Positron Emission Tomography (PET) scans are powerful medical imaging tools that provide detailed insights into the metabolic activity within your body. This overview will help you understand what a PET scan is, how it works, and why it might be recommended by your healthcare provider.
What is Positron Emission Tomography?
A Positron Emission Tomography (PET) scan is an advanced imaging technique used to visualize the biochemical and metabolic functions of your tissues and organs. During a PET scan, you will lie on a comfortable table that gently slides into a specialized scanner, often described as doughnut-shaped. The process, from start to finish, typically takes around 30 minutes for the scanning portion, during which the machine captures detailed images of the activity within your body.
Unlike other imaging tests that primarily show the structure of organs, a PET scan reveals how your tissues and organs are functioning at a cellular level. It achieves this by using a radioactive tracer, a special drug that highlights areas of metabolic activity. This tracer is crucial for detecting diseases, sometimes even before structural changes are visible on other scans like Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI). PET scans are frequently combined with CT or MRI to provide a more comprehensive view, known as PET-CT or PET-MRI scans.
The tracer, usually administered via injection into a vein in your arm or hand, circulates throughout your body. It accumulates in areas with higher metabolic activity, which are often indicative of disease processes. This concentration of the tracer allows doctors to pinpoint the exact location of the issue.
Why are Pet Scans Performed?
A PET scan is a valuable diagnostic tool for a wide range of medical conditions. Its ability to detect metabolic changes makes it particularly effective in identifying and monitoring diseases like cancer, heart problems, and various brain disorders. Healthcare providers utilize PET scans for several key reasons:
- Diagnosis: To help identify the underlying cause of symptoms and diagnose various conditions.
- Monitoring Disease Progression: To track the development and spread of diseases over time.
- Treatment Planning: To guide treatment strategies and assess the effectiveness of ongoing therapies.
Pet Scans for Cancer Detection and Management
Cancer cells are characterized by their rapid growth and high metabolic rate. This increased activity causes them to appear as bright spots on PET scans, making PET technology exceptionally useful in oncology. PET scans play a critical role in cancer care by:
- Cancer Detection: Identifying cancerous tumors, often in early stages.
- Staging Cancer: Determining if and where cancer has spread (metastasis) in the body.
- Treatment Monitoring: Evaluating how effectively cancer treatments, such as chemotherapy or radiation therapy, are working.
- Detecting Recurrence: Finding if cancer has returned after treatment.
It is important to note that while PET scans are highly sensitive to metabolic activity, they are not foolproof for cancer diagnosis. Some non-cancerous conditions can also exhibit increased metabolic activity and appear similar to cancer on PET scans. Additionally, not all types of cancer are detectable by PET scans. However, PET-CT and PET-MRI scans are effective in visualizing many types of solid tumors, including cancers of the:
- Brain
- Breast
- Cervix
- Colorectal area
- Esophagus
- Head and Neck
- Lung
- Lymphatic System (Lymphoma)
- Pancreas
- Prostate
- Skin (Melanoma)
- Thyroid
Pet Scans for Heart Disease Assessment
PET scans are also valuable in cardiology, particularly for assessing blood flow to the heart muscle. By revealing areas of reduced blood flow, PET scans can help diagnose conditions like coronary artery disease. This information is crucial for determining the best course of treatment, such as:
- Bypass Surgery Consideration: Assessing the need for coronary artery bypass surgery to improve blood flow.
- Angioplasty Decisions: Evaluating if angioplasty, a procedure to open blocked heart arteries, would be beneficial.
Pet Scans for Brain Disorder Evaluation
In neurology, PET scans are used to investigate various brain disorders by examining metabolic activity patterns in the brain. They can be helpful in evaluating conditions such as:
- Brain Tumors: Identifying and characterizing brain tumors.
- Alzheimer’s Disease: Detecting characteristic patterns of reduced metabolic activity associated with Alzheimer’s.
- Seizure Disorders (Epilepsy): Locating the areas of the brain causing seizures.
Understanding the Risks Associated with Pet Scans
For a PET scan, a small amount of radioactive tracer is necessary to produce the images. While radiation exposure is a concern, the dose used in PET scans is minimal, and the risk of long-term negative effects is very low. However, it’s important to be aware of potential risks:
- Radiation Exposure to Unborn Babies: If you are pregnant or think you might be, inform your healthcare provider as the tracer could expose your fetus to radiation.
- Radiation Exposure to Breastfeeding Infants: Similarly, if you are breastfeeding, there is a potential for minimal radiation exposure to your child through breast milk.
- Allergic Reactions: Although rare, allergic reactions to the tracer are possible.
It is crucial to discuss any concerns and weigh the benefits and risks of a PET scan with your healthcare provider before undergoing the procedure.
