Mavadia-Shukla Jessica, Fathi Payam, Liang Wenxuan, Wu Shaoguang, Sears Cynthia, Li Xingde
Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA.
Department of Medicine- Infectious Disease, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA.
Biomed Opt Express. 2018 Jul 17;9(8):3731-3739. doi: 10.1364/BOE.9.003731. eCollection 2018 Aug 1.
We present the first, most compact, ultrahigh-resolution, high-speed, distal scanning optical coherence tomography (OCT) endoscope operating at 800 nm. Achieving high speed imaging while maintaining an ultrahigh axial resolution is one of the most significant challenges with endoscopic OCT at 800 nm. Maintaining an ultrahigh axial resolution requires preservation of the broad spectral bandwidth of the light source throughout the OCT system. To overcome this critical limitation we implemented a distal scanning endoscope with diffractive optics to minimize loss in spectral throughput. In this paper, we employed a customized miniature 900 µm diameter DC micromotor fitted with a micro reflector to scan the imaging beam. We integrated a customized diffractive microlens into the imaging optics to reduce chromatic focal shift over the broad spectral bandwidth of the Ti:Sapphire laser of an approximately 150 nm 3dB bandwidth, affording a measured axial resolution of 2.4 µm (in air). The imaging capability of this high-speed, ultrahigh-resolution distal scanning endoscope was validated by performing 3D volumetric imaging of mouse colon at 50 frames-per-second (limited only by the A-scan rate of linear CCD array in the spectral-domain OCT system and sampling requirements). The results demonstrated that fine microstructures of colon could be clearly visualized, including the boundary between the absorptive cell layer and colonic mucosa as well the crypt patterns. Furthermore, this endoscope was employed to visualize morphological changes in an enterotoxigenic (ETBF) induced colon tumor model. We present the results of our feasibility studies and suggest the potential of this system for visualizing time dependent morphological changes associated with tumorigenesis on murine models .
我们展示了首款最紧凑、超高分辨率、高速、远端扫描的800纳米光学相干断层扫描（OCT）内窥镜。在800纳米的内窥镜OCT中，要在保持超高轴向分辨率的同时实现高速成像，是最重大的挑战之一。保持超高轴向分辨率需要在整个OCT系统中保留光源的宽光谱带宽。为克服这一关键限制，我们采用了带有衍射光学元件的远端扫描内窥镜，以尽量减少光谱通量的损失。在本文中，我们使用了一个定制的直径900微米的直流微型电机，其配有一个微反射镜来扫描成像光束。我们将一个定制的衍射微透镜集成到成像光学元件中，以减少在钛宝石激光器约150纳米3分贝带宽的宽光谱带宽上的色差焦移，测得的轴向分辨率为2.4微米（在空气中）。通过以每秒50帧的速度对小鼠结肠进行三维容积成像（仅受光谱域OCT系统中线性CCD阵列的A扫描速率和采样要求限制），验证了这种高速、超高分辨率远端扫描内窥镜的成像能力。结果表明，结肠的细微微观结构可以清晰地可视化，包括吸收细胞层与结肠黏膜之间的边界以及隐窝模式。此外，该内窥镜被用于观察产肠毒素性（ETBF）诱导的结肠肿瘤模型中的形态变化。我们展示了可行性研究的结果，并提出了该系统在可视化小鼠模型上与肿瘤发生相关的时间依赖性形态变化方面的潜力。
