Multiphoton tomographic imaging: a potential optical biopsy tool for detecting gastrointestinal inflammation and neoplasia

Moxifloxacin promotes two-photon microscopic imaging for discriminating different stages of DSS-induced colitis on mice

BACKGROUND

Accurate diagnosis of patients with ulcerative colitis (UC) can reduce their risk of developing colorectal cancer. This study intended to explore whether moxifloxacin, an agent with fluorescence potential, could promote two-photon microscopy (TPM) diagnosis for mice with dextran sodium sulfate (DSS)-induced colitis, which could imitate human UC.

METHODS

32 Balb/c mice were randomly divided into 4 groups: control, acute colitis, remission colitis and chronic colitis. Fluorescence parameters, imaging performance, and tissue features of different mouse models were compared under moxifloxacin-assisted TPM and label-free TPM.

RESULTS

Excitation wavelength of 720 nm and moxifloxacin labeling time of 2 min was optimal for moxifloxacin-assisted TPM. With moxifloxacin labeling for colonic tissues, excitation power was decreased to 1/10 of that without labeling while fluorescence intensity was increased to 10-fold of that without labeling. Photobleaching was negligible after moxifloxacin labeling and moxifloxacin fluorescence kept stable within 2 h. Compared with the control group, moxifloxacin fluorescence was reduced in the three colitis groups (P < 0.05). Meanwhile, the proportion of enhanced moxifloxacin fluorescence regions was (22.4 ± 1.6)%, (7.7 ± 1.0)%, (13.5 ± 1.7)% and (5.0 ± 1.3)% in the control, acute, remission and chronic groups respectively, with significant reduction in the three colitis groups (P < 0.05). Besides, variant tissue features of experimental colitis models were presented under moxifloxacin-assisted TPM, such as crypt opening, glandular structure, adjacent glandular space and moxifloxacin distribution.

CONCLUSIONS

With unique biological interaction between moxifloxacin and colonic mucosa, moxifloxacin-assisted TPM imaging is feasible and effective for accurate diagnosis of different stages of experimental colitis.

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.

Moxifloxacin as a contrast agent of two-photon microscopic imaging for detecting colorectal diseases

Since two-photon microscopy (TPM) can obtain high-resolution images at cellular and subcellular level and moxifloxacin has multiphoton fluorescence characteristic, our study aimed to explore the feasibility and diagnostic value of moxifloxacin-assisted TPM in different human colorectal diseases, including low-grade intraepithelial neoplasia (LGIN), high-grade intraepithelial neoplasia (HGIN) and cancer tissues. Excitation power for TPM imaging with and without moxifloxacin was (2.74 ± 0.16) mW and (0.28 ± 0.02) mW, respectively (p < 0.05). Whether labeled with moxifloxacin or not, images of normal, LGIN, HGIN and cancer tissues all reached the strongest signal at 30 μm from the mucosa. Normalized fluorescence intensity of TPM images with moxifloxacin was approximately 10 times stronger than that without moxifloxacin. Fluorescence signal was differed significantly in normal, LGIN, HGIN and cancer tissues with or without moxifloxacin (p < 0.05). Besides, moxifloxacin-assisted TPM could present variant tissue features with different colorectal diseases, such as the crypt opening, glandular structure, adjacent glandular space and fluorescence distribution.

Label-Free Characterization and Quantification of Mucosal Inflammation in Common Murine Colitis Models With Multiphoton Imaging

BACKGROUND

Clinical challenges in inflammatory bowel diseases require microscopic in vivo evaluation of inflammation. Here, label-free imaging holds great potential, and recently, our group demonstrated the advantage of using in vivo multiphoton endomicroscopy for longitudinal animal studies. This article extends our previous work by in-depth analysis of label-free tissue features in common colitis models quantified by the multiphoton colitis score (MCS).

METHODS

Fresh mucosal tissues were evaluated from acute and chronic dextran sulfate sodium (DSS), TNBS, oxazolone, and transfer colitis. Label-free imaging was performed by using second harmonic generation and natural autofluorescence. Morphological changes in mucosal crypts, collagen fibers, and cellularity in the stroma were analyzed and graded.

