Perfusion Changes by Hyperspectral Imaging in a Burn Model

BACKGROUND: Early excision and skin grafting of full-thickness and deep-dermal burns is therapeutically advantageous. However, while full-thickness burns are clinically evident, differentiating between superficial versus deep partial-thickness burns presents a diagnostic challenge, with only 50-75% accuracy. Superficial-dermal burns heal, while deep-dermal burns often require excision and skin grafting. Decision of surgical treatment is often delayed until burn depth is definitively identified. This study’s aim is to establish a thermal burn model in mice in order to assess the ability of Hyperspectral Imaging (HSI) in differentiating burn depth. METHODS: Burns of graded severity were generated on the dorsum of seventy-six hairless mice with a brass rod heated to 50, 60, 70, 80, or 90°C. Perfusion and oxygenation parameters of the injured skin were measured with HSI, a non-invasive method of wide-field, diffuse reflectance spectroscopy at 2 minutes, 1 hour, 24 hours, 48 hours, and 72 hours after wounding. Burn depth was measured histologically (n=44) at 72 hours post injury using Masson’s trichrome staining. RESULTS: Three discrete levels of burn depth were verified histologically, as follows in order of increasing depth: intermediate-dermal, deep-dermal, and full-thickness injury. At 24 hours post injury, total hemoglobin increased by 67% and 18% in intermediate and deep dermal burns, respectively. In contrast, total hemoglobin decreased by 64% in full-thickness burns. Differences in deoxygenated hemoglobin, total hemoglobin, and oxygen saturation for all group comparisons were statistically significant (p CONCLUSION: HSI was able to differentiate among three discrete levels of burn injury. This is likely due to its correlation with skin perfusion: superficial burn injury causes an inflammatory response and increased perfusion to the burn site, while deeper burns destroy the dermal microvasculature and a decrease in perfusion follows. This study supports further investigation in the use of HSI in early burn depth assessment

Translational Model for External Volume Expansion in Irradiated Skin

Introduction: External Volume Expansion (EVE) treatment has gained popularity in breast reconstruction, enriching recipient sites for fat grafting. For patients receiving radiotherapy (XRT), results of EVE use vary, partly because the effects of EVE on irradiated tissue are not well understood. Based on our previous work with EVE and XRT, we developed a new translational model to investigate the effects of EVE in the setting of chronic radiation skin injury. Methods: Twenty-Eight SKH1-E mice received 50Gy of beta-radiation to each flank. Animals were monitored until chronic radiation fibrosis developed (8 weeks). EVE was then applied to one side for 6hrs on 5 consecutive days. The opposite side served as control. Hyperspectral Imaging (HSI) was used to assess perfusion changes before and after EVE. Mice were sacrificed at 5 days (n=14) and 15 days (n=14) after last application for histological analysis. Tissue samples were stained for vascularity (CD31) and collagen composition (Picro-Sirius red). Results: All animals developed skin fibrosis 8 weeks post-radiation, and changes in perfusion verified skin damage. EVE application induced edema on treated sides. Five days post-application, both sides were hypo-perfused as seen by HSI; with the EVE side 13% more ischemic than the untreated side (p\u3c0.001). Perfusion returned to control side levels by day 15. Blood vessels increased 20% by day 5 in EVE versus control. Collagen composition showed no difference in scar index analysis. Conclusion: EVE temporarily augments radiation-induced hypo-perfusion, likely due to transient edema. Fibrosis remained unchanged after EVE, possibly accounting for the limited expansion seen in patients. It appears that EVE induces angiogenic effect but does not affect dermal collagen composition. Future efforts should focus on reducing fibrosis post radiation to allow EVE to achieve its full potential, to benefit irradiated patients