Path length resolved optical Doppler perfusion monitoring

Laser Doppler blood flowmetry is a non-invasive technique for monitoring blood microcirculation in biological tissues and has been used in clinics for last three decades [1]. In spite of its important advantages such as high spatial resolution, noninvasiveness and real-time monitoring, this technique has several problems limiting its use in clinical practice [2,3]. This is partly caused by the fact that LDPM cannot measure in absolute flow units, by the large flux-signal fluctuations and by the lack of standardization of laser Doppler perfusion monitors. The complexity and randomness of the microvascular network further complicates the measurement situation. An important limitation of this technique is the dependence of perfusion signal on the photon path lengths [4-6]. Coherence domain path length resolved optical Doppler perfusion monitoring, of which the basic technique is developed in this thesis, will overcome this limitation. This will enable to correctly interpret the inter-and intra-individual variations in the LDF readings introduced by the variance in individual photon path lengths due to changes in tissue optical properties and probe geometry.