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Journal of Biomedical Optics • Open Access

Temperature elevation profile inside the rat brain induced by a laser beam
Author(s): Ali Ersen; Ammar Abdo; Mesut Sahin

Paper Abstract

The thermal effect may be a desired outcome or a concerning side effect in laser–tissue interactions. Research in this area is particularly motivated by recent advances in laser applications in diagnosis and treatment of neurological disorders. Temperature as a side effect also limits the maximum power of optical transfer and harvesting of energy in implantable neural prostheses. The main objective was to investigate the thermal effect of a near-infrared laser beam directly aimed at the brain cortex. A small, custom-made thermal probe was inserted into the rat brain to make direct measurements of temperature elevations induced by a free-air circular laser beam. The time dependence and the spatial distribution of the temperature increases were studied and the maximum allowable optical power was determined to be 2.27  W/cm 2 for a corresponding temperature increase of 0.5°C near the cortical surface. The results can be extrapolated for other temperature elevations, where the margin to reach potentially damaging temperatures is more relaxed, by taking advantage of linearity. It is concluded that the thermal effect depends on several factors such as the thermal properties of the neural tissue and of its surrounding structures, the optical properties of the particular neural tissue, and the laser beam size and shape. Because so many parameters play a role, the thermal effect should be investigated for each specific application separately using realistic in vivo models.

Paper Details

Date Published: 27 January 2014
PDF: 8 pages
J. Biomed. Opt. 19(1) 015009 doi: 10.1117/1.JBO.19.1.015009
Published in: Journal of Biomedical Optics Volume 19, Issue 1
Show Author Affiliations
Ali Ersen, New Jersey Institute of Technology (United States)
Ammar Abdo, New Jersey Institute of Technology (United States)
Mesut Sahin, New Jersey Institute of Technology (United States)

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