Spectrum- and time-resolved endogenous multiphoton signals reveal quantitative differentiation of premalignant and malignant gastric mucosa

Quantitative multiphoton imaging of cell metabolism, stromal fibers, and keratinization enables label-free discrimination of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) features atypical clinical manifestations and a low 5-year survival rate (< 5% in many developing countries where most of the disease occurs). Precise ESCC detection and grading toward timely and effective intervention are therefore crucial. In this study, we propose a multidimensional, slicing-free, and label-free histopathological evaluation method based on multispectral multiphoton fluorescence lifetime imaging microscopy (MM-FLIM) for precise ESCC identification. To assess the feasibility of this method, comparative imaging on fresh human biopsy specimens of different ESCC grades is performed. By constructing fluorescence spectrum- and lifetime-coded images, ESCC-induced morphological variations are unveiled. Further quantification of cell metabolism and stromal fibers reveals potential indicators for ESCC detection and grading. The specific identification of keratin pearls provides additional support for the early detection of ESCC. These findings demonstrate the viability of using MM-FLIM and the series of derived indicators for histopathological evaluation of ESCC. As there is an increasing interest in developing multiphoton endoscopes and multiphoton FLIM systems for clinical use, the proposed method would probably allow noninvasive, label-free, and multidimensional histological detection and grading of ESCC in the future.

Ultraviolet metasurface-assisted photoacoustic microscopy with great enhancement in DOF for fast histology imaging

Pathology interpretations of tissue rely on the gold standard of histology imaging, potentially hampering timely access to critical information for diagnosis and management of neoplasms because of tedious sample preparations. Slide-free capture of cell nuclei in unprocessed specimens without staining is preferable; however, inevitable irregular surfaces in fresh tissues results in limitations. An ultraviolet metasurface with the ability to generate an ultraviolet optical focus maintaining < 1.1-µm in lateral resolution and ∼290 µm in depth of field (DOF) is proposed for fast, high resolution, label-free photoacoustic histological imaging of unprocessed tissues with uneven surfaces. Microanatomical characteristics of the cell nuclei can be observed, as demonstrated by the mouse brain samples that were cut by hand and a ∼3 × 3-mm2 field of view was imaged in ∼27 min. Therefore, ultraviolet metasurface-assisted photoacoustic microscopy is anticipated to benefit intraoperative pathological assessments and basic scientific research by alleviating laborious tissue preparations.

Ultraviolet metalens for photoacoustic microscopy with an elongated depth of focus

Ultraviolet photoacoustic microscopy (UV-PAM) can achieve in vivo imaging without exogenous markers and play an important role in pathological diagnosis. However, traditional UV-PAM is unable to detect enough photoacoustic signals due to the very limited depth of focus (DOF) of excited light and the sharp decrease in energy with increasing sample depth. Here, we design a millimeter-scale UV metalens based on the extended Nijboer-Zernike wavefront-shaping theory which can effectively extend the DOF of a UV-PAM system to about 220 μm while maintaining a good lateral resolution of 1.063 μm. To experimentally verify the performance of the UV metalens, a UV-PAM system is built to achieve the volume imaging of a series of tungsten filaments at different depths. This work demonstrates the great potential of the proposed metalens-based UV-PAM in the detection of accurate diagnostic information for clinicopathologic imaging.

Toward next-generation endoscopes integrating biomimetic video systems, nonlinear optical microscopy, and deep learning

According to the World Health Organization, the proportion of the world's population over 60 years will approximately double by 2050. This progressive increase in the elderly population will lead to a dramatic growth of age-related diseases, resulting in tremendous pressure on the sustainability of healthcare systems globally. In this context, finding more efficient ways to address cancers, a set of diseases whose incidence is correlated with age, is of utmost importance. Prevention of cancers to decrease morbidity relies on the identification of precursor lesions before the onset of the disease, or at least diagnosis at an early stage. In this article, after briefly discussing some of the most prominent endoscopic approaches for gastric cancer diagnostics, we review relevant progress in three emerging technologies that have significant potential to play pivotal roles in next-generation endoscopy systems: biomimetic vision (with special focus on compound eye cameras), non-linear optical microscopies, and Deep Learning. Such systems are urgently needed to enhance the three major steps required for the successful diagnostics of gastrointestinal cancers: detection, characterization, and confirmation of suspicious lesions. In the final part, we discuss challenges that lie en route to translating these technologies to next-generation endoscopes that could enhance gastrointestinal imaging, and depict a possible configuration of a system capable of (i) biomimetic endoscopic vision enabling easier detection of lesions, (ii) label-free in vivo tissue characterization, and (iii) intelligently automated gastrointestinal cancer diagnostic.

