Transversal ultrasound light guiding deep into scattering media

TL;DR

This paper introduces a novel ultrasound-guided light delivery method that significantly enhances deep tissue optical penetration, overcoming scattering limitations for biomedical applications.

Contribution

The study demonstrates a new ultrasound-based technique to create waveguides in scattering media, enabling deeper light penetration than previous methods.

Findings

Waveguides support light propagation up to 20 mm deep in tissue phantoms.

Ultrasound-induced structures increase light intensity in deep tissue regions.

Method shows potential for improved optical diagnostics and treatments in biomedicine.

Abstract

Biomedical applications requiring tissue diagnosis, activation, and treatment could be substantially leveraged by optical methods, owing to their unique feature set. However, their widespread application is severely limited by the strong light scattering that occurs in many tissues of interest, which dramatically limits achievable penetration depths. Here we demonstrate a new method to solve this issue by utilizing free-running ultrasound waves, transversal to the light propagation direction, to guide light into deeper tissue regions. We study the formation of the ultrasound-induced refractive index structures and waveguides using simple ultrasound field configurations and analyze their effects on the propagation of short light pulses. Our results show waveguide support and associated light intensity increase up to the depths of at least 20 mm in Intralipid-20% phantoms with a reduced scattering coeffcient close to real tissue. Thus we present an important milestone towards low-loss light delivery, focusing and manipulation in deep tissue.