Increasing the optical penetration depth of LED-based NIRS systems by comparing different beam profiles Mohia Mirbagheri1, Nasser Hakimi1, Elias Ebrahimzadeh1,2,3,4, Kambiz Pourrezaee5 and S. Kamaluddin Setaradan1. **1 Center for Excellence in Intelligent Processing and Control, Faculty of Electrical and Computer Engineering, Technical Faculty,** **University of Tehran, Tehran, Iran** **2 Department of Clinical Neuroscience, University of Calgary, Calgary, Alberta, Canada** **3 Hotchkiss Brain Institute, Kamin School of Medicine, University of Calgary, Calgary, Alberta, Canada** **4 MR Seaman Family Research Center, University of Calgary, Calgary, Alberta, Canada** **5 School of Biomedical Engineering, Health Sciences and Systems, Drexel University, Philadelphia, PA, 19104, USA** Near-infrared spectroscopy (NIRS) is a non-invasive brain imaging technique that involves quantifying the concentrations of oxy- and deoxy-hemoglobin resolved by measuring the attenuation of near-infrared (NIR) light.. within tissue.. Previous studies have shown that NIR light is most affected by those target layers. Cortex ... NIR light produced by a laser source penetrates deeper areas of tissue than an LED source, although the laser requires more expensive instrumentation ... In this study, we investigate the effect of uniform and Gaussian beam profiles on increasing the penetration depth of LED light ... Recently produced beam profiles were compared using planar and non-spherical lenses used in LED sources, in order to increase LED indications as well. Light detector... For analysis performance, two experiments were performed by scanning the interior of a liquid phantom by static and dynamic (pulsating) absorbers... Monte Carlo simulations were also performed to compare with the experiment.. The results showed that the Gaussian beam profile and especially the Bi-Convex lenses applied to the source and detector lead to greater light penetration depth in the liquid phantom close to the laser source. Profiles