As a noninvasive imaging modality, optical coherence tomography (OCT) has been proven useful for early diagnosis of malignant cancers as well as image-guided interventions. However, OCT is only effective for subsurface imaging due to the limited penetration depth of light. To overcome this limitation, endoscopic OCT has been developed in which a flexible OCT probe is inserted into a body cavity for imaging internal organs. Current endoscopic probes, implemented based on the fiber optic Michelson interferometer (FOMI), fiber optic Mach-Zehnder interferometer (FOMZI), or fiber optic Fizeau interferometer (FOFI), have a number of drawbacks such as poor phase stability, downlead sensitivity and non-extendable probe length for FOMI and FOMZI, limited working distance and reduced sensitivity for MOFI. These drawbacks have hindered the clinical applications of endoscopic OCT. The objective of this AREA application is to develop a new common-path OCT (CP-OCT) probe with extended and adjustable working distance, high phase stability, high spatial resolution, and negligible downlead sensitivity for in vivo endoscopic optical biopsy. The key innovation in this program is a novel ultracompact, in-axis beam-splitting, common-path Michelson interferometer that effectively circumvents the polarization and dispersion mismatch issues to achieve a high phase stability and extendable probe length. Two specific aims are designed in this program, including: 1) Development of a novel ultracompact CP- OCT endoscopic probe, and 2) Evaluation and demonstration of the developed CP-OCT probe using a swept source OCT (SSOCT) system. The optical and mechanical designs of the new OCT probe will be performed and the design results will be used to guide the implementation of a lab-style prototype. A bench-top SSOCT system will be implemented for performance evaluation and technology demonstration of the developed OCT probe. It is anticipated that this work will lay a solid foundation to expand our existing research scope and make contributions to the Nation's biomedical research and education. Upon successful achievement of the specific aims, a subsequent phase of research (through R15 or R21 mechanism) will be pursued. An important objective/task embedded in this AREA proposal is to strengthen the health-related research environment at the Missouri University of Science and Technology (MST). This AREA research topic has been carefully chosen to leverage our existing strengths in optical fiber interferometers, photonic micro structures, devices and sensors. Undergraduate and graduate students will receive direct trainings in health-related research. In addition, some of the research results will be converted to class instruction materials to expose a large student body at MST to health-related research topics. PHS 398/2590 (Rev. 11/07) Page Continuation Format Page PUBLIC HEALTH RELEVANCE: The main objective of this proposal is to develop a novel common-path OCT probe with extended and adaptable working distance, high phase stability, high spatial resolution, and negligible downlead sensitivity for in vivo endoscopic optical biopsy. The new endoscopic OCT probe has a great potential for early diagnosis of malignant cancers as well as image-guided interventions in human internal organs.