Miniature in vivo MEMS-based line-scanned dual-axis confocal microscope for point-of-care pathology

Abstract

There is a need for miniature optical-sectioning microscopes to enable in vivo interrogation of tissues as a real-time and noninvasive alternative to gold-standard histopathology. Such devices could have a transformative impact for the early detection of cancer as well as for guiding tumor-resection procedures. Miniature confocal microscopes have been developed by various researchers and corporations to enable optical sectioning of highly scattering tissues, all of which have necessitated various trade-offs in size, speed, depth selectivity, field of view, resolution, image contrast, and sensitivity. In this study, a miniature line-scanned (LS) dual-axis confocal (DAC) microscope, with a 12-mm diameter distal tip, has been developed for clinical point-of-care pathology. The dual-axis architecture has demonstrated an advantage over the conventional singleaxis confocal configuration for reducing background noise from out-offocus and multiply scattered light. The use of line scanning enables fast frame rates (16 frames/sec is demonstrated here, but faster rates are possible), which mitigates motion artifacts of a hand-held device during clinical use. We have developed a method to actively align the illumination and collection beams in a DAC microscope through the use of a pair of rotatable alignment mirrors. Incorporation of a custom objective lens, with a small form factor for in vivo clinical use, enables our device to achieve an optical-sectioning thickness and lateral resolution of 2.0 and 1.1 microns respectively. Validation measurements with reflective targets, as well as in vivo and ex vivo images of tissues, demonstrate the clinical potential of this high-speed optical-sectioning microscopy device.

Visualizing epithelial expression of EGFR in vivo with distal scanning side-viewing confocal endomicroscope

“…The lateral and axial resolution was 5 and 6.5 μm, respectively, and images were collected at 5 frames per sec. A handheld 12 mm diameter dual axes confocal microscope has been demonstrated using a lateral scanning electrostatic MEMS mirror with a resonance frequency of ~200 Hz39. Line scanning was performed to improve the imaging speed to 16 frames per sec.…”

Gigapixel surface imaging of radical prostatectomy specimens for comprehensive detection of cancer-positive surgical margins using structured illumination microscopy

“…Techniques applied to date have included depth-sensitive tomography techniques such as optical coherence tomography1011121314 and photoacoustic tomography15, as well as optical sectioning techniques such as reflectance and fluorescence scanning confocal microscopy and label-free nonlinear microscopies1617181920212223242526272829. These techniques have shown promising results for imaging of smaller specimens such as skin cancer resections1721, gross pathology sections of larger resection specimens16172527, and core needle biopsies30.…”

Assessing the imaging performance of light sheet microscopies in highly scattering tissues

“…The LS-DAC geometry was identical to the PS-DAC geometry, except that in this case (as described previously) a line of illumination was used, i.e. focusing was performed in the x i dimension only, which allows for direct imaging along the y i dimension [14,20,21]. Similarly, for WF-LSM, a low NA i of 0.03 (focused only in the x i dimension), coupled to a higher collection NA c of 0.30 was used, similar to what has been used previously by other groups [2][3][4]16].…”

“…al. [8]), which have successfully been utilized for reflectance and fluorescence imaging of thick, highly scattering tissues in a number of ex-vivo and in-vivo studies [9][10][11][12][13][14]. Furthermore, recent reports have demonstrated LSM in novel "open-top" or "inverted" imaging geometries that are more compatible for the imaging of conventionally mounted specimens of arbitrary size [15][16][17], as well as the use of confocal line detection for improved contrast in scattering samples [18].…”