RESULTS

Our approach discriminated between healthy (mean MCS = 2.5) and inflamed tissue (mean MCS > 5) in all models, and the MCS was validated by hematoxylin and eosin scoring of the same samples (85.2% agreement). Moreover, specific characteristics of each phenotype were identified. While TNBS, oxazolone, and transfer colitis showed high cellularity in stroma, epithelial damage seemed specific for chronic, acute DSS and transfer colitis. Crypt deformations were mostly observed in acute DSS.

CONCLUSIONS

Quantification of label-free imaging is promising for in vivo endoscopy. In the future, this could be valuable for monitoring of inflammatory pathways in murine models, which is highly relevant for the development of new inflammatory bowel disease therapeutics.

Multiphoton Microscopy for Identifying Collagen Signatures Associated with Biochemical Recurrence in Prostate Cancer Patients

Prostate cancer is a heterogeneous disease that remains dormant for long periods or acts aggressively with poor clinical outcomes. Identifying aggressive prostate tumor behavior using current glandular-focused histopathological criteria is challenging. Recent evidence has implicated the stroma in modulating prostate tumor behavior and in predicting post-surgical outcomes. However, the emergence of stromal signatures has been limited, due in part to the lack of adoption of imaging modalities for stromal-specific profiling. Herein, label-free multiphoton microscopy (MPM), with its ability to image tissue with stromal-specific contrast, is used to identify prostate stromal features associated with aggressive tumor behavior and clinical outcome. MPM was performed on unstained prostatectomy specimens from 59 patients and on biopsy specimens from 17 patients with known post-surgery recurrence status. MPM-identified collagen content, organization, and morphological tumor signatures were extracted for each patient and screened for association with recurrent disease. Compared to tumors from patients whose disease did not recur, tumors from patients with recurrent disease exhibited higher MPM-identified collagen amount and collagen fiber intensity signal and width. Our study shows an association between MPM-identified stromal collagen features of prostate tumors and post-surgical disease recurrence, suggesting their potential for prostate cancer risk assessment.

Influence of hematoxylin and eosin staining on the quantitative analysis of second harmonic generation imaging of fixed tissue sections

Second harmonic generation (SHG) microscopy has emerged over the past two decades as a powerful tool for tissue characterization and diagnostics. Its main applications in medicine are related to mapping the collagen architecture of in-vivo, ex-vivo and fixed tissues based on endogenous contrast. In this work we present how H&E staining of excised and fixed tissues influences the extraction and use of image parameters specific to polarization-resolved SHG (PSHG) microscopy, which are known to provide quantitative information on the collagen structure and organization. We employ a theoretical collagen model for fitting the experimental PSHG datasets to obtain the second order susceptibility tensor elements ratios and the fitting efficiency. Furthermore, the second harmonic intensity acquired under circular polarization is investigated. The evolution of these parameters in both forward- and backward-collected SHG are computed for both H&E-stained and unstained tissue sections. Consistent modifications are observed between the two cases in terms of the fitting efficiency and the second harmonic intensity. This suggests that similar quantitative analysis workflows applied to PSHG images collected on stained and unstained tissues could yield different results, and hence affect the diagnostic accuracy.

The Status of Advanced Imaging Techniques for Optical Biopsy of Colonic Polyps

The progressive miniaturization of photonic components presents the opportunity to obtain unprecedented microscopic images of colonic polyps in real time during endoscopy. This information has the potential to act as "optical biopsy" to aid clinical decision-making, including the possibility of adopting new paradigms such as a "resect and discard" approach for low-risk lesions. The technologies discussed in this review include confocal laser endomicroscopy, optical coherence tomography, multiphoton microscopy, Raman spectroscopy, and hyperspectral imaging. These are in different stages of development and clinical readiness, but all show the potential to produce reliable in vivo discrimination of different tissue types. A structured literature search of the imaging techniques for colorectal polyps has been conducted. The significant developments in endoscopic imaging were identified for each modality, and the status of current development was discussed. Of the advanced imaging techniques discussed, confocal laser endomicroscopy is in clinical use and, under optimal conditions with an experienced operator, can provide accurate histological assessment of tissue. The remaining techniques show potential for incorporation into endoscopic equipment and practice, although further component development is needed, followed by robust prospective validation of accuracy. Optical coherence tomography illustrates tissue "texture" well and gives good assessment of mucosal thickness and layers. Multiphoton microscopy produces high-resolution images at a subcellular resolution. Raman spectroscopy and hyperspectral imaging are less developed endoscopically but provide a tissue "fingerprint" which can distinguish between tissue types. Molecular imaging may become a powerful adjunct to other techniques, with its ability to precisely label specific molecules within tissue and thereby enhance imaging.

