What are the steps to order a PET/CT scan?

How to Order a PET/CT Scan

To order a PET/CT scan, you must submit a written request that includes complete patient information, clinical indication, and specific scan parameters while ensuring proper patient preparation for optimal imaging results. 1

Patient Preparation Requirements

Pre-Scan Instructions

• Fasting requirements: Patient must fast for at least 4 hours prior to the scan 1
• Hydration: Instruct patient to drink 1L of water during the 2 hours before injection 1
• Activity restrictions:
  • Avoid strenuous exercise for at least 6 hours (preferably 24 hours) before the scan
  • Patient should remain seated or recumbent during the uptake phase
  • Keep patient warm starting 30-60 minutes before injection to minimize brown fat uptake 1

Blood Glucose Management

• Check blood glucose upon arrival
• For clinical studies: Blood glucose should be <11 mmol/L (200 mg/dL) 1
• For research studies: Blood glucose typically should be between 7-8.3 mmol/L (126-150 mg/dL) 1
• For diabetic patients, check glucose levels early to allow time for correction if needed

Medication Considerations

• Discontinue parenteral nutrition and glucose-containing IV fluids at least 4 hours before injection 1
• For patients on somatostatin analogs (when using DOTATATE scans):
  • Long-acting analogs: 28-day washout period
  • Short-acting analogs: 2-day washout period 2

Writing the Order

Essential Order Components

1. Patient demographics: Full name, date of birth, weight, height (precise measurements are critical for SUV calculations) 1
2. Clinical information:
   • Diagnosis and known tumor sites
   • Relevant comorbidities (especially diabetes, inflammation)
   • Previous imaging results with dates
   • Recent treatments (chemotherapy, radiation, surgery) 1
3. Scan specifications:
   • Type of radiopharmaceutical (e.g., [18F]FDG)
   • Anatomical coverage (e.g., skull vertex to mid-thigh or whole body) 1
   • Whether contrast is needed (if yes, include kidney function results) 1
   • Any special positioning requirements (e.g., arms up vs. down) 1
   • For radiation planning: specify need for treatment position and immobilization devices 1

Special Considerations

• For head and neck tumors: Consider a two-step protocol with arms down for head/neck portion, then arms up for body scan 1
• For radiation therapy planning: Specify need for patient positioning in treatment position using same immobilization devices 1
• For claustrophobic patients: Note this in the order to allow for premedication planning 1

Common Pitfalls to Avoid

1. Inadequate patient preparation: Failure to properly instruct patients about fasting and activity restrictions leads to poor image quality 1

2. Insufficient clinical information: Omitting relevant history, previous imaging results, or recent treatments can lead to misinterpretation 1

3. Unclear anatomical coverage: Not specifying the required scan range may result in incomplete imaging of relevant areas 1

4. Overlooking renal function: When contrast is needed, failing to check kidney function can lead to complications 1

5. Not accounting for diabetes: Hyperglycemia significantly affects image quality; special scheduling and preparation may be needed 1

By following these guidelines, you can ensure proper ordering of PET/CT scans that will yield high-quality, diagnostic images while minimizing radiation exposure and optimizing patient care.