medication to make you sleepy) during your PET-MRI, follow these instructions.

What To Do the Day Before Your PET-MRI

Arrange for someone to take you home

You must have a responsible care partner take you home after your procedure. A responsible care partner is someone who can help you get home safely. They should be able to contact your care team if they have any concerns. Make sure to plan this before the day of your procedure.

If you don’t have a responsible care partner to take you home, call one of the agencies below. They’ll send someone to go home with you. There’s a charge for this service, and you’ll need to provide transportation. It’s OK to use a taxi or car service, but you still need a responsible care partner with you.

Agencies in New York Agencies in New Jersey
VNS Health: 888-735-8913 Caring People: 877-227-4649
Caring People: 877-227-4649  


Instructions for eating and drinking: 8 hours before your arrival time

  • Stop eating 8 hours before your arrival time, if you have not already. 
    • Your healthcare provider may tell you to stop eating earlier. If they do, follow their instructions.
  • 8 hours before your arrival time, do not eat or drink anything except these clear liquids:
    • Water.
    • Soda.
    • Clear juices, such as lemonade, apple, and cranberry juices. Do not drink orange juice or juices with pulp.
    • Black coffee or tea (without any type of milk or creamer).
    • Sports drinks, such as Gatorade®.
    • Gelatin, such as Jell-O®.
    You can keep having these until 2 hours before your arrival time.

What To Do the Day of Your PET-CT

Instructions for drinking: 2 hours before your arrival time

 Stop drinking 2 hours before your arrival time. This includes water.


Contact Information

If you have any questions or concerns, call the Molecular Imaging and Therapy Service (MITS, or the Nuclear Medicine service) at 212-639-6652. You can reach a staff member Monday through Friday from to After , during the weekend, and on holidays, call 212-639-2000.

Exercises to help you relax for your MRI

You can use breathing exercises before or during your scan to help you feel more comfortable. Exercises that use little to no movement, such as conscious breathing, are safe to use during your scan. Other exercises, such as deep breathing, cause more movement and should not be done during your scan.


Deep breathing exercises to use before your PET-MRI only

Do not use deep breathing during your MRI. It can cause your body to move too much while you’re in the PET-MRI machine.

You can practice deep breathing by following these steps:

  1. Place 1 hand on your stomach, just above your belly button. If you’re right-handed, use your right hand. If you’re left-handed, use your left hand.
  2. Breathe out completely through your mouth.
  3. If you can, close your eyes and breathe in slowly and deeply through your nose. Feel your stomach push up on your hand. Imagine that air is filling your whole body from the bottom up.
  4. Pause for a couple of seconds. Then, breathe out slowly through your mouth or nose. Try to breathe out completely and imagine the air leaving your lungs, mouth, or nose.
  5. As you breathe out, allow your body to relax and go limp—like a rag doll.

Repeat this exercise 5 to 10 times.

Relaxation exercises to use before or during your PET-MRI

Here are some things you can do before your PET-MRI to help with claustrophobia, anxiety, or both.

Acupressure for Stress and Anxiety

Body Scan Meditation 

Breathing Exercises to Prepare for Procedures 

Managing Anxiety about Medical Scans and Procedures 

Guided Imagery Meadow Meditation 

Guided Imagery Meditation to Promote Comfort and Wellness 

Managing Anxiety 

Managing Scanxiety During Your Cancer Treatment

Mindful Breathing Meditation 

Mindful Movement Meditation 

Relaxation Exercises to Practice Before and During Your MRI

Last Updated

Monday, July 31, 2023

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