What is the recommended imaging protocol for identifying perforators in a CT scan prior to DIEP (Deep Inferior Epigastric Perforator) flap surgery?

CT Angiography Protocol for DIEP Flap Perforator Identification

CT angiography (CTA) is the gold standard imaging modality for identifying perforators in DIEP flap surgery, with a sensitivity of 100% for perforators >1mm and significantly improved surgical outcomes. 1

Recommended CTA Protocol

Technical Parameters

• Acquisition Method: Thin-section CT timed to coincide with peak arterial enhancement 1
• Scanning Direction: Reversed caudal-cranial scanning from pubic symphysis toward umbilicus to improve DIEA enhancement 1
• Contrast Administration:
  • Single contrast-enhanced phase with region of interest for automatic injection placed on the femoral artery 1
  • Timing is critical to ensure optimal DIEA enhancement 1

Image Processing Requirements

• Primary Reconstructions: Transverse reconstructions 1
• Secondary Processing:
  • Multiplanar reformations (MPR) 1
  • 3D renderings (required element for CTA) 1
  • Maximum intensity projection (MIP) images 1
  • 3D skin surface-rendered images 1

Perforator Analysis

• Localization: Perforators identified on MIP images along the anterior rectus sheath 1
• Mapping: Perforator locations superimposed onto 3D skin surface-rendered images 1
• Visualization: Axial and sagittal MIP images used to depict perforator course through subcutaneous tissues and intramuscular portion 1

Critical Information to Report

• Location: Position where perforator pierces anterior rectus sheath in relation to umbilicus 1
• Size: Caliber of perforator (larger caliber preferred for flap viability) 1
• Course: Intramuscular path (shorter course preferred for easier dissection) 1
• Ranking: Perforators ranked based on size, location, and intramuscular course 1
• Additional Information:
  • Venous communication between right and left abdomen 1
  • Cutaneous perforators 1
  • Parameters for calculating flap viability and weights 1

Clinical Benefits of CTA

• Decreased length of surgery 1
• Decreased flap loss rate 1, 2
• Decreased hernia rate 1
• Decreased intraoperative blood loss 1
• Shorter mean inpatient stay 1
• Reduced learning curve compared to handheld Doppler 1
• Increased surgeon confidence 1

Common Pitfalls and Considerations

• Perforator Movement: The position of perforators within subcutaneous tissues can move with applied pressure, but the rectus sheath remains immobile relative to the umbilicus - this is why reporting location at the rectus sheath is critical 1
• Ideal Perforator Selection: The most difficult diagnostic challenge is selecting the "best" perforator 1
  • Ideal perforator should have largest caliber available 1
  • Medially located within the flap with extended vascular territory beyond midline 1
  • Short intramuscular course for successful dissection 1
• Radiation Exposure: CTA involves radiation exposure, which is why a single contrast-enhanced phase is recommended 1
• Alternative Imaging: MRA is a reasonable alternative for patients with concerns about radiation or iodinated contrast 1
• Concordance Issues: Studies show approximately 67.3% concordance between preoperatively identified perforators and those ultimately selected during surgery 3

Advantages Over Other Modalities

• Versus Color Doppler US: CTA is more intuitive, can be referenced in the operating room, and shows superior accuracy 1
• Versus Arteriography: CTA avoids invasive procedure risks and ionic contrast exposure 1
• Versus Standard CT: CTA with 3D rendering provides essential information about perforator course and relationships 1