Position:  Postdoctoral Fellow

Current Institution:  Georgia Institute of Technology

Abstract:  Emerging Techniques in Contrast-Enhanced Ultrasound Imaging

Ultrasound — a real-time, high-resolution, portable, non-ionizing, and cost-effective imaging technique — continues to proliferate in the clinical environment. Unfortunately, contrast and consequently sensitivity and specificity of ultrasound imaging is relatively low compared to other imaging modalities. Therefore, ultrasound imaging is often combined with contrast agents, such as microbubbles, for more effective diagnosis and image-guided therapy.  Previously, we developed a noninvasive microsurgery strategy using ultrasonic microbubble cavitation to reduce cardiac tissue for hypertrophic cardiomyopathy treatment. However, one major limitation of traditional microbubbles is their micrometer size, which constrains them inside vessels and prevents them from reaching their extravascular targets. To address this limitation, we introduced a combined ultrasound-photoacoustic (USPA) imaging system and dual-modality imaging contrast agent — optically triggered perfluorohexane nanodroplets (PFHnDs). Under laser irradiation, these liquid nanodroplets can vaporize into gaseous microbubbles. In their liquid form, nanometer size PFHnDs can be delivered to compartments outside of vasculature, and once delivered, optically activated PFHnDs convert to microbubbles serving as contrast agents. The laser-induced vaporization of PFHnDs also provides photoacoustic contrast, which makes PFHnDs a dual USPA contrast agent.  A unique features of PFHnDs is that after activation, they stochastically condense to liquid droplets within a few milliseconds. The vaporization followed by recondensation can be triggered repeatedly upon each laser pulse, creating “blinking” ultrasound (and photoacoustic) signals. This enables super-resolution and contrast-enhanced ultrasound imaging. Furthermore, external manipulation of vaporization-recondensation dynamics can be used to increase imaging contrast or to assess the properties of tissue surrounding PFHnDs. As an example, I will present my recent work on using ultrasound imaging transmit pulse to manipulate dynamic behavior of optically vaporized PFHnDs. Finally, I will discuss the role of ultrasound together with light and nanotechnology in future research.”

Bio:
Yiying Zhu is a postdoctoral fellow in the Georgia Tech’s School of Electrical and Computer Engineering, where she works in the Ultrasound Imaging and Therapeutics Research Laboratory. The laboratory is an integral part of Georgia Institute of Technology and Emory University School of Medicine focusing on contemporary challenges in biomedical imaging and therapeutics.  She received a PhD in biomedical engineering (2017) and a master’s degree in electrical engineering (2013), both from the University of Michigan, where she received an Endowment for the Development of Graduate Education (2016) recognizing the impact of her dissertation research. She received a bachelor’s degree in electrical engineering from the University of Birmingham in the U.K. and a bachelor’s degree in telecommunication engineering from Huazhong University of Science and Technology in China in 2011.   Her research interest is to develop advanced imaging techniques using ultrasound together with light and nanotechnology. She aims to dedicate her career to teaching and research.