High-Resolution Rapid Diagnostic Imaging of Whole Prostate Biopsies Using Video-Rate Fluorescence Structured Illumination Microscopy

Structured illumination microscopy for cancer identification in diagnostic breast biopsies

Breast cancer is the second most common cancer diagnosed in women in the US with almost 280,000 new cases anticipated in 2023. Currently, on-site pathology for location guidance is not available during the collection of breast biopsies or during surgical intervention procedures. This shortcoming contributes to repeat biopsy and re-excision procedures, increasing the cost and patient discomfort during the cancer management process. Both procedures could benefit from on-site feedback, but current clinical on-site evaluation techniques are not commonly used on breast tissue because they are destructive and inaccurate. Ex-vivo microscopy is an emerging field aimed at creating histology-analogous images from non- or minimally-processed tissues, and is a promising tool for addressing this pain point in clinical cancer management. We investigated the ability structured illumination microscopy (SIM) to generate images from freshly-obtained breast tissues for structure identification and cancer identification at a speed compatible with potential on-site clinical implementation. We imaged 47 biopsies from patients undergoing a guided breast biopsy procedure using a customized SIM system and a dual-color fluorescent hematoxylin & eosin (H&E) analog. These biopsies had an average size of 0.92 cm2 (minimum 0.1, maximum 4.2) and had an average imaging time of 7:29 (minimum 0:22, maximum 37:44). After imaging, breast biopsies were submitted for standard histopathological processing and review. A board-certified pathologist returned a binary diagnostic accuracy of 96% when compared to diagnoses from gold-standard histology slides, and key tissue features including stroma, vessels, ducts, and lobules were identified from the resulting images.

Current Landscape of Advanced Imaging Tools for Pathology Diagnostics

Histopathology relies on century-old workflows of formalin fixation, paraffin embedding, sectioning, and staining tissue specimens on glass slides. Despite being robust, this conventional process is slow, labor-intensive, and limited to providing two-dimensional views. Emerging technologies promise to enhance and accelerate histopathology. Slide-free microscopy allows rapid imaging of fresh, unsectioned specimens, overcoming slide preparation delays. Methods such as fluorescence confocal microscopy, multiphoton microscopy, along with more recent innovations including microscopy with UV surface excitation and fluorescence-imitating brightfield imaging can generate images resembling conventional histology directly from the surface of tissue specimens. Slide-free microscopy enable applications such as rapid intraoperative margin assessment and, with appropriate technology, three-dimensional histopathology. Multiomics profiling techniques, including imaging mass spectrometry and Raman spectroscopy, provide highly multiplexed molecular maps of tissues, although clinical translation remains challenging. Artificial intelligence is aiding the adoption of new imaging modalities via virtual staining, which converts methods such as slide-free microscopy into synthetic brightfield-like or even molecularly informed images. Although not yet commonplace, these emerging technologies collectively demonstrate the potential to modernize histopathology. Artificial intelligence-assisted workflows will ease the transition to new imaging modalities. With further validation, these advances may transform the century-old conventional histopathology pipeline to better serve 21st-century medicine. This review provides an overview of these enabling technology platforms and discusses their potential impact.

A Pilot Validation Study Comparing Fluorescence-Imitating Brightfield Imaging, A Slide-Free Imaging Method, With Standard Formalin-Fixed, Paraffin-Embedded Hematoxylin-Eosin-Stained Tissue Section Histology for Primary Surgical Pathology Diagnosis

CONTEXT.—

Digital pathology using whole slide images has been recently approved to support primary diagnosis in clinical surgical pathology practices. Here we describe a novel imaging method, fluorescence-imitating brightfield imaging, that can capture the surface of fresh tissue without requiring prior fixation, paraffin embedding, tissue sectioning, or staining.

OBJECTIVE.—

To compare the ability of pathologists to evaluate direct-to-digital images with standard pathology preparations.

DESIGN.—

One hundred surgical pathology samples were obtained. Samples were first digitally imaged, then processed for standard histologic examination on 4-μm hematoxylin-eosin-stained sections and digitally scanned. The resulting digital images from both digital and standard scan sets were viewed by each of 4 reading pathologists. The data set consisted of 100 reference diagnoses and 800 study pathologist reads. Each study read was compared to the reference diagnosis, and also compared to that reader's diagnosis across both modalities.

RESULTS.—

The overall agreement rate, across 800 reads, was 97.9%. This consisted of 400 digital reads at 97.0% versus reference and 400 standard reads versus reference at 98.8%. Minor discordances (defined as alternative diagnoses without clinical treatment or outcome implications) were 6.1% overall, 7.2% for digital, and 5.0% for standard.

CONCLUSIONS.—

Pathologists can provide accurate diagnoses from fluorescence-imitating brightfield imaging slide-free images. Concordance and discordance rates are similar to published rates for comparisons of whole slide imaging to standard light microscopy of glass slides for primary diagnosis. It may be possible, therefore, to develop a slide-free, nondestructive approach for primary pathology diagnosis.

Rapid digital pathology of H&E-stained fresh human brain specimens as an alternative to frozen biopsy

BACKGROUND

Hematoxylin and Eosin (H&E)-based frozen section (FS) pathology is presently the global standard for intraoperative tumor assessment (ITA). Preparation of frozen section is labor intensive, which might consume up-to 30 minutes, and is susceptible to freezing artifacts. An FS-alternative technique is thus necessary, which is sectioning-free, artifact-free, fast, accurate, and reliably deployable without machine learning and/or additional interpretation training.

METHODS

We develop a training-free true-H&E Rapid Fresh digital-Pathology (the-RFP) technique which is 4 times faster than the conventional preparation of frozen sections. The-RFP is assisted by a mesoscale Nonlinear Optical Gigascope (mNLOG) platform with a streamlined rapid artifact-compensated 2D large-field mosaic-stitching (rac2D-LMS) approach. A sub-6-minute True-H&E Rapid whole-mount-Soft-Tissue Staining (the-RSTS) protocol is introduced for soft/frangible fresh brain specimens. The mNLOG platform utilizes third harmonic generation (THG) and two-photon excitation fluorescence (TPEF) signals from H and E dyes, respectively, to yield the-RFP images.

RESULTS

We demonstrate the-RFP technique on fresh excised human brain specimens. The-RFP enables optically-sectioned high-resolution 2D scanning and digital display of a 1 cm² area in <120 seconds with 3.6 Gigapixels at a sustained effective throughput of >700 M bits/sec, with zero post-acquisition data/image processing. Training-free blind tests considering 50 normal and tumor-specific brain specimens obtained from 8 participants reveal 100% match to the respective formalin-fixed paraffin-embedded (FFPE)-biopsy outcomes.

CONCLUSIONS

We provide a digital ITA solution: the-RFP, which is potentially a fast and reliable alternative to FS-pathology. With H&E-compatibility, the-RFP eliminates color- and morphology-specific additional interpretation training for a pathologist, and the-RFP-assessed specimen can reliably undergo FFPE-biopsy confirmation.

Label-free intraoperative histology of bone tissue via deep-learning-assisted ultraviolet photoacoustic microscopy

Obtaining frozen sections of bone tissue for intraoperative examination is challenging. To identify the bony edge of resection, orthopaedic oncologists therefore rely on pre-operative X-ray computed tomography or magnetic resonance imaging. However, these techniques do not allow for accurate diagnosis or for intraoperative confirmation of the tumour margins, and in bony sarcomas, they can lead to bone margins up to 10-fold wider (1,000-fold volumetrically) than necessary. Here, we show that real-time three-dimensional contour-scanning of tissue via ultraviolet photoacoustic microscopy in reflection mode can be used to intraoperatively evaluate undecalcified and decalcified thick bone specimens, without the need for tissue sectioning. We validate the technique with gold-standard haematoxylin-and-eosin histology images acquired via a traditional optical microscope, and also show that an unsupervised generative adversarial network can virtually stain the ultraviolet-photoacoustic-microscopy images, allowing pathologists to readily identify cancerous features. Label-free and slide-free histology via ultraviolet photoacoustic microscopy may allow for rapid diagnoses of bone-tissue pathologies and aid the intraoperative determination of tumour margins.

