Volumetric non-local-means based speckle reduction for optical coherence tomography

Abstract

We present a novel tomographic non-local-means based despeckling technique, TNode, for optical coherence tomography. TNode is built upon a weighting similarity criterion derived for speckle in a three-dimensional similarity window. We present an implementation using a two-dimensional search window, enabling the despeckling of volumes in the presence of motion artifacts, and an implementation using a three-dimensional window with improved performance in motion-free volumes. We show that our technique provides effective speckle reduction, comparable with B-scan compounding or out-of-plane averaging, while preserving isotropic resolution, even to the level of speckle-sized structures. We demonstrate its superior despeckling performance in a phantom data set, and in an ophthalmic data set we show that small, speckle-sized retinal vessels are clearly preserved in intensity images and in two orthogonal, cross-sectional views. TNode does not rely on dictionaries or segmentation and therefore can readily be applied to arbitrary optical coherence tomography volumes. We show that despeckled esophageal volumes exhibit improved image quality and detail, even in the presence of significant motion artifacts.

Quantitative reconstruction of time-varying 3D cell forces with traction force optical coherence microscopy

“…Additional future experiments will be needed to determine whether the loss of fine cellular structures by our algorithm has any significant impact on the accuracy of CTF reconstructions. More advanced algorithms may yield improved cell tracings with higher fidelity 30 , and this aspect of TF-OCM merits further work. Future iterations of TF-OCM may also benefit from the incorporation of hardware-based speckle reduction methods 31,32 .…”

“…This study required the use of speckle reduction methods to perform TF-OCM based on automated analysis of time-lapse OCM image data. Future implementations of TF-OCM based purely upon OCT/OCM imaging will likely continue to rely on speckle reduction procedures 30-32 . However, TF-OCM could also be performed in conjunction with co-registered fluorescence imaging to capture images of cell geometry without speckle.…”

Speckle reduction in visible-light optical coherence tomography using scan modulation

“…Other techniques include multiwavelength averaging, 12 , 13 modulation of light wavefront, 14 and nonlocal, software-based averaging. 15 …”

Aperture phase modulation with adaptive optics: a novel approach for speckle reduction and structure extraction in optical coherence tomography

“…A weakness of these methods is that the number of uncorrelated speckle patterns that can be created is typically small, limiting the degree of speckle suppression by averaging. Speckle reduction methods using digital post-processing have also been proposed [21][22][23][24][25]. However, digital post-processing usually reduces speckle by spatial averaging or filtering, which necessarily reduces image resolution.…”