Simultaneous estimation of bidirectional particle flow and relative flux using MUSIC-OCT: phantom studies

Abstract

In an optical coherence tomography (OCT) scan from a living tissue, red blood cells (RBCs) are the major source of backscattering signal from moving particles within microcirculatory system. Measuring the concentration and velocity of RBC particles allows assessment of RBC flux and flow, respectively, to assess tissue perfusion and oxygen/nutrition exchange rates within micro-structures. In this paper, we propose utilizing spectral estimation techniques to simultaneously quantify bi-directional particle flow and relative flux by spectral estimation of the received OCT signal from moving particles within capillary tubes embedded in tissue mimicking phantoms. The proposed method can be directly utilized for in vivo quantification of capillaries and microvessels. Compared to the existing methods in the literature that can either quantify flow direction or power, our proposed method allows simultaneous flow (velocity) direction and relative flux (power) estimation.

Fig. 1

(A) A cross-section of the flow phantom structure. (B) Clutter rejected from structure measurements showing flowing particles (dB). (C) Estimated particle velocities (flow) based on MUSIC center frequency of the spectrum peak (shown from [−π π] in the rectangle area of Fig. 1(A). (D) Estimated moving particle flux based on MUSIC peak (dB). Color bars in dB. Scale bar = 400 μm.

Fig. 2

(A) Estimated flow rate by integrating total velocity of particles from the tube cross-section. The estimated flow follows a linear line as a function of syringe pump flow rate (r ≥ 0.99). (B) Estimated flux by integrating total MUSIC peak at the tube-cross section. The estimated flux is almost linear as a function of syringe pump flow rate (r ≥ 0.93).

Fig. 3

(A) Estimated velocity. Flow profiles of four syringe flow velocities (125, 150, 175 and 200 μL/min) along the tube with various concentration of particles. (B) Estimated MUSIC power peak for the profiles shown in Fig. 3(A). (C) Estimated MUSIC flux profile.

Fig. 4

Comparison between PRCD(A), PDV(B) and SV(C) methods of measuring total flow.