Rapid On-Site Microscopy and Mapping of Diagnostic Biopsies for See-And-Treat Guidance of Localized Prostate Cancer Therapy

Prostate cancer continues to be the most diagnosed non-skin malignancy in men. While up to one in eight men will be diagnosed in their lifetimes, most diagnoses are not fatal. Better lesion location accuracy combined with emerging localized treatment methods are increasingly being utilized as a treatment option to preserve healthy function in eligible patients. In locating lesions which are generally <2cc within a prostate (average size 45cc), small variance in MRI-determined boundaries, tumoral heterogeneity, patient characteristics including location of lesion and prostatic calcifications, and patient motion during the procedure can inhibit accurate sampling for diagnosis. The locations of biopsies are recorded and are then fully processed by histology and diagnosed via pathology, often days to weeks later. Utilization of real-time feedback could improve accuracy, potentially prevent repeat procedures, and allow patients to undergo treatment of clinically localized disease at earlier stages. Unfortunately, there is currently no reliable real-time feedback process for confirming diagnosis of biopsy samples. We examined the feasibility of implementing structured illumination microscopy (SIM) as a method for on-site diagnostic biopsy imaging to potentially combine the diagnostic and treatment appointments for prostate cancer patients, or to confirm tumoral margins for localized ablation procedures. We imaged biopsies from 39 patients undergoing image-guided diagnostic biopsy using a customized SIM system and a dual-color fluorescent hematoxylin & eosin (H&E) analog. The biopsy images had an average size of 342 megapixels (minimum 78.1, maximum 842) and an average imaging duration of 145 s (minimum 56, maximum 322). Comparison of urologist's suspicion of malignancy based on MRI, to pathologist diagnosis of biopsy images obtained in real time, reveals that real-time biopsy imaging could significantly improve confirmation of malignancy or tumoral margins over medical imaging alone.

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.

Evaluation of an Integrated Spectroscopy and Classification Platform for Point-of-Care Core Needle Biopsy Assessment: Performance Characteristics from Ex Vivo Renal Mass Biopsies

PURPOSE

To evaluate a transmission optical spectroscopy instrument for rapid ex vivo assessment of core needle cancer biopsies (CNBs) at the point of care.

MATERIALS AND METHODS

CNBs from surgically resected renal tumors and nontumor regions were scanned on their sampling trays with a custom spectroscopy instrument. After extracting principal spectral components, machine learning was used to train logistic regression, support vector machines, and random decision forest (RF) classifiers on 80% of randomized and stratified data. The algorithms were evaluated on the remaining 20% of the data set held out during training. Binary classification (tumor/nontumor) was performed based on a decision threshold. Multinomial classification was also performed to differentiate between the subtypes of renal cell carcinoma (RCC) and account for potential confounding effects from fat, blood, and necrotic tissue. Classifiers were compared based on sensitivity, specificity, and positive predictive value (PPV) relative to a histopathologic standard.

RESULTS

A total of 545 CNBs from 102 patients were analyzed, yielding 5,583 spectra after outlier exclusion. At the individual spectra level, the best performing algorithm was RF with sensitivities of 96% and 92% and specificities of 90% and 89%, for the binary and multiclass analyses, respectively. At the full CNB level, RF algorithm also showed the highest sensitivity and specificity (93% and 91%, respectively). For RCC subtypes, the highest sensitivity and PPV were attained for clear cell (93.5%) and chromophobe (98.2%) subtypes, respectively.

CONCLUSIONS

Ex vivo spectroscopy imaging paired with machine learning can accurately characterize renal mass CNB at the time of tissue acquisition.

Ultrafast 3D histological imaging based on a minutes-time scale tissue clearing and multidirectional selective plane illumination microscopy

Conventional histopathological examinations are time-consuming and labor-intensive, and are insufficient to depict 3D pathological features intuitively. Here we report an ultrafast 3D histological imaging scheme based on optimized selective plane illumination microscopy (mSPIM), a minutes-time scale clearing method (FOCM), and a deep learning-based image enhancement algorithm (SRACNet) to realize histological preparation and imaging of clinical tissues. Our scheme enables 1-minute clearing and fast imaging (up to 900 mm²/min) of 200 µm-thick mouse kidney slices at micron-level resolution. With hematoxylin and eosin analog, we demonstrated the detailed 3D morphological connections between glomeruli and the surrounding tubules, which is difficult to identify in conventional 2D histology. Further, by the preliminary verification on human kidney tissues, this study will provide new, to the best of our knowledge, feasible histological solutions and inspirations in future 3D digital pathology.

Rapid Histological Assessment of Prostate Specimens in the Three-dimensional Space by Hydrophilic Tissue Clearing and Confocal Microscopy

Microscopic examination of biopsied and resected prostatic specimens is the mainstay in the diagnosis of prostate cancer. However, conventional analysis of hematoxylin and eosin (H&E)-stained tissue is time-consuming and offers limited two-dimensional (2D) information. In the current study, we devised a method-termed Prostate Rapid Optical examination for cancer STATus (proSTAT)-for rapid screening of prostate cancer using high-resolution 2D and three-dimensional (3D) confocal images obtained after hydrophilic tissue clearing of 100-µm-thick tissue slices. The results of the proSTAT method were compared with those of traditional H&E stains for the analysis of cores (n=15) obtained from radical prostatectomy specimens (n=5). Gland lumen formation, consistent with Gleason pattern 3, was evident following tracking of multiple optical imaging sections. In addition, 3D rendering allowed visualizing a tubular network of interconnecting branches. Rapid 3D fluorescent labeling of tumor protein p63 accurately distinguished prostate adenocarcinoma from normal tissue and benign lesions. Compared with conventional stains, the 3D spatial and molecular information extracted from proSTAT may significantly increase the amount of available data for pathological assessment of prostate specimens. Our approach is amenable to automation and-subject to independent validation-can find a wide spectrum of clinical and research applications.

Label-free multimodal nonlinear optical imaging of needle biopsy cores for intraoperative cancer diagnosis

SIGNIFICANCE

Needle biopsy (NB) procedures are important for the initial diagnosis of many types of cancer. However, the possibility of NB specimens being unable to provide diagnostic information, (i.e., non-diagnostic sampling) and the time-consuming histological evaluation process can cause delays in diagnoses that affect patient care.

AIM

We aim to demonstrate the advantages of this label-free multimodal nonlinear optical imaging (NLOI) technique as a non-destructive point-of-procedure evaluation method for NB tissue cores, for the visualization and characterization of the tissue microenvironment.

APPROACH

A portable, label-free, multimodal NLOI system combined second-harmonic generation (SHG) and third-harmonic generation and two- and three-photon autofluorescence (2PF, 3PF) microscopy. It was used for intraoperative imaging of fresh NB tissue cores acquired during canine cancer surgeries, which involved liver, lung, and mammary tumors as well as soft-tissue sarcoma; in total, eight canine patients were recruited. An added tissue culture chamber enabled the use of this NLOI system for longitudinal imaging of fresh NB tissue cores taken from an induced rat mammary tumor and healthy mouse livers.

