What is a PET Scan?
A PET (Positron Emission Tomography) scan is an imaging test that uses a radioactive tracer to look for disease in the body. For the scan, the patient receives an injection of a small amount of radioactive glucose sugar. Cancer cells metabolize sugar faster than normal cells, so they absorb more of the radioactive tracer.
The patient then lies in a PET scanner, which has detectors that pick up signals from the tracer. A computer analyzes the signals and converts them into 3D images. Areas where the tracer has accumulated show up brighter on the images, which may indicate cancer or infection.
What Does a PET Scan Detect?
A PET scan is often used to:
- Detect cancer and see how far it has spread
- See if cancer treatment is working
- Find a potential cancer recurrence
- Identify areas of inflammation or infection
- Evaluate brain function and heart function
PET scans are helpful for spotting lung, breast, colon, head and neck, and cervical cancers. It provides different information than CT and MRI scans. PET visualizes cellular activity and metabolism in the body.
Can a PET Scan Detect Infection?
Yes, a PET scan may light up areas of infection or inflammation in the body. For this purpose, a different radioactive tracer called FDG (fluorodeoxyglucose) is used rather than the standard FDG tracer for cancer. FDG accumulates at sites of inflammation and infection.
Areas of infection show up as bright spots on PET images. However, a PET scan cannot differentiate cancer from infection or inflammation based on images alone. Your doctor will interpret the results along with your symptoms and other test results.
Types of Infections Seen on PET Scan
Some common infections that may be detected on a PET scan include:
- Abscesses from bacterial infections
- Osteomyelitis (bone infection)
- Inflamed lymph nodes or lymphadenitis
- Inflammation of organs like pancreatitis or appendicitis
- Inflammatory bowel diseases like Crohn’s or ulcerative colitis
- Rheumatoid arthritis flare-ups
- Sarcoidosis granulomas
Advantages of PET for Infection
- Full body scan can detect multiple sites of infection
- Helps identify specific location of infection
- Quantifies severity of inflammation
- No radiation exposure from CT scans
- May identify hidden infections not seen on other tests
PET Scan vs CT Scan for Infection
PET and CT scans are both useful for imaging infection, but work differently:
- PET shows metabolic activity of infection
- CT reveals anatomical structure and changes
Using PET and CT together provides the most information by correlating anatomy and function. However, PET alone can identify infection without CT radiation exposure.
Advantages of PET vs CT
- Higher sensitivity for detecting infection
- Quantifies intensity of infection
- No additional radiation exposure
- Can scan whole body in one session
Limitations of PET
- Difficult to locate precise anatomical area of infection
- Exposure to radioactive tracer
- High cost compared to CT scan
- Limited availability of scanners
How to Prepare for a PET Scan
There are important steps to take before a PET scan:
- No eating for 6 hours prior
- Drink plenty of water to stay hydrated
- Avoid exercise or strenuous activity 24 hours before
- Stop taking any medications that may interfere with results
- Arrange transportation since you cannot drive after scan
- Wear comfortable loose clothing without metal
- Expect the appointment to take 2-4 hours total
Make sure to follow all instructions from your doctor in advance. Tell your provider if pregnant, breastfeeding, claustrophobic, or have any allergies.
PET Scan Results for Infection
Your doctor will review the PET scan images and radionuclide tracer activity to interpret if infection is present. Results are usually ready within 2-3 days after the test.
Areas of brightly concentrated tracer will highlight regions of infection and inflammation. However, other conditions like cancer can look similar, so your doctor will consider your specific symptoms and medical history.
PET scans detect metabolic changes at the cellular level, often before anatomical changes are visible on CT or MRI. This makes it a powerful tool for identifying infection before it progresses.
Next Steps After PET Scan
If a PET scan finds an infection, typical next steps include:
- Start antibiotic treatment if infection is localized
- Drainage or surgery to remove abscess
- Biopsy to sample infected tissue for culture
- Further imaging like CT scan to pinpoint anatomy
- Treat underlying inflammatory condition
- Monitor response to treatment with follow-up PET scans
Your doctor will determine appropriate treatment based on your individual symptoms and type of infection found on the PET scan.
Conclusion
PET scans are a valuable imaging tool that can detect areas of infection and inflammation in the body. They are sensitive for identifying infectious processes early, before they become widespread or cause damage. While PET scans have some limitations, they provide molecular imaging data that can improve diagnosis and treatment when infections are suspected.
FAQs
Can a PET scan tell the difference between cancer and infection?
While PET scans can detect both cancer and infection, they cannot definitively distinguish between the two based on imaging alone. Doctors must interpret the PET results in context with your symptoms, medical history, and other test findings to make an accurate diagnosis.
What does infection or inflammation look like on a PET scan?
Areas of infection and inflammation appear brighter on PET scan images due to increased metabolic activity and tracer uptake. However, malignant tumors can also appear bright, so your doctor must correlate the PET findings with other information to diagnose the cause.
Can a PET scan detect an infection anywhere in the body?
Yes, a PET scan surveys the entire body and can highlight infection or inflammation anywhere, including bones, organs, tissues, and lymph nodes. Some exceptions are the brain and urinary tract, which may require other scans.
How long do PET scan results take?
It takes 2-3 days to get PET scan results. The radioactive tracers require time to decay before images can be reconstructed by computers and then interpreted by radiologists. Urgent cases can be prioritized to get results faster if needed.
When might a PET scan be used to look for infection?
A PET scan can be used when there are signs of infection like high white blood cell count or fever of unknown origin. It helps identify the source in cases of possible hidden systemic infection not found by other tests. PET scans are also used to monitor treatment response.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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