Assessing 661nm Photobiomodulation Light Fluence Rate Transmission for Optimal Dose Delivery

Photobiomodulation (PBM) is a non-ionizing, non-thermal, low-power laser, or LED light therapy with diverse clinical applications for pain management, wound healing, dermatology, oral health, neurorehabilitation, and oncology. The capability of PBM to promote cell proliferation and migration makes it a potential treatment alternative, especially for patients unresponsive to conventional methods. A key challenge of PBM is determining the optimal dosage parameters, which include wavelength, fluence, power, pulse structure, irradiance, time, and interval duration. Given the therapeutic goal of stimulating a biological response, delivering light to a predictable penetration depth is critical. This study aims to characterize PBM light transmission for the 661nm wavelength in 500mW and 1W power outputs across different soft tissue types relevant in the head and neck region. We developed a unique preclinical model using five non-fixed, intact porcine mandibles representative of the dental oral craniofacial complex to explore this concept of accurate penetration depth of the 661nm wavelength. We captured maximum light fluence measurements (mW/cm^2) at distances 2-14mm using an isotropic detector connected to a real-time dosimetry system. All experimental sites underwent digital imaging and histological processing for architectural investigation, followed by proprietary software analysis to correlate distance, density, tissue type, and max light fluence values. Preliminary findings indicate a general reduction in max fluence as the distance values increased. A notable finding was the significant increase in max fluence in sites composed of adipose tissue compared to muscle tissue, highlighting the impact of tissue architecture and tissue optical properties on PBM light delivery. These results emphasize the need for further optimization of PBM dosing protocols for maximal therapeutic benefits.