RESULTS

The intraoperative NLOI system was used to assess fresh canine NB specimens during veterinary cancer surgeries. Histology-like morphological features were visualized by the combination of four NLOI modalities at the point-of-procedure. The NLOI results provided quantitative information on the tissue microenvironment such as the collagen fiber orientation using Fourier-domain SHG analysis and metabolic profiling by optical redox ratio (ORR) defined by 2PF/(2PF + 3PF). The analyses showed that the canine mammary tumor had more randomly oriented collagen fibers compared to the tumor margin, and hepatocarcinoma had a wider distribution of ORR with a lower mean value compared to the liver fibrosis and the normal-appearing liver. Moreover, the loss of metabolic information during tissue degradation of fresh murine NB specimens was shown by overall intensity decreases in all channels and an increase of mean ORR from 0.94 (standard deviation 0.099) to 0.97 (standard deviation 0.077) during 1-h longitudinal imaging of a rat mammary tumor NB specimen. The tissue response to staurosporine (STS), an apoptotic inducer, from fresh murine liver NB specimens was also observed. The mean ORR decreased from 0.86 to 0.74 in the first 40 min and then increased to 0.8 during the rest of the hour of imaging, compared to the imaging results without the addition of STS, which showed a continuous increase of ORR from 0.72 to 0.75.

CONCLUSIONS

A label-free, multimodal NLOI platform reveals microstructural and metabolic information of the fresh NB cores during intraoperative cancer imaging. This system has been demonstrated on animal models to show its potential to provide a more comprehensive histological assessment and a better understanding of the unperturbed tumor microenvironment. Considering tissue degradation, or loss of viability upon fixation, this intraoperative NLOI system has the advantage of immediate assessment of freshly excised tissue specimens at the point of procedure.

Rapid slide-free and non-destructive histological imaging using wide-field optical-sectioning microscopy

Histopathology based on formalin-fixed and paraffin-embedded tissues has long been the gold standard for surgical margin assessment (SMA). However, routine pathological practice is lengthy and laborious, failing to guide surgeons intraoperatively. In this report, we propose a practical and low-cost histological imaging method with wide-field optical-sectioning microscopy (i.e., High-and-Low-frequency (HiLo) microscopy). HiLo can achieve rapid and non-destructive imaging of freshly-excised tissues at an extremely high acquisition speed of 5 cm²/min with a spatial resolution of 1.3 µm (lateral) and 5.8 µm (axial), showing great potential as an SMA tool that can provide immediate feedback to surgeons and pathologists for intraoperative decision-making. We demonstrate that HiLo enables rapid extraction of diagnostic features for different subtypes of human lung adenocarcinoma and hepatocellular carcinoma, producing surface images of rough specimens with large field-of-views and cellular features that are comparable to the clinical standard. Our results show promising clinical translations of HiLo microscopy to improve the current standard of care.

Versatile chip-based nanoscopy becomes ready for histopathology assessment

Nanoscopy is a mature technology used routinely in life science to obtain images well below the optical diffraction limit. But the use of nanoscopy in histopathology assessment is very limited mostly due to the low throughput of traditional nanoscopic techniques. So far, Chip-nanoscopy, nanoscopy in which sample illumination is performed by an integrated photonic chip instead of bulk optics, has been shown to provide an enhanced field of view and throughput for cell biology. Now, a new development shows that chip-nanoscopy also offers interesting progress for the study of histological samples offering a complementary technique to electron microscopy for histopathology assessment.

Real-time diagnosis and Gleason grading of prostate core needle biopsies using nonlinear microscopy

Rapid histologic assessment of fresh prostate biopsies may reduce patient anxiety, aid in biopsy sampling, and enable specimen triaging for molecular/genomic analyses and research that could benefit from fresh tissue analysis. Nonlinear microscopy (NLM) is a fluorescence microscopy technique that can produce high-resolution images of freshly excised tissue resembling formalin-fixed paraffin-embedded (FFPE) H&E. NLM enables evaluation of tissue up to ~100 µm below the surface, analogous to serial sectioning, but without requiring microtome sectioning. One hundred and seventy biopsies were collected from 63 patients who underwent in-bore MRI or MRI/ultrasound fusion biopsy procedures. Biopsies were stained in acridine orange and sulforhodamine 101, a nuclear and cytoplasmic/stromal fluorescent dye, for 45 s. Genitourinary pathologists evaluated the biopsies using NLM by translating the biopsies in real time to areas of interest and NLM images were recorded. After NLM evaluation, the biopsies were processed for standard FFPE H&E and similarities and differences between NLM and FFPE H&E were investigated. Accuracies of NLM diagnoses and Gleason scores were calculated using FFPE histology as the gold standard. Pathologists achieved a 92.4% sensitivity (85.0-96.9%, 95% confidence intervals) and 100.0% specificity (94.3-100.0%) for detecting carcinoma compared to FFPE histology. The agreement between the Grade Group determined by NLM versus FFPE histology had an unweighted Cohen's Kappa of 0.588. The average NLM evaluation time was 2.10 min per biopsy (3.08 min for the first 20 patients, decreasing to 1.54 min in subsequent patients). Further studies with larger patient populations, larger number of pathologists, and multiple institutions are warranted. NLM is a promising method for future rapid evaluation of prostate needle core biopsies.

Chip-based multimodal super-resolution microscopy for histological investigations of cryopreserved tissue sections

Histology involves the observation of structural features in tissues using a microscope. While diffraction-limited optical microscopes are commonly used in histological investigations, their resolving capabilities are insufficient to visualize details at subcellular level. Although a novel set of super-resolution optical microscopy techniques can fulfill the resolution demands in such cases, the system complexity, high operating cost, lack of multi-modality, and low-throughput imaging of these methods limit their wide adoption for histological analysis. In this study, we introduce the photonic chip as a feasible high-throughput microscopy platform for super-resolution imaging of histological samples. Using cryopreserved ultrathin tissue sections of human placenta, mouse kidney, pig heart, and zebrafish eye retina prepared by the Tokuyasu method, we demonstrate diverse imaging capabilities of the photonic chip including total internal reflection fluorescence microscopy, intensity fluctuation-based optical nanoscopy, single-molecule localization microscopy, and correlative light-electron microscopy. Our results validate the photonic chip as a feasible imaging platform for tissue sections and pave the way for the adoption of super-resolution high-throughput multimodal analysis of cryopreserved tissue samples both in research and clinical settings.

Slide Over: Advances in Slide-Free Optical Microscopy as Drivers of Diagnostic Pathology

Conventional analysis using clinical histopathology is based on bright-field microscopy of thinly sliced tissue specimens. Although bright-field microscopy is a simple and robust method of examining microscope slides, the preparation of the slides needed is a lengthy and labor-intensive process. Slide-free histopathology, however, uses direct imaging of intact, minimally processed tissue samples using advanced optical-imaging systems, bypassing the extended workflow now required for the preparation of tissue sections. This article explains the technical basis of slide-free microscopy, reviews common slide-free optical microscopy techniques, and discusses the opportunities and challenges involved in clinical implementation.

Ex Vivo Fluorescence Confocal Microscopy in Specimens of the Liver: A Proof-of-Concept Study

Ex vivo Fluorescence Confocal Microscopy (FCM) is a technique providing high-resolution images of native tissues. The method is increasingly used in surgical settings in areas of dermatology and urology. Only a few publications exist about examinations of tumors and non-neoplastic lesions of the liver. We report on the application of FCM in biopsies, surgical specimens and autopsy material (33 patients, 39 specimens) of the liver and compare the results to conventional histology. Our preliminary examinations indicated a perfect suitability for tumor diagnosis (ĸ = 1.00) and moderate/good suitability for the assessment of inflammation (ĸ = 0.4-0.6) with regard to their severity and localization. Macro-vesicular steatosis was reliably detected, micro-vesicular steatosis tended to be underestimated. Cholestasis and eosinophilic granules in granulocytes were not represented in the scans. The tissue was preserved as native material and maintained its quality for downstream histological, immunohistological and molecular examinations. In summary, FCM is a material sparing method that provides rapid feedback to the clinician about the presence of tumor, the degree of inflammation and structural changes. This can lead to faster therapeutic decisions in the management of liver tumors, treatment of hepatitis or in liver transplant medicine.