Rapid and label-free histological imaging of unprocessed surgical tissues via dark-field reflectance ultraviolet microscopy

Routine examination for intraoperative histopathologic assessment is lengthy and laborious. Here, we present the dark-field reflectance ultraviolet microscopy (DRUM) that enables label-free imaging of unprocessed and thick tissues with subcellular resolution and a high signal-to-background ratio. To the best of our knowledge, DRUM provides image results for pathological assessment with the shortest turnaround time (2-3 min in total from sample preparation to tissue imaging). We also proposed a virtual staining process to convert DRUM images into pseudo-colorized images and enhance the image familiarity of pathologists. By imaging various tissues, we found DRUM can resolve cell nuclei and some extranuclear features, which are comparable to standard H&E images. Furthermore, the essential diagnostic features of intraoperatively excised tumor tissues also can be revealed by DRUM, demonstrating its potential as an additional aid for intraoperative histopathology.

Label-free identification of human glioma xenograft of mouse brain with quantitative ultraviolet photoacoustic histology imaging

The ability to unveil molecular specificities of endogenous nonfluorescent chromophores of ultraviolet photoacoustic imaging technology enables label-free histology imaging of tissue specimens. In this work, we exploit ultraviolet photoacoustic microscopy for identifying human glioma xenograft of mouse brain ex vivo. Intrinsically excellent imaging contrast of cell nucleus at ultraviolet photoacoustic illumination along with good spatial resolution allows for discerning the brain glioma of freshly-harvested thick brain slices, which circumvents laborious time-consuming preparations of the tissue specimens including micrometer-thick slicing and H&E staining that are prerequisites in standard histology analysis. The identification of tumor margins and quantitative analysis of tumor areas is implemented, representing good agreement with the standard H&E-stained observations. Quantitative ultraviolet photoacoustic microscopy can access fast pathological assessment to the brain tissues, and thus potentially facilitates intraoperative brain tumor resection to precisely remove all cancerous cells and preserve healthy tissue for maintaining its essential function.

Application of Multiphoton Microscopic Imaging in Study of Gastric Cancer

Multiphoton microscopy (MPM) imaging relies on the nonlinear interaction between ultrashort optical pulses and the samples to achieve image contrast. Featuring larger penetration depth, less phototoxicity, 3-dimensional sectioning capability, no need for labeling, MPM become a powerful medical imaging technique that can identify structural characteristics of tissues at the cellular and subcellular levels. In this review paper, we introduce the working principle of MPM imaging, present the current results of MPM imaging applied to the study of gastric tumors, and discuss the future prospects of this interdisciplinary research field.

In vivo imaging in experimental spinal cord injury – Techniques and trends

Introduction

Traumatic Spinal Cord Injury (SCI) is one of the leading causes of disability in the world. Treatment is limited to supportive care and no curative therapy exists. Experimental research to understand the complex pathophysiology and potential mediators of spinal cord regeneration is essential to develop innovative translational therapies. A multitude of experimental imaging methods to monitor spinal cord regeneration in vivo have developed over the last years. However, little literature exists to deal with advanced imaging methods specifically available in SCI research.

Research Question

This systematic literature review examines the current standards in experimental imaging in SCI allowing for in vivo imaging of spinal cord regeneration on a neuronal, vascular, and cellular basis.

Material and Methods

Articles were included meeting the following criteria: experimental research, original studies, rodent subjects, and intravital imaging. Reviewed in detail are microstructural and functional Magnetic Resonance Imaging, Micro-Computed Tomography, Laser Speckle Imaging, Very High Resolution Ultrasound, and in vivo microscopy techniques.

Results

Following the PRISMA guidelines for systematic reviews, 689 articles were identified for review, of which 492 were sorted out after screening and an additional 104 after detailed review. For qualitative synthesis 93 articles were included in this publication.

Discussion and Conclusion

With this study we give an up-to-date overview about modern experimental imaging techniques with the potential to advance the knowledge on spinal cord regeneration following SCI. A thorough knowledge of the strengths and limitations of the reviewed techniques will help to optimally exploit our current experimental armamentarium in the field.

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In vivo imaging is essential to enhance the understanding of SCI pathophysiology.

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Multiple experimental imaging methods have evolved over the past years.

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Detailed review of in vivo (f)MRI, μCT, VHRUS, and Microcopy in experimental SCI.

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Experimental imaging allows for longitudinal examination to the cellular level.

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Knowledge of the strengths and limitations is essential for future research.

