This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The broad, long term objective of the proposed research is to develop a high speed noninvasive endoscopic functional optical coherence tomographic (OCT) system using microelectromechanical system (MEMS) technology for early diagnosis of tumors in gastrointestinal (GI), respiratory, and urogenital tracts. Functional optical coherence tomography uses coherent gating techniques to obtain information on tissue structure and blood flow dynamics at discrete spatial locations in highly scattering biological tissues. The exceptionally high spatial resolution (2~10 5m) of functional OCT allows noninvasive imaging of both in vivo tissue structure and blood flow dynamics simultaneously. We propose to combine the advances in biomedical imaging and MEMS technology to develop a high speed, compact, and fast endoscopic functional OCT with a miniaturized probe. This is a collaborative project that involves principal investigators with expertise in biomedical optics, endoscopic imaging, and silicon and polymer MEMS technology.
The specific aims of this work are to: 1) design and develop a high speed, fiber optic based high resolution functional OCT system for endoscopic imaging of in vivo tissue structure and blood flow dynamics in GI tracks, and investigate and develop hardware systems and imaging processing algorithms for speckle noise minimization and imaging enhancement; 2) develop scanning probes with silicon MEMS technology; 3) develop scanning probes with polymer MEMS technology; and 4) Integrate and characterize endoscopic system. Several novel concepts are proposed in the design and development of endoscopic functional OCT. First, miniaturized scanning probe is designed and developed using both silicon and polymer MEMS technology. The scanning probes developed using MEMS technology have the advantage that they are compact, robust, low cost, low power requirement, and high speed. In addition, OCT is a coherent imaging technique that depends upon the spati al and temporal coherence of the optical waves for image detection. This same coherence also gives rise to speckle, which degrades the quality of functional images and makes boundaries between highly scattering structures in tissue difficult to resolve. Hardware and imaging processing algorithms for speckle noise reduction will be investigated to increase the quality of functional OCT image. Furthermore, lateral resolution of the current endoscopic OCT that uses axial scanning followed by lateral scanning is limited by the focal depth of the probe beam. The high scanning rate of the probe made with MEMS technology offers the potential to increase lateral resolution by performing lateral scanning first in order to maintain the beam waist at the zero optical path length. Finally, a scanning probe fabricated with MEMS technology has the potential to provide three-dimensional imaging of tissue structure and physiology with high imaging speed. Although not a focus of this proposal, the scanning probe technology developed in this proposal can also be used for endoscopic confocal and two-photon imaging.
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