High-Throughput, Label-Free and Slide-Free Histological Imaging by Computational Microscopy and Unsupervised Learning

Rapid and high-resolution histological imaging with minimal tissue preparation has long been a challenging and yet captivating medical pursuit. Here, the authors propose a promising and transformative histological imaging method, termed computational high-throughput autofluorescence microscopy by pattern illumination (CHAMP). With the assistance of computational microscopy, CHAMP enables high-throughput and label-free imaging of thick and unprocessed tissues with large surface irregularity at an acquisition speed of 10 mm2 /10 s with 1.1-µm lateral resolution. Moreover, the CHAMP image can be transformed into a virtually stained histological image (Deep-CHAMP) through unsupervised learning within 15 s, where significant cellular features are quantitatively extracted with high accuracy. The versatility of CHAMP is experimentally demonstrated using mouse brain/kidney and human lung tissues prepared with various clinical protocols, which enables a rapid and accurate intraoperative/postoperative pathological examination without tissue processing or staining, demonstrating its great potential as an assistive imaging platform for surgeons and pathologists to provide optimal adjuvant treatment.

Rapid histological imaging of bone without microtome sectioning using nonlinear microscopy

Tissue preparation for histologic evaluation of bone is particularly lengthy, limiting its use in intraoperative or intraprocedural histological evaluation. Nonlinear microscopy (NLM) is an optical sectioning microscopy method that can visualize pathology in freshly excised tissue without requiring physical microtome sectioning. This study describes a rapid protocol for NLM imaging of bone and associated cartilage. NLM imaging was performed on 71 specimens of normal bone as well as arthritic, malignant and inflammatory bone tissue from 40 patients who underwent joint replacement, amputation, bone marrow biopsy or autopsy. Specimens ranged in size from core needle biopsies to transections of entire femoral heads. Specimens were stained with acridine orange and sulforhodamine 101, nuclear and cytoplasmic/stromal fluorescent dyes, for 5 min, then rinsed for 30 s. NLM fluorescent images were displayed using colors analogous to hematoxylin and eosin (H&E) to facilitate interpretation. Pathologists examined NLM images of the specimens in real time by rapidly translating the specimen to areas of interest, similar to a standard transmission light microscope. By adjusting the NLM focus depth, images from a few-μm-thick layer could be obtained down to ~100 μm below the tissue surface, analogous to serial sectioning. Following real-time NLM imaging, the tissue was processed for conventional paraffin histology, and H&E slides were compared to recorded NLM images. Similarities and differences between NLM and paraffin H&E were assessed. NLM enabled visualization of normal bone architecture, including the lamellar matrix and osteocytes of trabecular bone, articular cartilage, as well as pathological bone features such osteoarthritis, osteomyelitis, and malignancy with an appearance resembling the paraffin H&E. Differences such as changes in cell border sharpness, cellular and nucleolar size, and color patterns were noted, suggesting that training is required for accurate evaluation of bone pathology with NLM. Irregular surface contours and debris generated by gross tissue preparation of bone can make some regions difficult to evaluate with NLM, but the ability to perform rapid three-dimensional translation and sub-surface imaging reduced these problems. NLM is a promising technique for rapid evaluation of bone pathology. Further studies assessing diagnostic performance are warranted.

Deep learning 2D and 3D optical sectioning microscopy using cross-modality Pix2Pix cGAN image translation

Structured illumination microscopy (SIM) reconstructs optically-sectioned images of a sample from multiple spatially-patterned wide-field images, but the traditional single non-patterned wide-field images are more inexpensively obtained since they do not require generation of specialized illumination patterns. In this work, we translated wide-field fluorescence microscopy images to optically-sectioned SIM images by a Pix2Pix conditional generative adversarial network (cGAN). Our model shows the capability of both 2D cross-modality image translation from wide-field images to optical sections, and further demonstrates potential to recover 3D optically-sectioned volumes from wide-field image stacks. The utility of the model was tested on a variety of samples including fluorescent beads and fresh human tissue samples.

Rapid non-destructive volumetric tumor yield assessment in fresh lung core needle biopsies using polarization sensitive optical coherence tomography

Adequate tumor yield in core-needle biopsy (CNB) specimens is essential in lung cancer for accurate histological diagnosis, molecular testing for therapeutic decision-making, and tumor biobanking for research. Insufficient tumor sampling in CNB is common, primarily due to inadvertent sampling of tumor-associated fibrosis or atelectatic lung, leading to repeat procedures and delayed diagnosis. Currently, there is no method for rapid, non-destructive intraprocedural assessment of CNBs. Polarization-sensitive optical coherence tomography (PS-OCT) is a high-resolution, volumetric imaging technique that has the potential to meet this clinical need. PS-OCT detects endogenous tissue properties, including birefringence from collagen, and degree of polarization uniformity (DOPU) indicative of tissue depolarization. Here, PS-OCT birefringence and DOPU measurements were used to quantify the amount of tumor, fibrosis, and normal lung parenchyma in 42 fresh, intact lung CNB specimens. PS-OCT results were compared to and validated against matched histology in a blinded assessment. Linear regression analysis showed strong correlations between PS-OCT and matched histology for quantification of tumors, fibrosis, and normal lung parenchyma in CNBs. PS-OCT distinguished CNBs with low tumor content from those with higher tumor content with high sensitivity and specificity. This study demonstrates the potential of PS-OCT as a method for rapid, non-destructive, label-free intra-procedural tumor yield assessment.

Feasibility study for ex vivo fluorescence confocal microscopy (FCM) on diagnostic prostate biopsies

Background

Fluorescence confocal microscopy (FCM) is a novel micro-imaging technique providing optical sections of examined tissue. The method has been well established for the diagnosis of tumours in dermatological specimens. Preliminary results found good feasibility when this technique was used to examine prostate cancer (PCa) specimens.

Methods

We report on the application of FCM in magnet resonance imaging (MRI)-fused prostate biopsies (10 patients, total number of biopsy specimens: n=121) and compare the results to conventional histology.

Results

Specific structures of the prostatic tissue were very well represented in the FCM images comparable to conventional histology. Prostate carcinoma was diagnosed with good sensitivity (79/68%) and high specificity (100%) by two pathologists with substantial/almost perfect levels of agreement with the results of conventional histology (kappa 0.79/0.86). Depending on the quality of the scans, malignant lesions of 1.8 mm and more in diameter were reliably diagnosed. Smaller lesions were rated as suspect for malignancy, but could not be consistently differentiated from reactive changes. Optimal image qualities were achieved in focus depths of up to 50 µm, whereas deeper scans led to insufficient representation of cytological features. Pre-treatment with acridine orange (AO) did not alter immunoreactivity of the tissue or its feasibility for fluorescence in situ hybridization (FISH) analyses and adequate amounts of DNA could be extracted for further polymerase chain reaction (PCR)-based examinations.

Conclusions

FCM seems to be a promising tool for the timely diagnosis in cases of PCa in patients requiring therapy. In particular, this technique is a material-sparing method that conserves the biopsies as unfixed material for further analysis such as molecular tumour companion diagnosis.

FalseColor-Python: A rapid intensity-leveling and digital-staining package for fluorescence-based slide-free digital pathology

Slide-free digital pathology techniques, including nondestructive 3D microscopy, are gaining interest as alternatives to traditional slide-based histology. In order to facilitate clinical adoption of these fluorescence-based techniques, software methods have been developed to convert grayscale fluorescence images into color images that mimic the appearance of standard absorptive chromogens such as hematoxylin and eosin (H&E). However, these false-coloring algorithms often require manual and iterative adjustment of parameters, with results that can be inconsistent in the presence of intensity nonuniformities within an image and/or between specimens (intra- and inter-specimen variability). Here, we present an open-source (Python-based) rapid intensity-leveling and digital-staining package that is specifically designed to render two-channel fluorescence images (i.e. a fluorescent analog of H&E) to the traditional H&E color space for 2D and 3D microscopy datasets. However, this method can be easily tailored for other false-coloring needs. Our package offers (1) automated and uniform false coloring in spite of uneven staining within a large thick specimen, (2) consistent color-space representations that are robust to variations in staining and imaging conditions between different specimens, and (3) GPU-accelerated data processing to allow these methods to scale to large datasets. We demonstrate this platform by generating H&E-like images from cleared tissues that are fluorescently imaged in 3D with open-top light-sheet (OTLS) microscopy, and quantitatively characterizing the results in comparison to traditional slide-based H&E histology.

