10 Things You Must Do to Prepare for an Accurate PET-CT Scan

Follow Fasting Instructions Strictly: Why this is critical for image quality.

When your doctor schedules a PET-CT scan, the first and most crucial instruction you'll receive is to fast for a specific period beforehand, typically 4-6 hours. This isn't merely a formality; it's a fundamental requirement for obtaining clear, diagnostically useful images. The science behind this is straightforward. The PET-CT scan works by detecting metabolic activity. You'll receive an injection of a radioactive tracer, most commonly a form of glucose. Since cancer cells are often highly metabolic and consume glucose at a much higher rate than normal cells, they "light up" on the scan. If you have recently eaten, the sugar from your food will raise your blood glucose levels. This means the active cancer cells and your normal, well-fed cells will be in competition for the tracer. The result can be a "diluted" signal, where the cancerous areas don't stand out as vividly against the background. This can lead to unclear images, potentially masking smaller tumors or making it difficult to distinguish between normal and abnormal tissue. Following the fasting instructions to the letter ensures that your body is in a metabolic state that allows the tracer to highlight areas of concern with maximum clarity. The team at your chosen petctscancentre will provide you with explicit guidelines on how long to fast and what, if any, clear fluids are permitted. Adhering strictly to these instructions is the single most impactful step you can take to contribute to an accurate scan.

Hydrate Well Before and After: The role of water in flushing out the tracer.

While you are required to fast from food, drinking water is not only allowed but strongly encouraged both before and after your scan. Proper hydration serves two essential purposes. First, being well-hydrated makes it easier for the nursing staff to locate a suitable vein for the tracer injection, making the process smoother and more comfortable for you. Second, and more importantly, water acts as a natural flushing agent for your system. After the scan is complete, the radioactive tracer will naturally decay and be eliminated from your body, primarily through urine. By drinking plenty of water before your appointment, you help prepare your kidneys for this process. Continuing to drink a good amount of water for the rest of the day after your scan will help expedite the flushing of the tracer from your system, minimizing your radiation exposure time. It's a simple, safe, and effective way to aid your body's own natural detoxification processes. Your local petctscancentre will likely recommend you consume several glasses of water in the hours leading up to your appointment, unless instructed otherwise for specific medical reasons.

Avoid Strenuous Exercise: How physical activity can interfere with results.

It might seem counterintuitive, but you should avoid vigorous exercise for at least 24 hours before your PET-CT scan. Activities like running, heavy weightlifting, intense cycling, or even a strenuous aerobic class can significantly alter your body's metabolic landscape. When you engage in strenuous exercise, your muscles work hard and require fuel. This leads to increased glucose uptake in the muscles you've been using. For instance, a long run can cause the muscles in your legs to become metabolically active. When the radioactive tracer is injected, it may be disproportionately absorbed by these recovering muscles instead of being available to highlight potentially cancerous cells. This can create "hot spots" in your muscles that are unrelated to disease, which can be misinterpreted by the radiologist or obscure the actual areas of concern. To ensure that the scan reflects your body's baseline metabolic state and not the temporary effects of a workout, it is vital to rest. Light activities like gentle walking are generally acceptable, but it's best to confirm this with the petctscancentre when you receive your preparation instructions.

Discuss Your Medications: A vital step to ensure nothing skews the scan.

One of the most critical conversations you will have in preparation for your scan is with your referring doctor and the staff at the imaging facility about all the medications you are taking. This includes not just prescription drugs, but also over-the-counter medicines, vitamins, supplements, and herbal remedies. Certain medications can influence your metabolism, blood sugar levels, or even the distribution of the tracer, potentially leading to inaccurate scan results. For example, some diabetes medications like insulin or metformin need to be managed carefully around the time of the scan. Your doctor will provide you with specific instructions on which medications to take and which to pause before your appointment. Never stop or adjust your medication regimen on your own without explicit medical guidance. A comprehensive review of your medications ensures that the scan provides a true picture of your health, free from pharmaceutical interference. When you speak with the team at the petctscancentre, have a complete and up-to-date list ready for them.

Wear Comfortable, Metal-Free Clothing: For your comfort and to avoid artifacts.

