PET Scan: Why & What to Expect

I remember a patient, let’s call him David, sitting across from me in the clinic, his hands clasped tightly. He’d just been told he needed a PET scan, and the worry was written all over his face. “Doc,” he said, “what exactly is this thing? It sounds serious.” It’s a common feeling, that mix of uncertainty and concern when you hear about a test you’re not familiar with. So, let’s talk about it, just like I talked with David.

So, What Exactly is a PET Scan?

A Positron Emission Tomography (PET) scan is a special kind of imaging test. Think of it as a way for us to see how your organs and tissues are actually working on a cellular level. It’s not just a static picture.

Here’s the gist: we use a safe, injectable substance called a radiotracer. This is a tiny bit of radioactive material – and I mean tiny, and safe. This tracer travels through your bloodstream and is absorbed by your body’s cells. The clever part? Diseased cells, especially active ones like cancer cells, tend to gobble up more of this tracer than healthy cells. The PET scanner then detects these areas of higher absorption, showing up as “hot spots” on the images it creates. This helps us pinpoint potential health problems.

We often use PET scans to help diagnose cancer and to see how cancer treatment is progressing. But they’re also really useful for looking at certain heart conditions and brain issues.

How is a PET Scan Different from a CT or MRI?

That’s a great question, and one I get a lot!

• CT (Computed Tomography) scans use X-rays to create detailed pictures of your organs and body structures.
• MRI (Magnetic Resonance Imaging) scans use powerful magnets and radio waves to do something similar. Both give us still images.

A PET scan is different because it shows us function – how an organ is behaving in real-time. Because it looks at cellular changes, a PET scan can sometimes spot problems earlier than a CT or MRI.

Sometimes, you might have what’s called a PET-CT. This combines both types of scans at the same time. The CT gives us the detailed anatomical picture, and the PET shows us the cellular activity. Together, they create 3D images that can give us a really accurate diagnosis. There’s also a newer technology, the PET/MRI scan, which is excellent for soft tissue cancers, like in the brain or liver. It gives incredibly high-contrast images.

What Does a PET Scan Help Us Find?

Your doctor might suggest a PET scan if they want to check for signs of:

• Cancer: This includes many types, like breast cancer, lung cancer, and thyroid cancer.
• Heart problems: Things like coronary artery disease or checking the damage after a heart attack.
• Brain disorders: This could be brain tumors, epilepsy, dementia, or Alzheimer’s disease.

Essentially, a PET scan can measure vital functions like blood flow, how your body is using oxygen, and how it’s metabolizing sugar (glucose). It helps us identify organs and tissues that aren’t working quite right.

When Would I Actually Need a PET Scan?

If we suspect cancer, a PET scan is a very valuable tool. It can help detect cancer and confirm a diagnosis.

If you’ve already been diagnosed with cancer, we might use PET scans during your treatment journey to:

• See if the cancer has spread (what we call metastasized).
• Check how well the treatment is working.
• Find out if cancer has come back after treatment (this is called recurrence).
• Get a better idea of the cancer’s outlook (the prognosis).

For heart issues, a PET scan can:

• Show us the effects of a heart attack on different areas of your heart.
• Help us identify parts of the heart muscle that might benefit from procedures like an angioplasty or coronary artery bypass surgery.

And if you’re having neurological symptoms, a PET scan can help us evaluate brain abnormalities like tumors, seizures, or other conditions affecting your central nervous system.