Visualizing ultrastructural details of placental tissue with super-resolution structured illumination microscopy

Super-resolution fluorescence microscopy is a widely employed technique in cell biology research, yet remains relatively unexplored in the field of histopathology. Here, we describe the sample preparation steps and acquisition parameters necessary to obtain fluorescent multicolor super-resolution structured illumination microscopy (SIM) images of both formalin-fixed paraffin-embedded and cryo-preserved placental tissue sections. We compare super-resolved images of chorionic villi against diffraction-limited deconvolution microscopy and show the significant contrast and resolution enhancement attainable with SIM, demonstrating the applicability of this imaging technique for both clinical diagnosis and biological research.

Nonlinear microscopy for detection of prostate cancer: analysis of sensitivity and specificity in radical prostatectomies

Intraoperative evaluation of specimens during radical prostatectomy using frozen sections can be time and labor intensive. Nonlinear microscopy (NLM) is a fluorescence microscopy technique that can rapidly generate images that closely resemble H&E histology in freshly excised tissue, without requiring freezing or microtome sectioning. Specimens are stained with nuclear and cytoplasmic/stromal fluorophores, and NLM evaluation can begin within 3 min of grossing. Fluorescence signals can be displayed using an H&E color scale, facilitating pathologist interpretation. This study evaluates the accuracy of prostate cancer detection in a blinded reading of NLM images compared with the gold standard of formalin-fixed, paraffin-embedded H&E histology. A total of 122 freshly excised prostate specimens were obtained from 40 patients undergoing radical prostatectomy. The prostates were grossed, dissected into specimens of ~10 × 10 mm with 1-4 mm thickness, stained for 2 min for nuclear and cytoplasmic/stromal contrast, and then rinsed with saline for 30 s. NLM images were acquired and multiple images were stitched together to generate large field of view, centimeter-scale digital images suitable for reading. Specimens were then processed for standard paraffin H&E. The study protocol consisted of training, pretesting, and blinded reading phases. After a washout period, pathologists read corresponding paraffin H&E slides. Three pathologists achieved a 95% or greater sensitivity with 100% specificity for detecting cancer on NLM compared with paraffin H&E. Pooled sensitivity and specificity was 97.3% (93.7-99.1%; 95% confidence interval) and 100.0% (97.0-100.0%), respectively. Interobserver agreement for NLM reading had a Fleiss κ = 0.95. The high cancer detection accuracy and rapid specimen preparation suggest that NLM may be useful for intraoperative evaluation in radical prostatectomy.

Automated gigapixel circumferential surface microscopy of the prostate

Positive surgical margins, or cancer cells found at the boundary of an excised tumor mass, are a significant problem in the management of many cancers resulting in worsened patient outcomes. The problem is exacerbated in organ sites such as the prostate, where unnecessarily wide local excisions can result in significant deterioration of post-operative quality of life due to collateral damage to neighboring structures. Yet, at the same time, incomplete tumor removal results in worsened prognosis and need for additional interventions. Here, we report the design and development of a rapid and completely automated system for intraoperative gigapixel ex vivo microscopy of the circumferential surgical prostate margin within intra-operative timeframes, called the Automated Prostate Positioning System (APPS). The APPS leverages the rotational geometry of the prostate and high speed structured illumination microscopy (SIM) to generate continuous gigapixel panoramas of the fresh intact prostate circumference, including areas of the prostate adjacent to the neurovascular bundles, the rectum, and the bladder wall. Our previous work using SIM and a manual prostate handling method demonstrated the promise of the imaging technique for accurate detection of positive surgical margins. Our work here advances the technology toward clinical adoption, by demonstrating 10% greater tissue surface coverage fraction, 1.6× faster imaging throughput, and reduced number of required operator steps, compared to our prior approach. The APPS may be operated by a single person in the operating room suite within intraoperative time limits, while simultaneously delivering nearly two orders of magnitude higher tissue surface coverage than destructive and labor-intensive frozen section analysis techniques.

Ex vivo fluorescence confocal microscopy: prostatic and periprostatic tissues atlas and evaluation of the learning curve

Ex vivo fluorescence confocal microscopy (FCM) is an optical technology that provides fast H&E-like images of freshly excised tissues, and it has been mainly used for "real-time" pathological examination of dermatological malignancies. It has also shown to be a promising tool for fast pathological examination of prostatic tissues. We aim to create an atlas for FCM images of prostatic and periprostatic tissues to facilitate the interpretation of these images. Furthermore, we aimed to evaluate the learning curve of images interpretation of this new technology. Eighty fresh and unprepared biopsies obtained from radical prostatectomy specimens were evaluated using the FCM VivaScope® 2500 M-G4 (Mavig GmbH, Munich, Germany; Caliber I.D.; Rochester NY, USA) by two pathologists. Images of FCM with the corresponding H&E are illustrated to create the atlas. Furthermore, the two pathologists were asked to re-evaluate the 80 specimens after 90 days interval in order to assess the learning curve of images' interpretation of FCM. FCM was able to differentiate between different types of prostatic and periprostatic tissues including benign prostatic glands, benign prostatic hyperplasia, high-grade intraepithelial neoplasm, and prostatic adenocarcinoma. As regards the learning curve, FCM demonstrated a short learning curve. We created an atlas that can serve as the base for urologists and pathologists for learning and interpreting FCM images of prostatic and periprostatic tissues. Furthermore, FCM images is easily interpretable; however, further studies are required to explore the potential applications of this new technology in prostate cancer diagnosis and management.

Spatial heterogeneity of nanomedicine investigated by multiscale imaging of the drug, the nanoparticle and the tumour environment

Genetic and phenotypic tumour heterogeneity is an important cause of therapy resistance. Moreover, non-uniform spatial drug distribution in cancer treatment may cause pseudo-resistance, meaning that a treatment is ineffective because the drug does not reach its target at sufficient concentrations. Together with tumour heterogeneity, non-uniform drug distribution causes “therapy heterogeneity”: a spatially heterogeneous treatment effect. Spatial heterogeneity in drug distribution occurs on all scales ranging from interpatient differences to intratumour differences on tissue or cellular scale. Nanomedicine aims to improve the balance between efficacy and safety of drugs by targeting drug-loaded nanoparticles specifically to tumours. Spatial heterogeneity in nanoparticle and payload distribution could be an important factor that limits their efficacy in patients. Therefore, imaging spatial nanoparticle distribution and imaging the tumour environment giving rise to this distribution could help understand (lack of) clinical success of nanomedicine. Imaging the nanoparticle, drug and tumour environment can lead to improvements of new nanotherapies, increase understanding of underlying mechanisms of heterogeneous distribution, facilitate patient selection for nanotherapies and help assess the effect of treatments that aim to reduce heterogeneity in nanoparticle distribution.

In this review, we discuss three groups of imaging modalities applied in nanomedicine research: non-invasive clinical imaging methods (nuclear imaging, MRI, CT, ultrasound), optical imaging and mass spectrometry imaging. Because each imaging modality provides information at a different scale and has its own strengths and weaknesses, choosing wisely and combining modalities will lead to a wealth of information that will help bring nanomedicine forward.

Molecular Imaging in Oncology: Advanced Microscopy Techniques

Preclinical studies usually require high levels of morphological, functional, and biochemical information at subcellular resolution. This type of information cannot be obtained from clinical imaging techniques, such as MRI, PET/CT, or US. Luckily, many microscopy techniques exist that can offer this information, also for malignant tissues and therapeutic approaches. In this overview, we discuss the various advanced optical microscopy techniques and their applications in oncological research. After a short introduction in Sect. 16.1, we continue in Sect. 16.2 with a discussion on fluorescent labelling strategies, followed in Sect. 16.3 by an in-depth description of confocal, light-sheet, two-photon, and super-resolution microscopy. We end in Sect. 16.4 with a focus on the applications, specifically in oncology.

