Ultra High-Resolution Optical Imaging Catheters

光学相干断层扫描（OCT）是一种用于评估软组织地下结构和功能的体积成像方式。它是超声成像的光学模拟，提高了分辨率，但降低了穿透深度。高分辨率OCT（10微米）已经使眼科和心脏病学中的一些新的临床成像应用成为可能。超高分辨率OCT （1um）已经证明了检测组织中癌症及其前驱病变所需的细胞分辨率。实现超高分辨率需要更宽的光谱带和更短的中心波长，这涉及到技术挑战。最重要的挑战是分散的管理。虽然自由空间光学系统中的色散可以通过精心的干涉仪设计和选择光学元件来补偿色散来管理，但（基于光纤的）成像导管中的色散管理更具挑战性。该项目的目标是开发新的光纤成像导管，使小腔器官（如肺、胃肠道和输卵管）的超高分辨率OCT成为可能。为实现这一目标，已确定了四个技术目标。首先是开发一个测试平台OCT系统来评估候选的高分辨率成像导管。第二个目标是开发微型共径光纤导管。设计将包括在制造时调整样品-参考振幅分割比和参考延迟位置的能力。第三个目标是开发用于扩展焦深的微型光学系统。这有助于在更长的深度范围内保持横向分辨率。最终目标是开发新的扫描方法。方法包括将旋转驱动转换为正向和侧视扫描，以及使用多波束扫描进行NURD校正。成像导管的设计、制造和验证是一个反复的过程。内部光纤处理能力使该设计周期能够快速迭代。学员使用内部光学和机械CAD软件进行初步设计工作。使用自由空间光学的台式系统已经证明了具有细胞分辨率的OCT成像，但尚未过渡到适用于腔内器官的基于纤维的成像导管。这项工作将使基于纤维的肺小周围气道OCT成像成为可能，并将首次使肺上皮细胞分辨率成像成为可能。这可能导致在不切除组织样本的情况下诊断癌症。

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.