Contrast agents for confocal microscopy: how simple chemicals affect confocal images of normal and cancer cells in suspension

Effects of six kinds of sperm staining methods on human sperm size and evaluation of their staining effects

BACKGROUND

Large- and small-headed sperm are common morphological abnormalities. If different sperm staining methods affect sperm size, they will make a difference in the accuracy of sperm morphological analysis results. In this case, the normal reference values of sperm head parameters for different staining methods should be established.

METHODS

Six sperm staining methods, including Papanicolaou, Diff-Quik, Shorr, Hematoxylin-eosin (HE), Wright, and Wright-Giemsa staining, were used to stain the sperm smears of 25 semen samples, respectively. Sperm head parameter's length (L), width (W), area (A), perimeter, acrosomal area (Ac), and the derived values L/W and Ac/A of 2500 sperm (100 for each specimen) per staining method were measured by a computer-aided sperm morphological analysis system.

RESULTS

The highest sperm head length and width were observed with the Wright-Giemsa and Wright staining, followed by the Diff-Quik. The lowest sperm head length and width were observed with the Papanicolaou staining, and the sperm head length and width of HE and Shorr staining were between those of Papanicolaou and Diff-Quik staining. There was the same trend in changes in sperm head area and perimeter. Diff-Quik and Shorr staining could clearly distinguish acrosome and nucleus, followed by HE staining, whereas the boundary between acrosome and nucleus was not evident in Papanicolaou, Wright, and Wright-Giemsa staining.

CONCLUSION

Different staining methods influence sperm size, and the normal reference values of sperm head parameters of each staining method should be established. Diff-Quik and Shorr staining may be suitable methods for routine sperm morphological analysis.

In-vivo and ex-vivo optical clearing methods for biological tissues: review

Every optical imaging technique is limited in its penetration depth by scattering occurring in biological tissues. Possible solutions to overcome this problem consist of limiting the detrimental effects of scattering by reducing optical inhomogeneities within the sample. This can be achieved either by using physical methods (such as refractive index matching solutions) or by chemical methods (such as the removal of scatterers), based on tissue transformation protocols. This review provides an overview of the current state-of-the-art methods used for both ex-vivo and in-vivo optical clearing of biological tissues. We start with a brief history of the development of the most widespread clearing methods across the new millennium, then we describe the working principles of both physical and chemical methods. Clearing methods are then reviewed, pointing the attention of the reader on both physical and chemical methods, classified based on the tissue size and type for each specific application. A small section is reserved for methods that have already found in-vivo applications at the research level. Finally, a detailed discussion highlighting both the most relevant results achieved and the new ongoing developments in this field is reported in the last part, together with future perspectives for the clearing methodology.

Optimization of Classification Strategies of Acetowhite Temporal Patterns towards Improving Diagnostic Performance of Colposcopy

Efforts have been being made to improve the diagnostic performance of colposcopy, trying to help better diagnose cervical cancer, particularly in developing countries. However, improvements in a number of areas are still necessary, such as the time it takes to process the full digital image of the cervix, the performance of the computing systems used to identify different kinds of tissues, and biopsy sampling. In this paper, we explore three different, well-known automatic classification methods (k-Nearest Neighbors, Naïve Bayes, and C4.5), in addition to different data models that take full advantage of this information and improve the diagnostic performance of colposcopy based on acetowhite temporal patterns. Based on the ROC and PRC area scores, the k-Nearest Neighbors and discrete PLA representation performed better than other methods. The values of sensitivity, specificity, and accuracy reached using this method were 60% (95% CI 50–70), 79% (95% CI 71–86), and 70% (95% CI 60–80), respectively. The acetowhitening phenomenon is not exclusive to high-grade lesions, and we have found acetowhite temporal patterns of epithelial changes that are not precancerous lesions but that are similar to positive ones. These findings need to be considered when developing more robust computing systems in the future.