FalseColor-Python: A rapid intensity-leveling and digital-staining package for fluorescence-based slide-free digital pathology

Slide-free digital pathology techniques, including nondestructive 3D microscopy, are gaining interest as alternatives to traditional slide-based histology. In order to facilitate clinical adoption of these fluorescence-based techniques, software methods have been developed to convert grayscale fluorescence images into color images that mimic the appearance of standard absorptive chromogens such as hematoxylin and eosin (H&E). However, these false-coloring algorithms often require manual and iterative adjustment of parameters, with results that can be inconsistent in the presence of intensity nonuniformities within an image and/or between specimens (intra- and inter-specimen variability). Here, we present an open-source (Python-based) rapid intensity-leveling and digital-staining package that is specifically designed to render two-channel fluorescence images (i.e. a fluorescent analog of H&E) to the traditional H&E color space for 2D and 3D microscopy datasets. However, this method can be easily tailored for other false-coloring needs. Our package offers (1) automated and uniform false coloring in spite of uneven staining within a large thick specimen, (2) consistent color-space representations that are robust to variations in staining and imaging conditions between different specimens, and (3) GPU-accelerated data processing to allow these methods to scale to large datasets. We demonstrate this platform by generating H&E-like images from cleared tissues that are fluorescently imaged in 3D with open-top light-sheet (OTLS) microscopy, and quantitatively characterizing the results in comparison to traditional slide-based H&E histology.

Acridine Orange: A Review of Novel Applications for Surgical Cancer Imaging and Therapy

Introduction: Acridine orange (AO) was first extracted from coal tar in the late nineteenth century and was used as a fluorescent dye. In this paper, we review emergent research about novel applications of AO for fluorescence surgery and cancer therapy. Materials and methods: We performed a systematic search in the MEDLINE, PubMed, Cochrane library, Google Scholar, Embase, Web of Science, and Scopus database using combinations of the term "acridine orange" with the following: "surgical oncology," "neuropathology," "microsurgery," "intraoperative fluorescence," "confocal microscopy," "pathology," "endomicroscopy," "guidance," "fluorescence guidance," "oncology," "surgery," "neurooncology," and "photodynamic therapy." Peer-reviewed articles published in English were included in this review. We have also scanned references for relevant articles. Results: We have reviewed studies on the various application of AO in microscopy, endomicroscopy, intraoperative fluorescence guidance, photodynamic therapy, sonodynamic therapy, radiodynamic therapy. Conclusion: Although the number of studies on the clinical use of AO is limited, pilot studies have demonstrated the safety and feasibility of its application as an intraoperative fluorescent dye and as a novel photo- and radio-sensitizator. Further clinical studies are necessary to more definitively assess the clinical benefit AO-based fluorescence guidance, therapy for sarcomas, and to establish feasibility of this new approach for the treatment of other tumor types.

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.

"Real-time" Assessment of Surgical Margins During Radical Prostatectomy: State-of-the-Art

Histopathologic examination of the pathologic specimens using hematoxylin & eosin stains represents the backbone of the modern pathology. It is time-consuming; thus, "real-time" assessment of prostatic and periprostatic tissue has gained special interest in the diagnosis and management of prostate cancer. The current study focuses on the review of the different available techniques for "real-time" evaluation of surgical margins during radical prostatectomy (RP). We performed a comprehensive search of the Medline database to identify all the articles discussing "real-time" or intraoperative assessment of surgical margins during RP. Several filters were applied to the search to include only English articles performed on human subjects and published between January 2000 and March 2019. The search revealed several options for pathologic assessment of surgical margins including intraoperative frozen sections, confocal laser endomicroscopy, optical spectroscopy, photodynamic diagnosis, optical coherence tomography, multiphoton microscopy, structured illumination microscopy, 3D augmented reality, and ex vivo fluorescence confocal microscope. Frozen section represents the gold standard technique for real-time pathologic examinations of surgical margins during RP; however, several other options showed promising results in the initial clinical trials, and considering the rapid development in the field of molecular and cellular imaging, some of these options may serve as an alternative to frozen section.

Comparing histologic evaluation of prostate tissue using nonlinear microscopy and paraffin H&E: a pilot study

Rapid histological assessment of large areas of prostate tissue is required for many intraoperative consultation scenarios such as margin evaluation. Nonlinear microscopy (NLM) enables imaging of large (whole mount) specimens without freezing or cryotoming. This study demonstrates rapid histological imaging of unsectioned prostate cancer surgical specimens using nonlinear microscopy and compares features of prostate pathology to standard paraffin embedded H&E histology. Fresh or formalin fixed specimens were stained in 2.5 min with fluorescent nuclear and stromal dyes. Nonlinear microscopy images of unsectioned tissues were generated by nonlinear (two-photon) excitation of the fluorophores, where fluorescence is only emitted from tissue at the microscope focus, avoiding the need for physical sectioning. The images were displayed in real time using a color scale similar to H&E, then tissues were processed for standard paraffin embedded H&E histology. Seventy nonlinear microscopy and corresponding paraffin H&E images of fresh and fixed prostate specimens (15 cancer, 55 benign) from 24 patients were read by genitourinary pathologists to assess if nonlinear microscopy could achieve an equivalent evaluation to paraffin embedded H&E histology. Differences between nonlinear microscopy images and paraffin H&E slides, including cytoplasmic color and stromal density, were observed, however nonlinear microscopy images could be interpreted with minimal training. Nonlinear microscopy enabled visualization of benign, atrophic and hyperplastic glands and stroma, ejaculatory ducts, vasculature and inflammatory changes. Nonlinear microscopy enabled identification of typical and variants of adenocarcinoma, as well as Gleason patterns. Perineural invasion and extraprostatic extension could also be assessed. Nonlinear microscopy images closely resemble paraffin H&E slides and enable rapid assessment of normal prostate architecture, benign conditions, and carcinoma in freshly excised and fixed specimens. Nonlinear microscopy can image large regions of tissue, equivalent to multiple frozen section tissue blocks, within minutes because cryotoming/microtoming are not required, making it a promising technique for intraoperative consultation.

Slide-free imaging of hematoxylin-eosin stained whole-mount tissues using combined third-harmonic generation and three-photon fluorescence microscopy

Intraoperative margin assessment of surgical tissues during cancer surgery is clinically important, especially in the case of tissue conserving surgery like Mohs micrographic surgery in which minimization of the surgical area is considered crucial. Frozen pathology is the gold standard of assessing excised tissues for signs of remaining cancerous lesions. The current protocol, however, is time-consuming and labor-intensive. Instead of the complex frozen sectioning, staining, and traditional white light microscopy imaging protocol, optically sectioned histopathological imaging of hematoxylin-eosin stained whole-mount skin tissues with a subfemtoliter resolution is demonstrated by using nonlinear microscopy in this study. With our proposed method, the reagents of staining and the contrast of imaging are fully consistent with the current clinical standard of frozen pathology, thus facilitating rapid intraoperative assessment of surgical tissues for future applications. Image: Slide-free nonlinear microscopy imaging of H&E stained whole-mount skin tissue showing the morphology of sweat glands.

Ex vivo fluorescence confocal microscopy: the first application for real-time pathological examination of prostatic tissue

OBJECTIVE

To report the first application of ex vivo fluorescence confocal microscopy (FCM) - a novel optical technology that is capable of providing fast microscopic imaging of unfixed tissue specimens- in the urological field assessing its diagnostic accuracy for non neoplastic and cancerous prostate tissue (prostatic adenocarcinoma) compared to the 'gold standard' histopathological diagnoses.

