Photoacoustic wave propagation in 3D heterogeneous human skin tissue model using first-order k-space modeling at different wavelengths

Abstract

The photoacoustic (PA) effect exploits the rapid conversion of absorbed optical energy into acoustic waves, producing a detectable pressure signal response and replicating the energy deposition profile from a specific medium depth. This study examines how wavelength-dependent optical parameters influence the photoacoustic wave generation in a 3D heterogeneous human skin tissue model using first-order k-space modeling across nine wavelengths through the k-Wave toolbox for wave propagation and MCMatlab to model energy absorption. The findings suggest that the shorter wavelengths yield a stronger pressure response due to more confined energy deposition in the presence of chromophores, specifically melanin. As the wavelength increases, deeper penetration occurs, and the transition of primary absorbers from melanin-dominated to hemoglobin-dominated happens which produces a broader energy distribution across the tissue layers, lowering peak pressures. The spectral analysis demonstrates at ≥ 5 Mhz, there is a PA signal attenuation that becomes more prominent as the wavelength increases. Understanding the effect of the absorption dynamics in generating pressure response across different wavelengths can be beneficial in selecting proper laser parameters for specific high spatial resolution and non-invasive diagnostic imaging such as photoacoustic imaging.