Previous research has shown that after electrical stimulation of peripheral nerves, changes in optical properties occur in the surrounding tissue. Understanding the origins of these optical changes may lead to development of a clinical tool for the early detection of peripheral neuropathy. This study used light at 690 nm and 830 nm from laser diodes to probe four separate tissue regions atop the median nerve in the forearm during electrical stimulation of the same median nerve in the palm of the hand in healthy subjects. Optical measurements were made during baseline and vascular occlusion conditions. Changes in optical intensity after stimulation represent an optical response peaking between 80 and 160 ms post-stimulus. Optical responses during baseline showed positive and negative optical responses occurring in different regions, with one subject showing an optical response of -0.3% at 690 nm and -0.4% at 830 nm in one region and +0.2% at 690 nm and +0.5% at 830 nm in another region. These results are consistent with the vascular responses to nerve stimulation where positive or negative optical responses would be induced by different positions of the vasculature relative to the optical measurement location. In a different subject who underwent both venous and arterial occlusion, positive and negative optical responses were also seen in different regions. The optical response during venous occlusion was +0.8% at 690 nm and +1% at 830 nm in one region, and -0.8% at 690 nm and -1% at 830 nm in another region, and similar results were also seen during arterial occlusion in this subject. The fact that the wavelength-dependence of the optical response is largely unaffected by vascular occlusion further suggests that the vasculature, featuring a large optical contrast in tissues, is inducing the optical response.
|Commitee:||Bergethon, Peter, Cronin-Golomb, Mark|
|School Location:||United States -- Massachusetts|
|Source:||MAI 47/05M, Masters Abstracts International|
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