Rapid evaluation of fresh ex vivo kidney tissue with full-field optical coherence tomography

High-resolution full-field optical coherence tomography microscope for the evaluation of freshly excised skin specimens during Mohs surgery: A feasibility study

Histopathology for tumor margin assessment is time-consuming and expensive. High-resolution full-field optical coherence tomography (FF-OCT) images fresh tissues rapidly at cellular resolution and potentially facilitates evaluation. Here, we define FF-OCT features of normal and neoplastic skin lesions in fresh ex vivo tissues and assess its diagnostic accuracy for malignancies. For this, normal and neoplastic tissues were obtained from Mohs surgery, imaged using FF-OCT, and their features were described. Two expert OCT readers conducted a blinded analysis to evaluate their diagnostic accuracies, using histopathology as the ground truth. A convolutional neural network was built to distinguish and outline normal structures and tumors. Of the 113 tissues imaged, 95 (84%) had a tumor (75 basal cell carcinomas [BCCs] and 17 squamous cell carcinomas [SCCs]). The average reader diagnostic accuracy was 88.1%, with a sensitivity of 93.7%, and a specificity of 58.3%. The artificial intelligence (AI) model achieved a diagnostic accuracy of 87.6 ± 5.9%, sensitivity of 93.2 ± 2.1%, and specificity of 81.2 ± 9.2%. A mean intersection-over-union of 60.3 ± 10.1% was achieved when delineating the nodular BCC from normal structures. Limitation of the study was the small sample size for all tumors, especially SCCs. However, based on our preliminary results, we envision FF-OCT to rapidly image fresh tissues, facilitating surgical margin assessment. AI algorithms can aid in automated tumor detection, enabling widespread adoption of this technique.

Methods and applications of full-field optical coherence tomography: a review

SIGNIFICANCE

Full-field optical coherence tomography (FF-OCT) enables en face views of scattering samples at a given depth with subcellular resolution, similar to biopsy without the need of sample slicing or other complex preparation. This noninvasive, high-resolution, three-dimensional (3D) imaging method has the potential to become a powerful tool in biomedical research, clinical applications, and other microscopic detection.

AIM

Our review provides an overview of the disruptive innovations and key technologies to further improve FF-OCT performance, promoting FF-OCT technology in biomedical and other application scenarios.

APPROACH

A comprehensive review of state-of-the-art accomplishments in OCT has been performed. Methods to improve performance of FF-OCT systems are reviewed, including advanced phase-shift approaches for imaging speed improvement, methods of denoising, artifact reduction, and aberration correction for imaging quality optimization, innovations for imaging flux expansion (field-of-view enlargement and imaging-depth-limit extension), new implementations for multimodality systems, and deep learning enhanced FF-OCT for information mining, etc. Finally, we summarize the application status and prospects of FF-OCT in the fields of biomedicine, materials science, security, and identification.

RESULTS

The most worth-expecting FF-OCT innovations include combining the technique of spatial modulation of optical field and computational optical imaging technology to obtain greater penetration depth, as well as exploiting endogenous contrast for functional imaging, e.g., dynamic FF-OCT, which enables noninvasive visualization of tissue dynamic properties or intracellular motility. Different dynamic imaging algorithms are compared using the same OCT data of the colorectal cancer organoid, which helps to understand the disadvantages and advantages of each. In addition, deep learning enhanced FF-OCT provides more valuable characteristic information, which is of great significance for auxiliary diagnosis and organoid detection.

CONCLUSIONS

FF-OCT has not been completely exploited and has substantial growth potential. By elaborating the key technologies, performance optimization methods, and application status of FF-OCT, we expect to accelerate the development of FF-OCT in both academic and industry fields. This renewed perspective on FF-OCT may also serve as a road map for future development of invasive 3D super-resolution imaging techniques to solve the problems of microscopic visualization detection.

Imaging Inflammation - From Whole Body Imaging to Cellular Resolution

Imaging techniques have evolved impressively lately, allowing whole new concepts like multimodal imaging, personal medicine, theranostic therapies, and molecular imaging to increase general awareness of possiblities of imaging to medicine field. Here, we have collected the selected (3D) imaging modalities and evaluated the recent findings on preclinical and clinical inflammation imaging. The focus has been on the feasibility of imaging to aid in inflammation precision medicine, and the key challenges and opportunities of the imaging modalities are presented. Some examples of the current usage in clinics/close to clinics have been brought out as an example. This review evaluates the future prospects of the imaging technologies for clinical applications in precision medicine from the pre-clinical development point of view.

Toward image quality assessment in optical coherence tomography (OCT) of rat kidney

BACKGROUND

Optical coherence tomography (OCT) is a useful tool for the evaluation of structure and function of the kidney, but the image quality can be effected by many factors.

OBJECTIVE

The objective of this study was to assess the image quality of different OCT systems in OCT imaging of the living kidney.

