What Nurses Need to Know About PET Scans

Positron emission tomography (PET) scans are imaging tools used primarily in oncology, neurology, and cardiology to visualize metabolic activity within the body. This guide outlines essential information for nurses regarding PET scan procedures, applications, and clinical considerations. 

What is a PET scan? 

A type of nuclear medicine imaging, PET scans use a small quantity of radioactive material (radiotracer) to detect physiological activity. The most commonly used tracer is fluorodeoxyglucose (FDG), a radioactive form of glucose. Cells with high metabolic rates, such as cancer cells, absorb more of the tracer and appear as bright spots on the scan. 

How long does a PET scan take? 

The entire process typically takes two to three hours. This includes: 

• Pre-scan preparation and tracer injection 
• A waiting period of 30 to 90 minutes for the tracer to distribute 
• The scan itself, which takes 20 to 45 minutes. Patients are usually advised to rest quietly during the uptake phase to prevent nonspecific muscular or cardiac uptake. 

What does a PET scan show? 

PET scans detect metabolic changes in tissues, making them especially useful for identifying cancer, assessing treatment response, detecting neurological disorders, and evaluating myocardial viability. High FDG uptake often corresponds to areas of increased cellular activity, such as tumors or inflammation. 

After a PET scan, how long are you radioactive? 

The radiotracer used in PET scans decays quickly. Most of the radioactivity is eliminated from the body within 6 to 12 hours.  

Patients are advised to drink fluids and urinate frequently to expedite excretion. Close contact with vulnerable individuals (e.g., infants, pregnant women) should be limited for the remainder of the day. 

Will an infection light up on a PET scan? 

Yes. Infections and inflammatory processes can exhibit high FDG uptake due to increased metabolic activity of immune cells. While this helps detect abscesses or osteomyelitis, it may also confound interpretation if inflammation is mistaken for malignancy. 

What is the meaning of FDG uptake in a PET scan? 

FDG uptake refers to how much radioactive glucose analog is absorbed by tissues. High uptake (hypermetabolism) may indicate malignancy, inflammation, or infection. standardized uptake values (SUVs) help quantify FDG accumulation and assess the degree of metabolic activity. 

What is a PET scan used to diagnose? 

PET scans are commonly used to: 

• Detect and stage cancers (e.g., lung, lymphoma, colorectal). 
• Evaluate cancer recurrence or metastasis. 
• Monitor therapy effectiveness. 
• Identify areas of epileptic focus in the brain. 
• Assess Alzheimer’s disease or other neurodegenerative diseases. 
• Evaluate myocardial perfusion and viability. 

What is a high SUV on a PET scan? 

A high SUV (Standardized Uptake Value) indicates significant radiotracer absorption, typically suggesting active disease.  

While there is no universal cutoff, SUVs >2.5 are often considered suspicious for malignancy. However, values must be interpreted in a clinical context, as infections or recent interventions can also elevate SUVs. 

Why rest before a PET scan? 

Physical activity before a PET scan can increase FDG uptake in skeletal or cardiac muscles, compromising image quality. Patients are instructed to rest and avoid strenuous exercise for 24 hours prior to the scan and remain still during the uptake phase. 

What is the difference between a PET scan and a CT scan? 

CT scans give comprehensive anatomical images using X-rays, while PET scans detect metabolic activity using radioactive tracers. Often, PET and CT are combined into a PET/CT scan, enabling precise localization of functional abnormalities within anatomical structures. 

What do nurses need to know about PET scans? 

Nurses are essential in PET scan preparation and follow-up: 

• Verify patient fasting status (typically four to six hours). 
• Screen for diabetes, as blood glucose levels affect FDG uptake. 
• Confirm medication use that may interfere with results. 
• Provide patient education on the scan process and post-scan precautions. 
• Assist with IV access for tracer injection. 
• Ensure radiation safety protocols are followed. 
• Monitor for allergic or vasovagal reactions.