Thermal impact of near-infrared laser in advanced noninvasive optical brain imaging.

Mina Nourhashemi,Fabrice Wallois,Mahdi Mahmoudzadeh

doi:10.1117/1.nph.3.1.015001

Mina Nourhashemi, Fabrice Wallois + Show 1 more

Open Access

https://doi.org/10.1117/1.nph.3.1.015001

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Journal: Neurophotonics	Publication Date: Jan 14, 2016
Citations: 24	License type: cc-by

Affiliation: University of Picardie Jules Verne

Abstract

The propagation of laser light in human tissues is an important issue in functional optical imaging. We modeled the thermal effect of different laser powers with various spot sizes and different head tissue characteristics on neonatal and adult quasirealistic head models. The photothermal effect of near-infrared laser (800nm) was investigated by numerical simulation using finite-element analysis. Our results demonstrate that the maximum temperature increase on the brain for laser irradiance between 0.127 (1mW) and [Formula: see text] (100mW) at a 1mm spot size, ranged from 0.0025°C to 0.26°C and from 0.03°C to 2.85°C at depths of 15.9 and 4.9mm in the adult and neonatal brain, respectively. Due to the shorter distance of the head layers from the neonatal head surface, the maximum temperature increase was higher in the neonatal brain than in the adult brain. Our results also show that, at constant power, spot size changes had a lesser heating effect on deeper tissues. While the constraints for safe laser irradiation to the brain are dictated by skin safety, these results can be useful to optimize laser parameters for a variety of laser applications in the brain. Moreover, combining simulation and adequate in vitro experiments could help to develop more effective optical imaging to avoid possible tissue damage.

Highlights

Conventional optical imaging systems typically include certain basic components such as various types of lasers and flexible fiber optics.[1]
We investigate the effect of lasers on neonatal and adult head tissues in the lower NIR spectrum (600 to 900 nm) used in functional optical imaging
The following sections describe the effects of blood perfusion, various skin and brain absorption and scattering coefficients, laser spot size, and different tissue thickness on the temperature distribution in head tissues

Summary

Introduction

Conventional optical imaging systems typically include certain basic components such as various types of lasers and flexible fiber optics.[1]. No obvious thermal impacts are detected at skin temperatures of 37°C to 41°C, a temperature increase above 41°C and up to 50°C likely results in reversible membrane alterations.[25,27,28] The normal

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