Novel approach to laser Doppler measurement of pulpal blood flow

A modified laser Doppler flowmetry technique that significantly improves the performance of the current technique in measuring pulpal blood flow is described. A preliminary model demonstrates that, by using a forward-scattered geometry, the detected signal will have a much higher signal-to-noise ratio and calibration capacity. The forward-scattered signal is readily detectable because teeth are relatively thin organs with moderate optical loss. Preliminary experiments comparing forward-scattered detection with conventional back-scattered detection were carried out using an extracted, perfused human molar. The results showed that: (1) the existing back-scattering method produced readings that fluctuated by as much as 187% in response to small changes in sensor position relative to the tooth and (2) the forward-scattered method produced consistent readings (within 10%) that were independent of the sensor position, a signal-to-noise ratio that was at least 5.6 times higher than that obtained by the back-scattering method, and a linear response to flow rate. The results validated the findings of the preliminary model and clearly showed the superiority of the forward-scattering geometry. © 1997 Society of Photo-Optical Instrumentation Engineers