TECHNIQUE Strengths Weaknesses
NON-INVASIVE NON-INVASIVE NON-INVASIVE
Acoustic Doppler Sonography (HHD) Colour-coded Duplex Sonography (DS) Common and cost-effective method for locating perforators or axial pattern flap pedicles. DS provides a more detailed information on vessel anatomy. HHD may yield false positives due to high sensitivity. DS demands extensive anatomical knowledge, proving time-consuming and technically challenging. DS is unable to provide three-dimensional information about vascular anatomy.
Near Infrared Spectroscopy (NIRS) Allows non-invasive measurement of oxygen level changes, demonstrating high accuracy in differentiating between venous and arterial compromise in free flaps. Currently lacking dedicated flap assessment systems. Higher cost than other systems.
Hyperspectral Imaging (HSI)
Provides effective real-time evaluation of tissue properties and early detection of flap issues.
High-cost No clear superiority over other techniques.
Thermal Imaging (TI) Non-invasive, low-cost, smartphone-based imaging for early detection of vascular insults. Provides valuable postoperative monitoring in pedicled flaps. Limited to surface temperature changes. Specificity may vary.
Photoplethysmography (PPG) Non-contact measurement of tissue blood volume changes, aiding in differentiating between venous and arterial thrombosis in free flaps. Requires prior visualization of vascular anatomy for effective use during postoperative monitoring.
INVASIVE TECHNIQUES INVASIVE TECHNIQUES INVASIVE TECHNIQUES
Contrast-enhanced Ultrasound (CEUS) Integrates vascular ultrasound with contrast agents, providing accuracy in locating small-lumen perforating vessels. Invasive nature; may involve risks associated with contrast agents.
Computed Tomography Angiography (CTA) High accuracy, shorter examination times, and visualization of smaller vessels. Involves ionizing radiation, limiting use in certain patient populations.
Near-infrared Fluorescence Angiography with ICG (NIRF) Real-time visualization of vessel structure, aiding in surgical planning and predicting tissue flap survival. Expensive, Invasive due to intravenous injection; potential risks associated with ICG use.
Implantable Doppler Probe
Rapid detection of compromise, especially in non-visible flaps.
Controversial findings regarding sensitivity and false-negative results. May not offer advantages in all cases.