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Page 4 of 15 Ali et al. Plast Aesthet Res 2021;8:35 https://dx.doi.org/10.20517/2347-9264.2021.29

CTA has some disadvantages that need to be considered as well. It is expensive, exposes the patient to
radiation, has contraindications in certain patient populations, and is static, therefore, limiting its ability for
[13]
intraoperative use. Shen et al. have tried to address this by reporting a method of designing virtual and
printed templates that can be used intraoperatively to facilitate harvest.

Infrared thermography
Infrared thermography (IT) is another technique that has been described in identifying perforators in flap
reconstruction. A sensor is used to create a thermogram that identifies “hot spots” which should correlate
with perforators. This technique has been described in isolation as well as in combination with CTA and
ultrasound in flap planning. Xiao et al. recently reported IT in comparison to CDU in ALT flap harvest.
[14]
[15]
They reported a 94.3% sensitivity and 85.7% specificity in identifying perforators. Pereira et al. reported a
much higher sensitivity and specificity of 100% and 98%, respectively. One major limitation of IT is its
inability to provide information about the course of the perforator. Therefore, this technique is only useful
in identifying where a perforator may be located. The size and course will not be determined until it is
explored intraoperatively.

Photoacoustic tomography
Photoacoustic tomography (PAT) is a 3-dimensional (3D) vascular mapping technology that has recently
been used in preoperative planning for flap harvest [16,17] . This technology uses energy from a near infrared
pulse laser which is absorbed by hemoglobin. The red blood cells become swollen and emit ultrasonic waves
which can be detected with ultrasound. This allows for 3D mapping of subcutaneous vessels without the use
of contrast. This technology can be particularly useful in the harvest of perforator based ALT free flaps due
to its ability to map the supra-fascial course of the vessels. Tsuge et al. showed PAT is comparable to
[16]
ultrasound in the evaluation of supra-fascial perforator branching patterns and is better than ultrasound at
showing oblique and horizontally oriented branches. This can be particularly useful in the process of
[18]
thinning ALT flaps to expand its utility in defects requiring a thin flap . PAT is limited in its ability to
[16]
examine branching patterns deep to the fascia and is also unable to distinguish arteries from veins .
PAT is a newer technology still under development. One of its main limitations for clinical use is the lack of
anatomical reference points precluding its intraoperative use . Tsuge et al. attempted to address this in
[16]
[17]
their clinical trial by developing a transparent sheet with mapping that could be sterilized and used
intraoperatively. Although they were able to show correlation between mapping and intraoperative findings,
further refinement will be needed to overcome errors introduced by the skin incision and retraction of
tissue. Continued advancements in this technology will be needed before it is widely used for perforator
mapping.

Color duplex ultrasonography
Interest in ultrasound based perforator mapping has become increasingly popular due to low cost,
availability, lack of contrast/radiation, and accuracy in mapping perforators. It also has the added benefit of
[3]
[19]
preoperative and intraoperative use to help facilitate decreased harvest and operative times . Kehrer et al.
published a step-by step guide in perforator mapping which will allow the microsurgeon to complete all
mapping independent of the radiology department. Although there is certainly a learning curve,
experienced microsurgeons have the advantage of intimate knowledge of the anatomy accelerating their
mastery of ultrasound techniques. Ultrasound can be applied to all perforator based flaps allowing for more
complex flap design.