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Journal of Biomedical Optics • Open Access

Spatial sensitivity of acousto-optic and optical near-infrared spectroscopy sensing measurements
Author(s): Sonny Gunadi; Terence S. Leung

Paper Abstract

Near-infrared spectroscopy (NIRS) is a popular sensing technique to measure tissue oxygenation noninvasively. However, the region of interest (ROI) is often beneath a superficial layer, which affects its accuracy. By applying focused ultrasound in the ROI, acousto-optic (AO) techniques can potentially minimize the effect of physiological changes in the superficial layer. Using absorption perturbation experiments in both transmission and reflection modes, we investigated the spatial sensitivity distributions and mean penetration depths of an AO system based on a digital correlator and two popular NIRS systems based on i. intensity measurements using a single source and detector configuration, and ii. spatially resolved spectroscopy. Our results show that for both transmission and reflection modes, the peak relative sensitivities of the two NIRS systems are near to the superficial regions, whereas those of the AO technique are near to the ROIs. In the reflection mode, when the ROI is deeper than 14 mm, the AO technique has a higher absolute mean sensitivity than the two NIRS techniques. As the focused ultrasound is moved deeper into the turbid medium, the mean penetration depth increases accordingly. The focused ultrasound can shift the peak relative sensitivity of the AO measurement toward its focused region.

Paper Details

Date Published: 1 December 2011
PDF: 11 pages
J. Biomed. Opt. 16(12) 127005 doi: 10.1117/1.3660315
Published in: Journal of Biomedical Optics Volume 16, Issue 12
Show Author Affiliations
Sonny Gunadi, Univ. College London (United Kingdom)
Terence S. Leung, Univ. College London (United Kingdom)


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