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Proceedings Paper

Oxygen saturation in free-diving whales: optical sensor development
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Paper Abstract

Mass stranding of live whales has been explained by proposing many natural or human-related causes. Recent necropsy reports suggest a link between the mass stranding of beaked whales and the use of naval mid-frequency sonar. Surprisingly, whales have experienced symptoms similar to those caused by inert gas bubbles in human divers. Our goal is to develop a compact optical sensor to monitor the consumption of the oxygen stores in the muscle of freely diving whales. To this end we have proposed the use of a near-infrared phase-modulated frequency-domain spectrophotometer, in reflectance mode, to probe tissue oxygenation. Our probe consists of three main components: radiofrequency (RF) modulated light sources, a high-bandwidth avalanche photodiode with transimpedance amplifier, and a RF gain and phase detector. In this work, we concentrate on the design and performance of the light sensor, and its corresponding amplifier unit. We compare three state-of-the-art avalanche photodiodes: one through-hole device and two surface-mount detectors. We demonstrate that the gain due to the avalanche effect differs between sensors. The avalanche gain near maximum bias of the through-hole device exceeds by a factor of 2.5 and 8.3 that of the surface-mount detectors. We present the behavior of our assembled through-hole detector plus high-bandwidth transimpedance amplifier, and compare its performance to that of a commercially available module. The assembled unit enables variable gain, its phase noise is qualitatively lower, and the form factor is significantly smaller. Having a detecting unit that is compact, flexible, and functional is a milestone in the development of our tissue oxygenation tag.

Paper Details

Date Published: 21 February 2013
PDF: 8 pages
Proc. SPIE 8592, Biomedical Applications of Light Scattering VII, 859201 (21 February 2013); doi: 10.1117/12.2008547
Show Author Affiliations
Enoch Gutierrez-Herrera, Wellman Ctr. for Photomedicine and Harvard Medical School (United States)
Paulino Vacas-Jacques, Wellman Ctr. for Photomedicine and Harvard Medical School (United States)
Rox Anderson, Wellman Ctr. for Photomedicine and Harvard Medical School (United States)
Warren Zapol, Massachusetts General Hospital (United States)
Walfre Franco, Wellman Ctr. for Photomedicine and Harvard Medical School (United States)

Published in SPIE Proceedings Vol. 8592:
Biomedical Applications of Light Scattering VII
Adam P. Wax; Vadim Backman, Editor(s)

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