Essential Guide to Your PET Scan
#8 Essential Guides
If this is your first PET scan, the anxiety is real. When the doctors start throwing around terms like “radioactive tracer” and “metabolic mapping,” it’s easy to spiral. Having been through this multiple times, I can tell you that the anticipation is often worse than the reality.
I have had to slide into that donut-shaped machine 9 times since September 2022. It’s intimidating the first time and just as dreadful every other time too. I must take a sedative (Valium) to do it. Yet, it is not hard, and the process itself is completely passive and non-invasive.
Practical Note: Dress warmly and wear clothes without metal zippers or snaps. Sweats are your best friend here. Scanning rooms are usually freezing.
What is Metabolic Mapping?
Let’s start with the most confusing term: metabolic mapping. Here is what I hope is an east to understand explanation.
Cancer cells are selfish and hungry. They divide fast and they grow fast. They consume energy, specifically glucose (sugar), much faster than your healthy cells do.
A PET scan exploits this hunger. Radiology gives you a dose of radioactive sugar. Then, they let you sit for about 45 minutes to an hour while your cells absorb it. The cancer cells pull the radioactive material directly into themselves (they eat it). When they slide you into the scanner, the machine takes a literal map of your metabolism. The scan is looking for radiation. The areas that glow the brightest on the monitor are the ones burning the most energy. It’s a targeted spotlight on what’s happening inside your body.
The Prep
Prep starts the day before.
You need to avoid strenuous exercise for 24 hours before your appointment. A physical workout makes your muscles hungry for energy. If your muscles are starved for sugar, they will soak up the radioactive tracer, making you glow on the scan which will ruin the test’s accuracy.
You also need to fast for 4 to 6 hours before you arrive, no food, no sugary drinks, just water. They want your blood sugar to be on the low side so that when they introduce the tracer, those bad cancer cells are starving and ready to eat. They will not do the PET scan if your blood sugar is too high, which happened to me, four times.
Practical Note: Stay within normal limits for your blood sugar. Having blood sugar at the lower end of those limits is helpful for your PET scan. Having your blood sugar below normal levels is a medical emergency. Having low blood sugar does not stop or slow cancer from spreading. Talk to your doctor.
Tracer Injection & Absorption: The Waiting Game
When you arrive, a radiology tech may hook you up to an IV and inject FDG (fluorodeoxyglucose), which is the radioactive glucose. Mine radiology office had me drink about 8 ounces of a red liquid, which tastes like stale Kool-Aid.
Then comes the hardest part of the whole ordeal, doing absolutely nothing. For about 60 minutes, you will sit in a dim, quiet room. No reading, no chewing gum, no scrolling on your phone. Any
brain or muscle activity burns glucose. You want the tracer to settle naturally, not rush to your hand because you were swiping on your phone. It’s like a forced meditation and I usually fall asleep.
The Scan Time
Once your waiting time is up, they will walk you to the scanner. Now is the time to use the restroom as once the scan starts, you can’t stop. The scanner looks like a giant, futuristic donut. You’ll lie flat on your back on a narrow bed. The bed slides slowly into the ring. A PET scan isn’t loud like an MRI. It takes about 30 to 45 minutes. The only thing you must do is stay perfectly still.
If you’re claustrophobic, tell your tech. Better yet, tell your oncologist. I am. As I mentioned, I took Valium before my PET scans, which were prescribed in advance.
Recovery & Follow-Up: Flushing It Out
When the machine slides you out, you’re done. There are no side effects. You aren’t going to feel dizzy or sick from the tracer. You may feel stiff from lying still for so long.
Your primary job now is to flush the radiation out of your system.
Resume your normal diet and drink a lot of water for the rest of the day. The radiation leaves your body mostly through your urine over the next few hours.
For the results, don’t ask the tech. They aren’t legally allowed to tell you anything. The images go to a radiologist, who interprets the glowing spots (the metabolic map) and sends the report to your oncologist. Usually, within a few days, your doctor will walk you through exactly what they found. Some medical groups have an electronic records system (mine is called MyChart) and the results may be posted there before you speak to your doctor.
I know how overwhelming these days can feel.
That’s why I wrote NOT BROKEN: The Unfiltered Daily Truth in Fighting Cancer.
It’s the book I wish I had when I was trying to process the diagnosis, navigate treatment, and hold onto myself through it all.
If this article resonated with you, the book, NOT BROKEN The Unfiltered Daily Truth in Fighting Cancer, goes deeper into the day-to-day realities of cancer—honestly, practically, and without filters.
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