Limitations of photoacoustic measurement of burn depth

Noninvasive burn depth measurements would allow clinicians to manage burn injury better and improve treatment outcomes. Additionally, knowledge of the burn depth would allow surgeons to excise thermally damaged tissue without harming the underlying healthy tissue which is the source of epithelial cells important for proper healing response. We propose a photoacoustic method for inducing acoustic waves in burns. We used an Nd:YAG laser coupled to an optical fiber probe to deliver laser light to burn injury. Subsequent acoustic wave analysis results in burn depth profiling. We test ex vivo pig skin and optical diffusion theory to extrapolate these measurements to determine the maximum depth determined by this probe. We found that our probe can determine burn depths up to 2.8 mm. We propose changes to extend this depth to about 5 mm, the full thickness of human skin.