Identification of Objective Morphometric Markers of Xerostomia in the Oral Mucosa Epithelium with In Vivo Confocal Microscopy

The purpose of this work was to determine whether the morphology of the oral mucosa epithelium (OME) of patients with xerostomia differ from patients without xerostomia. In total, 34 patients with dry eye disease (DED) with or without xerostomia were examined at The Norwegian Dry Eye Disease Clinic with in vivo confocal microscopy of the lower lip. In addition, age- and gender-matched healthy controls (HC) were included. DED patients with xerostomia had a higher superficial to deep backscatter ratio compared with DED patients without xerostomia (p=0.002) and HC (p=0.001). Regression analysis demonstrated that this ratio was related to xerostomia independently of gender and age (p<0.001). Sensitivity and specificity of detecting xerostomia were 0.78 and 0.85, respectively, when using a superficial to deep backscatter ratio cut-off value of 0.995 (p=0.004). The mean nucleus to cytosol backscatter ratio in the superficial OME was lower in patients with xerostomia than in those without xerostomia (p=0.034). In vivo confocal microscopy is a potential tool for evaluating the oral cavity and to assess changes in the OME associated with xerostomia, objectively and quantitatively. The cause of the increased backscatter in the superficial OME in xerostomia, however, remains to be elucidated.

Optical clearing agent perfusion enhancement via combination of microneedle poration, heating and pneumatic pressure

BACKGROUND AND OBJECTIVE

Optical clearing agents (OCAs) have shown promise for increasing the penetration depth of biomedical lasers by temporarily decreasing optical scattering within the skin. However, their translation to the clinic has been constrained by lack of practical means for effectively perfusing OCA within target tissues in vivo. The objective of this study was to address this limitation through combination of a variety of techniques to enhance OCA perfusion, including heating of OCA, microneedling and/or application of pneumatic pressure over the skin surface being treated (vacuum and/or positive pressure). While some of these techniques have been explored by others independently, the current study represents the first to explore their use together.

STUDY DESIGN/MATERIALS AND METHODS

Propylene glycol (PG) OCA, either at room-temperature or heated to 45°C, was topically applied to hydrated, body temperature ex vivo porcine skin, in conjunction with various combinations of microneedling pre-treatment (0.2 mm length microneedles, performed prior to OCA application), vacuum pre-treatment (17-50 kPa, performed prior to OCA application), and positive pressure post-treatment (35-172 kPa, performed after OCA application). The effectiveness of OCA perfusion was characterized via measurements of transmittance, reduced scattering coefficient, and penetration depth at a number of medically-relevant laser wavelengths across the visible spectrum.

RESULTS

Topical application of room-temperature (RT) PG led to an increase in transmittance across the visible spectrum of up to 21% relative to untreated skin. However, only modest increases were observed with addition of various combinations of microneedling pre-treatment, vacuum pre-treatment, and positive pressure post-treatment. Conversely, when heated PG was used in conjunction with these techniques, we observed significant increases in transmittance. Using an optimal PG perfusion enhancement protocol consisting of 45°C heated PG + microneedle pre-treatment + 35 kPa vacuum pre-treatment + 103 kPa positive pressure post-treatment, we observed up to 68% increase in transmittance relative to untreated skin, and up to 46% increase relative to topical RT PG application alone. Using the optimal PG perfusion enhancement protocol, we also observed up to 30% decrease in reduced scattering coefficient relative to untreated skin, and up to 20% decrease relative to topical RT PG alone. Finally, using the optimal protocol, we observed up to 25% increase in penetration depth relative to untreated skin, and up to 23% increase relative to topical RT PG alone.

CONCLUSIONS

The combination of heated PG, microneedling pre-treatment, vacuum pre-treatment, and positive pressure-post treatment were observed to significantly enhance the perfusion of topically applied PG. Although further studies are required to evaluate the efficacy of combined perfusion enhancement techniques in vivo, the current results suggest promise for facilitating the translation of OCAs to the clinic.

Fluorescence lifetime imaging and reflectance confocal microscopy for multiscale imaging of oral precancer

Optical imaging techniques using a variety of contrast mechanisms are under evaluation for early detection of epithelial precancer; however, tradeoffs in field of view (FOV) and resolution may limit their application. Therefore, we present a multiscale multimodal optical imaging system combining macroscopic biochemical imaging of fluorescence lifetime imaging (FLIM) with subcellular morphologic imaging of reflectance confocal microscopy (RCM). The FLIM module images a 16×16 mm² tissue area with 62.5 μm lateral and 320 ps temporal resolution to guide cellular imaging of suspicious regions. Subsequently, coregistered RCM images are acquired at 7 Hz with 400 μm diameter FOV, <1  μm lateral and 3.5 μm axial resolution. FLIM-RCM imaging was performed on a tissue phantom, normal porcine buccal mucosa, and a hamster cheek pouch model of oral carcinogenesis. While FLIM is sensitive to biochemical and macroscopic architectural changes in tissue, RCM provides images of cell nuclear morphology, all key indicators of precancer progression.

