High Resolution, Deep Imaging Using Confocal Time-of-flight Diffuse Optical Tomography

TL;DR

This paper introduces a confocal time-of-flight diffuse optical tomography technique that achieves millimeter resolution in deep tissue imaging, significantly faster reconstruction, and paves the way for real-time, high-resolution imaging beyond traditional limits.

Contribution

The paper presents a novel confocal ToF-DOT method with multiplexed illumination and a fast reconstruction algorithm, enabling millimeter resolution and real-time imaging deep within tissue.

Findings

Achieved millimeter spatial resolution in highly scattered tissue.

Reduced reconstruction time by 100 times using a new convolutional approximation.

Demonstrated potential for real-time deep tissue imaging.

Abstract

Light scattering by tissue severely limits how deep beneath the surface one can image, and the spatial resolution one can obtain from these images. Diffuse optical tomography (DOT) is one of the most powerful techniques for imaging deep within tissue -- well beyond the conventional $\sim$10-15 mean scattering lengths tolerated by ballistic imaging techniques such as confocal and two-photon microscopy. Unfortunately, existing DOT systems are limited, achieving only centimeter-scale resolution. Furthermore, they suffer from slow acquisition times and slow reconstruction speeds making real-time imaging infeasible. We show that time-of-flight diffuse optical tomography (ToF-DOT) and its confocal variant (CToF-DOT), by exploiting the photon travel time information, allow us to achieve millimeter spatial resolution in the highly scattered diffusion regime ($> 50 $ mean free paths). In addition, we demonstrate two additional innovations: focusing on confocal measurements, and multiplexing the illumination sources allow us to significantly reduce the measurement acquisition time. Finally, we rely on a novel convolutional approximation that allows us to develop a fast reconstruction algorithm, achieving a 100$\times$ speedup in reconstruction time compared to traditional DOT reconstruction techniques. Together, we believe that these technical advances serve as the first step towards real-time, millimeter resolution, deep tissue imaging using DOT.