A Positron Emission Tomography (PET) scan is an advanced imaging technique that provides detailed insights into the metabolic activity within your body’s tissues and organs. Unlike other imaging tests that primarily focus on structure, a Pet Scan reveals how your body’s cells are functioning at a biochemical level. This capability makes it invaluable for detecting diseases, often in their earliest stages, by identifying atypical metabolic activity before structural changes become apparent on tests like CT scans or MRIs.
Understanding Positron Emission Tomography
A PET scan utilizes a special radioactive drug, known as a tracer, to highlight areas of metabolic activity. During the procedure, which typically lasts around 30 minutes within a doughnut-shaped scanner, you’ll lie comfortably on a narrow table as the machine captures detailed images. These images reflect the distribution of the tracer, which accumulates in areas with higher metabolic rates, often indicating disease processes.
Why is a PET Scan Performed?
PET scans are powerful diagnostic tools used across a spectrum of medical specialties. Their ability to detect subtle changes in metabolic activity makes them crucial for diagnosing, monitoring, and managing various conditions, including:
- Cancer: PET scans are particularly effective in oncology due to cancer cells’ characteristically high metabolic rate.
- Heart Disease: By visualizing blood flow and metabolic function in the heart, PET scans can help identify areas of damage or reduced blood supply.
- Brain Disorders: PET scans play a significant role in evaluating brain function and detecting neurological conditions.
Cancer Detection and Management with PET Scans
Cancer cells are metabolically more active than normal cells, leading to a higher uptake of the radioactive tracer during a PET scan. This difference makes cancerous tissues appear as bright spots on the images, allowing for:
- Early Cancer Detection: PET scans can detect cancers at an early stage, sometimes before other imaging techniques.
- Staging Cancer: Determining if cancer has spread to other parts of the body (metastasis) is crucial for treatment planning. PET scans are highly effective in whole-body staging.
- Monitoring Treatment Response: PET scans can assess whether cancer treatment, such as chemotherapy or radiation therapy, is effectively reducing metabolic activity in tumors.
- Detecting Cancer Recurrence: In patients with a history of cancer, PET scans can help identify if the cancer has returned.
PET-CT and PET-MRI Scans: Enhanced Diagnostic Accuracy
Often, PET scans are combined with CT or MRI scans to provide both functional and anatomical information. This fusion, known as PET-CT or PET-MRI, enhances diagnostic accuracy by overlaying metabolic activity onto detailed structural images. This is particularly useful for pinpointing the exact location of abnormal metabolic activity. While PET scans excel at identifying metabolic changes, CT and MRI provide detailed anatomical context, leading to a more comprehensive understanding of the condition. Many solid tumors can be effectively evaluated using PET-CT or PET-MRI, including cancers of the:
- Brain
- Breast
- Cervix
- Colorectal region
- Esophagus
- Head and Neck
- Lung
- Lymphatic System (Lymphoma)
- Pancreas
- Prostate
- Skin (Melanoma)
- Thyroid
PET Scans for Heart Health Evaluation
In cardiology, PET scans are used to assess blood flow and heart muscle function. They can identify areas of reduced blood flow, indicating potential ischemia or damage to the heart muscle. This information is vital for deciding on the best course of treatment, such as:
- Coronary Artery Bypass Grafting (CABG): PET scans can help determine if a patient would benefit from bypass surgery to improve blood flow to the heart.
- Angioplasty and Stenting: For patients with clogged arteries, PET scans can help assess the severity and location of reduced blood flow, guiding decisions about angioplasty to open blocked arteries.
Assessing Brain Disorders with PET Scans
PET scans are valuable in neurology for evaluating various brain disorders by measuring metabolic activity in different brain regions. They can aid in the diagnosis and management of conditions such as:
- Alzheimer’s Disease: PET scans can detect patterns of decreased metabolic activity characteristic of Alzheimer’s, helping differentiate it from other forms of dementia.
