Both local and systemic photon-induced changes in the circulation may be involved in the bioeffects of low-light therapy (LLT) including low level laser therapy (LLLT). Amplification of the direct effects of photon absorption may be due in part to changes induced by photons in immune cells while in transit through the dermal capillaries. The peripheral location of these capillaries makes their contents readily accessible to photons. The longer the duration of treatment, the greater will be the number of cells in transit that can be affected by photons. These cells and their secretions circulate around the body, increasing the range and duration of phototherapy. This amplification may be caused in part by indirect effects initiated in cells that have not absorbed photons by regulatory proteins such as cytokines secreted by cells that have absorbed photons. Direct and indirect photon-induced increases in both the microcirculation and the macrocirculation have been reported; examples of these are described. A circulation-based mechanism by which exposure of the scalp to photons can produce intracranial and extracranial changes is proposed.

Date Published: 17 February 2010
PDF: 7 pages
Proc. SPIE 7552, Mechanisms for Low-Light Therapy V, 755205 (17 February 2010); doi: 10.1117/12.843172

Published in SPIE Proceedings Vol. 7552:
Mechanisms for Low-Light Therapy V
Michael R. Hamblin; Ronald W. Waynant; Juanita Anders, Editor(s)