Optical time-stretch confocal microscopy at 1 μm

We demonstrate optical time-stretch confocal microscopy in the 1 μm spectral window for high-speed and high-resolution cellular imaging. In contrast to the prior demonstrations of time-stretch imaging, which all operated in the telecommunication band, the present work extends the utility of this imaging modality to a wavelength regime (~1 μm), which is well known to be the optimal diagnostic window in biophotonics. This imaging technique enables us to image the nasopharyngeal epithelial cells with cellular resolution (<2 μm), at a line scan rate of 10 MHz, and with a field of view as wide as ~0.44 mm × 0.1 mm. We also theoretically and experimentally characterized the system performance. As the low-loss dispersive fibers for the time-stretch process as well as other essential optical components for enhancing the imaging sensitivity are commonly available at 1 μm, time-stretch confocal microscopy in this wavelength range could usher in realizing high-speed cell imaging with an unprecedented throughput.

Effects of acetic acid on light scattering from cells

Acetic acid has been used for decades as an aid for the detection of precancerous cervical lesions, and the use of acetic acid is being investigated in several other tissues. Nonetheless, the mechanism of acetowhitening is unclear. This work tests some of the hypotheses in the literature and measures changes in light scattering specific to the nucleus and the cytoplasm. Wide angle side scattering from both the nucleus and the cytoplasm increases with acetic application to tumorigenic cells, with the increase in nuclear scattering being greater. In one cell line, the changes in nuclear scattering are likely due to an increase in number or scattering efficiency of scattering centers smaller than the wavelength of excitation light. There are likely several cellular changes that cause acetowhitening and the cellular changes may differ with cell type. These results should lead to a better understanding of acetowhitening and potentially the development of adjunct techniques to improve the utility of acetic acid application. For the well-studied case of cervical tissue, acetowhitening has been shown to be sensitive, but not specific for oncogenic changes needing treatment.

Optical technologies and molecular imaging for cervical neoplasia: a program project update

There is an urgent global need for effective and affordable approaches to cervical cancer screening and diagnosis. In developing nations, cervical malignancies remain the leading cause of cancer-related deaths in women. This reality may be difficult to accept given that these deaths are largely preventable; where cervical screening programs have been implemented, cervical cancer-related deaths have decreased dramatically. In developed countries, the challenges of cervical disease stem from high costs and overtreatment. The National Cancer Institute-funded Program Project is evaluating the applicability of optical technologies in cervical cancer. The mandate of the project is to create tools for disease detection and diagnosis that are inexpensive, require minimal expertise, are more accurate than existing modalities, and can be feasibly implemented in a variety of clinical settings. This article presents the status and long-term goals of the project.

Review: Optical Micrometer Resolution Scanning for Non-invasive Grading of Precancer in the Human Uterine Cervix

Management of cervical precancer is archetypal for other cancer prevention programmes but has to consider diagnostic and logistic challenges. Numerous optical tools are emerging for non-destructive near real-time early diagnosis of precancerous lesions of the cervix. Non-destructive, real-time imaging modalities have reached pre-commercial status, but high resolution mapping tools are not yet introduced in clinical settings. The NCBI PubMed web page was searched using the keywords ‘CIN diagnosis’ and the combinations of ‘cervix {confocal, optical coherence tomography, ftir, infrared, Raman, vibrational, spectroscopy}’. Suitable titles were identified and their relevant references followed. Challenges in precancer management are discussed. The following tools capable of non-destructive high resolution mapping in a clinical environment were selected: confocal microscopy, optical coherence tomography, IR spectroscopy, and Raman spectroscopy. Findings on the clinical performance of these techniques are put into context in order to assist the reader in judging the likely performance of these methods as diagnostic tools. Rationale for carrying out research under the prospect of the HPV vaccine is given.

Optical imaging for cervical cancer detection: solutions for a continuing global problem

Cervical cancer is the leading cause of cancer death for women in developing countries. Optical technologies can improve the accuracy and availability of cervical cancer screening. For example, battery-powered digital cameras can obtain multi-spectral images of the entire cervix, highlighting suspicious areas, and high-resolution optical technologies can further interrogate such areas, providing in vivo diagnosis with high sensitivity and specificity. In addition, targeted contrast agents can highlight changes in biomarkers of cervical neoplasia. Such advances should provide a much needed global approach to cervical cancer prevention.

