Computational analysis of light diffusion and thermal effects during Transcranial Photobiomodulation

Area of Science:

• Biomedical Engineering
• Neuroscience
• Photomedicine

Background:

• Transcranial photobiomodulation (tPBM) is a non-invasive brain stimulation technique using light.
• tPBM shows potential for neurological and neuropsychiatric conditions.
• Key technological questions involve light penetration and thermal effects.

Purpose of the Study:

• To computationally simulate light propagation and thermal effects of tPBM.
• To use a high-resolution, anatomically realistic 3D model.
• To quantify light penetration and temperature changes in the brain.

Main Methods:

• Utilized a 3D high-resolution (1 mm) anatomically realistic model.
• Simulated light propagation and thermal effects from a single source at the F3 location (10-20 EEG).
• Applied a dose of 100 mW/cm².

Main Results:

• Light distribution at the brain showed blurring due to scalp, skull, and CSF.
• Approximately 1% of injected irradiance reached the gray matter.
• Scalp absorbed the majority of light (~65%), with a nominal 0.38°C temperature rise.
• Negligible temperature increase was observed in the brain.

Conclusions:

• The study provides a realistic simulation of tPBM light dosimetry and thermal effects.
• Findings highlight significant light attenuation by cranial tissues.
• Results indicate minimal thermal risk to the brain with tPBM.