Fluorescence microscopy beyond the ballistic regime by ultrasound pulse guided digital phase conjugation

TL;DR

This paper introduces a novel fluorescence microscopy technique that surpasses traditional depth limits in scattering tissues by integrating ultrasound modulation with digital phase conjugation, enabling high-resolution 3D imaging deep inside biological samples.

Contribution

It presents a new method combining ultrasound pulse modulation and digital phase conjugation to achieve deep, 3D fluorescence imaging beyond the ballistic regime in scattering media.

Findings

Achieved imaging depth of up to thirteen scattering path lengths.

Enabled fluorescence and spectroscopy measurements inside highly scattering media.

Demonstrated near isotropic 3D localized sound-light interaction.

Abstract

Fluorescence microscopy has revolutionized biomedical research over the past three decades. Its high molecular specificity and unrivaled single molecule level sensitivity have enabled breakthroughs in a variety of research fields. For in vivo applications, its major limitation is the superficial imaging depth as random scattering in biological tissues causes exponential attenuation of the ballistic component of a light wave. Here we present fluorescence microscopy beyond the ballistic regime by combining single cycle pulsed ultrasound modulation and digital optical phase conjugation. We demonstrate near isotropic 3D localized sound-light interaction with an imaging depth as high as thirteen scattering path lengths. With the exceptionally high optical gain provided by the digital optical phase conjugation system, we can deliver sufficient optical power to a focus inside highly scattering media for not only fluorescence microscopy but also a variety of linear and nonlinear spectroscopy measurements. This technology paves the way for many important applications in both fundamental biology research and clinical studies.