FDG Scan
What Is an FDG PET Scan?
An FDG PET scan is an imaging test that shows how tissues and organs in your body function. It combines two powerful tools:
- PET scan (Positron Emission Tomography): A type of scan that uses a small amount of radioactive material to detect changes in the body at a cellular level.
- FDG (fluorodeoxyglucose): A special sugar containing a small amount of radioactivity, which is the tracer used in many PET scans.
What is FDG in PET scan?
FDG is a type of sugar that has been slightly modified and combined with a radioactive atom.
Your body processes FDG similarly to normal sugar, which is called glucose. Because of this, it’s especially good at highlighting high-energy and high-use areas in the body, including:
- Inflammation
- Infection
- Cancer
FDG is injected into your vein before the scan and spreads throughout your body. The PET scan can then detect where the FDG collects the most. Areas that take up a lot of FDG show up more brightly on the scan.
What Is FDG Uptake?
FDG uptake describes how much FDG a particular part of your body absorbs. Most tissues take up some FDG, but areas with higher metabolic activity absorb more.
For example, cancer cells often use more sugar than normal cells, so they absorb more FDG. These areas are said to have increased FDG uptake. Inflammation or healing tissue can also show increased absorption.
Some areas of the body, like the brain and heart, naturally have high FDG uptake even when healthy.
Doctors interpret the scan by looking at how much FDG different tissues absorb. Areas of high uptake can signal where additional testing or treatment might be needed.
What Does It Mean If Something Is FDG-Avid?
When a doctor describes something as FDG-avid, a spot on the scan is clearly taking up more FDG than the surrounding tissue. It appears brighter on the scan.
This term is often used in cancer imaging. A tumor that is FDG-avid may be more active or aggressive.
However, not all FDG-avid areas are cancer. Infection, inflammation, and even healing after surgery can also show up as FDG-avid.
That’s why the FDG PET scan is usually used alongside other imaging tests like CT or MRI and clinical information to guide a diagnosis and treatment.
What Happens During an FDG PET Scan?
The entire process usually takes about two hours, but much of that time is spent waiting while the FDG spreads through your body.
You’ll receive a small injection of FDG into a vein, usually in your arm. Then, you’ll rest quietly for about 45 minutes while it travels through your body and is absorbed by your tissues.
After that, you’ll lie on a table that moves slowly through the PET scanner. This part usually takes 20 to 40 minutes and is entirely painless.
After the scan, you can go home and resume normal activities. Drinking plenty of water afterward helps flush the tracer from your system.
Is FDG Safe?
Yes, it is considered safe for most people. The radioactive material used in the scan is very small and usually leaves your body within a day or two. Most people don’t experience any side effects, although the injection may cause mild discomfort.
What Happens After the Scan?
A radiologist will review the images and prepare a report for your doctor. Depending on the results, your doctor might order more tests, start treatment, or simply continue to monitor your health.
It’s helpful to remember that not all areas of high FDG uptake are harmful, and not all low-uptake areas are safe. The scan is just one piece of the puzzle that your doctors use to make decisions about your care.
FDG Scan FAQs
1. Can a PET scan tell the difference between cancer and other conditions like inflammation?
Not always. Both cancer and other conditions can show increased FDG uptake, which means they may look similar on the scan. That’s why your doctor will interpret the results alongside other information, such as lab tests, physical exams, or biopsies.
2. What if nothing shows up on my FDG PET scan?
A normal scan means that no areas of concern were identified based on FDG uptake. This can be reassuring, especially if you’re being monitored for cancer recurrence. However, your doctor may still recommend follow-up based on your symptoms or medical history.
3. Do I have to fast before the scan?
Eating can affect how your body processes sugar. Since FDG is a form of sugar, having food in your system may interfere with the results. Your doctor will give you detailed instructions on how to prepare for the test.