PATIENTS AND METHODS

In all, 89 specimens from 13 patients with clinically localised prostate cancer were enrolled into the study. All patients underwent robot-assisted laparoscopic radical prostatectomy with fresh prostatic tissue biopsies taken at the end of each intervention using an 18-G biopsy punch. Specimens were randomly assigned to the three collaborating pathologists for evaluation. Intra- and inter-observer agreement was tested by the means of Cohen's κ. The diagnostic performance was evaluated on receiver operating characteristic curve analysis.

RESULTS

The overall diagnostic agreement between FCM and histopathological diagnoses was substantial with a 91% correct diagnosis (κ = 0.75) and an area under the curve of 0.884 (95% confidence interval 0.840-0.920), 83.33% sensitivity, and 93.53% specificity.

CONCLUSION

FCM seems to be a promising tool for enhanced specimens' reporting performance, given its simple application and very rapid microscopic image generation (<5 min/specimen). This technique may potentially be used for intraoperative pathological specimens' analysis.

Rapid pathology of lumpectomy margins with open-top light-sheet (OTLS) microscopy

Open-top light-sheet microscopy is a technique that can potentially enable rapid ex vivo inspection of large tissue surfaces and volumes. Here, we have optimized an open-top light-sheet (OTLS) microscope and image-processing workflow for the comprehensive examination of surgical margin surfaces, and have also developed a novel fluorescent analog of H&E staining that is robust for staining fresh unfixed tissues. Our tissue-staining method can be achieved within 2.5 minutes followed by OTLS microscopy of lumpectomy surfaces at a rate of up to 1.5 cm2/minute. An image atlas is presented to show that OTLS image quality surpasses that of intraoperative frozen sectioning and can approximate that of gold-standard H&E histology of formalin-fixed paraffin-embedded (FFPE) tissues. Qualitative evidence indicates that these intraoperative methods do not interfere with downstream post-operative H&E histology and immunohistochemistry. These results should facilitate the translation of OTLS microscopy for intraoperative guidance of lumpectomy and other surgical oncology procedures.

Microscopy with ultraviolet surface excitation for wide-area pathology of breast surgical margins

Intraoperative assessment of breast surgical margins will be of value for reducing the rate of re-excision surgeries for lumpectomy patients. While frozen-section histology is used for intraoperative guidance of certain cancers, it provides limited sampling of the margin surface (typically <1  %   of the margin) and is inferior to gold-standard histology, especially for fatty tissues that do not freeze well, such as breast specimens. Microscopy with ultraviolet surface excitation (MUSE) is a nondestructive superficial optical-sectioning technique that has the potential to enable rapid, high-resolution examination of excised margin surfaces. Here, a MUSE system is developed with fully automated sample translation to image fresh tissue surfaces over large areas and at multiple levels of defocus, at a rate of ∼5  min  /  cm2. Surface extraction is used to improve the comprehensiveness of surface imaging, and 3-D deconvolution is used to improve resolution and contrast. In addition, an improved fluorescent analog of conventional H&E staining is developed to label fresh tissues within ∼5  min for MUSE imaging. We compare the image quality of our MUSE system with both frozen-section and conventional H&E histology, demonstrating the feasibility to provide microscopic visualization of breast margin surfaces at speeds that are relevant for intraoperative use.

Confocal Fluorescence Microscopy Platform Suitable for Rapid Evaluation of Small Fragments of Tissue in Surgical Pathology Practice

CONTEXT.—

Rapid advances in the fields of biophotonics, computer science, and instrumentation have allowed for high-resolution imaging of biologic tissues.

OBJECTIVE.—

To evaluate the quality of images from an optimized confocal fluorescence microscopy (CFM) platform for rapid evaluation of small fragments of tissue, compared with hematoxylin-eosin staining.

DESIGN.—

Tissue fragments (up to 1.0 × 0.3 cm) were stained with 0.6 mM acridine orange for 60 seconds and imaged using a CFM platform at 488-nm and 785-nm wavelength. The imaged tissues were then fixed in formalin and processed to generate hematoxylin-eosin-stained tissue sections. The quality of CFM images was scored on a scale of 0 to 3 on the basis of the percentage of the CFM images with recognizable tissue architecture (0, 0%; 1, <20%; 2, 20%-50%; 3, >50%). The diagnoses made using CFM images were compared with those made using histopathologic analysis of the hematoxylin-eosin-stained tissue sections.

RESULTS.—

We imaged 118 tissue fragments obtained from 40 breast, 23 lung, 39 kidney, and 16 liver surgical excision specimens. We acquired CFM images in 2 to 3 minutes; 95.8% (113 of 118) of images showed a quality score of 3, and 4.2% (5 of 118) had a score of 2. We achieved a sensitivity of 95.5%, specificity of 97.3%, positive predictive value of 95.5%, and negative predictive value of 97.3%.

CONCLUSIONS.—

Our results demonstrate the suitability of the CFM platform for rapid and accurate evaluation of small tissue fragments in surgical pathology practice.

Partial nephrectomy margin imaging using structured illumination microscopy

Partial nephrectomy (PN) is the recommended procedure over radical nephrectomy (RN) for patients with renal masses less than 4 cm in diameter (Stage T1a). Patients with less than 4 cm renal masses can also be treated with PN, but have a higher risk for positive surgical margins (PSM). PSM, when present, are indicative of poor clinical outcomes. The current gold-standard histopathology method is not well-suited for the identification of PSM intraoperatively due to processing time and destructive nature. Here, video-rate structured illumination microscopy (VR-SIM) was investigated as a potential tool for PSM detection during PN. A clinical image atlas assembled from ex vivo renal biopsies provided diagnostically useful images of benign and malignant kidney, similar to permanent histopathology. VR-SIM was then used to image entire parenchymal margins of tumor resection covering up to >1800× more margin surface area than standard histology. Aided by the image atlas, the study pathologist correctly classified all parenchymal margins as negative for PSM with VR-SIM, compared to standard postoperative pathology. The ability to evaluate large surgical margins in a short time frame with VR-SIM may allow it to be used intraoperatively as a "safety net" for PSM detection, allowing more patients to undergo PN over RN.

Multiplexed Optical Imaging of Tumor-Directed Nanoparticles: A Review of Imaging Systems and Approaches

In recent decades, various classes of nanoparticles have been developed for optical imaging of cancers. Many of these nanoparticles are designed to specifically target tumor sites, and specific cancer biomarkers, to facilitate the visualization of tumors. However, one challenge for accurate detection of tumors is that the molecular profiles of most cancers vary greatly between patients as well as spatially and temporally within a single tumor mass. To overcome this challenge, certain nanoparticles and imaging systems have been developed to enable multiplexed imaging of large panels of cancer biomarkers. Multiplexed molecular imaging can potentially enable sensitive tumor detection, precise delineation of tumors during interventional procedures, and the prediction/monitoring of therapy response. In this review, we summarize recent advances in systems that have been developed for the imaging of optical nanoparticles that can be heavily multiplexed, which include surface-enhanced Raman-scattering nanoparticles (SERS NPs) and quantum dots (QDs). In addition to surveying the optical properties of these various types of nanoparticles, and the most-popular multiplexed imaging approaches that have been employed, representative preclinical and clinical imaging studies are also highlighted.

Light-sheet microscopy for slide-free non-destructive pathology of large clinical specimens

For the 1.7 million patients per year in the U.S. who receive a new cancer diagnosis, treatment decisions are largely made after a histopathology exam. Unfortunately, the gold standard of slide-based microscopic pathology suffers from high inter-observer variability and limited prognostic value due to sampling limitations and the inability to visualize tissue structures and molecular targets in their native 3D context. Here, we show that an open-top light-sheet microscope optimized for non-destructive slide-free pathology of clinical specimens enables the rapid imaging of intact tissues at high resolution over large 2D and 3D fields of view, with the same level of detail as traditional pathology. We demonstrate the utility of this technology for various applications: wide-area surface microscopy to triage surgical specimens (with ~200 μm surface irregularities), rapid intraoperative assessment of tumour-margin surfaces (12.5 sec/cm2), and volumetric assessment of optically cleared core–needle biopsies (1 mm in diameter, 2 cm in length). Light-sheet microscopy can be a versatile tool for both rapid surface microscopy and deep volumetric microscopy of human specimens.

