Positron Emission Tomography, commonly known as a PET scan, is an advanced imaging technique that provides detailed 3D visuals of your body’s internal workings. Utilizing a mildly radioactive tracer, PET scans are adept at highlighting areas with heightened cellular activity, a hallmark of various conditions including cancer. This capability is crucial in cancer diagnosis, particularly in determining the extent of cancer spread within the body.
Often conducted in radiology or nuclear medicine departments on an outpatient basis, PET scans require specialized equipment typically found in major cancer centers. The procedure, managed by a radiographer, generally spans 45 to 60 minutes, with an additional hour allocated for preparation, primarily for the administration of the radioactive tracer injection.
To enhance diagnostic clarity, PET scans are frequently combined with CT scans, resulting in PET-CT scans that offer more intricate images. Similarly, PET-MRI scans integrate PET with MRI technology for an even more comprehensive view.
Why are PET Scans Necessary?
PET scans are instrumental in various aspects of cancer management, including:
- Cancer Detection: Identifying the presence of cancerous cells within the body.
- Staging Cancer: Determining the size of a tumor and whether cancer has metastasized or spread to other parts of the body. This is particularly relevant in assessing lymph node involvement.
- Distinguishing Cancer from Benign Lumps: Differentiating between cancerous and non-cancerous masses.
- Guiding Treatment Strategies: Informing decisions about the most effective treatment approaches for cancer.
- Monitoring Treatment Efficacy: Evaluating how well cancer treatments are working over time.
Post-treatment, PET scans play a vital role in distinguishing between active cancer and scar tissue. While CT scans might reveal residual tissue, PET scans can determine if this tissue is composed of active cancer cells or inactive scar tissue.
Crucially for our focus, PET scans are indeed used to detect cancer in the lymph nodes, especially those located centrally in the chest and other areas of the body. Lymph nodes are key sites for cancer spread, and PET scans offer a powerful tool to assess their involvement.
Preparing for a PET Scan
Adequate preparation is essential for an accurate PET scan. Typically, this involves fasting for 4 to 6 hours prior to the scan, although plain water consumption is usually permitted.
Patients may also be advised to avoid strenuous physical activity for 12 to 24 hours before their appointment.
For individuals with specific dietary concerns, such as diabetes, it’s crucial to contact the department in advance. Adjustments to diet, medication, and appointment scheduling may be necessary.
Those prone to claustrophobia should inform the medical staff beforehand. Measures can be taken to ensure comfort and alleviate anxiety, and in some cases, relaxation medication can be prescribed.
What to Expect During a PET Scan
At the Hospital
Upon arrival, patients may be asked to change into a hospital gown and remove jewelry and metallic items, as these can interfere with scan image quality.
The radioactive tracer injection is administered intravenously, typically through a cannula in the arm, approximately an hour before the scan. The radiation dose is minimal.
During this waiting period, it’s important to rest and minimize movement to allow the tracer to distribute throughout the body’s tissues effectively.
The tracer is often a radioactive form of glucose called FDG (fluorodeoxyglucose). Cancer cells, due to their rapid growth and metabolism, absorb more glucose than normal cells. This increased FDG uptake makes cancer cells appear brighter on the PET scan.
In the Scanning Room
Patients are then guided to the scanning room, which houses the doughnut-shaped PET scanner. Most scans are performed with the patient lying on their back on the scanner couch.
Once positioned, the radiographer will leave the room but maintain constant communication via intercom and visual monitoring through a window or TV screen.
Undergoing the PET Scan
The scanner couch gently moves through the PET machine, capturing images as it progresses. While the scan is painless, remaining still is crucial and can be slightly uncomfortable. Patients should communicate any discomfort or need to move to the radiographer.
The scanner operates with a consistent background noise, and in many facilities, music can be provided to enhance patient comfort.
Upon completion, the radiographer assists the patient in getting up from the scanner.
After the PET Scan
Following the scan, the cannula is removed, and patients can resume their normal eating and drinking habits.
Drinking plenty of fluids post-scan is recommended to help flush the radioactive tracer from the body.
While the radiation exposure is minimal and dissipates quickly, as a precaution, close contact with pregnant women, infants, and young children should be limited for 6 hours post-scan.
If sedation was administered, arrangements for transportation home and overnight supervision are necessary. Furthermore, driving, alcohol consumption, operation of heavy machinery, and signing legal documents should be avoided for 24 hours.
For international travel within a week of the scan, carrying the appointment letter is advisable due to airport radiation monitors which might detect residual radiation.
Potential Risks
PET scans are generally safe, but as with any medical procedure, some risks are associated. The benefits are carefully weighed against these risks by medical professionals.
Potential risks include:
Pregnancy
PET scans are typically avoided during pregnancy unless absolutely necessary due to potential radiation risks to the fetus. Pregnancy or suspected pregnancy should be communicated to the department beforehand.
Breastfeeding
Breastfeeding mothers should inform the department in advance, as temporary cessation of breastfeeding and milk storage may be advised post-tracer injection.
Radiation Exposure
The minimal radiation exposure from the tracer carries a slight, theoretical increase in future cancer risk. Concerns should be discussed with a doctor.
Bruising and Swelling
Minor bruising at the injection site is possible. Rarely, tracer leakage outside the vein can cause swelling and discomfort.
Allergic Reactions
Allergic reactions to the tracer are infrequent but can occur, manifesting as weakness, sweating, and breathing difficulties. Any unusual symptoms should be immediately reported to the radiographer.
Receiving Your Results
Specialist doctors analyze the scan images, and results are usually available within 1 to 2 weeks. Results are not provided immediately after the scan.
The waiting period can be anxiety-provoking. Inquiring about result timelines and having contact information for support, such as a specialist nurse or support organizations like Cancer Research UK nurses (0808 800 4040), can be helpful.
More Information
Comprehensive resources on cancer tests, treatments, and support are readily available for those diagnosed with cancer. PET scans are a valuable tool in this landscape, particularly for understanding lymph node involvement and guiding effective cancer management.
