Is it okay to drink water prior to a cardiac Positron Emission Tomography (PET) scan?

Drinking Water Before a Cardiac PET Scan

Yes, it is not only okay but recommended to drink plain water prior to a cardiac PET scan. 1

Hydration Recommendations for Cardiac PET Scans

The European Association of Nuclear Medicine (EANM) guidelines specifically address hydration before PET/CT scans, including cardiac studies:

• Pre-scan hydration: Adequate prehydration is important to ensure low concentration of FDG in the urine (reducing artifacts) and for radiation safety reasons 1
• Recommended amount: Consumption of approximately 1 liter of water during the 2 hours prior to injection is suggested 1
• Type of fluid: Only plain (unflavored) water is permitted 1

Special Considerations for Cardiac PET Imaging

For cardiac PET scans specifically, there are additional important considerations:

• When evaluating lesions in the heart or close to the myocardium, patients should follow a low carbohydrate diet for 24 hours prior to the PET/CT study, or at least have a low carbohydrate meal before starting the 6-hour fasting period 1
• This dietary preparation helps switch the myocardium from using glucose to using fatty acids as an energy source, which reduces background glucose uptake by the heart muscle and improves image quality 1

What to Avoid Before the Scan

While plain water is encouraged, patients should avoid:

• Food for at least 4 hours prior to the scan
• Coffee or caffeinated beverages (even if "sugarless" as they may contain traces of carbohydrates)
• "Sugar-free" beverages
• Any liquids other than plain water
• Strenuous exercise for at least 6 hours (preferably 24 hours) before the scan 1

Benefits of Proper Hydration

Controlled hydration protocols have been shown to:

• Lower background activity in soft tissues
• Reduce urinary activity in the bladder and kidneys
• Potentially increase tumor-to-background contrast, improving image quality 2

Practical Protocol

1. Fast from food and beverages other than plain water for at least 4 hours before the scan
2. Drink approximately 1 liter of plain water during the 2 hours before the FDG injection
3. Void immediately before entering the scanner to reduce bladder activity 1
4. Follow any specific dietary instructions (like low carbohydrate diet) if provided by your healthcare team

Conclusion

Drinking plain water before a cardiac PET scan is beneficial and recommended by clinical guidelines. Proper hydration helps improve image quality while reducing radiation exposure, making it an important part of patient preparation for these studies.