7 Crucial Things You Need to Know Before Your First PET Scan

Hearing your doctor say, “We need to schedule a PET scan,” can instantly make your heart race. Whether you are being evaluated for cancer, a neurological condition, or an unexplained infection, it is completely normal to feel anxious about your first Positron Emission Tomography (PET) scan.

The fear of the unknown-combined with intimidating words like “radioactive tracer” – is often the hardest part of the process.
But here is the good news: a PET scan is a painless, safe, and incredibly powerful tool that gives your medical team a molecular-level map of what is happening inside your body.

To help you feel prepared, calm, and in control, here are the 7 crucial things you need to know before your first PET scan.

Your Diet the Day Before is Critical

Unlike an X-ray or an MRI, a PET scan actually requires you to alter your diet for about 24 hours before your appointment.

Because the most common PET scan tracer is a form of radioactive glucose (sugar), you need your body’s natural blood sugar levels to be as low as possible. If your blood sugar is too high, it can interfere with the results.

• The Day Before: Your doctor will likely ask you to follow a strict low-carbohydrate, no-sugar diet. You will need to avoid bread, pasta, fruit, alcohol, and sugary drinks. Instead, you’ll eat protein and non-starchy vegetables (like chicken, fish, eggs, and broccoli).
• The Day Of: You will usually be required to fast (eat nothing) for 4 to 6 hours before your scan. You can only drink plain, unflavored water.

You Will Receive a “Radioactive” Injection (But It’s Safe!)

The magic of a PET scan comes from a radiotracer, usually a drug called FDG (fluorodeoxyglucose).
When you arrive, a technologist will inject a small amount of this tracer into your vein through an IV.

Because diseases like cancer consume glucose (sugar) at a much faster rate than healthy cells, the FDG travels straight to those highly active areas. During the scan, those problem areas will “light up” on the computer screen.

Is it safe? Yes. The amount of radiation in the tracer is very low-similar to what you might receive from standard X-rays or a CT scan. It is safely processed and eliminated by your body within a day.

You Must Master the Art of Doing Nothing

After the injection, you don’t go into the scanner right away. The tracer takes time to travel through your bloodstream and absorb into your cells.

You will be placed in a dim, quiet room for about 45 to 60 minutes. During this “uptake” period, you must remain completely still and relaxed.

• No reading (it stimulates the brain).
• No scrolling on your phone (it stimulates the eyes and hands).
• No chewing gum or talking (it stimulates the jaw muscles).

If you move too much, the tracer will be absorbed by your healthy muscles, which can create glowing “false positives” on your scan. Use this time to meditate or take a nap!

Diabetics Require Special Instructions

If you have diabetes, a PET scan requires careful coordination. Because the scan relies heavily on your blood glucose levels, your standard insulin or medication routine might conflict with the fasting rules.

Never adjust your diabetes medication on your own. Call your imaging center a week before your scan. They will give you precise instructions on how to manage your diet, when to take your insulin, and what your target blood sugar should be on the morning of the test.

If your blood sugar is too high when you arrive, they may have to reschedule your appointment.

Dress for Ultimate Comfort (And Ditch the Metal)

When it comes to your PET scan wardrobe, think “lazy Sunday.” You want to wear loose, warm, and comfortable clothing.

Because metal can interfere with the imaging equipment, you will need to leave all metallic items at home or take them off before the scan. This includes:

• Jewelry and watches
• Belts with metal buckles
• Bras with metal underwires or clasps (a metal-free sports bra is highly recommended)
• Pants with zippers or metal buttons (sweatpants or leggings are perfect)

If your clothes are completely metal-free, the technologist may let you wear them during the scan instead of changing into a hospital gown.

The Scanner Looks Like a Giant Donut

If you are claustrophobic, you might be dreading the scanner. However, most patients find a PET scanner much easier to tolerate than an MRI machine.

A PET/CT scanner looks like a large, giant donut. The opening is wider and shorter than an MRI tube, meaning your head often remains outside the machine for a large portion of the test. Furthermore, PET scanners are completely silent, unlike the loud, banging noises associated with MRIs.

The actual time spent inside the scanner usually only takes 20 to 30 minutes.

You Need to Keep Your Distance After the Scan

Once the scan is over, you can immediately return to your normal diet and daily activities. However, because you still emit a very low level of radiation for a few hours, you need to follow a couple of safety protocols:

• Drink plenty of water: Hydration helps flush the radioactive tracer out of your system through your urine.
• Protect the vulnerable: For about 8 to 12 hours after your scan, you should avoid close, prolonged contact with pregnant women and infants. Keep a safe distance (about 6 feet) just to be absolutely safe.

A PET scan is a miraculous piece of medical technology that takes the guesswork out of diagnostics. By following your fasting instructions, relaxing during the waiting period, and wearing comfortable clothes, you are setting yourself up for a smooth, successful scan.