Positron Emission Tomography, commonly known as a PET scan, is an advanced medical imaging technique that provides detailed insights into the metabolic activity of your body’s tissues and organs. Unlike other imaging tests that primarily show the structure of organs, a PET scan reveals how these organs and tissues are functioning at a cellular level. This is achieved through the use of a radioactive tracer, allowing healthcare providers to detect diseases, often in their earliest stages, by identifying unusual metabolic activity. Understanding the procedure for a PET scan can help alleviate anxiety and prepare you for this important diagnostic tool.
Preparing for Your PET Scan
Before undergoing a PET scan, proper preparation is essential to ensure the accuracy of the results and your comfort during the process. Your healthcare provider will give you specific instructions, but generally, the preparation involves several key steps:
Consultation with Your Healthcare Provider
Open communication with your healthcare provider is the first step. It’s important to inform them about your complete medical history, including any pre-existing conditions such as diabetes, allergies, and any past reactions you may have had to medications or contrast materials. Specifically, you should discuss:
- Allergies: Mention any known allergies, especially to iodine or contrast dyes, although allergic reactions to PET scan tracers are rare.
- Current Medications: Provide a list of all medications you are currently taking, including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements. Some medications might need to be adjusted or temporarily stopped before the scan.
- Pregnancy and Breastfeeding: It’s crucial to inform your provider if you are pregnant or suspect you might be, or if you are breastfeeding. The radioactive tracer could potentially expose your unborn baby or child to radiation.
- Claustrophobia: If you have a fear of enclosed spaces (claustrophobia), let your provider know. They can take measures to make you more comfortable during the scan, such as providing relaxation medication.
Pre-Scan Instructions
Following pre-scan instructions diligently is crucial for obtaining clear and accurate PET scan images. These instructions typically include:
- Fasting: Usually, you will be asked to fast for at least four hours before your PET scan. This means no food or drinks, except for water. Fasting helps to ensure that the tracer is absorbed properly by your body.
- Avoid Strenuous Exercise: Refrain from strenuous physical activity for a couple of days prior to your scan. Exercise can affect the distribution of the tracer in your body and potentially alter the scan results.
- Hydration: Drink plenty of water in the hours leading up to your scan. Proper hydration helps with tracer circulation and can make it easier to locate your veins for tracer injection.
- Clothing: Wear comfortable, loose-fitting clothing to your appointment. You may be asked to change into a hospital gown for the procedure. Avoid wearing jewelry and metal accessories, as they may interfere with the scan.
Alt text: A Positron Emission Tomography (PET) scanner machine in a medical setting, highlighting its doughnut shape and patient table.
What Happens During the PET Scan Procedure
The PET scan procedure is generally straightforward and painless. From start to finish, it usually takes around two hours, with the actual scanning time being shorter. Here’s a step-by-step overview of what to expect during the process:
Arrival and Initial Steps
Upon arrival at the imaging facility, you will check in and may be asked to fill out a questionnaire to confirm your medical history and preparation. You will likely be asked to change into a hospital gown and empty your bladder before the procedure begins.
Tracer Injection
A member of the healthcare team, usually a nurse or technologist, 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. The amount of radiation in the tracer is minimal and considered safe.
Tracer Absorption Period
After the injection, you will be asked to rest quietly in a comfortable, reclining chair for about 30 to 60 minutes. During this uptake period, it’s important to remain still and silent, as movement can affect the tracer distribution. This time allows the tracer to travel through your body and be absorbed by the tissues and organs. Areas with higher metabolic activity, such as cancer cells, will absorb more of the tracer.
The Scan Itself
Once the uptake period is complete, you will be guided to the PET scanner room. The PET-CT or PET-MRI scanner is a large machine, often described as doughnut-shaped with a table that slides into the central opening. You will lie down on a narrow, padded table that will slowly move into the scanner.
During the scan, it is crucial to remain as still as possible to prevent blurring of the images. The scanner detects the radioactive tracer in your body and creates detailed images of metabolic activity. You may hear buzzing or clicking sounds from the machine during the scanning process, which typically lasts for about 30 minutes for a PET-CT scan and around 45 minutes for a PET-MRI scan.