Preparing for Your Pet Scan
To ensure the accuracy and safety of your PET scan, it’s important to follow your healthcare provider’s instructions carefully. You will typically be asked about:
- Allergies: Inform your provider about any past allergic reactions, especially to medications or contrast materials.
- Recent Illnesses and Medical Conditions: Disclose any recent illnesses or existing medical conditions, particularly diabetes, as they can affect test results.
- Medications and Supplements: Provide a complete list of all medications, vitamins, and herbal supplements you are currently taking.
- Pregnancy and Breastfeeding: Inform your provider if you are pregnant, suspect pregnancy, or are breastfeeding.
- Claustrophobia: If you have a fear of enclosed spaces (claustrophobia), let your provider know, as they can take steps to make you more comfortable.
General preparation guidelines usually include:
- Avoiding Strenuous Exercise: Refrain from intense physical activity for a couple of days leading up to the scan.
- Fasting Before the Scan: Typically, you will need to stop eating for at least four hours before your scheduled scan time.
What to Expect During a Pet Scan Procedure
PET-CT and PET-MRI scanners are large, sophisticated machines. The procedure itself is generally straightforward and does not usually require an overnight hospital stay. Upon arrival for your PET scan, you may be asked to:
- Change into a Hospital Gown: This ensures comfort and avoids any interference from clothing.
- Empty Your Bladder: This helps to improve image quality, particularly for scans of the pelvic area.
The procedure then involves:
- Tracer Injection: A healthcare professional will inject the radioactive tracer into a vein in your arm or hand. You might feel a brief cold sensation as the tracer is administered.
- Waiting Period (Uptake Phase): You will relax in a reclining chair for 30 to 60 minutes while the tracer circulates and is absorbed by your body’s tissues. It’s important to remain still and quiet during this time.
During the Scan:
Once the uptake phase is complete, you will be positioned on the narrow table of the scanner, which will then slide into the doughnut-shaped opening. It is crucial to remain as still as possible during the scanning process to prevent blurred images. The actual scan takes about 30 minutes for a PET-CT scan and approximately 45 minutes for a PET-MRI scan. During the scan, you will hear buzzing and clicking sounds from the machine. The test is painless, but if you experience anxiety due to enclosed spaces, inform the medical staff. Medication to help you relax can be provided if needed.
After the Procedure:
After the PET scan, you can typically resume your normal daily activities unless instructed otherwise by your healthcare provider. Drinking plenty of fluids is recommended to help flush the tracer out of your system.
Understanding Your Pet Scan Results
A radiologist, a doctor specialized in interpreting medical images, will analyze your PET scan images and send a report to your healthcare provider. The radiologist may compare your PET scan with other recent imaging tests, such as MRI or CT scans, for a comprehensive assessment. In some cases, PET images are combined with CT or MRI images to provide a more detailed and integrated view of your condition. Your healthcare provider will then discuss the results with you, explain their meaning, and outline any necessary next steps or treatment plans.
Clinical Trials and Pet Scan Advancements
Medical research is continuously advancing the applications and techniques of PET scans. Clinical trials are ongoing to explore new ways to use PET scans for prevention, detection, treatment, and management of various diseases. For those interested in the latest research, resources like Mayo Clinic clinical trials (Explore Mayo Clinic studies) offer information on current studies and advancements in the field.
By Mayo Clinic Staff
Positron emission tomography scan care at Mayo Clinic
Sept. 10, 2024
References
- Positron emission tomography — Computed tomography (PET/CT). Radiological Society of North America. https://www.radiologyinfo.org/en/info.cfm?pg=PET. Accessed April 6, 2021.
- What is PET? Society of Nuclear Medicine and Molecular Imaging. https://www.snmmi.org/AboutSNMMI/Content.aspx?ItemNumber=5649. Accessed April 6, 2021.
- Umterrainer M, et al. Recent advances of PET imaging in clinical radiation oncology. Radiation Oncology. 2020; doi:10.1186/s13014-020-01519-1.
- Adam A, et al., eds. Adrenal imaging. In: Grainger and Allison’s Diagnostic Radiology. 7th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed April 6, 2021.
- ACR-SPR practice parameters for performing FDG-PET/CT in oncology. American College of Radiology. https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards/Practice-Parameters-by-Modality. Accessed April 6, 2021.
- Cervical cancer. Radiological Society of North America. https://www.radiologyinfo.org/en/info.cfm?pg=cervicalcancer. Accessed April 8, 2021.
- Morrow ES. Allscripts EPSi. Mayo Clinic. April 6, 2021.
- Collins DA (expert opinion). Mayo Clinic. April 24, 2021.
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