Abstract
Bessel beams have recently been investigated as a means of improving deep-tissue microscopy in highly scattering and heterogeneous media. It has been suggested that the long depth-of-field and self-reconstructing property of a Bessel beam enables an increased penetration depth of the focused beam in tissues compared to a conventional Gaussian beam. However, a study is needed to better quantify the magnitude of the beam steering as well as the distortion of focused Gaussian and Bessel beams in tissues with microscopic heterogeneities. Here, we have developed an imaging method and quantitative metrics to evaluate the motion and distortion of low-numerical-aperture (NA) Gaussian and Bessel beams focused in water, heterogeneous phantoms, and fresh mouse esophagus tissues. Our results indicate that low-NA Bessel beams exhibit reduced beam-steering artifacts and distortions compared to Gaussian beams, and are therefore potentially useful for microscopy applications in which pointing accuracy and beam quality are critical, such as dual-axis confocal (DAC) microscopy.
Highlights
In recent years, there has been a renewed interest in exploiting Bessel beams as a form of illumination for deep-tissue laser-scanning microscopy [1,2,3,4,5,6,7]
In previous studies with tissue-like phantoms, our group and others have observed that heterogeneity-induced beam steering leads to a degradation in spatial resolution for dual-axis confocal (DAC) microscopy [24, 25]
When imaging beam foci within phantoms and fresh tissues, the motions of the Bessel beams were significantly reduced as compared to the Gaussian beams, indicating that Bessel beams are less sensitive to the heterogeneity-induced beam steering generated by these samples
Summary
There has been a renewed interest in exploiting Bessel beams as a form of illumination for deep-tissue laser-scanning microscopy [1,2,3,4,5,6,7]. There are two prominent features of a Bessel beam: its “non-diffracting” and “selfreconstructing” properties These features have been shown to benefit laser-scanning microscopy in large specimens with micro-architectural heterogeneities, such as cell clusters or embryos [1, 2]. The “self-reconstructing” property refers to the ability of this main lobe to propagate through highly heterogeneous media, even in the presence of obstructions that may block or distort the main lobe temporarily [2, 4, 11] This self-healing behavior is aided by the fact that each side lobe of a Bessel beam carries approximately the same amount of energy as the main lobe and continuously acts to reconstruct the main lobe as
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