Abstract
Cardiac and respiratory motions in animals are the primary source of image quality degradation in dynamic imaging studies, especially when using phase-resolved imaging modalities such as spectral-domain optical coherence tomography (SD-OCT), whose phase signal is very sensitive to movements of the sample. This study demonstrates a method with which to compensate for motion artifacts in dynamic SD-OCT imaging of the rodent cerebral cortex. We observed that respiratory and cardiac motions mainly caused, respectively, bulk image shifts (BISs) and global phase fluctuations (GPFs). A cross-correlation maximization-based shift correction algorithm was effective in suppressing BISs, while GPFs were significantly reduced by removing axial and lateral global phase variations. In addition, a non-origin-centered GPF correction algorithm was examined. Several combinations of these algorithms were tested to find an optimized approach that improved image stability from 0.5 to 0.8 in terms of the cross-correlation over 4 s of dynamic imaging, and reduced phase noise by two orders of magnitude in ~8% voxels.
Highlights
Optical coherence tomography (OCT) has provided an unprecedented tool for label-free structural imaging of biological systems [1]
We hypothesize that respiratory and cardiac motions will mainly cause, respectively, bulk image shifts (BISs) and global phase fluctuations (GPFs); a crosscorrelation maximization-based method will be effective for BIS compensation; GPFs will be suppressed by removing phase variations that are global in either the axial or the lateral direction; and an appropriate combination of BIS and GPF correction algorithms will sufficiently suppress motion artifacts
When this non-origincentered GPF (NGPF) correction was applied to each voxel independently, 97.0% of the voxels showed a decrease in noise, which was 1.5% larger than that yielded by the GPF correction in the previous section
Summary
Optical coherence tomography (OCT) has provided an unprecedented tool for label-free structural imaging of biological systems [1]. A 1-μm axial movement produces a large fluctuation of ~10 rad in the phase of the OCT signal when the center wavelength of the light source is 1300 nm Such motion-oriented noise becomes problematic in studies monitoring biological systems for a relatively long time (longer than several cycles of cardiac/respiratory motions). In this paper we propose a motion correction method that requires no external aid and is especially suitable for phase-resolved dynamic OCT imaging To this end, we hypothesize that respiratory and cardiac motions will mainly cause, respectively, bulk image shifts (BISs) and global phase fluctuations (GPFs); a crosscorrelation maximization-based method will be effective for BIS compensation; GPFs will be suppressed by removing phase variations that are global in either the axial or the lateral direction; and an appropriate combination of BIS and GPF correction algorithms will sufficiently suppress motion artifacts. Received 1 Apr 2011; revised 16 Jun 2011; accepted 21 Jun 2011; published 12 Oct 2011 24 October 2011 / Vol 19, No 22 / OPTICS EXPRESS 21259
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