High-Speed Blood Flow Imaging with Scanless Confocal Microscope

• Published in: IEEE Photonics Conference (Online) pp. 1 - 2
• Main Authors: Gong, Cheng, Kulkarni, Nachiket, Zhu, Wenbin, Nguyen, Christopher David, Curiel-Lewandrowski, Clara, Kang, Dongkyun
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.09.2019
• Subjects: Blood flow; In vivo; Microscopy; Optical microscopy; Skin; Visualization
• ISSN: 2575-274X
• DOI: 10.1109/IPCon.2019.8908407

We have developed a scanless confocal microscope and demonstrated high-speed cellular imaging of the human skin in vivo. Using the high imaging speed of 203 frames/sec, rapid blood flow was well visualized. Introduction Reflectance confocal microscopy (RCM) is an optical imaging tool that can visualize cellular details of the human tissue in vivo without having to remove the tissue from the patient [1]. RCM has a potential to examine dynamic events in the human subject such as blood flow. Previously, RCM has been used to visualize leukocytes in capillaries in inflammatory conditions [2]. Commercially available RCM devices, however, have a relatively slow imaging speed, 9 frames/sec, and therefore may have challenges in visualizing rapid blood flow. Recently, we have developed a low-cost scanless confocal microscope that uses a broadband light source, diffraction gratings, and slit aperture, to acquire confocal images with an inexpensive consumergrade CMOS camera [3]. While our first prototype of the scanless confocal microscope demonstrated cellular imaging of the human skin in vivo, its imaging speed was slow, 4.3 frames/sec, due to the use of the color CMOS sensor with the bayer filter and the poor coupling efficiently between the source and slit aperture. In this paper, we present high-speed confocal imaging of blood flow with our recent scanless confocal microscope. Method In the high-speed scanless confocal microscope (Fig. 1), a super luminescent light emitting diode (sLED) with the center wavelength of 840nm and bandwidth of 50nm was used as the light source. After collimated by an aspheric lens, the illumination light was diffracted by a diffraction grating and then focused by a cylindrical lens and an objective lens (water immersion; NA = 0.8) into multiple lines on the tissue, where each wavelength is focused as a distinctive line. Reflected light from the tissue was collected and collimated by the same objective lens, then diffracted by another diffraction grating and focused by an achromatic doublet (f = 30 mm) onto the detection slit. After filtered by the detection slit, the light was collimated by another achromatic doublet (f = 30 mm) and diffracted by the third grating and focused onto a CMOS sensor. Images from the CMOS sensor were transferred to a laptop via the standard USB3.0 protocol. The optics holders were custom designed and printed by 3D printers.