Label-free identification of human coronary atherosclerotic plaque based on a three-dimensional quantitative assessment of multiphoton microscopy images

The rupture of coronary atherosclerotic plaque (CAP) and the resulting intracoronary thrombosis account for most acute coronary syndromes. Thus, the early identification and risk assessment of CAP is crucial for timely medical intervention. In this study, we propose a quantitative and label-free method for human CAP identification using multiphoton microscopy (MPM) and three-dimensional (3D) image analysis techniques. By detecting the intrinsic MPM signals, the microstructures of collagen and elastin fibers within normal and CAP-lesioned human coronary artery walls were imaged. Using a 3D gray level co-occurrence matrix method and 3D weighted vector summation algorithm, quantitative indicators that characterize the spatial texture and orientation features of the fibers were extracted. We demonstrate that these indicators show superior accuracy and repeatability over 2D texture features in CAP discrimination. Furthermore, by combining the 3D microstructural indicators, a support vector machine model that classifies CAP from the normal arterial wall with an accuracy of >97% was established. In conjunction with advances in multiphoton endoscopy, the proposed method shows great potential in providing a quantitative, label-free, and real-time tool for the early identification and risk assessment of CAP in the future.

Bright Aggregation-Induced Emission Nanoparticles for Two-Photon Imaging and Localized Compound Therapy of Cancers

Photodynamic therapy (PDT), a noninvasive therapeutic strategy for cancer treatment, which always suffers from the low reactive oxygen species (ROS) yield of traditional organic dyes. Herein, we present lipid-encapsulated aggregation-induced emission nanoparticles (AIE NPs) that have a high quantum yield (23%) and a maximum two-photon absorption (TPA) cross-section of 560 GM irradiated by near-infrared light (800 nm). The AIE NPs can serve as imaging agents for spatiotemporal imaging of tumor tissues with a penetration depth up to 505 μm on mice melanoma model. Importantly, the AIE NPs can simultaneously generate singlet oxygen (¹O₂) and highly toxic hydroxyl radicals (•OH) upon irradiation with 800 nm irradiation for photodynamic tumor ablation. In addition, the AIE NPs can be effectively cleared from the mouse body after the imaging and therapy. This study provides a strategy to develop theranostic agents for cancer image-guided PDT with high brightness, superior photostability, and high biosafety.

Moxifloxacin based fluorescence imaging of intestinal goblet cells

Goblet cells (GCs) in the intestine are specialized epithelial cells that secrete mucins to form the protective mucous layer. GCs are important in maintaining intestinal homeostasis, and the alteration of GCs is observed in inflammatory bowel diseases (IBDs) and neoplastic lesions. In the Barrett's esophagus, the presence of GCs is used as a marker of specialized intestinal metaplasia. Various endomicroscopic imaging methods have been used for imaging intestinal GCs, but high-speed and high-contrast GC imaging has been still difficult. In this study, we developed a high-contrast endoscopic GC imaging method: fluorescence endomicroscopy using moxifloxacin as a GC labeling agent. Moxifloxacin based fluorescence imaging of GCs was verified by using two-photon microscopy (TPM) in the normal mouse colon. Label-free TPM, which could visualize GCs in a negative contrast, was used as the reference. High-speed GC imaging was demonstrated by using confocal microscopy and endomicroscopy in the normal mouse colon. Confocal microscopy was applied to dextran sulfate sodium (DSS) induced colitis mouse models for the detection of GC depletion. Moxifloxacin based GC imaging was demonstrated not only by 3D microscopies but also by wide-field fluorescence microscopy, and intestinal GCs in the superficial region were imaged. Moxifloxacin based endomicroscopy has a potential for the application to human subjects by using FDA approved moxifloxacin.

Depth-resolved NIR-II fluorescence mesoscope

NIR-II fluorescence imaging is a promising method for visualizing biological structures in deep tissue, owing to the advantages of significantly suppressed optical scattering and diminished autofluorescence in biological tissues. However, few NIR-II fluorescence imaging approaches can simultaneously achieve a large field of view, high resolution and superior penetration depth, while exhibiting optical sectioning capability. In this paper, we present a novel NIR-II fluorescence mesoscopy system based on the f-θ scanning scheme and confocal detection to overcome these limitations. When used with NIR-II fluorescent dyes, our setup performs NIR-II fluorescence imaging on samples as large as 7.5×7.5 mm2 with a lateral resolution of 6.3 µm. In addition, our system provides a depth-resolved imaging ability and zooming function. We successfully demonstrate in vivo cerebrovascular imaging of a mouse with local ischemia. Thus, our system provides new opportunities to explore the mechanism of cerebrovascular disease.

