Quantifying the influence of Bessel beams on image quality in optical coherence tomography

Abstract

Light scattered by turbid tissue is known to degrade optical coherence tomography (OCT) image contrast progressively with depth. Bessel beams have been proposed as an alternative to Gaussian beams to image deeper into turbid tissue. However, studies of turbid tissue comparing the image quality for different beam types are lacking. We present such a study, using numerically simulated beams and experimental OCT images formed by Bessel or Gaussian beams illuminating phantoms with optical properties spanning a range typical of soft tissue. We demonstrate that, for a given scattering parameter, the higher the scattering anisotropy the lower the OCT contrast, regardless of the beam type. When focusing both beams at the same depth in the sample, we show that, at focus and for equal input power and resolution, imaging with the Gaussian beam suffers less reduction of contrast. This suggests that, whilst Bessel beams offer extended depth of field in a single depth scan, for low numerical aperture (NA < 0.1) and typical soft tissue properties (scattering coefficient, μs = 3.7 mm−1 and high scattering anisotropy, g > 0.95), superior contrast (by up to ~40%) may be obtained over an extended depth range by a Gaussian beam combined with dynamic focusing.

Enhancement of image quality and imaging depth with Airy light-sheet microscopy in cleared and non-cleared neural tissue

“…This property has been extensively studied in both Bessel beams [12–14] and Airy beams [14–19], but all previous studies have only considered amplitude based obstructions whereas biological tissue is an ensemble of complex (amplitude and phase) objects. Recently, alternative mechanisms for the enhancement of Bessel beam-based imaging modalities have been proposed [20], which warrants further fundamental investigation. However, studies of a more applied nature are of equal merit.…”

Measurement of dynamic cell-induced 3D displacement fields in vitro for traction force optical coherence microscopy

“…Photon collection in beam-scanned OCM can be enhanced via the use of Bessel beam illumination, that can provide spatiallyinvariant transverse resolution and uniform photon collection over an extended depth range [68,69]. This approach requires use of separate illumination and collection beams (that can be difficult to align in practice) to enhance SNR [70,71], and is yet to demonstrate cell imaging over a depth range greater than ~200-300 μm.…”

“…While OCM images do suffer from aberrations, defocus, and a decrease in signal strength away from the focal plane, the development of hardware-and computationbased methods to mitigate these issues is an active and promising area of research in the field. For example, alternative signal collection schemes like Bessel beam illumination, dynamic focusing [71], and Gabor domain OCM [72] help maintain resolution and signal collection over large depth ranges. Computational methods like interferometric synthetic aperture microscopy [34] and CAO [35,[73][74][75] allow for the mitigation of defocus and aberrations, respectively.…”

Development of a reliable and reproducible phantom manufacturing method using silica microspheres in silicone

“…The initial phantom manufacturing method used (from here on denoted the "original method") was developed and successfully employed by Curatolo et al 13 The improved method was subsequently established after problems were encountered during implementation of the original method. All phantoms made using the original and improved methods were constructed using silica microspheres of 1-μm diameter, (Monospher ® 1000, Merck, Darmstadt, Germany) embedded within a 2-part addition curing, room temperature vulcanizing silicone rubber Elastosil ® RT 601 (Wacker Chemie AG, Munich, Germany).…”

“…7,8,10 The procedure presented by Bisaillon et al 7 for incorporating silica microspheres into silicone rubber is considered a robust method for producing phantoms with homogenously distributed microspheres, however alternative, often simpler methods for producing such phantoms have also been presented. 5,6,8 In this study, we present an existing method used by Curatolo et al 13 and discuss the problems encountered during its implementation. We devised an improved method to overcome the problems encountered during the implementation of the original method.…”