Abstract
We have developed a dual-beam Fourier domain optical Doppler tomography (FD-ODT) system to image zebrafish (Danio rerio) larvae. Two beams incident on the zebrafish with a fixed angular separation allow absolute blood flow velocity measurement to be made regardless of vessel orientation in a sagittal plane along which the heart and most of the major vasculature lie. Two spectrometers simultaneously acquire spectra from two interferometers with a typical (maximum) line rate of 18 (28) kHz. The system was calibrated using diluted milk and microspheres and a 0.5-mm thick flow cell. The average deviation from the set velocity from 1.4 to 34.6 mm/s was 4.1%. Three-dimensional structural raster videos were acquired of an entire fish, and through the head, heart, and upper tail of the fish. Coarse features that were resolved include the telencephalon, retina, both heart chambers (atrium and ventricle), branchial arches, and notochord. Other fine structures within these organs were also resolved. Zebrafish are an important tool for high-throughput screening of new pharmacological agents. The ability to generate high-resolution three-dimensional structural videos and accurately measure absolute flow rates in major vessels with FD-ODT provides researchers with additional metrics by which the efficacy of new drugs can be assessed.
Highlights
Fourier domain optical coherence tomography (FDOCT) is well suited for Doppler flowmetry [1]
The depth profile is acquired without moving parts, which results in improved phase stability and a decrease in the minimum detectable velocity threshold
In this paper we describe our extension of this approach with Fourier domain methodology and using two distinct channels for full range detection
Summary
Fourier domain optical coherence tomography (FDOCT) is well suited for Doppler flowmetry [1]. The depth profile is acquired without moving parts, which results in improved phase stability and a decrease in the minimum detectable velocity threshold. Short integration times increase the maximum detectable velocity threshold (before phase wrapping), further extending the flow measurement dynamic range. Low coherence techniques detect singly back-scattered light within the range gate of the interferometer and are sensitive only to the flow velocity vector parallel to the incident beam. The angle between the incident beam and the flow field must be precisely known before absolute velocity measurements can be calculated. If the angle between the beam and the flow field is unknown in all three dimensions, three separate measurements at different angles are required to fully resolve the absolute velocity
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