Label-free identification of early gastrointestinal neuroendocrine tumors via biomedical multiphoton microscopy and automatic image analysis

At present, early diagnosis and treatment is the most effective way to treat early gastrointestinal neuroendocrine tumors. Therefore, we attempted to carry out multiphoton imaging of early neuroendocrine tumors because of its ability to label-free image tissue microstructure at the cellular level. Imaging results show that this imaging technique can quickly identify the histopathological changes in mucosa and submucosa caused by tumor invasion. Furthermore, we performed automatic image analysis on SHG images and extracted two optical diagnostic features-collagen density and average intensity, and also found obvious differences in the density as well as average intensity of collagen fibers in tumor microenvironment using a series of quantitative analysis. These findings may further facilitate the development of multiphoton microscopic imaging technique for clinical use.

Review of the Application of Nanovesicles and the Human Interstitial Fluid in Gastrointestinal Premalignant Lesion Detection, Diagnosis, Prognosis and Therapy

Premalignant lesions arise from cells that abnormally proliferate and have a tendency to become cancerous. Developing methods to specifically target and remove these premalignant lesions is imperative to the prevention of malignant progression into gastrointestinal (GI) tumors. However, accurate detection and diagnosis of GI precancerous lesions is challenging, as these lesions show little or no structural change. Thus, this prevents early intervention and reduces the success rate of therapy. In this review, we performed a systematic analysis of the technological advancements in the combined application of nanovesicles (NVs) and the human interstitial fluid (HIF) to specifically target GI premalignant lesions. NVs, which include quantum dots (QDs), are small membranous vehicles of a nanometer diameter that are widely used as drug delivery vectors, therapeutic effectors and diagnostic sensors. HIF is the fluid that is present in human interstitial tissues (HITs) in which signaling molecules and agents travel and can be found throughout the body. HIF is exploited by tumor cells for their invasion, migration and spread. Because the HITs span the entire submucosa of the gastrointestinal tract, they have been increasingly targeted in GI tumor therapy. The challenges involved in the combined application of NVs and HIF in the detection, diagnosis, prognosis and therapy of GI premalignant lesions are also discussed.

Multiphoton microscopy in surgical oncology- a systematic review and guide for clinical translatability

BACKGROUND

Multiphoton microscopy (MPM) facilitates three-dimensional, high-resolution functional imaging of unlabeled tissues in vivo and ex vivo. This systematic review discusses the diagnostic value, advantages and challenges in the practical use of MPM in surgical oncology.

METHOD AND FINDINGS

A Medline search was conducted in April 2019. Fifty-three original research papers investigating MPM compared to standard histology in human patients with solid tumors were identified. A qualitative synopsis and meta-analysis of 14 blinded studies was performed. Risk of bias and applicability were evaluated. MPM can image fresh, frozen or fixed tissues up to a depth 1000 μm in the z-plane. Best results including functional imaging and virtual histochemistry are obtained by in vivo imaging or scanning fresh tissue immediately after excision. Two-photon excited fluorescence by natural fluorophores of the cytoplasm and second harmonic generation signals by fluorophores of the extracellular matrix can be scanned simultaneously, providing high resolution optical histochemistry comparable to standard histology. Functional parameters like fluorescence lifetime imaging or optical redox ratio provide additional objective information. A major concern is inability to visualize the nucleus. However, in a subpopulation analysis of 440 specimens, MPM yielded a sensitivity of 94%, specificity of 96% and accuracy of 95% for the detection of malignant tissue.

CONCLUSION

MPM is a promising emerging technique in surgical oncology. Ex vivo imaging has high sensitivity, specificity and accuracy for the detection of tumor cells. For broad clinical application in vivo, technical challenges need to be resolved.

In vivo identification of arteries and veins using two-photon excitation elastin autofluorescence

Distinguishing arteries from veins in vivo has a great significance in clinical practices and preclinical studies. Optical imaging methods such as two-photon microscopy can provide high-resolution morphological information of tissue and are therefore extremely suitable for imaging small blood vessels. However, few optical imaging methods allow in vivo identification of arteries and veins merely utilizing the autofluorescence signal of blood vessels. In this report, we found the arterial wall generates a remarkably stronger two-photon excitation autofluorescence (TPEA) signal compared with the venous wall based on BALB/c mice. According to histological analysis and fluorescence characteristic measurement, the contrast signal is confirmed to be from elastin fibers. Employing this unique feature, we propose an objective and effective artery-vein separation strategy that considers the presence of the elastin-TPEA border as the indicator of arteries. Using this strategy, the arterial and venous networks of the dorsal skin and cerebral cortex of BALB/c mice are demonstrated to be excellently mapped and accurately separated in vivo without depending on any exogenous contrast agent, empirical knowledge, and algorithm. This study may provide a novel technique for mapping arterial and venous networks for anatomic research as well as an extra aid to basic researches on the mechanism, diagnosis, and treatment of blood vessel-related diseases.