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Detection Of Necrosis Avidity Using Indocyanine Green Fluorescence In Human Wound Healing
Aos Karim1, Kishan Thadikonda1, Christie Lin2, Adam Uselmann2, Kevin Elicieiri1, Samuel Poore1, Angela Gibson1.
1University of Wisconsin, Madison, WI, USA, 2OnLume, Madison, WI, USA.

BACKGROUND: Indocyanine Green (ICG) fluorescence was recently shown to be an imaging biomarker for necrosis in a murine model of burn injury. No studies have shown ICG necrosis avidity in human wound healing. In this study, we hypothesized that necrosis avidity of ICG can be used to evaluate burn-induced necrosis in a human skin xenograft on a mouse, and flap necrosis in Deep Inferior Epigastric Perforator (DIEP) breast reconstruction patients.
METHODS: Normal human skin excised during reconstructive operations was obtained. A 1 cm x 2 cm full thickness piece of human skin tissue was grafted onto the dorsal flank of immunocompromised mice. Twelve weeks after grafting, the graft was burned at 150C for 5 seconds with a custom burn device. ICG was injected retro-orbitally at 1 mg/kg dose. ICG fluorescence and white light images were captured immediately as well as 24 hours later using a novel fluorescence imaging system compatible with ambient light. In our clinical study, breast reconstruction patients (n=4) were imaged intraoperatively after vascular anastomosis was completed, as well as 2, 24, 48, and 72 hours later using the SPY imaging system (Stryker, standard of care).
RESULTS: ICG fluorescence in the entire wound (~8 mm diameter) decreased immediately after burning the human skin xenograft in our murine model. Twenty-four hours after injury, ICG fluorescence signal was detected in the burn area (~5-6 mm diameter); a smaller area than what the Immediate post-burn perfusion analysis suggested. In all breast reconstruction patients, ICG perfusion signal showed well-perfused flaps. ICG signal intensity was highest 2-24 hours after surgery, and centered on areas of bruising at the edge of the flap with no ICG signal within the flap. Clinic follow-up revealed well-healed flaps with minimal epidermolysis around the edge of the flap, consistent with ICG findings.
CONCLUSIONS: In this study, delayed imaging validated the use ICG as a marker for necrotic tissue in murine human xenograft burn wounds and in a human post-surgical model. Consistent with previous research, qualitative ICG perfusion signal was inconsistent with the actual necrotic region seen. Monitoring ICG signal in post-mastectomy patients may highlight potentially ischemic areas that may later require excision.


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