What is the recommended dose and preparation for Fluorodeoxyglucose (FDG) injection for a Positron Emission Tomography/Computed Tomography (PET/CT) scan?

FDG Injection Protocol for PET/CT Scans

The recommended dose of Fluorodeoxyglucose (FDG) for an adult PET/CT scan is 185-370 MBq (5-10 mCi) administered intravenously, with proper patient preparation including 4-6 hours of fasting prior to injection. 1

Dosage and Administration

• The standard adult dose ranges from 185-370 MBq (5-10 mCi) for oncology, cardiology, and epilepsy studies 1
• Administration should be performed via an indwelling intravenous device after blood glucose determination 2
• The administration system must be able to deliver FDG with at least 97% accuracy (within 3% deviation) 2
• After injection, flush the administration syringe with at least 10 mL of normal saline (0.9% NaCl) using a three-way valve 2
• Measure residual activity in administration lines and IV access to calculate net administered FDG activity 2
• Report any problems with FDG administration and image the injection site if extravasation is suspected 2

Patient Preparation

• Patients must fast for at least 4-6 hours prior to FDG injection (no food, simple carbohydrates, or liquids other than plain water) 2, 1
• Blood glucose levels should be checked prior to FDG administration and should be less than 11 mmol/L (200 mg/dL) for optimal imaging 2, 3
• Patients should be adequately hydrated (consumption of 1L of water during the 2 hours prior to injection is recommended) 2
• Discontinue parenteral nutrition and intravenous fluids containing glucose at least 4 hours before FDG injection 2
• Patients should avoid strenuous exercise for at least 6 hours (preferably 24 hours) before the scan 2

Post-Injection Protocol

• Patients should remain seated or recumbent and silent during the uptake phase to minimize FDG uptake in muscles 2
• Keep patients warm starting 30-60 minutes before injection and throughout the uptake period to minimize brown fat accumulation 2
• The recommended interval between FDG administration and the start of image acquisition is 60 minutes (acceptable range: 55-75 minutes) 2
• Patients should void immediately before the PET/CT examination to reduce bladder activity 2
• For dedicated brain imaging, patients should be positioned in a quiet, dimly lit room before and during FDG uptake (at least 20 minutes) 2

Special Considerations

• For repeat scans in the same patient (especially for therapy response assessment), use the same uptake interval (within 10 minutes), PET/CT system, and acquisition/reconstruction settings 2
• During the waiting period, patients may drink an additional 500 mL of water to reduce bladder and ureter activity that could impair interpretation of pelvic lesions 2
• The total effective dose from a PET/CT procedure is approximately 14.2 mSv for males and 17.2 mSv for females (for a 370 MBq FDG dose) 4
• For breastfeeding mothers, close contact with infants should be limited for 12 hours after injection, although interruption of breastfeeding is not necessary 2

Common Pitfalls and Caveats

• Ensure blood glucose is stabilized before FDG administration, especially in diabetic patients who may need glucose management the day before and day of the scan 1
• Avoid coffee or caffeinated beverages, even if "sugar-free," as they may contain traces of carbohydrates 2
• FDG uptake is significantly affected by blood glucose levels; hyperglycemia can reduce tumor uptake and affect image quality 2, 3
• The accuracy of SUV measurements depends on strict adherence to the uptake time protocol 2
• For cardiac imaging, different protocols may be used (fasting vs. glucose load) depending on the clinical question 1