Is Hyperspectral Imaging Suitable for Assessing Collateral Circulation Prior Radial Forearm Free Flap Harvesting? Comparison of Hyperspectral Imaging and Conventional Allen’s Test

Abstract

(1) Background: This cross-sectional study aims to compare a new and non-invasive approach using hyperspectral imaging (HSI) with the conventional modified Allen’s test (MAT) for the assessment of collateral perfusion prior to radial forearm free flap harvest in healthy adults. (2) HSI of the right hand of 114 patients was recorded. Here, three recordings were carried out: (I) basic status (perfusion), (II) after occlusion of ulnar and radial artery (occlusion) and (III) after releasing the ulnar artery (reperfusion). At all recordings, tissue oxygenation/superficial perfusion (StO2 (0–100%); 0–1 mm depth), tissue hemoglobin index (THI (0–100)) and near infrared perfusion index/deep perfusion (NIR (0–100); 0–4 mm depth) were assessed. A modified Allen’s test (control) was conducted and compared with the HSI-results. (3) Results: Statistically significant differences between perfusion (I) and artery occlusion (II) and between artery occlusion (II) and reperfusion (III) could be observed within the population with a non-pathological MAT (each <0.001). Significant correlations were observed for the difference between perfusion and reperfusion in THI and the height of the MAT (p < 0.05). Within the population with a MAT >8 s, an impairment in reperfusion was shown (each p < 0.05) and the difference between perfusion and reperfusion exhibited a strong correlation to the height of the MAT (each p < 0.01). (4) Conclusions: The results indicate a reliable differentiation between perfusion and occlusion by HSI. Therefore, HSI could be a useful tool for verification of the correct performance of the MAT as well as to confirm the final diagnosis, as it provides an objective, reproducible method whose results strongly correlate with those obtained by MAT. What is more, it can be easily applied by non-medical personnel.

Thermal, Hyperspectral, and Laser Doppler Imaging: Non-Invasive Tools for Detection of The Deep Inferior Epigastric Artery Perforators—A Prospective Comparison Study

“…Retailing at several thousand Euros, the device requires significant investment. While we could not reproduce the promising results of Goetze et al in our study and are unable to recommend the device for perforator detection with the described cooling protocol, it has been demonstrated to be of significant value following surgical anastomosis for perfusion monitoring and to detect underperfused areas within the flap in other studies [48,49]. Some authors postulate it to be even more effective than the gold standard for flap monitoring, clinical assessment and handheld Doppler [50,51].…”

Comparison of Hyperspectral Imaging and Microvascular Doppler for Perfusion Monitoring of Free Flaps in an In Vivo Rodent Model

“…Tissue oxygen saturation includes arterial and venous blood and detects changes in the tissue oxygen supply. It is largely based on the venous part (75%) of the microcirculation and its oxygen saturation after oxygen delivery to the surrounding tissue [ 1 , 37 ]. Although there are no uniform standard values to date, the StO 2 values in healthy people are usually around 50–70% [ 38 ].…”

“…With this index parameter, in combination with StO 2 or NPI, arterial supply or venous outflow problems can be recognized and differentiated. As a further index parameter, the TWI describes the relative water content in the tissue area under consideration [ 1 , 22 , 35 , 36 , 37 ]. For the evaluation and quantitative determination of the four parameters, a circular region of interest (ROI; 100 pixel), which contains the mean value of the spectral and spatial information per pixel, was manually positioned on the images, always in the same flap area.…”

Long-Term Donor Site Morbidity and Flap Perfusion Following Radial versus Ulnar Forearm Free Flap—A Randomized Controlled Prospective Clinical Trial

“…All surgical procedures were performed by two different experienced surgeons at the department of oral and maxillofacial surgery, facial plastic surgery, University Medical Centre Mainz, Johannes Guttenberg University Mainz, Mainz, Germany in the period from October 2020 until December 2021. Allen's test (the only mandatory test) and Hyperspectral Imaging were routinely performed before surgery to demonstrate adequate blood flow from the radial or ulnar artery to the hand [7].…”

“…Harvesting of both flaps can only be performed if sufficient blood supply to the hand via the palmar arches has been ensured beforehand. More than 15 s are considered critical, indicating impaired blood circulation with the increased risk for palmar malperfusion [7]. According to the literature, flap survival can be considered equal between RFFF and UFFF, with the radial vascular pedicle being usually 3-4 cm longer and slightly larger in caliber [8].…”