Fig. 1. Experimental setup of a phase-sensitive MR-OCT system based on a bulk optics configuration. L1–L4, lenses; BS, beam splitter; ND, neutral density filter; AMP, VCM amplifier; OW; optical window; GD, galvo driver; CT, capillary tube; SP, syringe pump.

Fig. 2. Flow chart for MR-OCT phase data processing. Signal processing includes a band-pass filter for each order of reflection m. The phase signal is derived from the complex signal by use of a Hilbert transformation.

Fig. 3. Structural and phase difference images of a 300 μm capillary tube filled with 5% intralipid solution with a Doppler angle of 50°. (a) The successive structural images corresponding to twelve orders of reflection. The scan range for the first order was ∼60μm and the twelfth order was ∼720μm. (b) Stitched image of all twelve orders shown in (a). (c) The corresponding phase difference images of all orders shown in (a) and (d) the stitched phase difference image. Scale bar: 250 μm.

Fig. 4. Measured system sensitivity of the MR-OCT system for twelve orders of reflection. The measurement was recorded with a mirror as a sample and by placing a neutral density filter (OD=2) in the sample arm.

Fig. 5. Determination of phase sensitivity calculating the standard deviation on the phase fluctuations. (a) The phase fluctuations between the sequential A lines of the first-order reflection. (b) The calculated phase sensitivity of the MR-OCT system for twelve orders of reflection. The phase difference was recorded using a static mirror as the sample and by placing a neutral density filter (OD=2) in the sample arm path.

Fig. 6. MR-OCT phase difference images of 5% intralipid solution flowing through a capillary tube measured at various flow rates with a Doppler angle of 50°. (a) Structural image of a 300 μm capillary tube filled with intralipid solution. (b) Phase difference image at 0 μm/s and (c)–(h) phase difference images at 50, 100, 150, 200, 250, and 300 μm/s. PW, phase wrap. Scale bar: 250 μm.

Fig. 7. Validation of the phase measurements that are shown in Fig. 6. (a) Phase profile along the center of the capillary tube (horizontal) and the corresponding second-order polynomial fit at each flow rate. (b) Comparison of measured and pump velocity.

Fig. 8. In vivo chicken embryo imaging with phase-sensitive MR-OCT system. (a) Structural image of a chicken embryo vessel and (b) the corresponding phase difference image. (c) The A line and phase profile taken at two different positions P1 and P2. Scale bar: 500 μm.