Getting Ready for Your PET Scan

A PET scan is usually an outpatient procedure, meaning you’ll go home the same day. It’s really important to follow the preparation instructions you’re given. Generally, here’s what you can expect:

• Medication List: Make sure your doctor has an up-to-date list of all your medications, vitamins, and supplements. And any allergies, too.
• Pregnancy/Breastfeeding: If there’s any chance you could be pregnant, or if you’re breastfeeding, you absolutely must tell your doctor.
• Fasting: You’ll likely be asked not to eat anything for about six hours before the test. If you have diabetes, your doctor will give you specific instructions on this.
• Hydration: You can usually drink water.
• Caffeine: If the scan is for a heart problem, you’ll probably need to avoid caffeine for 24 hours beforehand.
• Comfort: Wear comfortable clothes. Leave metal items like jewelry, eyeglasses, dentures, and hairpins at home or be prepared to remove them.
• Anxiety: If you feel anxious in enclosed spaces (claustrophobia), let your doctor know. Sometimes, a mild sedative can be given to help you relax.

What Happens During the PET Scan?

Okay, so you’re prepped and ready. Here’s what the actual scan experience is like:

1. The Tracer: You’ll get an IV (intravenous) injection of the radiotracer. The most common one is called fluorodeoxyglucose (FDG), which is a type of sugar. Don’t worry, it’s a safe amount.
2. Waiting Time: You’ll then sit quietly in a chair for about an hour. This gives the tracer time to travel through your bloodstream and get absorbed by your organs and tissues. It’s important to relax and not move around too much, as activity can send the tracer to muscles instead of the areas we want to see. You won’t feel the tracer working.
3. Contrast Dye (Maybe): If you’re having a PET-CT, you might also get an IV injection of a contrast dye. This helps make the CT images sharper.
4. The Scanner: You’ll lie on a comfortable exam table that slides into the PET scanner. The machine itself is often described as a big doughnut – about 30 inches wide.
5. The Scan: The scan itself usually takes about 30 minutes. The most important thing during this time is to lie very still. Movement can blur the images, a bit like taking a blurry photo.
6. Sounds: You’ll likely hear some buzzing and clicking sounds as the scanner does its work. This is normal.
7. Image Check: Before you leave, a technologist will quickly review the scans to make sure the images are clear and in focus.

How Long Does the Whole PET Scan Take?

The entire process, from when you arrive to when you’re done, usually takes about two hours. This includes the time for the tracer to absorb (up to 60 minutes), the scan itself (about 30 minutes), and a little waiting time for the image check.

Are There Any Risks with a PET Scan?

For most people, PET scans are very safe, and problems are rare. The amount of radiation in the tracer is very low and it doesn’t stay in your body for long. Drinking plenty of water after your scan helps flush it out even faster.

There are a few situations where we need to be extra cautious:

• Pregnancy and Breastfeeding: As I mentioned, if you’re pregnant or breastfeeding, you generally shouldn’t have a PET scan. The radiation could potentially harm a developing baby or pass into breast milk.
• Allergic Reactions: It’s extremely rare, but some people can have an allergic reaction to the radiotracer or the CT contrast dye. If this happens, the medical team is right there and can give you medication to stop the reaction quickly.
• Diabetes: If you have diabetes, how your body absorbs the sugar in the tracer can sometimes affect the scan results. Your doctor will give you specific advice on how to manage your diet and medications before the test to ensure the best possible images.

What About My PET Scan Results?

After your scan, a radiologist – a doctor who specializes in interpreting medical images, including PET scans – will carefully review the images. They’ll write up a report and send it to the doctor who ordered your scan. This process usually takes about 24 hours. Your doctor will then discuss the results with you.

Key Things to Remember About Your PET Scan

It’s a lot to take in, I know. So here are the main points:

• A PET scan shows how your organs and tissues are functioning by using a safe radioactive tracer.
• It’s often used to detect cancer, assess cancer treatment, and evaluate heart and brain conditions.
• It can sometimes find disease earlier than other imaging tests.
• Preparation is important – follow your doctor’s instructions carefully.
• The procedure involves an injection, a waiting period, and then lying still in the scanner.
• PET scans are generally very safe, with low radiation exposure.
• Results are usually available to your doctor within a day or so.

Knowing what to expect can make a big difference. We’re here to answer your questions and make sure you feel as comfortable as possible. You’re not alone in this.