- Brain Tumors: PET scans can help distinguish between tumor recurrence and treatment effects, and can also help in tumor grading.
- Epilepsy and Seizures: By identifying areas of abnormal brain metabolism, PET scans can help locate seizure foci in patients with epilepsy.
Understanding the Risks of a PET Scan
While PET scans are generally safe procedures, they do involve a small amount of radioactive tracer. It’s important to discuss the benefits and risks with your healthcare provider. The risks are typically low due to the small dose of radiation, but they include:
- Radiation Exposure: The amount of radiation is minimal and considered safe for most adults. However, it’s a consideration, especially for pregnant women.
- Pregnancy and Breastfeeding: The radioactive tracer could potentially expose an unborn baby or breastfeeding infant to radiation. Inform your doctor if you are pregnant or breastfeeding.
- Allergic Reactions: Allergic reactions to the tracer are rare but possible.
Preparing for Your PET Scan
Proper preparation is essential for ensuring the accuracy of your PET scan. Your healthcare provider will give you specific instructions, but general guidelines include:
- Medical History: Inform your doctor about any allergies, recent illnesses, medical conditions like diabetes, and all medications, vitamins, and herbal supplements you are taking.
- Pregnancy and Breastfeeding Status: Always inform your doctor if you are pregnant or breastfeeding.
- Claustrophobia: If you have a fear of enclosed spaces (claustrophobia), let your healthcare team know, as medication can be provided to help you relax.
- Fasting: Typically, you will need to fast for at least four hours before the scan to ensure accurate results, especially when scanning for diabetes or cancer.
- Avoid Strenuous Exercise: Refrain from strenuous physical activity for a couple of days before your scan, as it can affect tracer uptake.
What to Expect During a PET Scan Procedure
The PET scan procedure is generally straightforward and painless. From arrival to completion, expect the process to take around two hours, and it usually doesn’t require an overnight hospital stay.
- Preparation: Upon arrival, you may be asked to change into a hospital gown and empty your bladder.
- Tracer Administration: A healthcare professional will inject the radioactive tracer into a vein in your arm or hand. You might feel a brief cold sensation.
- Waiting Period: You will rest quietly in a reclining chair for 30 to 60 minutes while your body absorbs the tracer. It’s important to remain still and silent during this uptake period.
- Scanning: You will then lie on a narrow, padded table that slides into the PET scanner. The scanner, resembling a large doughnut, will move around you to capture images. It’s crucial to remain very still during the scanning process, which lasts about 30 minutes for a PET-CT and 45 minutes for a PET-MRI. The machine will make buzzing and clicking sounds.
- Managing Anxiety: If you experience anxiety or claustrophobia, inform the nurse or technologist. Medication can be provided to help you relax.
After Your PET Scan
Following the scan, you can usually resume your normal daily activities unless advised otherwise by your doctor.
- Hydration: Drink plenty of fluids to help flush the tracer out of your body.
Understanding Your PET Scan Results
A radiologist, a specialist in interpreting medical images, will analyze your PET scan images and provide a report to your healthcare provider.
- Result Interpretation: The radiologist may compare your PET scan images with previous scans like MRI or CT for a comprehensive assessment. Combined PET-CT or PET-MRI images provide detailed information about your condition.
- Discussion with Your Doctor: Your healthcare provider will discuss the results with you, explain the findings, and outline any necessary next steps, such as further tests, treatment options, or lifestyle adjustments.
Clinical Trials and PET Scan Advancements
PET scan technology is continually evolving, with ongoing clinical trials exploring new applications and tracers to improve disease detection, treatment monitoring, and overall patient care. These studies aim to refine PET scan techniques and expand their utility in various medical fields.
For more information on PET scans or related clinical trials, consult with your healthcare provider or refer to reputable medical resources.
Explore Mayo Clinic studies of tests and procedures to help prevent, detect, treat or manage conditions.
Positron emission tomography scan care at Mayo Clinic
Sept. 10, 2024
References:
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- 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.
