Measurement of burn depths in rats using multiwavelength photoacoustic depth profiling.

We perform measurement of photoacoustic (PA) signals for burned skin in rats in the spectral range of 500 to 650 nm. The wavelength dependence of PA signal amplitude shows characteristics similar to those of the absorption spectrum of hemoglobin, suggesting that the PA signal originates from blood in the uninjured skin tissue under the injured tissue layer. High-contrast signals are obtained in the spectral range of 532 to 580 nm. At 550 nm, a PA detector is scanned on the wounds and PA tomograms are obtained. The tomograms clearly show the zones of stasis, demonstrating that a 2-D PA measurement is useful for burn depth assessment.