Label-free in vivo pathology of human epithelia with a high-speed handheld dual-axis confocal microscope

There would be clinical value in a miniature optical-sectioning microscope to enable in vivo interrogation of tissues as a real-time and noninvasive alternative to gold-standard histopathology for early disease detection and surgical guidance. To address this need, a reflectance-based handheld line-scanned dual-axis confocal microscope was developed and fully packaged for label-free imaging of human skin and oral mucosa. This device can collect images at >15  frames/s with an optical-sectioning thickness and lateral resolution of 1.7 and 1.1  μm, respectively. Incorporation of a sterile lens cap design enables pressure-sensitive adjustment of the imaging depth by the user during clinical use. In vivo human images and videos are obtained to demonstrate the capabilities of this high-speed optical-sectioning microscopy device.

Evaluation of breast tissue with confocal strip-mosaicking microscopy: a test approach emulating pathology-like examination

Confocal microscopy is an emerging technology for rapid imaging of freshly excised tissue without the need for frozen- or fixed-section processing. Initial studies have described imaging of breast tissue using fluorescence confocal microscopy with small regions of interest, typically 750 × 750 ?? ? m 2 . We present exploration with a microscope, termed confocal strip-mosaicking microscope (CSM microscope), which images an area of 2 × 2 ?? cm 2 of tissue with cellular-level resolution in 10 min of excision. Using the CSM microscope, we imaged 34 fresh, human, large breast tissue specimens from 18 patients, blindly analyzed by a board-certified pathologist and subsequently correlated with the corresponding standard fixed histopathology. Invasive tumors and benign tissue were clearly identified in CSM strip-mosaic images. Thirty specimens were concordant for image-to-histopathology correlation while four were discordant.

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

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 single-axis confocal configuration for reducing background noise from out-of-focus 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.

Detection of skin cancer margins in Mohs excisions with high-speed strip mosaicing confocal microscopy: a feasibility study

BACKGROUND

Fluorescence confocal mosaicing microscopy is an emerging technology for rapid imaging of nuclear and morphological detail directly in excised tissue, without the need for frozen or fixed section processing. Basal cell carcinomas (BCCs) can be detected with high sensitivity and specificity in Mohs excisions with this approach. For translation to clinical trials and towards potentially routine implementation, a new and faster approach called strip mosaicing confocal microscopy was recently developed.

OBJECTIVES

To perform a preliminary assessment of fluorescence strip mosaicing confocal microscopy for detecting skin cancer margins in Mohs excisions.

METHODS

Tissue samples from 17 Mohs cases were imaged in the form of strip mosaics. Each mosaic was divided into two halves (submosaics) and graded by a Mohs surgeon and a dermatologist who were blinded to the pathology. The 34 submosaics were compared with the corresponding Mohs pathology.

RESULTS

The overall image quality was excellent for resolution, contrast and stitching in the 34 submosaics. Components of normal skin including the epidermis, dermis, dermal appendages and subcutaneous tissue were easily visualized. The preliminary measures of sensitivity and specificity were both 94% for detecting skin cancer margins.

CONCLUSIONS

The new strip mosaicing approach represents another advance in confocal microscopy for imaging of large areas of excised tissue. Strip mosaicing may enable rapid assessment of BCC margins in fresh excisions during Mohs surgery and may serve as an adjunct to frozen pathology.

Abstract P2-03-03: Feasibility of evaluation of breast tissue using confocal microscopy with strip mosaicing

Background: Confocal microscopic strip mosaicing (CSM) provides noninvasive optical sectioning and high resolution, which allows for imaging of nuclear and morphological detail in freshly excised tissue. CSM can image large areas of tissue at micron-level resolution in minutes, which may offer an advantage over standard histology that requires days. We have conducted a preliminary investigation of the feasibility of this technology for the evaluation of breast tissue from surgical excision specimens.

