Advancing burn wound monitoring: A non-invasive photoacoustic imaging approach

Visual assessment of burn wounds is subjective and often fails to detect hemoglobin-weighted vascular changes that mark phase transitions. We evaluated photoacoustic imaging (PAI) using relative hemoglobin (Hb rel ), an internally normalized wound-to-healthy tissue comparison, to detect these transitions. Moist-thermal burns were induced ex vivo on Sprague-Dawley rat skin and imaged on days 1, 7, and 14 using a custom frequency-domain PAI system with an 808-nm diode laser and condenser microphone. Raster scanning with Fourier-transform-based signal extraction provided optimal contrast at a 15 kHz modulation frequency and a 50% duty cycle. Hb rel values reached 162% ± 10% on day 1, declined to 142% ± 10% on day 7, and 111% ± 2% on day 14, reflecting reduced vasodilation and progressive healing. These findings demonstrate that PAI can differentiate healthy tissue from burn regions, highlighting its potential as an adjunct tool for monitoring burn wound recovery. • Low-cost 808 nm photoacoustic imaging (PAI) monitors burn-wound healing stages • PAI uncovers vascular changes invisible to conventional photography • Relative hemoglobin as a marker of hemoglobin rise and wound healing • Hemoglobin absorption provides intrinsic contrast for PAI wound monitoring