Ex Vivo Microscopy: A Promising Next-Generation Digital Microscopy Tool for Surgical Pathology Practice

CONTEXT.—

The rapid evolution of optical imaging modalities in recent years has opened the opportunity for ex vivo tissue imaging, which has significant implications for surgical pathology practice. These modalities have promising potential to be used as next-generation digital microscopy tools for examination of fresh tissue, with or without labeling with contrast agents.

OBJECTIVE.—

To review the literature regarding various types of ex vivo optical imaging platforms that can generate digital images for tissue recognition with potential for utilization in anatomic pathology clinical practices.

DATA SOURCES.—

Literature relevant to ex vivo tissue imaging obtained from the PubMed database.

CONCLUSIONS.—

Ex vivo imaging of tissues can be performed by using various types of optical imaging techniques. These next-generation digital microscopy tools have a promising potential for utilization in surgical pathology practice.

A Review of New and Emerging Techniques For Optical Diagnosis of Colonic Polyps

BACKGROUND AND AIMS

Endoscopic imaging is a rapidly progressing field and benefits from miniaturization of advanced imaging technologies, which may allow accurate real-time characterization of lesions. The concept of the "optical biopsy" to predict polyp histology has gained prominence in recent years and may become clinically applicable with the advent of new imaging technology. This review aims to discuss current evidence and examine the emerging technologies as applied to the optical diagnosis of colorectal polyps.

METHODS

A structured literature search and review has been carried out of the evidence for diagnostic accuracy of image-enhanced endoscopy and emerging endoscopic imaging technologies. The image-enhanced endoscopy techniques are reviewed, including their basic scientific principles and current evidence for effectiveness. These include the established image-enhancement technologies such as narrow-band imaging, i-scan, and Fuji intelligent chromoendoscopy. More recent technologies including optical enhancement, blue laser imaging, and linked color imaging are discussed. Adjunctive imaging techniques in current clinical use are discussed, such as autofluorescence imaging and endocytoscopy. The emerging advanced imaging techniques are reviewed, including confocal laser endomicroscopy, optical coherence tomography, and Raman spectroscopy.

CONCLUSIONS

Large studies of the established image-enhancement techniques show some role for the optical diagnosis of polyp histology, although results have been mixed, and at present only the technique of narrow-band imaging is appropriate for the diagnosis of low-risk polyps when used by an expert operator. Other image-enhancement techniques will require further study to validate their accuracy but show potential to support the use of a "resect-and-discard" approach to low-risk polyps. New technologies show exciting potential for real-time diagnosis, but further clinical studies in humans have yet to be performed.

Exploring Multiphoton Microscopy as a Novel Tool to Differentiate Chromophobe Renal Cell Carcinoma From Oncocytoma in Fixed Tissue Sections

Context.—

Distinguishing chromophobe renal cell carcinoma (chRCC), especially in the presence of eosinophilic cytoplasm, from oncocytoma on hematoxylin-eosin can be difficult and often requires time-consuming ancillary procedures that ultimately may not be informative.

Objective.—

To explore the potential of multiphoton microscopy (MPM) as an alternative and rapid diagnostic tool in differentiating oncocytoma from chRCC at subcellular resolution without tissue processing.

Design.—

Unstained, deparaffinized tissue sections from 27 tumors (oncocytoma [n = 12], chRCC [n = 12], eosinophilic variant of chRCC [n = 1], and atypical oncocytic renal neoplasm [n = 2]) were imaged with MPM. Morphologic evaluation and automated quantitative morphometric analysis were conducted to distinguish between chRCC and oncocytoma.