Design: In a prospective study, 80 fresh human breast tissue samples from surgical excision specimens of 24 patients were imaged using a prototype confocal strip scanner. Fresh tissue specimens were immersed in Acridine Orange (AO) for 45 seconds to stain the nuclei, then pressed against the glass imaging window and imaged with a 30X, 0.75 numerical aperture (measured) objective lens and a 488 nm laser. Images were acquired in two modes of contrast: in fluorescence (with AO), showing nuclear morphology, and in reflectance (endogenous), showing stroma. The use of fluorescence for nuclear staining mimics the use of hematoxylin in pathology, and the use of reflectance eosin. Use of two contrast modes allows the fluorescence image to be colorized purple and the reflectance image pink, producing confocal strip mosaics that mimic H&E histology in appearance. Specimens were subsequently fixed in formalin and routinely processed to obtain H&E stained sections. H&E and confocal images were compared by the study pathologist (M.M.)

Results: Freshly excised breast tissue samples as large as 2 cm x 2 cm were imaged in less than five minutes, with 1-micron resolution and measured optical sectioning of 6 microns. We compared the CSM images against standard histopathology images. In our series we evaluated the following histologies: 12 invasive carcinoma (11 ductal, 1 lobular), 3 ductal carcinoma in-situ, 3 lobular carcinoma in situ, 1 atypical lobular hyperplasia, 1 atypical ductal hyperplasia and various benign lesions such as fat necrosis, fibrocystic changes, and ductal hyperplasia. In confocal images invasive and in situ carcinoma as well as benign ducts and lobules were distinguished from surrounding stromal tissue. Limitations that are typically encountered in standard histology, such as distinguishing low grade ductal carcinoma in situ (DCIS) from lobular carcinoma in situ (LCIS) or atypical proliferations were encountered in the grayscale confocal images as well.

Conclusion: In this initial feasibility study, CSM produced images that could be diagnosed as benign or neoplastic by the study pathologist. Further study is needed to build an image library of breast histology and compare reproducibility of histologic diagnoses between CSM (grayscale and colorized images) and traditional optical microscopy, and assess interobserver reproducibility in diagnosis. CSM potentially provides rapid and noninvasive evaluation of breast parenchyma, and has a potential application for intraoperative margin assessment of resected breast specimens.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-03-03.

Confocal microscopy with strip mosaicing for rapid imaging over large areas of excised tissue

Confocal mosaicing microscopy is a developing technology platform for imaging tumor margins directly in freshly excised tissue, without the processing required for conventional pathology. Previously, mosaicing on 12-×-12  mm² of excised skin tissue from Mohs surgery and detection of basal cell carcinoma margins was demonstrated in 9 min. Last year, we reported the feasibility of a faster approach called "strip mosaicing," which was demonstrated on a 10-×-10  mm² of tissue in 3 min. Here we describe further advances in instrumentation, software, and speed. A mechanism was also developed to flatten tissue in order to enable consistent and repeatable acquisition of images over large areas. We demonstrate mosaicing on 10-×-10  mm² of skin tissue with 1-μm lateral resolution in 90 s. A 2.5-×-3.5  cm² piece of breast tissue was scanned with 0.8-μm lateral resolution in 13 min. Rapid mosaicing of confocal images on large areas of fresh tissue potentially offers a means to perform pathology at the bedside. Imaging of tumor margins with strip mosaicing confocal microscopy may serve as an adjunct to conventional (frozen or fixed) pathology for guiding surgery.

Rapid confocal imaging of large areas of excised tissue with strip mosaicing

Imaging large areas of tissue rapidly and with high resolution may enable rapid pathology at the bedside. The limited field of view of high-resolution microscopes requires the merging of multiple images that are taken sequentially to cover a large area. This merging or mosaicing of images requires long acquisition and processing times, and produces artifacts. To reduce both time and artifacts, we developed a mosaicing method on a confocal microscope that images morphology in large areas of excised tissue with sub-cellular detail. By acquiring image strips with aspect ratios of 10:1 and higher (instead of the standard ~1:1) and "stitching" them in software, our method images 10 × 10 mm(2) area of tissue in about 3 min. This method, which we call "strip mosaicing," is currently three times as fast as our previous method.

Line-scanning reflectance confocal microscopy of human skin: comparison of full-pupil and divided-pupil configurations

Line-scanning, with pupil engineering and the use of linear array detectors, may enable simple, small, and low-cost confocal microscopes for clinical imaging of human epithelial tissues. However, a fundamental understanding of line-scanning performance within the highly scattering and aberrating conditions of human tissue is necessary, to translate from benchtop instrumentation to clinical implementation. The results of a preliminary investigation for reflectance imaging in skin are reported.