Managing Claustrophobia
If you are claustrophobic, it’s important to communicate this concern to the healthcare team. They can take steps to alleviate your anxiety, such as administering medication to help you relax before the scan. In some cases, an open PET scanner might be an option, although these are less common.
After the PET Scan Procedure
Following the PET scan, the post-procedure instructions are generally simple, and you can usually resume your normal daily activities unless your healthcare provider advises otherwise.
Post-Scan Instructions
- Drink Plenty of Fluids: You will be encouraged to drink plenty of fluids, especially water, after the scan. This helps to flush the radioactive tracer out of your body through urine.
- Normal Activities: Unless specifically instructed by your doctor, you can typically return to your regular diet and activities immediately after the scan.
- No Overnight Stay: A PET scan is usually an outpatient procedure, meaning you can go home shortly after it is completed.
Understanding Your PET Scan Results
After the PET scan is completed, the images are carefully analyzed by a specialized doctor called a radiologist. The radiologist is trained to interpret scan images and will prepare a report of the findings for your healthcare provider.
Radiologist Interpretation
The radiologist will examine the PET scan images, looking for areas of unusual metabolic activity, which often appear as bright spots. They will assess the location, size, and intensity of these areas to identify any potential abnormalities.
Report to Your Healthcare Provider
The radiologist’s report is then sent to your healthcare provider, who will discuss the results with you in the context of your overall health and medical condition. The results of a PET scan can help in diagnosing various conditions, determining the stage of a disease, evaluating the effectiveness of treatment, or detecting a recurrence of disease.
Integration with Other Scans
PET scan images are often combined with images from other imaging tests, such as CT or MRI scans. This combination, known as PET-CT or PET-MRI, provides a more comprehensive view by overlaying metabolic information from the PET scan onto the detailed anatomical images from CT or MRI. This fusion technique enhances diagnostic accuracy and helps healthcare providers pinpoint the exact location of abnormal metabolic activity.
Alt text: Comparison of CT scan, PET scan, and combined PET-CT scan images illustrating how the combined scan enhances diagnostic clarity by merging structural and metabolic information.
Risks and Benefits of PET Scans
Like all medical procedures, PET scans have potential risks and benefits that should be considered.
Minimal Radiation Exposure
One of the primary concerns associated with PET scans is radiation exposure. However, the amount of radioactive tracer used is very small, resulting in a low level of radiation exposure. The benefits of obtaining a crucial diagnosis from a PET scan generally outweigh the minimal risk from this low radiation dose.
Rare Allergic Reactions
Allergic reactions to the tracer are rare but possible. These reactions are usually mild, such as rash or itching, but serious reactions can occur in very rare cases. Medical staff are prepared to manage any allergic reactions that may arise.
Pregnancy and Breastfeeding Considerations
As mentioned earlier, there is a potential risk of radiation exposure to unborn babies and infants. Therefore, PET scans are generally avoided during pregnancy and breastfeeding unless absolutely necessary and the benefits significantly outweigh the risks.
Benefits
Despite the minimal risks, PET scans offer significant benefits in diagnosing and managing various medical conditions. They are particularly valuable for:
- Early Disease Detection: PET scans can detect diseases, such as cancer, in their early stages, often before structural changes are visible on other imaging tests.
- Accurate Diagnosis: By providing information about metabolic activity, PET scans can help differentiate between benign and malignant conditions and contribute to a more accurate diagnosis.
- Treatment Monitoring: PET scans are used to monitor the effectiveness of treatments, such as chemotherapy or radiation therapy, by assessing changes in metabolic activity of tumors.
- Diagnosis of Various Conditions: Beyond cancer, PET scans are also effective in diagnosing heart problems, brain disorders like Alzheimer’s disease, and neurological conditions such as seizures, by identifying areas of abnormal function.
Alt text: PET scans comparing a healthy brain to a brain affected by Alzheimer’s disease, illustrating decreased metabolic activity in Alzheimer’s brain through color variation.
In conclusion, a PET scan is a powerful and relatively safe procedure that provides crucial insights into the metabolic function of the body. Understanding the procedure for a PET scan, from preparation to results, can make the process less daunting and help you appreciate the valuable information it provides for your health and medical care. If you have been recommended for a PET scan, discussing any concerns and understanding the process with your healthcare provider is always the best approach.
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.
