Recommended Hydration Regimen Before Cardiac PET Scans
The recommended hydration regimen before a cardiac PET scan is consumption of approximately 1 liter of plain water during the 2 hours prior to FDG injection, as specified in the EANM procedure guidelines for tumour imaging. 1
Specific Hydration Protocol for Cardiac PET
Pre-scan Hydration Requirements:
- Consume approximately 1 liter of plain water during the 2 hours before FDG injection
- This ensures:
- Sufficiently low concentration of FDG in urine (reducing artifacts)
- Improved radiation safety through faster tracer clearance
- Optimal image quality
Additional Hydration Guidelines:
- Patient should void immediately before the PET/CT examination to reduce bladder activity 1
- Avoid caffeinated beverages (including "sugar-free" ones) as they may contain traces of carbohydrates and have excitant effects 1
- Any intravenous fluids used for prehydration must not contain glucose 1
Rationale for Adequate Hydration
Proper hydration before cardiac PET imaging serves multiple purposes:
- Improved image quality: Reduces urinary concentration of the radiotracer
- Radiation safety: Enhances radiotracer clearance
- Patient comfort: Helps maintain normal physiological state during the scan
- Contrast protection: May help reduce risk of contrast-induced nephropathy if contrast is used
Special Considerations
For Patients with Diabetes:
- Blood glucose levels should be checked upon arrival
- If plasma glucose level is lower than 11 mmol/L (200 mg/dL), the FDG PET/CT study can proceed
- If plasma glucose level is higher than or equal to 11 mmol/L (200 mg/dL), consider rescheduling 1
For Patients with Kidney Disease:
- Hydration remains important but may need to be modified
- The basic principle of hydration follows from experimental studies and clinical experience, with isotonic or half-normal saline being the historical gold standards 1
- For patients undergoing contrast procedures, intravenous prehydration has been shown to be more effective than hydration only during contrast administration 2
Fasting Requirements
- Patients scheduled for morning PET/CT should not eat after midnight
- Those scheduled for afternoon studies may have a light breakfast at least 4 hours prior to appointment
- Avoid strenuous exercise for at least 6 hours (preferably 24 hours) before the study 1
Pitfalls to Avoid
- Insufficient hydration: Can lead to higher radiation exposure and poorer image quality
- Glucose-containing beverages: Can alter FDG uptake patterns and affect diagnostic accuracy
- Caffeinated drinks: May increase physiological FDG uptake in myocardium and skeletal muscles
- Excessive hydration in patients with heart failure: May exacerbate symptoms
The EANM guidelines provide the most specific and evidence-based recommendations for hydration before cardiac PET scans, emphasizing the importance of adequate plain water intake in the hours before radiotracer administration.