Simulation the Alzheimer brain response to 915 nm laser irradiation: Exploring power levels, laser configurations, temperature, and dosages for effective photobiomodulation therapy

Alzheimer’s disease (AD)−a progressive neurodegenerative disorder−affects millions of individuals worldwide. This study evaluates the effect of power variation in brain Photobiomodulation (PBM) therapy using a wavelength of 915 nm. This study evaluates the continuous wave (CW) and pulsed wave (PW) modes of laser irradiation using varying numbers of point laser sources (2, 4, and 9) distributed across the head. The pulse wave features include a frequency of 100 Hz, a duty cycle of 50 %, and variable average power levels of 10, 20, 25, 50, and 100 mW. The primary simulation conditions of the brain surface temperature and room temperature were set to 37 °C and 24 °C, respectively. The evaluation was performed by calculating the Pennes bioheat equation to determine the time-dependent tissue temperature response during laser irradiation. Power doses were also calculated after determining each layer’s fluence rate and total energy flux. The results indicate that using two, four, or nine laser sources with an average power of 10 mW is suitable for brain PBM therapy. The three laser configurations achieve sufficient energy flux distribution in the brain (GM, WM) while maintaining the skin temperature at 37 °C at lower power levels. This research confirms that two laser sources (915 nm) deliver the required therapeutic dose across the head for Alzheimer’s patients without causing thermal side effects.