METHODS

One swept-source OCT (SSOCT) of 1300 nm, one spectral domain OCT (SDOCT) of 1300 nm and another of 900 nm were used. A FeO phantom was used to establish the point spread function (PSF). Rat kidneys were imaged for image quality assessment. Light penetration in the kidney and the optical attenuation coefficient were also evaluated. The quantification of uriniferous tubules was carried out via the threshold segmentation of 3D OCT images.

RESULTS

The quality of kidney images was resolution dependent. SDOCT of 900 nm showed higher peak signal-to noise ratio and dynamic range. The spatial resolution in the light field could be derived from the PSF distribution along three mutually orthogonal axes. In conjunction with the PSF, the Lucy-Richardson algorithm could improve image quality but could not reveal more microstructural information. The penetration depth of 1300 nm was deeper than that of 900 nm. The attenuation coefficient of the kidney was 29 cm^-1 at 1300 nm and 50 cm^-1 at 900 nm (P < 0.001). More accurate measurement of uriniferous tubules was achieved with the SDOCT-900 due to its higher resolution.

CONCLUSIONS

Both SSOCT and SDOCT systems could be useful for imaging uriniferous tubules in the superficial layers of the cortex. The OCT image quality was highly correlated with the spatial resolution of OCT system.

Value of Full-Field Optical Coherence Tomography Imaging for the Histological Assessment of Head and Neck Cancer

BACKGROUND AND OBJECTIVES

In head and neck surgery, intraoperative and postoperative evaluation of tumor margins is achieved by histopathological assessment, which is a multistep process. Intraoperative analysis of tumor margins to obtain a preliminary diagnosis is usually carried out on frozen sections. Analysis of frozen sections is challenging due to technical difficulties in processing. Full-field optical coherence tomography (FFOCT) provides ex vivo images of fresh tissue samples at a microscopic scale without tissue processing. The objectives of our study were to define the diagnostic criteria required to interpret head and neck FFOCT images and to evaluate the reliability of a histological diagnosis made on an "optical biopsy" produced by head and neck FFOCT imaging compared with conventional histology.

STUDY DESIGN/MATERIALS AND METHODS

First, we established an atlas of comparative images (FFOCT/standard histology) and defined the diagnostic criteria based on FFOCT images. Two pathologists subsequently performed a blinded review on 57 FFOCT images (32 patients). Specificity and sensitivity were measured by comparison with the standard histological diagnosis. The primary endpoint was major concordance, defined as two classifications leading to the same therapeutic decision (treatment/no treatment).

RESULTS

Pathologists identified four main criteria for tissue diagnosis on FFOCT images: heterogeneous cell distribution, stromal reaction, coiling, and keratinization abnormalities. The correlation study showed good results, with sensitivity from 88% to 90% and specificity from 81% to 87%, regardless of whether the FFOCT image review was performed by a pathologist with or without previous experience in optical imaging.

CONCLUSIONS

Our results demonstrate that FFOCT images can be used by pathologists for differential diagnosis, and that high-resolution FFOCT imaging can provide an assessment of microscopic architecture in head and neck tissues without tissue processing requirements. Lasers Surg. Med. © 2020 Wiley Periodicals, Inc.

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.

[Optical coherence tomography of bladder resection specimen]

INTRODUCTION

The diagnosis of bladder urothelial tumors is based on bladder resection and histological analysis of the specimen. The time to obtain the results of the histological analysis increases the treatment delay. Furthermore, the lack of muscle on the specimen forces the surgeon to practice on other procedure. Full field optical coherence tomography (FFOCT) is a recent imaging technique to analyze tissue. The aim of our study was to evaluate the feasibility and diagnostic accuracy of FFOCT to detect muscle and tumor in bladder resection specimen.

PATIENTS AND METHODS

We analyzed with the FFOCT technique bladder resection specimen of 24 consecutives patients. Three readers did the blind analyze of the images, looking for the presence of muscle and tumor on each specimen. Their results were compared with histological analysis to calculate diagnostic accuracy for each reader.

RESULTS

Mean sensibilities for the detection of muscle and tumor were respectively 75% and 81%. Mean specificities for the detection of muscle and tumor were respectively 78.3% and 55.3%.

CONCLUSIONS

Our results suggest that the FFOCT is feasible to analyze bladder resection specimen. Sensibilities and specificities calculated are encouraging for the detection of muscle and tumor. The accuracy of this detection and early-staging tool should be validated by larger studies.

LEVEL OF EVIDENCE

3.

A compact high-speed full-field optical coherence microscope for high-resolution in vivo skin imaging

A compact high-speed full-field optical coherence microscope has been developed for high-resolution in vivo imaging of biological tissues. The interferometer, in the Linnik configuration, has a size of 11 × 11 × 5 cm³ and a weight of 210 g. Full-field illumination with low-coherence light is achieved with a high-brightness broadband light-emitting diode. High-speed full-field detection is achieved by using part of the image sensor of a high-dynamic range CMOS camera. En face tomographic images are acquired at a rate of 50 Hz, with an integration time of 0.9 ms. The image spatial resolution is 0.9 μm × 1.2 μm (axial × transverse), over a field of view of 245 × 245 μm² . Images of human skin, revealing in-depth cellular-level structures, were obtained in vivo and in real-time without the need for stabilization of the subject. The system can image larger fields, up to 1 × 1 mm² , but at a reduced depth.