Results.—

The typical cases of oncocytomas (12 of 12) and chRCC (12 of 12) could be readily differentiated on MPM based on the morphologic features similar to hematoxylin-eosin. The most striking MPM signature of both of the tumors was the presence of autofluorescent intracytoplasmic granules, which are not seen on hematoxylin-eosin–stained slides. Although we saw these granules in both types of tumors, they appeared distinct, based on their size, shape, cytoplasmic distribution, and autofluorescence wavelengths, and were valuable in arriving at a definitive diagnosis. For oncocytomas and chRCC, high diagnostic accuracies of 100% and 83.3% were achieved on blinded MPM and morphometric analysis, respectively.

Conclusions.—

To the best of our knowledge, this is the first demonstration of MPM to distinguish chRCC from oncocytoma in fixed tissues. Our study was limited by small sample size and only a few variants of oncocytic tumors. Prospective studies are warranted to assess the utility of MPM as a diagnostic aid in oncocytic renal tumors.

Non-linear optical imaging and quantitative analysis of the pathological changes in normal and carcinomatous human colorectal muscularis

Non-linear optical (NLO) imaging based on two-photon excitation (2PE) and second harmonic generation (SHG) has been widely used to image microstructures of biomedical specimens over the last two decades. We employed NLO imaging technology to investigate the histology of normal and carcinomatous human colorectal muscularis in transverse and longitudinal views. Results show there are different patterns of pathological changes of muscularis in tissue structure and cell morphology from both views. The NLO imaging provides identical histological information as the H&E images but requires neither stain nor tissue processing. Our study indicates that NLO imaging technology shows more detailed microstructure, which is a critical complementary tool in pathological diagnosis of colorectal tumours. It suggests that NLO imaging could be a very important diagnostic tool to help pathologists realise the real time early detection of human colorectal tumours in the foreseeable future.

Imaging normal and cancerous human gastric muscular layer in transverse and longitudinal sections by multiphoton microscopy

Multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) has been widely used for imaging microstructure of biological tissues. In this article, we used MPM to investigate the microstructure changes of normal and cancerous human gastric muscular layer in transverse and longitudinal sections. The results displayed different patterns of microstructure changes of smooth muscular tissue, cell morphology and interstitial fibers in transverse and longitudinal sections, being similar to standard histopathological images but without the need for tissue processing. Our study demonstrated that MPM can bring more detailed complementary information on tissue architecture through observing transverse and longitudinal sections of tissues, which are the important pathological information when the pathologists diagnose the gastrointestinal lesions. These observations indicate that MPM could be an important potential tool to provide real-time pathological diagnosis for gastric cancer in the future. SCANNING 38:357-364, 2016. © 2015 Wiley Periodicals, Inc.

In vivo nonlinear optical imaging to monitor early microscopic changes in a murine cutaneous squamous cell carcinoma model

Early detection of cutaneous squamous cell carcinoma (cSCC) can enable timely therapeutic and preventive interventions for patients. In this study, in vivo nonlinear optical imaging (NLOI) based on two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG), was used to non-invasively detect microscopic changes occurring in murine skin treated topically with 7,12-dimethylbenz(a)anthracene (DMBA). The optical microscopic findings and the measured TPEF-SHG index show that NLOI was able to clearly detect early cytostructural changes in DMBA treated skin that appeared clinically normal. This suggests that in vivo NLOI could be a non-invasive tool to monitor early signs of cSCC. In vivo axial NLOI scans of normal murine skin (upper left), murine skin with preclinical hyperplasia (upper right), early clinical murine skin lesion (lower left) and late or advanced murine skin lesion (lower right).

Label-free and depth resolved optical sectioning of iron-complex deposits in sickle cell disease splenic tissue by multiphoton microscopy

Multiphoton microscopy (MPM) imaging of intrinsic two-photon excited fluorescence (TPEF) is performed on humanized sickle cell disease (SCD) mouse model splenic tissue. Distinct morphological and spectral features associated with SCD are identified and discussed in terms of diagnostic relevance. Specifically, spectrally unique splenic iron-complex deposits are identified by MPM; this finding is supported by TPEF spectroscopy and object size to standard histopathological methods. Further, iron deposits are found at higher concentrations in diseased tissue than in healthy tissue by all imaging methods employed here including MPM, and therefore, may provide a useful biomarker related to the disease state. These newly characterized biomarkers allow for further investigations of SCD in live animals as a means to gain insight into the mechanisms impacting immune dysregulation and organ malfunction, which are currently not well understood.

