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FDG PET-CT scan

What is an F-18 FDG PET-CT Scan?

An F-18 FDG PET-CT scan combines two powerful imaging technologies into one examination:

  • PET (Positron Emission Tomography): Shows how cells are functioning by tracking glucose (sugar) metabolism
  • CT (Computed Tomography): Provides detailed anatomical images of body structures

This combination creates comprehensive images that show both the structure of your body and how cells are using energy. For cancer evaluation, this is particularly valuable because cancer cells typically use more glucose than normal cells.

How F-18 FDG PET-CT Works in Cancer Detection

The scan uses a radioactive form of glucose called F-18 FDG (fluorodeoxyglucose). This works because:

  1. Cancer cells generally grow more rapidly than normal cells
  2. To fuel this rapid growth, cancer cells consume more glucose (sugar)
  3. The F-18 FDG tracer mimics glucose but contains a radioactive component
  4. Cancer cells absorb this tracer more eagerly than most normal cells
  5. The PET scanner detects the radiation emitted from these areas
  6. Areas with high tracer uptake (potential cancer sites) appear as “hot spots” on the scan
  7. The CT portion provides precise anatomical location of these hot spots

This makes F-18 FDG PET-CT particularly effective for detecting many types of cancer, often before structural changes are visible on conventional imaging.

Oncology Applications of F-18 FDG PET-CT

This scan is used in cancer care for:

Cancer Diagnosis and Staging

  • Determining if a suspicious mass is cancerous
  • Finding the primary tumor site when cancer has been detected elsewhere
  • Determining if and where cancer has spread (metastasized)
  • Establishing the extent of disease (staging) to guide treatment decisions

Treatment Planning and Monitoring

  • Helping plan radiation therapy or surgical approaches
  • Evaluating response to chemotherapy, immunotherapy, or radiation
  • Detecting residual cancer after treatment
  • Distinguishing between active tumor and scar tissue

Surveillance and Recurrence Detection

  • Monitoring for cancer recurrence after treatment
  • Regular surveillance in high-risk patients
  • Investigating new symptoms in cancer survivors

Common Cancer Types Evaluated with F-18 FDG PET-CT

This scan is particularly valuable for evaluating:

  • Lung cancer
  • Lymphoma
  • Colorectal cancer
  • Breast cancer
  • Melanoma
  • Head and neck cancers
  • Esophageal cancer
  • Cervical cancer
  • Ovarian cancer
  • Many other less common malignancies

Can F-18 FDG PET-CT be used for other, non-oncology indications?

Yes, FDG PET-CT can be used to help physicians better understand other disease processes – notably infection / inflammation, neurological processes such as dementia, and cardiac pathology.

Compared to PET-CT for Infection/Inflammation

While both cancer and infection/inflammation show increased FDG uptake:

  • Cancer typically shows more intense, focused uptake patterns
  • Infection often shows more diffuse uptake patterns
  • The clinical context and specific uptake patterns help differentiate between them
  • Your doctor’s knowledge of your specific situation guides interpretation
  • Follow-up scans may be needed to monitor changes over time

Compared to Brain PET-CT

  • Oncology PET-CT: Focuses on detecting abnormal glucose metabolism throughout the body
  • Brain PET-CT: Evaluates normal vs. abnormal patterns of glucose metabolism within the brain
  • Brain scans require different patient preparation (brain rest before imaging)
  • Brain scans use different imaging parameters and interpretation criteria

Compared to Cardiac PET-CT

  • Oncology PET-CT: Evaluates cancer activity throughout the body
  • Cardiac PET-CT: Assesses heart muscle viability and blood flow
  • Cardiac scans often require special dietary preparation and medications

Preparing for Your F-18 FDG PET-CT for Cancer Evaluation

Dietary Preparation (Very Important)

12 hours before your appointment:

  • Follow a strict low-carbohydrate diet to reduce background glucose levels
  • Foods allowed:
    • Meat (beef, chicken, fish)
    • Hard cheese
    • Tofu
    • Eggs
    • Butter
    • Non-starchy vegetables (broccoli, spinach, cauliflower)
  • Foods NOT allowed:
    • Cereal and grains
    • Pasta and rice
    • Milk and yogurt
    • Bread and crackers
    • Sugar, honey, and sweets
    • Starchy vegetables (potatoes, corn, peas)
    • Fruit and fruit juices

6 hours before your appointment:

  • Stop eating completely
  • Continue drinking water as normal
  • Take regular medications unless instructed otherwise

Special Instructions for Diabetic Patients

  • Inform the department about your diabetes when scheduling
  • For morning appointments:
    • You may have a slice of toast with your morning medication
    • If insulin-dependent, take only half your usual dose
  • Your blood glucose will be tested before the scan
  • Ideal blood glucose level should be below 150-180 mg/dL (8.3-10 mmol/L)
  • If your blood sugar is too high, you may receive insulin or your scan may need to be rescheduled

Additional Preparation

  • Avoid strenuous exercise for 24 hours before the scan
  • Wear warm, comfortable clothing without metal components
  • Bring any previous scan results or reports if done at other facilities
  • Plan to spend 2-2½ hours at the imaging facility

What to Expect During Your F-18 FDG PET-CT for Cancer

Upon Arrival

  1. Your blood glucose level will be checked
  2. A brief medical history will be taken
  3. An IV line will be placed in your arm or hand

Tracer Injection and Uptake Period

  1. The F-18 FDG radioactive tracer will be injected through your IV
  2. You’ll rest quietly in a warm, comfortable room for 60-90 minutes
  3. It’s essential to remain still and relaxed during this time
  4. Minimal talking or movement is recommended to prevent muscle uptake of the tracer
  5. You may be asked to drink water to help flush the tracer through your kidneys

Scanning Procedure

  1. You’ll lie on an examination table that moves through the scanner
  2. The scanner has a large ring opening (not enclosed like an MRI)
  3. The scanning process is quiet and painless
  4. You’ll need to lie still during the scan
  5. The actual scanning takes approximately 20-30 minutes
  6. For some cancer types, additional delayed images may be taken

After Your Scan

  • You can resume normal activities and diet immediately
  • Drink plenty of fluids to help flush the tracer from your body
  • The small amount of radiation will leave your body naturally within 24 hours
  • Avoid close contact with pregnant women and young children for 6 hours after the scan
  • A nuclear medicine physician will analyze your images and send a report to your doctor
  • Your doctor will discuss the results with you at your follow-up appointment

Understanding Your Results

  • Positive findings: Areas with higher tracer uptake than background tissue may indicate cancer
  • Negative findings: No abnormal uptake suggests absence of active cancer in detectable amounts
  • False positives: Some non-cancerous conditions can show increased uptake (inflammation, infection, recent surgery sites)
  • Limitations: Very small tumors or certain types of cancer may not show increased FDG uptake

It’s important to understand that while F-18 FDG PET-CT is highly sensitive for detecting many cancers, your doctor will interpret the results in context with your clinical history, physical examination, laboratory tests, and other imaging studies.

Medical Aid Coverage

Most medical schemes and private insurance companies cover F-18 FDG PET-CT imaging for cancer indications, especially for staging and treatment evaluation. Coverage usually follows prescribed minimum benefit guidelines. Contact your insurance provider for specific information about your coverage. Our staff can assist with providing motivation letters if needed for insurance approval.

If you have any questions or concerns about your F-18 FDG PET-CT scan for cancer evaluation, please contact our department or discuss them with your healthcare provider.

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