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Dartmouth Engineer - The Magazine of Thayer School of EngineeringDartmouth Engineer - The Magazine of Thayer School of Engineering

Light Scattering Device Could Quickly Detect Cancer and Guide Surgery

By Anna Fiorentino
September 2015 • Thayer By Degrees:

PhD student David “Bo” McClatchy ’13 placed his scarred hand under a small light projector. Minutes later, the device had analyzed the resulting images for differences between McClatchy’s normal skin and his scar—based on the light-scattering properties of the tissue. The results became part of a study published in 2014 and was the first evidence that this imaging technique could be used to detect cancer and guide breast tumor resections.

Currently, the standard of practice for determining if the margins of tissue are free of residual cancer after a breast cancer resection is by microscopic sampling of tissue by a pathologist—a process that is so slow that if margins are not clear, the patient must return for a second operation days later. While the concept of using light to determine if tissue is normal or cancerous has been researched for years, this new device significantly speeds up the process.

Bo McClatchy
David “Bo” McClatchy ’13

“Processing the tissue so that it can be fixed, cut, stained, and evaluated by a pathologist takes one to two days,” says McClatchy. “We hope that our technique will help guide surgeons during breast-conserving surgery and give them insight as to whether there might be residual cancer on the margins of the resected specimen.”

McClatchy and the rest of the self-proclaimed “Light Scattering Team” in the Optics in Medicine Lab at Dartmouth are the first to use this approach to quantify the scattering of light in the outer layer of tissue. Included on that team, lead by Professors Brian Pogue and Keith Paulsen, are assistant professors Stephen Chad Kanick and Venkataramanan Krishnaswamy, as well as Jonathan Elliot, Research Associate and Postdoctoral Fellow and Lecturer in Cancer Research.

Suspended above the tissue, the projector emits patterns of light and a camera measures the light intensity bouncing off the tissue surface. This technique creates clear and detailed images of small tissue structures superior to the blurry images offered by existing wide-field optical imaging methods.

“By only probing the outer layer of tissue through high spatial frequency domain imaging, one can gain sensitivity to the amount of backscattered light relative to diffusive multiply scattered light,” McClatchy says. “Then by analyzing this effect at multiple wavelengths of light, it’s possible to quantify the direction of light scattering.”

“They figured out many years ago here at Dartmouth that to successfully detect cancer or guide surgery, you need to obtain a measurement that localizes light from tiny points on tissue,” says Kanick. “But until this new technique, optical measurement of the tissue involved sampling at one pixel, scanning that point across the tissue surface and measuring it again—a process that took hours even to do a tiny piece of tissue.”

It’s taken the team six years to trim this measurement process down to minutes.

“We started using structured light imaging for this purpose about three years ago, and my own work has focused on using this type of measurement to quantitatively image tissue microstructure,” says Kanick. “We have many projects that are reaching the publication-phase, where we will show new types of images of tissue microstructure that have not previously been shown.”

Light Scattering Device
The new device located in the Advanced Imaging Center at Dartmouth-Hitchcock.

The “Light Scattering Team” published their proof of concept demonstrating that sub-diffusive light scattering works and experimentally validating the model on a tissue—including McClatchy’s hand scar—in a journal by the Optical Society of America in 2014 and have since presented their findings at conferences.

McClatchy, who’s primary role is performing experiments and helping interpret and analyze results, first began documenting the light scattering results as an undergrad at Thayer. 

“I was enrolled in the MS Program after getting my AB with Brian Pogue as my advisor, and was planning on obtaining a BE/MS,” says McClatchy. He became interested in using light scattering in breast imaging and transferred to the PhD Program in the fall of 2013.

While this work is still in the early stages, the group has a project from the National Institute of Standards and Technology aimed at standardizing the scattering approach so that other groups in the field can compare observations. The team is also starting a new project that images freshly resected breast tissue by combining the wide-field optical technique with X-ray computed tomography. This work is in collaboration with PerkinElmer, through a recently awarded grant from the National Institutes of Health. 

“Looking forward, the ultimate goal of this system is to guide resections during breast conserving surgery by giving the surgeon both tomographic information about the specimen's core with the CT and superficial morphology information with the optics,” says McClatchy.

Tags: alumni, engineering in medicine, faculty, innovation, research, students

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