360 In Vivo Characterization of Burn Wound and Skin Graft Healing in a Porcine Model using Spatial Frequency Domain Imaging

Abstract

Spatial frequency domain imaging (SFDI) is a wide-field optical imaging technique enabling non-invasive quantitative determination of sub-surface tissue properties. It provides structural information via the reduced scattering coefficient and chromophore concentrations (e.g. oxy- and de-oxyhemoglobin). We investigated SFDI for assessing healing progression in a porcine model of burn wounds treated with split-thickness skin grafts. Anesthetized Yorkshire pigs received deep partial thickness burns to their dorsum. Four days afterwards the wounds were debrided and autologous meshed split-thickness skin grafts were then applied. The wounds were imaged periodically over 60 days using SFDI at 9 wavelengths and their optical properties were determined. Concurrently, biopsies were taken for histological evaluation and comparison with the SFDI data. Additionally, one burn wound was debrided but received no treatment. Images and biopsies were also taken from regions of healthy skin as controls. All experiments followed protocols reviewed and approved by the Institutional Animal Care and Use Committee. The split-thickness skin grafts exhibited a decrease in scattering after grafting that recovered to values close to that of uninjured skin in 60 days, whereas the scattering of the debrided wound with no graft did not recover to baseline (Figure 1). These changes in scattering correlated with structural changes during healing that were evident in histology. Furthermore, the recovery in scattering for the grafts was less at longer wavelengths that penetrate deeper, indicating less complete healing at greater depths, which also agreed with histology. SFDI is capable of characterizing healing in porcine models of burn wounds and skin grafts. Changes in optical properties measured by SFDI tracked structural changes observed in histology. SFDI provides quantitative information on the subsurface properties of tissue without the need for invasive biopsies. SFDI can non-invasively evaluate wound healing therapies/strategies for burns. This can aid the development of new treatments that can ultimately shorten recovery times and improve outcomes.