Hyperspectral imaging as a novel diagnostic tool in microcirculation of wounds.

Monitoring of perfusion is a cornerstone in surgery, phlebology and basic science to proof wound healing by interventions. In chronic wound management it is of utmost importance to realize and parametrize wound bed perfusion to verify actual, and plan further treatment by noninvasive diagnostics. Up to now monitoring is based on visual inspection of wounds as conventionally practiced over more than decades. The main problems of visual inspection are the lack of standardization and comparability because of interindividual variations. Therefore technical performance with contact free probes based on standardized perfusion measuring is strongly needed. Hyperspectral imaging (HSI) was investigated to overcome manual and visual wound inspection in monitoring of wound healing. HSI works noninvasive, and imaging of relevant perfusion parameters is possible without the need of contrast enhancing drugs.
METHODS: HSI technology uses imaging spectroscopic analysis in visual and near infrared spectrum to get information on imaged tissue in less than 10 s. Tissue is radiated by broad spectrum light and the following parameters are calculated from remitted spectra: the grade of oxygenation and the volume proportion of hemoglobin (in superficial and also deeper (8 mm) tissues. The calculated data comprise the "Tissue hemoglobin oxygen saturation" (StO2) as percental oxygenation index to assess superficial perfusion (VIS-spectrum), the "Near infrared perfusion" (NIR) to assess deeper perfusion (near infrared spectrum) and the "Tissue hemoglobin index" (THI) to measure the percental volume of hemoglobin of surface perfusion (VIS-spectrum). The measurements of these parameters are calculated as false color-coded perfusion results on screen.We investigated different kind of wounds (combustion, infection, ulcer wounds, wounds in immune disorders, trauma wounds) determining superficial and deeper oxygen saturation, hemoglobin distribution and water content using hyperspectral imaging with TIVITA™ Tissue system.
RESULTS: Hyperspectral Imaging allowed easy real time determination and visualization of hemodynamically relevant parameters- superficial and deeper oxygen saturation, total hemoglobin and tissue water content. In the patient with scleroderma, acral lesions with decreased perfusion correlated well with necrotic skin aspects.HSI clearly revealed macroscopic conspicuous suture wounds after Dupuytren surgery, infected soft tissue wounds with strong inflammatory hyperemia, edema in burn injuries, spatial geometry of abscess formation and chronic ulcer wounds. All measurements influenced further surveillance decisions. Hyperspectral imaging seems suitable for routine diagnostics and monitoring of skin and soft tissue lesions like acute and chronic wounds. It allows surveillance of postoperative suture wounds and burn wounds. Special indications may be transplant surveillance and monitoring of therapeutical interventions.