Stephen A. Boppart, M.D., Ph.D. Assistant Professor, Department of Electrical and Computer Engineering, Bioengineering Resident Physician, College of Medicine University of Illinois at Urbana-Champaign Urbana, IL Optical Contrast Agents for Optical Coherence Tomography Contrast agents in medical and biological imaging enhance the sensitivity of detection and improve the diagnostic ability of the imaging technique by site-specifically labeling tissues or cells of interest. Optical coherence tomography (OCT) is an emerging biomedical imaging technology that can perform high-resolution “optical biopsies” of tissue microstructure in situ and in real-time. Despite the integration of OCT into multiple medical and biological disciplines, no optical contrast agents have been developed for this technology. To date, OCT has relied on inherent optical scattering differences within tissue, often limiting the diagnostic capability. OCT is capable of cellular-resolution imaging and may ultimately have a role in the early diagnosis of human malignancies. Although morphological differences between normal and neoplastic tissue can be obvious at later stages of tumor development, limitations for OCT detection remain for early-stage tumors or for tumors that are morphologically (or optically) similar to surrounding normal tissue. The goal of this project, therefore, is to develop and investigate optical contrast agents for OCT to enhance diagnostic imaging capabilities and to enable site-specific labeling of tissue structures and cells, including early-stage and metastatic tumors. A potential class of OCT contrast agents includes protein-coated microspheres generated with high-intensity ultrasound sonication techniques. These microspheres are capable of encapsulating air, melanin, or particles that alter the OCT beam. In addition, their protein shell can be modified to localize the contrast agent to early-stage tumors. The specific aims of this project include: Generate potential OCT optical contrast agents such as air-filled microspheres and isolated and microencapsulated particles that scatter or absorb the incident OCT beam. Characterize OCT contrast agents in artificial tissue models using optical techniques including oblique-incidence optical fiber reflectometry and high-resolution OCT imaging at multiple near-infrared wavelengths. Modify the surface proteins of microspheres to alter in vivo properties and to enable localization to tumors in animal models. The development and use of optical contrast agents for OCT imaging will permit site-specific labeling of tumors, thereby enhancing the ability of OCT to detect early neoplastic changes in vivo, and improve the visualization of tumors during image-guided surgical resections. Copyright 2001 The Whitaker Foundation 1700 North Moore Street, Suite 2200, Arlington VA 22209 (703) 528-2430     info@whitaker.org