Comfort is key during a PET-CT scan, as you will need to lie still on a narrow table for a period that can range from 20 to 45 minutes. Wearing loose, soft, and comfortable clothing will help you remain relaxed and motionless, which is essential for capturing sharp images. More importantly, you must avoid any clothing with metal parts. Zippers, snaps, buckles, underwires in bras, and even some decorative metallic threads can interfere with the CT component of the scan. Metal causes "artifacts"—streaks or shadows on the final images that can obscure important anatomical details and make interpretation difficult. To prevent this, you will likely be asked to change into a hospital gown. However, by choosing metal-free attire from the start, you can often avoid changing altogether or at least minimize what you need to remove, making the process quicker and more comfortable. The staff at your petctscancentre will appreciate your preparedness, and it contributes to a smoother, more efficient scanning process for everyone involved.

Inform the PET-CT Scan Centre of Any Allergies.

Transparency about your health history is non-negotiable for a safe scanning experience. It is absolutely essential that you inform the petctscancentre of any allergies you have before your appointment. While allergic reactions to the radioactive tracer (FDG) are exceedingly rare, it's still vital information for the medical team to have. Furthermore, the PET-CT scan often involves a second injection: intravenous contrast dye used for the CT portion to enhance the visibility of blood vessels and organs. Allergic reactions to iodine-based contrast media, though uncommon, are a known possibility. By informing the staff in advance, they can take necessary precautions. For patients with a known allergy, they may choose to use a different type of contrast, pre-medicate you with antihistamines or steroids to reduce the risk of a reaction, or have emergency medications readily available. Your safety is their highest priority, and this information allows them to tailor the procedure to your specific needs.

Disclose if You Are Pregnant or Breastfeeding.

If you are pregnant, suspect you might be pregnant, or are currently breastfeeding, you must disclose this information to your doctor and the petctscancentre as soon as possible. The use of radiation in a PET-CT scan, while at a low level considered safe for most adults, poses a potential risk to a developing fetus. The medical team will carefully weigh the diagnostic benefits of the scan against the potential risks to the pregnancy. In some cases, the scan may be postponed, or an alternative imaging method that does not use radiation, such as an MRI or ultrasound, may be recommended. If you are breastfeeding, special precautions are needed. The radioactive tracer can pass into your breast milk. You will receive specific instructions, which may include pumping and storing breast milk beforehand and avoiding close contact with the baby for a short period after the scan. Full disclosure ensures the safety of both you and your child.

Arrive Early to Complete Paperwork.

Plan to arrive at your appointment at least 20-30 minutes earlier than your scheduled time. A medical imaging appointment involves more than just the scan itself. There is essential administrative and clinical paperwork to complete. This includes confirming your personal and insurance details, signing consent forms that explain the procedure and its risks, and answering detailed questions about your medical history and current condition. Rushing through this process can cause unnecessary stress and increase the chance of forgetting to mention an important detail. Arriving early gives you the time to fill out these forms calmly and thoroughly, ensuring all information is accurate. It also allows the staff at the petctscancentre to process your paperwork without delaying the schedule for other patients. A calm, unrushed start sets a positive tone for the entire experience.

Bring a List of Your Current Medications.

Do not rely on your memory when it comes to your medications. Before you go to the petctscancentre, take the time to write down a comprehensive list of all substances you are taking. This list should be detailed and include:

1. Prescription medications: Include the drug name, dosage, and how often you take it.
2. Over-the-counter drugs: Such as pain relievers, cold medicine, or antacids.
3. Vitamins and supplements: Including iron, vitamin D, fish oil, etc.
4. Herbal or natural remedies: These can have significant effects and must be disclosed.

Having this list in hand ensures that you can provide accurate and complete information to both the technologist and the radiologist. This is a critical step for your safety and for the accuracy of the scan interpretation, as it helps the experts distinguish between normal physiological uptake and potential medication-induced changes.

Plan for a Relaxing Day Afterwards.

While the PET-CT scan itself is not physically painful or particularly draining, it can be a mentally taxing experience. The anticipation, the need to remain still, and the overall clinical environment can be stressful for many people. Therefore, it is highly advisable to plan a calm and restful day for yourself after your appointment. If possible, take the day off work or clear your schedule of demanding tasks and obligations. Avoid scheduling important meetings, running strenuous errands, or caring for young children alone. Use this time to decompress. Go for a gentle walk, read a book, watch a movie, or simply rest. This is also in line with the advice to hydrate well, as you'll be at home and close to a bathroom. Giving yourself this space to recover mentally and continue flushing the tracer from your system is an important part of the overall process. A good petctscancentre will often recommend this, understanding that patient well-being encompasses both the physical procedure and the emotional experience.