Three‐dimensional irradiance and temperature distributions resulting from transdermal application of laser light to human knee—A numerical approach

• Published in: Journal of biophotonics Vol. 16; no. 9; pp. e202200283 - n/a
• Main Authors: Chaki, Chironjeet, De Taboada, Luis, Tse, Kwong Ming
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH & Co. KGaA 01.09.2023; Wiley Subscription Services, Inc
• Subjects: Absorption; Chromophores; Continuous radiation; Electromagnetic absorption; high‐intensity laser therapy; Irradiance; Irradiation; Knee; Laser applications; laser photobiomodulation; Lasers; light absorption‐driven thermal effect; Light therapy; Light transmittance; light‐tissue interaction; Photons; Skin; Therapeutic applications; Tissues; Wavelengths; light-tissue interaction; irradiance; laser photobiomodulation; light absorption-driven thermal effect; high-intensity laser therapy
• ISSN: 1864-063X; 1864-0648
• DOI: 10.1002/jbio.202200283

The use of light for therapeutic applications requires light‐absorption by cellular chromophores at the target tissues and the subsequent photobiomodulation (PBM) of cellular biochemical processes. For transdermal deep tissue light therapy (tDTLT) to be clinically effective, a sufficiently large number of photons must reach and be absorbed at the targeted deep tissue sites. Thus, delivering safe and effective tDTLT requires understanding the physics of light propagation in tissue. This study simulates laser light propagation in an anatomically accurate human knee model to assess the light transmittance and light absorption‐driven thermal changes for eight commonly used laser therapy wavelengths (600–1200 nm) at multiple skin‐applied irradiances (W cm−2) with continuous wave (CW) exposures. It shows that of the simulated parameters, 2.38 W cm−2 (30 W, 20 mm beam radius) of 1064 nm light generated the least tissue heating −4°C at skin surface, after 30 s of CW irradiation, and the highest overall transmission—approximately 3%, to the innermost muscle tissue. In order to deliver safe and effective transdermal deep tissue light therapy, we simulate laser light propagation in an anatomical human knee model to assess the light transmittance and absorption‐driven thermal changes for various commonly used near‐infrared wavelengths (600–1200 nm) at multiple skin‐applied irradiances. Our study provides a robust methodology and guidance for investigating high intensity light therapy dosing prior to clinical research, ensuring safe and effective tDTLT delivery.