Multicore fiber bundles for imaging and stimulating optogenetically modified neurons have been largely adopted in neurophotonics research. They allow for directed, single-cell stimulation and imaging of neuronal activity. An inherent limitation of these bundles is the presence and detection of the empty space between individual fibers, resulting in a loss of significant amounts of data, and reduced image quality due to pixilation effects. We propose a novel approach and algorithm to depixelation and image reconstruction from fiber bundles that utilizes multiple image frames collected during on-axis fiber bundle rotation. The approach involves first acquiring the Fourier transform of a stationary, unrotated image, followed by its rotated counterparts. The phase information from each image is then acquired, cross-correlated, and the angle of rotation determined from this correlation. Rotated images are then weighed and summed to generate a final reconstructed, depixelated image. Simulations were initially performed using Matlab demo images. Experimentation was done with a resolution chart, and thereafter with a cell culture. 488 nm and 561 nm continuous wave laser sources (Coherent, Inc.) were used for imaging GCaMP6s and C1V1-mCherry, respectively, in hippocampal neuronal cultures. The light sources were coupled to a multicore fiber bundle (Schott, 1534702) containing 4,200, 7.5 µm fibers. Cell cultures were prepared from 2 day old transgenic mice (GCaMP6s, Jackson Labs) transfected with C1V1(E122T/E162T)-TS-p2A-mCherry (Karl Deisseroth, Stanford). The results demonstrate this as an effective technique alongside fiber bundle imaging, serving as a useful and powerful tool for removing undesired artifacts associated with these fibers.
Carlos Renteria, Javier Suarez, Parijat Sengupta, and Stephen A. Boppart, "Reconstruction and depixelation of multicore fiber bundle images by fiber bundle rotation (Conference Presentation)," Proc. SPIE 10481, Neural Imaging and Sensing 2018, 104810Q (Presented at SPIE BiOS: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291297.5751488533001.
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