Compact Forward-Viewing Endoscopic Optical Coherence Tomography

光学相干层析成像（OCT）是一种三维高分辨率光学成像技术。它被广泛用于眼睛内部结构的成像，也正在寻找一系列其他医学应用，如皮肤病学和心脏病学。它与传统显微镜的不同之处在于，干涉测量法与宽带或可调光源一起用于实现光学切片。通过光学切片和多重散射光的固有抑制，OCT成像能够穿透散射组织内部1至2mm，从而实现3D体积成像。使用傅里叶域OCT技术，可以在几秒钟内收集、重建和显示整个体积。内窥镜OCT将OCT的高分辨率体积成像能力带入人体内部，为微创诊断和介入监测开辟了新的可能性。大多数内窥镜OCT系统在侧视配置下工作，其中图像从OCT探头径向向外获取，外观类似于内窥镜超声。这对于狭窄的管状结构（如血管和部分胃肠道）成像效果很好，但对于耳鼻喉（ENT）、上呼吸道或一般外科指导等区域并不理想。这些应用将受益于前瞻性的探索；实际上是一种内窥镜，可以从组织表面下产生高分辨率的正面图像或体积。然而，使用当前技术构建前视OCT内窥镜具有挑战性，因为它们需要在探头中内置二维纤维扫描机制；这种扫描通常要么体积大，速度慢，要么扫描范围有限，并导致复杂的设备。该项目首次提出并评估了在没有小型化扫描仪的情况下为正面观察内窥镜增加深度分辨能力的解决方案。该研究将探索一种新的方法，用于远端控制散射和干扰，这种方法可以以适配器的形式小型化，该适配器可以安装在光纤成像束或微型相机上。研究人员最近为这种微型适配器申请了专利，该适配器利用了一种称为全场扫描源OCT的技术，其中捕获了多个图像，每个图像在不同的照明波长下，并进行处理以恢复OCT体积。到目前为止，还没有通过纤维束进行高质量深度分辨率成像的报道，因此，如果该项目成功，将代表纤维束成像领域的重大进步。该项目的目的是证明该方法是开发具有临床实用性的紧凑型前视OCT探针的可行和实用途径。该项目的早期阶段涉及对新技术的全面了解。与此同时，将与临床合作伙伴就设计要求提供建议，共同开发小型化设计。然后将开发包装原型，使用一系列模型和组织样本进行表征和验证。在对核心探针设计进行验证研究的同时，还将寻求其他科学途径，包括将探针与其他成像方式（如荧光）结合起来。该项目将建立在肯特大学应用光学小组25年来制造OCT仪器的经验基础上，以及在开发内窥镜显微镜和OCT探针以及通过纤维束进行相干成像方面取得的成就。工业合作伙伴将提供微型光纤组件、紧凑型探头封装和微型相机方面的专业知识，而来自主要医院的临床合作伙伴将为开发用于耳、鼻、喉和肺上呼吸道的实际临床应用的探头提供建议和支持。

Optical coherence tomography (OCT) is a 3D high-resolution optical imaging technology. It is widely used for imaging internal structures of the eye and is also finding a range of other medical applications such as in dermatology and cardiology. It differs from conventional microscopy in that interferometry, together with a broadband or tunable optical source, is used to achieve optical sectioning. Through optical sectioning, and the intrinsic rejection of multiply-scattered light, OCT imaging is able to penetrate 1 to 2 mm inside scattering tissue, allowing 3D volumetric imaging. Using Fourier domain OCT techniques entire volumes can be collected, reconstructed and displayed in seconds.Endoscopic OCT brings the high-resolution volumetric imaging capabilities of OCT to the interior of the body, opening up new possibilities for minimally-invasive diagnosis and interventional monitoring. Most endoscopic OCT systems work in a side-viewing configuration, where images are acquired radially outwards from the OCT probe, similar in appearance to endoscopic ultrasound. This works well for imaging narrow, tube-like structures (such blood vessels and parts of the gastrointestinal tract), but it is not ideal for areas such as the ear, nose and throat (ENT), for the upper airways, or for general surgical guidance. These applications would benefit from a probe that is forward looking; effectively an endoscope which produces high resolution en-face images or volumes from beneath the tissue surface. However, forward-viewing OCT endoscopes are challenging to build with current technology as they require a two-dimensional fibre scanning mechanism to be built into the probe head; this scanning is typically either bulky, slow, or limited in scanning range, and leads to complex devices. This project, for the first time, proposes and evaluates solutions which add depth-resolving capabilities to en-face viewing endoscopes without a miniaturised scanner. The research will explore a new approach for distal control of scattering and interference which is amenable to miniaturisation in the form of an adapter which could be fitted to a fibre imaging bundle or a miniature camera. The investigators have recently patented an approach for such a miniature adapter that makes use of a technique called full-field swept source OCT, where multiple images are captured, each at a different illumination wavelength, and processed to recover the OCT volume. To date there has been no report of good quality depth resolved imaging via a fibre bundle, and so if successful this project will represent a significant advance in the field of fibre bundle imaging.The aims of the project are to demonstrate that the approach is a feasible and practical route to developing compact forward-viewing OCT probes with clinical utility. The earlier stages of the project involve developing a full understanding of the new technology. In parallel, a design will be developed for miniaturisation in collaboration with clinical partners advising on the design requirements. Packaged prototypes will then be developed, characterised and validated using a range of phantoms and tissue samples. In parallel with validation studies on the core probe design, additional scientific avenues will be pursued, including to combine the probe with other imaging modalities such as fluorescence.The project will build on 25 years of experience of building OCT instrumentation in the Applied Optics Group at the University of Kent, as well as achievements in developing endoscopic microscopes and OCT probes and performing coherent imaging though fibre bundles. Industrial partners will provide expertise in miniaturised fibre optic components, compact probe packaging, and miniature cameras, while clinical partners from major hospitals will provide advice and support in developing the probe towards practical clinical applications in ear, nose and throat and the upper airways of the lungs.