A Comparison of Thermal Imaging to Doppler in Perforator Vessel Identification

Abstract

Background: Precise identification of perforators is necessary for perforator flap planning and success. Various localizing modalities are currently utilized. Doppler is the perioperative modality of choice but can be time consuming and operator dependent. Thermal imaging is an affordable, easy-to-use technology that produces a color image based on surface temperature. This study aims to compare the proficiency and speed of thermal imaging to Doppler in perforator identification.

Methods: Twenty-one participants (42 thighs) were studied. A circle with a 5-cm radius at the midpoint between theanterior superior iliac spine and lateral patella was marked. Two investigators independently utilized either Doppler or thermal imaging to identify perforators within the marked territory. Thermal hotspots were marked first with invisible UV ink to blind the other investigator, who then scanned the same territory with Doppler. Concordance was determined if respective perforator markings between modalities aligned within 1 cm. After first pass, any nonconcordant thermal hotspots were rescanned with Doppler. Initial time taken and number of perforators found at first pass, first-pass concordance, and overall concordance after Doppler rescan were recorded.

Results: At first pass, average time to identify perforators using Doppler was 3.57 minutes and 1.06 minutes using thermal imaging (P < 0.001). Among 42 ALT flap territories, 143 perforators were identified by Doppler and 142 by thermal imaging on initial scan, from which there was 72.5% initial concordance between modalities. Of the 39 nonconcordant thermal hotspots on first pass, an additional 29 then had a Doppler signal confirmed on rescan, resulting in an overall concordance of 93%.

Conclusions: When used as an adjunct for flap planning, thermal imaging allows more efficient perforator identification by more quickly scanning a cutaneous territory and unmasking perforators missed by handheld Doppler alone.

Keywords: ALT; Doppler; FLIR; flap planning; perforator identification; thermal imaging.