Advances and challenges in label-free nonlinear optical imaging using two-photon excitation fluorescence and second harmonic generation for cancer research

Nonlinear optical imaging (NLOI) has emerged to be a promising tool for bio-medical imaging in recent times. Among the various applications of NLOI, its utility is the most significant in the field of pre-clinical and clinical cancer research. This review begins by briefly covering the core principles involved in NLOI, such as two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG). Subsequently, there is a short description on the various cellular components that contribute to endogenous optical fluorescence. Later on the review deals with its main theme--the challenges faced during label-free NLO imaging in translational cancer research. While this review addresses the accomplishment of various label-free NLOI based studies in cancer diagnostics, it also touches upon the limitations of the mentioned studies. In addition, areas in cancer research that need to be further investigated by label-free NLOI are discussed in a latter segment. The review eventually concludes on the note that label-free NLOI has and will continue to contribute richly in translational cancer research, to eventually provide a very reliable, yet minimally invasive cancer diagnostic tool for the patient.

Gradient index lens based combined two-photon microscopy and optical coherence tomography

We report a miniaturized probe-based combined two-photon microscopy (TPM) and optical coherence tomography (OCT) system. This system is to study the colorectal cancer in mouse models by visualizing both cellular and structural information of the colon in 3D with TPM and OCT respectively. The probe consisted of gradient index (GRIN) lenses and a 90° reflecting prism at its distal end for side-viewing, and it was added onto an objective lens-based TPM and OCT system. The probe was 2.2 mm in diameter and 60 mm in length. TPM imaging was performed by raster scanning of the excitation focus at the imaging speed of 15.4 frames/s. OCT imaging was performed by combining the linear sample translation and probe rotation along its axis. This miniaturized probe based dual-modal system was characterized with tissue phantoms containing fluorescent microspheres, and applied to image mouse colonic tissues ex vivo as a demonstration. As OCT and TPM provided structural and cellular information of the tissues respectively, this probe based multi-modal imaging system can be helpful for in vivo studies of preclinical animal models such as mouse colonic tumorigenesis.

Stromal alterations as quantitative optical biomarkers of epithelial tumor progression

Stroma plays an important role during epithelial tumor progression. Probing stroma alteration may become an intrinsic indicator for evaluating epithelial tumor progression. In this review, we summarize our recent works on stromal alterations as quantitative optical biomarkers of epithelial tumor progression by use of nonlinear optical microscopy.

Multiphoton microscopy: a potential "optical biopsy" tool for real-time evaluation of lung tumors without the need for exogenous contrast agents

CONTEXT

Multiphoton microscopy (MPM) is an emerging, nonlinear, optical-biopsy technique, which can generate subcellular-resolution images from unprocessed and unstained tissue in real time.

OBJECTIVE

To assess the potential of MPM for lung tumor diagnosis.

DESIGN

Fresh sections from tumor and adjacent nonneoplastic lung were imaged with MPM and then compared with corresponding hematoxylin-eosin slides.

RESULTS

Alveoli, bronchi, blood vessels, pleura, smokers' macrophages, and lymphocytes were readily identified with MPM in nonneoplastic tissue. Atypical adenomatous hyperplasia (a preinvasive lesion) was identified in tissue adjacent to the tumor in one case. Of the 25 tumor specimens used for blinded pathologic diagnosis, 23 were diagnosable with MPM. Of these 23 cases, all but one adenocarcinoma (15 of 16; 94%) was correctly diagnosed on MPM, along with their histologic patterns. For squamous cell carcinoma, 4 of 7 specimens (57%) were correctly diagnosed. For the remaining 3 squamous cell carcinoma specimens, the solid pattern was correctly diagnosed in 2 additional cases (29%), but it was not possible to distinguish the squamous cell carcinoma from adenocarcinoma. The other squamous cell carcinoma specimen (1 of 7; 14%) was misdiagnosed as adenocarcinoma because of pseudogland formation. Invasive adenocarcinomas with acinar and solid pattern showed statistically significant increases in collagen. Interobserver agreement for collagen quantification (among 3 observers) was 80%.