In vivo confocal scanning laser microscopy in dermatology

The need to improve the diagnostic accuracy and sensitivity for skin tumours has led to the development of new non-invasive, in vivo techniques including ultrasound, dermoscopy, digital photography, confocal scanning laser microscopy, magnetic resonance imaging and optical coherence tomography. Of all these in vivo techniques, only confocal scanning laser microscopy allows for the examination of the epidermis and papillary dermis at a resolution approaching histological detail. This review article looks at some of the most important applications of this new technology, highlighting its qualities and limitations.

In vivo optical biopsy of hamster oral cavity with epi-third-harmonic-generation microscopy

The first in vivo optical virtual biopsy based on epi-third-harmonic-generation (THG) microscopy is successfully demonstrated using Syrian hamster oral mucosa as a model system. Without complex physical biopsy procedures, epi-THG microscopy can provide high spatial resolution dynamic images of oral mucosa and sub-mucosa in all three dimensions. The demonstrated intra-vital epi-THG microscopy provide high resolution observation of blood flow in the capillary and could be a promising tool to image angiogenesis, which is an important feature for many human diseases including malignancies. The system setup of epi-THG microscopy can be easily integrated with other nonlinear optical microscopy such as second-harmonic generation and multi-photon fluorescence microscopy by using the same laser system to provide better integrated molecular and structural information for future clinical diagnosis. By adding 6% acetic acid solution on the mucosa, THG contrast on the borders of nuclei was found to be greatly enhanced due to the alterations of their linear and nonlinear THG susceptibilities. With a virtual-transition-based technology without using fluorescence, the optical epi-THG biopsy we demonstrated shows promise for future noninvasive in vivo diseases examinations.

Novel optical detection system for in vivo identification and localization of cervical intraepithelial neoplasia

A noncontact optical detection system is developed for the in vivo identification and localization of high-grade cervical intraepithelial neoplasia (CIN 2,3). Diagnostic scans of the entire human cervix are performed following acetic acid application employing three integrated optical measurements: laser-induced fluorescence spectroscopy, white light diffuse reflectance spectroscopy, and video imaging. Full cervical scans comprising 499 interrogation locations at 1-mm spatial resolution are completed in 12 s. Diffuse reflectance and fluorescence spectra with signal-to-noise ratios of better than 100-to-1 are collected between 360 and 720 nm in increments of 1 nm, with an inherent spectral resolution of 8 nm. Glare reduction and optical vignetting are handled with a novel illumination scheme and subsequent spectral arbitration algorithms. The system is designed and found to be well below acceptable safe optical exposure levels. Typical reproducibility across multiple systems is approximately 5%, providing reliable and accurate detection of in vivo cervical neoplasia in normal clinical use.

Detection of morphological changes of the ovine cervix in response to sex steroids using a fluorescence confocal endomicroscope

OBJECTIVE

This study examined morphological changes of the ovine cervix in response to sex steroids using confocal microscopy.

STUDY DESIGN

Experimental animals were ovariectomized, and the hormonal status of 4 groups of ewes (n = 5) was manipulated using sex steroids (no replacement, estradiol, progesterone, estradiol, and progesterone). The results were correlated with control ewes (n = 7) in naturally occurring reproductive states (estrus and midluteal).

RESULTS

Plasma progesterone concentrations of experimental animals were comparable with those observed during normal reproduction. Confocal microscopy enabled subcellular resolution of the cervical epithelium and the detection of morphological changes associated with alterations in progesterone and estradiol in both artificially manipulated and naturally cycling ewes. Differences in nuclear size, distribution, and density could be differentiated in confocal images and histologic sections of ectocervix from animals in estrus and in the presence of exogenous estradiol.

CONCLUSION

Confocal microscopy has potential diagnostic value for the detection of cellular and subcellular changes of the cervical epithelium.

Optically tunable nanoparticle contrast agents for early cancer detection: model-based analysis of gold nanoshells

Many optical diagnostic approaches rely on changes in scattering and absorption properties to generate optical contrast between normal and diseased tissue. Recently, there has been increasing interest in using exogenous agents to enhance this intrinsic contrast with particular emphasis on the development for targeting specific molecular features of disease. Gold nanoshells are a class of core-shell nanoparticles with an extremely tunable peak optical resonance ranging from the near-UV to the mid-IR wavelengths. Using current chemistries, nanoshells of a wide variety of core and shell sizes can easily be fabricated to scatter and/or absorb light with optical cross sections often several times larger than the geometric cross section. Using gold nanoshells of different size and optical parameters, we employ Monte Carlo models to predict the effect of varying concentrations of nanoshells on tissue reflectance. The models demonstrate the importance of absorption from the nanoshells on remitted signals even when the optical extinction is dominated by scattering. Furthermore, because of the strong optical response of nanoshells, a considerable change in reflectance is observed with only a very small concentration of nanoshells. Characterizing the optical behavior of gold nanoshells in tissue will aid in developing nanoshells as contrast agents for optical diagnostics.

