University of Rochester SPIE Student Chapter

Himanshu Shekhar
Electrical and Computer Engineering

Assessment of Cardiovascular Risk with Nonlinear Intravascular Ultrasound Imaging

Tuesday, August 30
12:00- 1:00 PM
Goergen 101

Coronary Artery Disease (CAD) is a leading cause of death in America. It is characterized by the deposition of plaque on the walls of the coronary arteries of the heart. Heart attacks occur when high-risk plaques rupture in the advanced stages of CAD, causing clots that block the oxygen supply to the heart, often resulting in death.

Currently, a significant issue facing cardiologists is that of reliably identifying rupture prone plaque. If plaque vulnerability can be objectively assessed, aggressive drug therapy/ interventional methods can be employed to save those most at risk. However, X-ray angiography, the current clinical imaging technique for coronary imaging, is limited in its ability to assess plaque vulnerability.

My presentation will provide an overview of our efforts towards developing a diagnostic imaging technique to reliably predict the rupture proneness of coronary plaque.

We are adapting Intravascular Ultrasound (IVUS), for the assessment of the functional features of CAD by exploiting the nonlinear acoustic behavior of Ultrasound Contrast Agents. Intravascular Ultrasound uses high frequency ultrasound to generate cross sectional images of the anatomy of the coronary artery with a catheterized transducer. Ultrasound Contrast Agents are stabilized micrometer sized bubbles, which enable the imaging of plaque vulnerability markers, such as neovascularity and perfusion. Nonlinear acoustic backscatter from ultrasound contrast agents enables higher imaging specificity.

My presentation would discuss the advantages associated with nonlinear imaging modes, the dynamics of ultrasound contrast agents and

Dr. Robert Saunders
Program Officer
Roundtable on Value and Science-Driven Health Care
Institute of Medicine of the National Academics

An Overview of Science Policy Careers

Tuesday, August 23
12:15- 2:00 PM
Goergen 108

The term science policy encompasses two disparate concepts: one is considering the policies for the scientific enterprise (such as research funding or stem cell research guidelines), while the second is applying scientific knowledge to pressing public policy questions (such as energy policy or security). While science plays a role in deciding these policies, other factors come into
play as well, including political considerations, economic factors, and values. Given this complexity, what role can scientists play? In addition to considering the role of science in science policy, this talk will also explore career paths in science policy and how students can enter this arena.

Yuzhe Xiao
The Institute of Optics

Adiabatic Wavelength Conversion in Travelling-wave and Resonant Photonic Structures

Tuesday, August 16
12:00- 1:00 PM
Goergen 101

All-optical signal processing, especially wavelength conversion plays a crucial role in modern lightwave systems. Many ways of wavelength conversion use nonlinear effects that require high power and phase matching. Recently, it was found that the spectrum of light can change inside a linear medium whose refractive index changes with time. The term adiabatic wavelength conversion (AWC) is used to describe this optical phenomenon. Methods such finite-difference time-domain (FDTD) simulations and a modal approach, have been used to study this effect. In this talk, we present a new approach for understanding AWC by developing a linear system model for the dynamic photonic structures. The model is first applied to a travelling-wave device to reveal a new physical picture of AWC: a rescaling of transit time by dynamic refractive index changes of the medium. We show that temporal changes in the refractive index not only shift the pulse spectrum but also lead to pulse compression and spectral broadening as well as to phase changes. In the optical resonators, our approach correctly predicts the spectral shift related to AWC. More importantly, it allows us to study the temporal and spectral evolution of an optical pulse that has been ignored so far. Our method is applicable to a broad range of integrated photonic structures, including silicon micro-rings and photonic crystal resonators, and is useful for applications ranging from all-optical signal processing to routing, as well as optical buffering.