Handheld laser scanning microscope catheter for real-time and in vivo confocal microscopy using a high definition high frame rate Lissajous MEMS mirror

MEMS-Based Portable Reflection Confocal Microscope for In Vivo Skin Imaging

This study aims to develop a portable reflective confocal microscope (PCRM) based on MEMS micro-mirrors for in vivo skin imaging. The design of PCRM is intended to overcome the limitations of traditional invasive biopsies and bulky desktop microscopes, enabling handheld operation and access to hard-to-reach skin areas. This research innovatively integrates MEMS technology into the PCM through precise mechanical design, using an 830 nm laser and a commercial Olympus objective lens, achieving a lateral resolution of 1.24 μm and an axial resolution of 5.3 μm, with imaging at a speed of 11 f/s over a field of view of 530 × 500 μm. PCRM successfully imaged various skin layers, including capillary blood flow, demonstrating diagnostic potential for skin lesions and providing a compact, high-performance solution for non-invasive skin imaging suitable for clinical applications.

Light-sheet microscopy enabled by a miniaturized plane illuminator

We present a implementation method of light-sheet microscopy utilizing a highly miniaturized device that produces light-sheet illumination while immersed in the sample container. Our miniaturized plane illuminator (MPI) internally equips a two-axis beam-scanning mechanism based on a magnetostatically driven optical fiber cantilever. A light sheet is produced by fast scanning of the focused beam in an axis while the illumination plane can move in the other axis for positioning and 3D imaging. Our MPI device is so compact in a 1.5 mm-thick needle form that it can be conveniently placed in the right vicinity of the imaging sample. Because the illumination is directly given in the sample-surrounding medium, a great deal of operational flexibility is obtained with an uncompromised beam quality. We could build a light-sheet microscopy system with a conventional inverted microscope frame by attaching our MPI upgrade kit as an add-on module. In this study, the optical and electromechanical characteristics of our MPI device were carefully investigated. As well, light-sheet microscopy imaging of various samples was performed to validate the practical power of our technique. We found our MPI can provide a low-cost and easy-to-use imaging mode, and make the light-sheet microscopy more available in various applications.

Miniature side-view dual axes confocal endomicroscope for repetitive in vivo imaging

A side-view dual axes confocal endomicroscope is demonstrated that can be inserted repetitively in hollow organs of genetically engineered mice for in vivo real-time imaging in horizontal and vertical planes. Near infrared (NIR) excitation at λex = 785 nm was used. A monolithic 3-axis parametric resonance scan mirror was fabricated using micro-electro-mechanical systems (MEMS) technology to perform post-objective scanning in the distal end of a 4.19 mm diameter instrument. Torsional and serpentine springs were designed to "switch" the mode of imaging between vertical and horizontal planes by tuning the actuation frequency. This system demonstrated real-time in-vivo images in horizontal and vertical planes with 310 µm depth and 1.75 and 7.5 µm lateral and axial resolution. Individual cells and discrete mucosal structures could be identified.

Spatial and directional contrast dependence in Lissajous-scanning projection systems

Scanning-based image formation fundamentally differs from its classical lens-based counterpart. Therefore, established classical performance evaluation methods fail to determine the theoretical limitations of scanning-based optical systems. We developed a simulation framework and a novel performance evaluation process to evaluate the achievable contrast in scanning systems. Applying these tools, we conducted a study determining the resolution limits of different Lissajous scanning approaches. For the first time, we identify and quantify spatial and directional dependencies of the optical contrast and demonstrate their significant impact on the perceived image quality. We prove that the observed effects are more pronounced for Lissajous systems with high ratios of the two scanning frequencies. The presented method and results can lay the foundation for a more sophisticated application-specific design of next-generation scanning systems.

Confocal laser endomicroscope with distal MEMS scanner for real-time histopathology

Confocal laser endomicroscopy is an emerging methodology to perform real time optical biopsy. Fluorescence images with histology-like quality can be collected instantaneously from the epithelium of hollow organs. Currently, scanning is performed at the proximal end of probe-based instruments used routinely in the clinic, and flexibility to control the focus is limited. We demonstrate use of a parametric resonance scanner packaged in the distal end of the endomicroscope to perform high speed lateral deflections. An aperture was etched in the center of the reflector to fold the optical path. This design reduced the dimensions of the instrument to 2.4 mm diameter and 10 mm length, allowing for forward passage through the working channel of a standard medical endoscope. A compact lens assembly provides lateral and axial resolution of 1.1 and 13.6 μm, respectively. A working distance of 0 μm and field-of-view of 250 μm × 250 μm was achieved at frame rates up to 20 Hz. Excitation at 488 nm was delivered to excite fluorescein, an FDA-approved dye, to generate high tissue contrast. The endomicroscope was reprocessed using a clinically-approved sterilization method for 18 cycles without failure. Fluorescence images were collected during routine colonoscopy from normal colonic mucosa, tubular adenomas, hyperplastic polyps, ulcerative colitis, and Crohn's colitis. Individual cells, including colonocytes, goblet cells, and inflammatory cells, could be identified. Mucosal features, such as crypt structures, crypt lumens, and lamina propria, could be distinguished. This instrument has potential to be used as an accessory during routine medical endoscopy.