Ultra High-Resolution Optical Imaging Catheters

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Optical coherence tomography (OCT) is a volumetric imaging modality used to assess the subsurface structure and function of soft tissue. It is the optical analog to ultrasonography with improved resolution but albeit decreased penetration depth. High resolution OCT (10 um) has enabled several new clinical imaging applications in ophthalmology and cardiology. Ultra-high resolution OCT (1um) has demonstrated the cellular resolution required to detect cancer and its precursor lesions in tissue.There are technical challenges involved with the shift to broader spectral bands and shorter center wavelengths required to achieve ultra-high resolution. The paramount challenge is the management of dispersion. While dispersion in free-space optical system can be managed though careful interferometer design and the selection of optical elements to compensate dispersion, management of dispersion in (fiber-based) imaging catheters is significantly more challenging. The goal of this program is to develop new fiber-optic imaging catheters that will enable ultra-high resolution OCT in small luminal organs such as the lung, gastrointestinal tract, and fallopian tubes. Four technical objectives have been identified to achieve this goal.The first is to develop a testbed OCT system to evaluate candidate high-resolution imaging catheters. The second objective is to develop miniature common-path fiber-optic catheters. Designs will include the ability to adjust the sample-reference amplitude split ratio and the position of reference delay at the time of fabrication.The third objective is to develop miniature optics for extended depth-of-focus. This is required to help maintain lateral resolution over a longer ranging depth.The final objective is to develop novel scanning methodologies. Approaches will include the translation of a rotational drive into forward and side-looking scans, and scanning using multiple beams for NURD correction.The design, fabrication and validation of imaging catheters is an iterative process. In-house fiber-processing capabilities enable this design cycle to iterate quickly. Trainees do the initial design work using in-house optical and mechanical CAD software.OCT imaging with cellular resolution has been demonstrated using benchtop systems that employ free-space optics but has not yet transitioned into fiber-based imaging catheters suitable for luminal organs. This work will enable fiber-based OCT imaging of the small peripheral airways of the lung, and will for the first time, enable cellular resolution images of lung epithelium. This may lead to the diagnosis of cancer without the removal of tissue samples.