Positron Emission Tomography, commonly known as a PET scan, is an advanced imaging technique that utilizes a specialized machine, often referred to as a Pet Scanner, to produce detailed three-dimensional pictures of the body’s internal functions. Unlike other imaging tests that primarily focus on structure, a PET scan reveals how your tissues and organs are working at a cellular level, highlighting metabolic and biochemical activity.
During a PET scan procedure, you will recline on a comfortable, narrow table that smoothly glides into the pet scanner, a device characterized by its large, circular opening. This scan is typically completed within approximately 30 minutes, during which it meticulously captures images reflecting the metabolic processes occurring within your body.
A PET scan is distinguished by its ability to detect diseases, such as cancer, in their earliest stages, often before they are visible on other types of scans like CT scans or MRIs. This is achieved through the use of a radioactive tracer, a safe and minimally radioactive substance, which is introduced into your body, usually via an injection. This tracer allows the pet scanner to identify areas of both normal and abnormal metabolic activity. Areas with higher metabolic activity, often indicative of disease, will appear brighter on the PET images. These images are frequently combined with CT or MRI scans to provide an even more comprehensive view, known as PET-CT or PET-MRI scans.
Why Doctors Recommend a Pet Scanner Examination
The pet scanner is a powerful tool in modern medicine, enabling healthcare providers to diagnose, monitor, and manage a wide range of medical conditions effectively. Its unique ability to visualize metabolic activity makes it particularly valuable in several key areas:
Cancer Detection and Management
Cancer cells are characterized by their rapid growth and high metabolic rate, which makes them readily detectable by a pet scanner. In PET scans, cancerous tissues often appear as bright spots due to their increased uptake of the radioactive tracer. PET scans are instrumental in:
- Early Cancer Detection: Identifying tumors, sometimes before they are detectable by other imaging methods.
- Staging Cancer: Determining if and where cancer has spread (metastasis) within the body.
- Monitoring Treatment Effectiveness: Assessing whether cancer treatments, such as chemotherapy or radiation therapy, are successfully reducing metabolic activity in tumors.
- Detecting Recurrence: Identifying if cancer has returned after treatment.
While incredibly useful, it’s important to note that PET scan results need careful interpretation. Non-cancerous conditions can sometimes mimic cancer on a PET scan, and not all types of cancer are detectable with this technology. However, many solid tumors can be effectively evaluated using PET-CT and PET-MRI, including cancers of the:
- Brain
- Breast
- Cervix
- Colorectal area
- Esophagus
- Head and Neck
- Lung
- Lymphatic System
- Pancreas
- Prostate
- Skin
- Thyroid
Assessing Heart Health
The pet scanner plays a crucial role in evaluating heart conditions by revealing areas of reduced blood flow to the heart muscle. This information is vital for guiding treatment decisions, such as whether a patient would benefit from:
- Coronary Artery Bypass Surgery: To reroute blood flow around blocked arteries.
- Angioplasty: A procedure to open clogged arteries and improve blood flow.
By visualizing blood flow and metabolic activity within the heart, PET scans provide valuable insights for managing heart disease.
Investigating Brain Disorders
PET scans are also utilized to investigate various brain disorders, including:
- Brain Tumors: Identifying and assessing the metabolic activity of brain tumors.
- Alzheimer’s Disease: Detecting patterns of decreased metabolic activity characteristic of Alzheimer’s.
- Seizure Disorders: Identifying areas of abnormal brain metabolism that may be causing seizures.
In the context of brain disorders, the pet scanner helps clinicians understand functional abnormalities that may not be apparent through structural imaging alone.
Understanding the Risks Associated with a Pet Scanner
While PET scans are generally safe procedures, it’s important to be aware of potential risks:
- Radiation Exposure: A radioactive tracer is used, but the amount of radiation is very low, minimizing the risk of long-term effects.
- Pregnancy and Breastfeeding: The tracer could expose an unborn baby or breastfeeding infant to radiation. It’s crucial to inform your healthcare provider if you are pregnant or breastfeeding.
- Allergic Reactions: Although rare, allergic reactions to the tracer are possible.
Discussing these risks and benefits with your healthcare provider will help you make an informed decision about undergoing a PET scan.
Preparing for Your Pet Scanner Appointment
Proper preparation is essential for ensuring the accuracy and success of your PET scan. Your healthcare provider will give you detailed instructions, but general guidelines include:
- Allergies and Medical Conditions: Inform your provider of any allergies, past allergic reactions, recent illnesses, or existing medical conditions, particularly diabetes.
- Medications and Supplements: Provide a list of all medications, vitamins, and herbal supplements you are currently taking.
- Pregnancy and Breastfeeding Status: Clearly communicate if you are pregnant or breastfeeding.
- Claustrophobia: If you have a fear of enclosed spaces (claustrophobia), let your provider know, as they can take measures to make you more comfortable.
- Fasting: Typically, you will be asked to refrain from eating for four hours before the scan.
- Avoid Strenuous Exercise: Avoid intense physical activity for a couple of days leading up to your appointment.
What to Expect During the Pet Scanner Procedure
The PET-CT or PET-MRI pet scanner resembles a large doughnut-shaped machine, similar in appearance to CT and MRI scanners. The entire process, from start to finish, usually takes around two hours and generally does not require an overnight hospital stay.
Upon arrival, you may be asked to:
- Change into a hospital gown.
- Empty your bladder.
The radioactive tracer is then administered, usually through an injection into a vein in your arm or hand. You might feel a brief cold sensation as the tracer is injected. You will then relax in a reclining chair for 30 to 60 minutes, allowing the tracer to distribute throughout your body.
During the Scan
Once the tracer has been absorbed, you will lie down on the narrow table, which will slide into the pet scanner. It is crucial to remain as still as possible during the scan to prevent blurred images. A PET-CT scan typically takes about 30 minutes, while a PET-MRI scan may take around 45 minutes. During the scan, you will hear buzzing and clicking sounds from the machine.
The procedure is painless. If you experience anxiety due to enclosed spaces, inform the medical staff; they can provide medication to help you relax.
After the Scan
After the PET scan, you can usually resume your normal 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 Scanner Results
A radiologist, a specialist in interpreting medical images, will analyze your PET scan images and provide a report to your healthcare provider. The radiologist may compare your PET scan images with previous scans, such as CT or MRI, or combine the images for a more detailed assessment. Your healthcare provider will then discuss the results with you and explain their implications for your health and treatment plan.
Clinical Trials and Pet Scanner Technology
Explore Mayo Clinic studies are continuously advancing the field of medical imaging, including pet scanner technology. Clinical trials are ongoing to further refine PET scan techniques, expand their applications, and improve patient outcomes.
Positron emission tomography scan care at Mayo Clinic
Sept. 10, 2024
References:
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- 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.
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- Collins DA (expert opinion). Mayo Clinic. April 24, 2021.