CONCLUSIONS

Our pilot study provides a proof of principle that MPM can differentiate neoplastic from nonneoplastic lung tissue and identify tumor subtypes. If confirmed in a future, larger study, we foresee real-time intraoperative applications of MPM, using miniaturized instruments for directing lung biopsies, assessing their adequacy for subsequent histopathologic analysis or banking, and evaluating surgical margins in limited lung resections.

Efficient 1856 nm emission from Tm,Mg:LiNbO3 laser

Efficient continuous-wave laser emission at 1856 nm from a Tm,Mg:LiNbO(3) crystal slab with high Tm(3+) doping concentration is reported. A maximum output power of 2.62 W is realized with a slope efficiency of 19.6% and the beam quality factor M(2) of 1.7 at room temperature. We believe that this is the first demonstration of watt-level laser operation in Tm,Mg:LiNbO(3) crystal and the output power is four orders of magnitude higher than that reported previously in Tm-doped LiNbO(3) crystal. Performance degradation due to the photorefractive effect under high intensity 1856 nm laser is not observed thanks to the co-doping of magnesium ions. Quantitative analysis about the long-term photorefractive effect is also provided. Multi-wavelength laser operation is realized by using different narrow-band output couplers. This demonstration opens up a viable pathway towards 2-μm integrated optic devices for achieving laser oscillation, electro-optic and nonlinear optical effects within just one sample simultaneously.

Real-time optical diagnosis for surgical margin in low rectal cancer using multiphoton microscopy

BACKGROUND

Multiphoton microscopy (MPM), based on advances in the field of nonlinear optics and femtosecond lasers, has been shown to provide detailed real-time information on tissue architecture and cell morphology in live tissue. The purpose of this study was to evaluate the feasibility of using MPM to make real-time optical diagnoses for surgical margins in low rectal cancers.

METHODS

Thirty fresh, unfixed, and unstained full-thickness surgical margins of low rectal cancers underwent MPM examination and then went through intraoperative frozen procedures and routine pathological procedures. MPM images were compared with the gold standard hematoxylin-eosin (H-E) stained images.

RESULTS

MPM images were acquired by two channels: broadband autofluorescence from cells and second harmonic generation (SHG) from tissue collagen. Peak multiphoton signal intensity was detected in mucosa excited at 800 nm. There were significant differences between negative surgical margins and positive surgical margins under MPM examination. In negative surgical margins, MPM revealed regular tissue architecture and cell morphology, including a typical foveolar pattern with central, round crypt openings, and glands lined by epithelial and goblet cells. SHG signals could be detected around the glands. In positive surgical margins, MPM demonstrated irregular tubular structures, reduced stroma, and cellular and nuclear pleomorphisms. Cancer cells were characterized by an irregular size and shape, enlarged nuclei, and an increased nuclear-cytoplasmic ratio. SHG signals were significantly decreased in positive surgical margins compared with negative surgical margins. MPM images were comparable to H-E stained images.

CONCLUSIONS

We demonstrated the feasibility of using MPM to make real-time optical diagnoses for surgical margins in low rectal cancer. With the miniaturization and integration of colonoscopy or probes, MPM has the potential to provide real-time noninvasive optical diagnosis for surgical margins in low rectal cancer in the near future.

Stereotaxic device for optical imaging of mice hind feet

Imaging of in vivo model systems, especially mouse models, has revolutionized our understanding of normal and pathological developments. However, mice present several challenges for imaging. They are living and therefore breathing organisms with a fast heart rate (>500 beat/min), which necessitates the need for restraints and positioning controls that do not compromise their normal physiology. We present here a device that immobilizes the rear legs of a mouse while retaining the ability to position both the hind feet and legs for reproducible imaging deep below the skin's surface. The device is highly adjustable to accommodate mice, 5 weeks of age and older. The function of this device is demonstrated by imaging the vasculature ∼250 μm beneath the skin in the hind leg. Whereas the overall dimensions are for a motorized stage (Märzhäuser Wetzlar GmbH, Wetzlar, Germany), minor modifications would allow it to be customized for use with most commercially available stages that accept an insert.

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.