A New Instrument for Continuous Measurement of Tissue Blood Flow by Light Beating Spectroscopy

TLDR

Light beating spectroscopy offers a theoretical basis for tissue blood‑flow measurement, and a detection technique is described that suppresses laser‑mode interference and wide‑band beam amplitude noise. A new instrument for measuring regional tissue blood flow using the laser Doppler principle is reported. The instrument uses a differential detector technique that reduces common‑mode noise to a negligible level, enabling suppression of laser‑mode interference and wide‑band beam amplitude noise without affecting the blood‑flow signal. The instrument proved highly stable and sensitive, allowing continuous tissue blood‑flow recordings in both laboratory and bedside settings.

Abstract

A new instrument for measurement of regional tissue blood flow based on the laser Doppler principle is reported. The theoretical background of light beating spectroscopy is discussed and a detection technique which makes possible the suppression of the adverse effects of laser-mode interference and wide-band beam amplitude noise is described. Instead of using a single square-law photodetector a differential detector technique is introduced that reduces common-mode noise to a negligible level, without influencing the blood flow related signal. The new instrument has proved to be highly stable and sensitive. Continuous recordings of tissue blood flow can be performed in the laboratory as well as at the bedside.