Reflectance confocal microscopy for characterization of mammary ductal structures and development of neoplasia in genetically engineered mouse models of breast cancer

The earliest steps of breast cancer begin with aberrations in mammary ductal structure. Techniques that enable an investigator to image in situ and then analyze the same tissue using biochemical tools facilitates identification of genetic networks and signaling pathways active in the imaged structure. Cellular confocal microscopy (VivaCell-TiBa, Rochester, New York) is used to image mammary ductal structures and surrounding vasculature in situ in intact wild-type and genetically engineered mice that develop ER alpha-initiated ductal carcinoma in situ (DCIS) and ER alpha-driven invasive mammary cancer. In wild-type mice, normal mammary ductal structures that appear from puberty through lactation are visualized and serially sectioned optically, and a developmental atlas is created. Altering tissue preparation enabled visualization of the vasculature surrounding the ductal structures. In the genetically engineered mice, aberrant mammary ductal structures and cancers are imaged and compared to corresponding normal structures. Different preparation techniques are able to preserve tissue for routine histological analyses and RNA isolation. Comparative studies demonstrate that reflectance confocal imaging provides more cellular detail than carmine-alum-stained mammary gland whole mounts and equivalent detail with hematoxylin and eosin stained tissue sections. In summary, reflectance confocal microscopy is a tool that can be used to rapidly and accurately analyze mammary gland structure.

Biophotonic and Other Physical Methods for Characterizing Oral Mucosa

This article discusses biophotonic and other physical methods for characterizing oral mucosa.

Glucose and mannitol diffusion in human dura mater

An in vitro experimental study of the control of the human dura mater optical properties at administration of aqueous solutions of glucose and mannitol has been presented. The significant increase of the dura mater optical transmittance under action of immersion liquids has been demonstrated. Diffusion coefficients of glucose and mannitol in the human dura mater tissue at 20 degrees C have been estimated as (1.63 +/- 0.29) x 10(-6)cm(2)/s and as (1.31 +/- 0.41) x 10(-6) cm(2)/s, respectively. Experiments show that administration of immersion liquids allows for the effective control of tissue optical characteristics that make dura mater more transparent, thereby increasing the ability of light penetration through the tissue.

View of Normal Human Skin In Vivo as Observed Using Fluorescent Fiber-Optic Confocal Microscopic Imaging

Fluorescence confocal scanning laser microscopy, using a miniaturized handheld scanner, was performed to visualize the microscopic architecture of normal human epidermis in vivo. Fluorescein sodium (approximately 20 microL of 0.2% wt/vol) was administered via intradermal injection to normal skin on the volar forearm of 22 patients. The skin was imaged continuously from 1 to 15 min after injection. Fluorescein was excited at 488 nm and the fluorescent emission was detected at > 505 nm. In each subject, a series of images was collected at increasing depth, from superficial stratum corneum to papillary dermis. Features observed in confocal images were compared to those seen in hematoxylin- and eosin-stained sections of skin. The confocal images demonstrated the architecture of superficial skin in the horizontal plane. There was a transition in keratinocyte size, shape, and morphology with progressive imaging into the deeper epidermal layers. Superficial dermis and microscopic capillaries with blood flow were easily observed. The morphologic patterns associated with the major cell types of the epidermis were consistent with those known from conventional histology. We report the ability of in vivo fluorescence point scanning laser confocal microscopy to produce real-time, high-resolution images of the microscopic architecture of normal human epidermis using a noninvasive imaging technology.

Dual-axis confocal microscope for high-resolution in vivo imaging

We describe a novel confocal microscope that uses separate low-numerical-aperture objectives with the illumination and collection axes crossed at angle theta from the midline. This architecture collects images in scattering media with high transverse and axial resolution, long working distance, large field of view, and reduced noise from scattered light. We measured transverse and axial (FWHM) resolution of 1.3 and 2.1 microm, respectively, in free space, and confirm subcellular resolution in excised esophageal mucosa. The optics may be scaled to millimeter dimensions and fiber coupled for collection of high-resolution images in vivo.