What are the guidelines for a whole-body Positron Emission Tomography/Computed Tomography (PET/CT) scan?

From the Guidelines

Whole-body PET/CT scans should be performed following specific guidelines to ensure accurate imaging and patient safety, including fasting for 4-6 hours, avoiding strenuous exercise and substances like caffeine, alcohol, or nicotine, and maintaining normal hydration 1.

Key Guidelines for Whole-Body PET/CT Scans

• Patients should fast for at least 4 hours before the procedure to minimize background uptake in normal tissues and optimize tracer distribution throughout the body 1.
• Diabetic patients require special preparation to ensure blood glucose levels are ideally below 150-200 mg/dL for optimal imaging, as high glucose levels can interfere with FDG uptake and image interpretation 1.
• Patients should wear comfortable clothing without metal components or remove all metal objects before the scan to prevent artifacts on the CT images 1.
• The procedure involves an intravenous injection of a radioactive tracer (typically 18F-FDG) followed by a 60-90 minute uptake period where the patient must rest quietly, allowing the tracer to accumulate in areas of high metabolic activity 1.
• The actual scanning takes about 20-30 minutes, during which time the patient must remain still to ensure high-quality images 1.
• After the scan, patients should avoid close contact with pregnant women and young children for approximately 6 hours due to the radioactive material 1.

Importance of Guidelines

These guidelines are crucial for ensuring the quality and accuracy of whole-body PET/CT scans, which are used for diagnosing, staging, and monitoring various diseases, including cancer 1. By following these guidelines, healthcare providers can optimize the diagnostic potential of PET/CT scans and provide patients with the best possible care.

Additional Considerations

• Whole-body acquisition using a PET or PET/CT system should encompass at least the region between the base of the skull and the mid thigh, and can be acquired in either two- or three-dimensional mode 1.
• The PET projection data should be corrected for random coincidences, scatter, and attenuation in accordance with manufacturer’s recommendations to ensure accurate quantification of tracer uptake 1.

From the FDA Drug Label

The recommended dose of [ 18F]FDG for an adult (70 kg) is within the range 185-370 MBq (5-10 mCi), intravenous injection. It is recommended that PET imaging be initiated within 40 minutes of [ 18F]FDG injection.

The guidelines for a whole-body Positron Emission Tomography/Computed Tomography (PET/CT) scan using FDG (IV) include:

• Administering a dose of 185-370 MBq (5-10 mCi) for an adult (70 kg) via intravenous injection 2
• Initiating PET imaging within 40 minutes of FDG injection 2
• The indications for use include assessing abnormal glucose metabolism to assist in the evaluation of malignancy, and identifying regions of abnormal glucose metabolism associated with foci of epileptic seizures 2 Key points to consider:
• Dose calculation: The final dose for the patient should be calculated using proper decay factors from the time of the EOS, and measured by a suitable radioactivity calibration system before administration 2
• Imaging timing: The time interval between doses of FDG should be long enough to allow substantial decay (physical and biological) of previous administrations 2

From the Research

Guidelines for Whole-Body PET/CT Scan

• The whole-body PET/CT scan is an important investigation tool in malignancy patients, helping to ascertain the metabolic activity and exact stage of the disease 3.
• It is essential to carefully evaluate PET/CT and clinical correlation in malignancy patients to accomplish suitable treatment 3.
• The addition of CT imaging to PET improves the interpretation of PET images, and integrated PET/CT scanners can produce functional PET and anatomical CT data in one session 4.
• PET/CT has several advantages over PET, including shorter image acquisition time, better accuracy in anatomically localizing focal areas of abnormal tracer uptake, and the possibility to stage a disease in one single step 4.

Clinical Applications of PET/CT

• PET/CT is used for the staging and follow-up of various neoplasms, and [18F]FDG is the most common PET tracer used 4, 5.
• FAPI PET/CT has been shown to have a higher sensitivity than [18F]FDG PET/CT in detecting metastatic lung cancer lesions 5.
• Whole-body PET FDG imaging can accurately detect metabolically active tumor foci in patients with bronchogenic carcinomas, metastatic lesions to the thorax, and Hodgkin disease 6.
• PET/CT imaging has been used for the assessment of different types of lung cancer, including non-small cells lung cancer, broncho-alveolar carcinoma, small cells lung cancer, lung neuroendocrine tumours, and solitary pulmonary nodules 7.

Considerations for PET/CT Interpretation

• False positive results can exist, and certain diseases other than cancer may show increased uptake, highlighting the need for careful evaluation and clinical correlation 3.
• Any abnormal FDG accumulation in PET/CT scan at unusual locations should be evaluated carefully and confirmed histopathologically 3.
• The sensitivity and specificity of PET/CT can vary depending on the type of cancer and the tracer used, emphasizing the importance of selecting the appropriate tracer and interpretation criteria 5.