Raman-Encoded Molecular Imaging with Topically Applied SERS Nanoparticles for Intraoperative Guidance of Lumpectomy

Intraoperative identification of carcinoma at lumpectomy margins would enable reduced re-excision rates, which are currently as high as 20% to 50%. Although imaging of disease-associated biomarkers can identify malignancies with high specificity, multiplexed imaging of such biomarkers is necessary to detect molecularly heterogeneous carcinomas with high sensitivity. We have developed a Raman-encoded molecular imaging (REMI) technique in which targeted nanoparticles are topically applied on excised tissues to enable rapid visualization of a multiplexed panel of cell surface biomarkers at surgical margin surfaces. A first-ever clinical study was performed in which 57 fresh specimens were imaged with REMI to simultaneously quantify the expression of four biomarkers HER2, ER, EGFR, and CD44. Combined detection of these biomarkers enabled REMI to achieve 89.3% sensitivity and 92.1% specificity for the detection of breast carcinoma. These results highlight the sensitivity and specificity of REMI to detect biomarkers in freshly resected tissue, which has the potential to reduce the rate of re-excision procedures in cancer patients. Cancer Res; 77(16); 4506-16. ©2017 AACR.

Direct comparison between confocal and multiphoton microscopy for rapid histopathological evaluation of unfixed human breast tissue

Rapid histopathological examination of surgical specimen margins using fluorescence microscopy during breast conservation therapy has the potential to reduce the rate of positive margins on postoperative histopathology and the need for repeat surgeries. To assess the suitability of imaging modalities, we perform a direct comparison between confocal fluorescence microscopy and multiphoton microscopy for imaging unfixed tissue and compare to paraffin-embedded histology. An imaging protocol including dual channel detection of two contrast agents to implement virtual hematoxylin and eosin images is introduced that provides high quality imaging under both one and two photon excitation. Corresponding images of unfixed human breast tissue show that both confocal and multiphoton microscopy can reproduce the appearance of conventional histology without the need for physical sectioning. We further compare normal breast tissue and invasive cancer specimens imaged at multiple magnifications, and assess the effects of photobleaching for both modalities using the staining protocol. The results demonstrate that confocal fluorescence microscopy is a promising and cost-effective alternative to multiphoton microscopy for rapid histopathological evaluation of ex vivo breast tissue.

DRAQ5 and Eosin ('D&E') as an Analog to Hematoxylin and Eosin for Rapid Fluorescence Histology of Fresh Tissues

Real-time on-site histopathology review of biopsy tissues at the point-of-procedure has great potential for significant clinical value and improved patient care. For instance, on-site review can aid in rapid screening of diagnostic biopsies to reduce false-negative results, or in quantitative assessment of biospecimen quality to increase the efficacy of downstream laboratory and histopathology analysis. However, the only currently available rapid pathology method, frozen section analysis (FSA), is too time- and labor-intensive for use in screening large quantities of biopsy tissues and is too destructive for maximum tissue conservation in multiple small needle core biopsies. In this work we demonstrate the spectrally-compatible combination of the nuclear stain DRAQ5 and the anionic counterstain eosin as a dual-component fluorescent staining analog to hematoxylin and eosin intended for use on fresh, unsectioned tissues. Combined with optical sectioning fluorescence microscopy and pseudo-coloring algorithms, DRAQ5 and eosin (“D&E”) enables very fast, non-destructive psuedohistological imaging of tissues at the point-of-acquisition with minimal tissue handling and processing. D&E was validated against H&E on a one-to-one basis on formalin-fixed paraffin-embedded and frozen section tissues of various human organs using standard epi-fluorescence microscopy, demonstrating high fidelity of the staining mechanism as an H&E analog. The method was then applied to fresh, whole 18G renal needle core biopsies and large needle core prostate biospecimen biopsies using fluorescence structured illumination optical sectioning microscopy. We demonstrate the ability to obtain high-resolution histology-like images of unsectioned, fresh tissues similar to subsequent H&E staining of the tissue. The application of D&E does not interfere with subsequent standard-of-care H&E staining and imaging, preserving the integrity of the tissue for thorough downstream analysis. These results indicate that this dual-stain pseudocoloring method could provide a real-time histology-like image at the time of acquisition and valuable objective tissue analysis for the clinician at the time of service.

Nondestructive Diagnosis of Kidney Cancer on 18-gauge Core Needle Renal Biopsy Using Dual-color Fluorescence Structured Illumination Microscopy

OBJECTIVE

To present a novel imaging technique used for rapid, nondestructive histological assessment of renal neoplasias using a dual-component fluorescence stain and structured illumination microscopy (SIM).

MATERIALS AND METHODS

After Institutional Review Board approval, 65 total biopsies were obtained from 19 patients undergoing partial or radical nephrectomy. Biopsies were stained with a dual-component fluorescent, and optically sectioned SIM images were obtained from the surface of the intact biopsies. Specimens were subsequently fixed and analyzed using hematoxylin and eosin (H&E) histopathologic methods and compared with SIM images. A single, board-certified pathologist blinded to specimens reviewed all SIM images and H&E slides, and determined the presence or absence of neoplasias. Results of blinded diagnosis of SIM were validated against traditional pathology.

RESULTS

Of the 19 patients, 15 underwent robotic partial nephrectomies and 4 underwent laparoscopic nephrectomies. Indications included clinical suspicion of renal cell carcinoma. In total, 65 biopsy specimens were available for review. Twenty-one specimens were determined to be neoplastic on H&E, whereas 41 represented benign renal tissue. The final sensitivity and specificity of our study were 79.2% and 95.1%, respectively.

CONCLUSION

SIM is a promising technology for rapid, near-patient, ex vivo renal biopsy assessment. By improving the ability to rapidly assess sufficiency of biopsy specimens and enabling immediate diagnostic capability, SIM aids in more effective biopsy performance, tissue triage, and patient counseling regarding management options. Additionally, because tissue is preserved, effective utilization of downstream diagnostic tests and molecular assessments are possible.

Virtual Hematoxylin and Eosin Transillumination Microscopy Using Epi-Fluorescence Imaging

We derive a physically realistic model for the generation of virtual transillumination, white light microscopy images using epi-fluorescence measurements from thick, unsectioned tissue. We demonstrate this technique by generating virtual transillumination H&E images of unsectioned human breast tissue from epi-fluorescence multiphoton microscopy data. The virtual transillumination algorithm is shown to enable improved contrast and color accuracy compared with previous color mapping methods. Finally, we present an open source implementation of the algorithm in OpenGL, enabling real-time GPU-based generation of virtual transillumination microscopy images using conventional fluorescence microscopy systems.

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

Achieving cancer-free surgical margins in oncologic surgery is critical to reduce the need for additional adjuvant treatments and minimize tumor recurrence; however, there is a delicate balance between completeness of tumor removal and preservation of adjacent tissues critical for normal post-operative function. We sought to establish the feasibility of video-rate structured illumination microscopy (VR-SIM) of the intact removed tumor surface as a practical and non-destructive alternative to intra-operative frozen section pathology, using prostate cancer as an initial target. We present the first images of the intact human prostate surface obtained with pathologically-relevant contrast and subcellular detail, obtained in 24 radical prostatectomy specimens immediately after excision. We demonstrate that it is feasible to routinely image the full prostate circumference, generating gigapixel panorama images of the surface that are readily interpreted by pathologists. VR-SIM confirmed detection of positive surgical margins in 3 out of 4 prostates with pathology-confirmed adenocarcinoma at the circumferential surgical margin, and furthermore detected extensive residual cancer at the circumferential margin in a case post-operatively classified by histopathology as having negative surgical margins. Our results suggest that the increased surface coverage of VR-SIM could also provide added value for detection and characterization of positive surgical margins over traditional histopathology.