Non-invasive flap-assessment techniques

Acoustic Doppler sonography (HHD) andColour-coded duplex sonography (DS)
Colour-coded duplex sonography (DS), a vital modality in medical diagnostics, combines the strengths of anatomic visualization and flow assessment through ultrasonography. This technique relies on two primary displays: color-flow Doppler and gray-scale B-mode imaging. Color-flow Doppler provides valuable insight into flow velocity distribution within tissues, highlighting areas of abnormal flow patterns such as turbulence or stenosis. This dynamic representation aids in the identification of vascular pathologies such as arterial occlusions or venous insufficiencies. In contrast, grey-scale B-mode imaging offers detailed anatomical images, allowing for precise localization of structures and abnormalities. This static view complements the dynamic information provided by colour-flow Doppler, enabling a comprehensive assessment of vascular and tissue health. By integrating these two displays, duplex sonography facilitates a thorough evaluation of vascular structures and flow dynamics, enhancing diagnostic accuracy and informing treatment decisions. [29]
HHD is considered the most common and cost-effective technique for finding perforators in breast surgery, for example. (see Figure 2) Although it can determine the relative position of a perforator, it carries the risk of false positive findings (for example other subcutaneous arteries and not perforators) due to its high sensitivity. Furthermore, this modality does not provide information on the exact anatomical course. However, it remains a useful tool for intraoperative evaluation of vessel courses and assessment of perforators. In comparison, DS provides more detailed information on vessel anatomy (see Figure 3), however, it requires in-depth knowledge of the anatomy and is more time-consuming and technically demanding. In comparison with the CTA and MTA mentioned below, the DS is unable to provide three-dimensional information about vascular anatomy. [30]