23 February 2012 The sensitivity of acousto-optic sensing measurements to absorption changes in superficial and deep layers
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Abstract
Near infrared spectroscopy is a widely adopted optical sensing technique to measure tissue oxygenation non-invasively in human tissues such as the brain and muscle. However, in many situations, the region of interest is beneath a superficial layer, e.g., muscle overlaid by a superficial layer of skin and fat, which can affect the accuracy of the optical measurement. By applying focused ultrasound in the region of interest, acousto-optic (AO) sensing techniques can potentially provide a measurement less susceptible to physiological changes in the superficial layer. In this work, a digital correlator based AO system has been used to perform a series of phantom experiments to assess the sensitivities of the AO and optical measurements (both in reflection modes) to absorption changes (μa = 0.0235, 0.05, 0.1, 0.2, and 0.3 cm-1) in three different locations, including one deep location (23 mm away from the surface) and two superficial locations (8 mm away from the surface). Our results show that the AO measurements have a higher sensitivity factor to the absorption change in the deeper location (177 % cm) than the optical measurements (16 % cm). For the two more superficial locations, the AO measurements have lower sensitivity factors (-5 % cm and 56 % cm) than the optical measurements (194 % cm and 101 % cm). This study has shown the potential of the AO technique for physiological monitoring, which requires a technique to be sensitive to oxygenation changes in the deeper layer while minimizing any contamination from the superficial layer.
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Terence S. Leung, Terence S. Leung, Sonny Gunadi, Sonny Gunadi, } "The sensitivity of acousto-optic sensing measurements to absorption changes in superficial and deep layers", Proc. SPIE 8223, Photons Plus Ultrasound: Imaging and Sensing 2012, 822326 (23 February 2012); doi: 10.1117/12.907839; https://doi.org/10.1117/12.907839
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