What are the steps to order a Positron Emission Tomography (PET) Computed Tomography (CT) scan?

How to Place an Order for PET/CT

To order a PET/CT scan, follow a standardized protocol that includes providing complete clinical information, specifying scan parameters, and ensuring proper patient preparation instructions are communicated to the patient.

Required Clinical Information

• Patient demographics: Full name, date of birth, weight, and height (critical for SUV calculations) 1
• Clinical diagnosis: Specific cancer type or suspected condition 1
• Relevant clinical history: Known tumor sites, previous treatments, and comorbidities (especially diabetes and inflammatory conditions) 2, 1
• Results of previous imaging studies: CT, MRI, previous PET/CT scans 2
• Recent treatments: Timing of chemotherapy, radiation, or surgery 1
• Laboratory values: Kidney function (if contrast is needed) 1

Scan Specifications to Include

• Anatomical coverage required: 2, 1

  • Whole-body (skull vertex to feet)
  • Torso (skull base to mid-thighs)
  • Limited area (specific region of interest)
  • Brain imaging (if needed)

• Type of CT scan needed: 2

  • Low-dose CT (for attenuation correction only)
  • Diagnostic CT with contrast (specify oral, IV, or both)

• Special positioning requirements: 2, 1

  • Arms up or down
  • For head and neck tumors: consider two-step protocol with arms down for head/neck portion and arms up for body scan
  • For radiation therapy planning: specify treatment position and need for immobilization devices

Patient Preparation Instructions

• Fasting requirements: Patient must fast for at least 4-6 hours prior to the scan 2, 1, 3
• Hydration: Patient should 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 1
• Medications: List any medications that should be continued or discontinued 2
• For diabetic patients: Special instructions for blood glucose management 1, 3
• For claustrophobic patients: Note need for possible premedication 1

Common Pitfalls to Avoid

• Inadequate clinical information leading to misinterpretation 1
• Unclear anatomical coverage resulting in incomplete imaging 1
• Overlooking renal function when contrast is needed 1
• Not accounting for diabetes, which can significantly affect image quality 1
• Failing to specify positioning requirements for radiation planning 2, 1

PET/CT Acquisition Protocols

Different acquisition strategies may be employed depending on clinical needs: 2

1. Strategy 1 (Basic Protocol):

   • CT topogram/scout scan
   • Low-dose CT scan
   • PET acquisition

2. Strategy 2 (With Diagnostic CT):

   • Option A: Basic protocol followed by contrast-enhanced diagnostic CT
   • Option B: Contrast-enhanced diagnostic CT first, then low-dose CT and PET with appropriate delay

3. Strategy 3 (Low-dose CT only):

   • CT topogram followed by low-dose CT and PET acquisition

4. Strategy 4 (Full Diagnostic Protocol):

   • CT topogram
   • Deep-inspiration thoracic CT scan (if needed)
   • Whole-body diagnostic CT scan
   • PET acquisition

By following these guidelines when placing a PET/CT order, you'll ensure that the imaging facility has all necessary information to perform an optimal study tailored to the patient's specific clinical needs.