The PI proposes to develop ms/LCI (multiple scattering/low coherence interferometry) to image through thick tissues with multiply scattered light. The specific tasks proposed are: 1. Instrument development:The system will be modified to enable optical scanning and multispectral interferometric imaging. Optical scanning will improve the speed of acquiring 2D images while inclusion of multiple illumination wavelengths will allow recovery of important biochemical information such as hemoglobin concentration and oxygenation. 2. Theoretical modeling:To better understand the mechanisms of imaging contrast in this approach the PI will take a dual pronged effort to model the light propagation. An analytical form is presented which is based on a random walk formalism that will be used to evaluate this imaging modality. To validate this model, they will also use Monte Carlo modeling as well as comparing to experimental results. 3. Demonstrate imaging of hemoglobin distribution in thick tissues.To demonstrate the utility of the method, they will image hemoglobin distribution through thick (~1 cm) tissues. Samples will include tissue phantoms, designed to validate the method, and ex vivo animal tissues, such as muscle and fat as would be encountered in breast imaging and retinal samples as would be used in OCT ophthalmic imaging, where penetration to the choroid has remained a challenge.

The proposed research will advance a novel imaging modality with unique potential to extend imaging depth. In addition, new multispectral interferometry instrumentation will advance optical engineering while the proposed random walk model will advance understanding of light propagation in tissues.

Project Report

This goal of this research project was to extend the depth penetration of optical imaging to improve its utility. Usually, scattering limits how deeply light can penetrate into tissue without creating a hazy background which eventually dominates the image. Different approaches try to reject this scattered light and may reach depths of 1-2 millimeters. The approach we have developed here instead uses scattered light for imaging rather than trying to eliminate it. The outcomes of this project was indeed successful realization of a new imaging modality. Our ms2/LCI (multispectral, multiple scattering, low coherence interferometry scheme) was able to create images of objects embedded in tissues up to 9 mm deep (see Figure). Further, the approach was shown to be useful to enable discrimination of tissue health by analyzing optical properties measured with the approach. Specifically, we were able to see spectroscopic changes (differences between the way light of various colors interacts with tissue) that revealed the presence of burns. Thus, the intellectual merit of this work is that it has advanced a novel imaging modality that extends imaging depth while also provide a potentially new method for assessing burn severity in the clinic. The research findings offer a significant broader impact by the creation of a novel optical imaging modality with broad potential clinical utility. However, there was also significant efforts for practical professional training. The postdoctoral associate engaged in this research was trained to develop, validate and apply the imaging system to experiments with tissue phantoms and actual human tissues, a significant opportunity for a researcher engaged in translational biophotonics efforts. The results of the research were also disseminated through journal articles and conference presentations, offering further training opportunities.

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Duke University
United States
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