Characterization of the bruise healing process using pulsed photothermal radiometry

An analytical model of mass diffusion and biochemical transformation kinetics in bruise development and healing process was recently developed in order to simulate bruised skin color at various time points and enable objective determination of the time of injury. However, parameters of the model were not determined directly. Instead, biologically plausable values were applied in prior analyses. Pulsed photothermal radiometry (PPTR) allows noninvasive determination of the laser-induced temperature depth profile in human skin. We have applied this technique to characterize dynamics of extravasated hemoglobin concentration profile evolution. By applying Monte Carlo simulation of laser energy deposition and simulation of PPTR signal, a more exact comparison with measured temperature profiles is possible. We show that PPTR depth profiling can be used to derive rather accurate estimates of the hemoglobin mass diffusivity, hemoglobin degradation time, as well as approximate skin geometry. This enables assessment of the bruise healing dynamics and could offer a valuable addition to existing bruise age determination techniques.