Coupling the chemical sensitivity of optical imaging and tissue-penetrating properties of ultrasound imaging, Carolyn Schutt, a Ph.D. student in bioengineering at the University of California, San Diego, is developing an imaging technique that could lead to highly sensitive light imaging deeper inside the body. The technique, which is promising for breast cancer diagnosis, received the grand prize at the UC San Diego Jacob School of Engineering Research Expo 2012, which took place last month.
Schutt's technique, which extracts chemical information from tissue scanned via ultrasound, uses gas-filled microbubble contrast agents that change their fluorescence intensity, or "blink," in response to the focused ultrasound. A solution of these microbubbles would be injected into the body to circulate through the bloodstream. When gas microbubbles encounter an ultrasound pressure wave, they contract and expand their outer surface in response to the pressure peaks and troughs. By loading the microbubble surface with a fluorescent dye that turns off when it is very close to other dye molecules, the ultrasound creates a blinking signal. Initially, less than 10% of the bubbles produced this modulating fluorescence. Analysis of the nanostructure by super-resolution microscopy showed that most of the dye partitioned into isolated clusters, which were likely preventing the dye from blinking in response to ultrasound. Schutt was able to manipulate the bubble nanostructure by heating the bubbles to melt their outer surface and distribute the dye more evenly, and then rapidly cooling them to lock in this distributed state. This melting and quick cooling process increased the fraction of blinking microbubbles to over 50%, making this a more viable imaging platform.
The blinking light can then be used to build up an image of the ultrasound-scanned tissue (a suspected tumor, for example) with the sensitivity and contrast offered by optical imaging. This capability could significantly improve present diagnostics as well as image-guided therapeutic capabilities. Schutt notes that X-ray mammography, the current standard, tends to yield a high false-positive rate, so the ability to extract chemical information could help to avoid unnecessary biopsies done on benign lesions.
Schutt, who was honored with the best poster award for the Department of NanoEngineering and Jacobs School-wide Rudee Outstanding Poster Award at the Research Expo, is also active in campus outreach and leadership programs. As a Gordon Scholar, Schutt participates in the Gordon Engineering Leadership Centerâs engineering leadership programs. In her current position as outreach chair of the Bioengineering Graduate Student Society, Schutt organized the groupâs exhibit at the recent San Diego Festival of Science and Engineering as well as a festival-wide science challenge for K-12 students to learn and discuss key science concepts.
For more information, please visit http://ucsdnews.ucsd.edu/newsrel/science/04-11OpticalImaging.asp.
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