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.

The clinical usefulness of optical coherence tomography during cancer interventions

INTRODUCTION

Tumor detection and visualization plays a key role in the clinical workflow of a patient with suspected cancer, both in the diagnosis and treatment. Several optical imaging techniques have been evaluated for guidance during oncological interventions. Optical coherence tomography (OCT) is a technique which has been widely evaluated during the past decades. This review aims to determine the clinical usefulness of OCT during cancer interventions focussing on qualitative features, quantitative features and the diagnostic value of OCT.

METHODS

A systematic literature search was performed for articles published before May 2018 using OCT in the field of surgical oncology. Based on these articles, an overview of the clinical usefulness of OCT was provided per tumor type.

RESULTS

A total of 785 articles were revealed by our search, of which a total of 136 original articles were available for analysis, which formed the basis of this review. OCT is currently utilised for both preoperative diagnosis and intraoperative detection of skin, oral, lung, breast, hepatobiliary, gastrointestinal, urological, and gynaecological malignancies. It showed promising results in tumor detection on a microscopic level, especially using higher resolution imaging techniques, such as high-definition OCT and full-field OCT.

CONCLUSION

In the near future, OCT could be used as an additional tool during bronchoscopic or endoscopic interventions and could also be implemented in margin assessment during (laparoscopic) cancer surgery if a laparoscopic or handheld OCT device will be further developed to make routine clinical use possible.

Fluorescence Detection of Cell Death in Liver of Mice Treated with Thioacetamide

The purpose of this study was to detect cell death in the liver of mice treated with thioacetamide (TAA) using fluorescence bioimaging and compare this outcome with that using conventional histopathological examination. At 6 weeks of age, 24 mice were randomly divided into three groups: group 1 (G1), control group; group 2 (G2), fluorescence probe control group; group 3 (G3), TAA-treated group. G3 mice were treated with TAA. Twenty-two hours after TAA treatment, G2 and G3 mice were treated with Annexin-Vivo 750. Fluorescence in vivo bioimaging was performed by fluorescence molecular tomography at two hours after Annexin-Vivo 750 treatment, and fluorescence ex vivo bioimaging of the liver was performed. Liver damage was validated by histopathological examination. In vivo bioimaging showed that the fluorescence intensity was increased in the right upper part of G3 mice compared with that in G2 mice, whereas G1 mice showed no signal. Additionally ex vivo bioimaging showed that the fluorescence intensity was significantly increased in the livers of G3 mice compared with those in G1 or G2 mice (p < 0.05). Histopathological examination of the liver showed no cell death in G1 and G2 mice. However, in G3 mice, there was destruction of hepatocytes and increased cell death. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining confirmed many cell death features in the liver of G3 mice, whereas no pathological findings were observed in the liver of G1 and G2 mice. Taken together, fluorescence bioimaging in this study showed the detection of cell death and made it possible to quantify the level of cell death in male mice. The outcome was correlated with conventional biomedical examination. As it was difficult to differentiate histological location by fluorescent bioimaging, it is necessary to develop specific fluorescent dyes for monitoring hepatic disease progression and to exploit new bioimaging techniques without dye-labeling.

Ex Vivo Confocal Fluorescence Microscopy for Rapid Evaluation of Tissues in Surgical Pathology Practice

CONTEXT

- Optical imaging techniques are currently available for imaging tissues without the need for any type of extensive tissue preparation. There are several applications for their potential use in surgical pathology practice.

OBJECTIVE

- To evaluate the feasibility of using a confocal fluorescence microscopy (CFM) platform for ex vivo examination of tissues obtained from surgical resections of breast, lung, kidney, and liver.

DESIGN

- Tissue fragments (0.5-1.0 cm) were immersed in 0.6 mM acridine orange for 6 seconds and imaged using a CFM platform at a 488-nm wavelength. The imaged tissues were subsequently fixed in formalin and processed routinely to generate hematoxylin-eosin-stained tissue sections. Mosaics of the grayscale CFM images were studied at different magnifications for recognition of the tissue and were compared with conventional histopathologic examination of hematoxylin-eosin tissue sections.

RESULTS

- We imaged 55 tissue fragments obtained from 16 breast (29%), 18 lung (33%), 14 kidney (25%), and 7 liver (13%) surgical excision specimens. Acridine orange labeled the nuclei, creating the contrast between nucleus and cytoplasm and thereby recapitulating the tissue architecture. We could obtain CFM images of good quality within 5 to 10 minutes that allowed recognition of the cytomorphologic details for categorization of the imaged tissue and were similar to histologic examination of hematoxylin-eosin tissue sections.

CONCLUSIONS

- The ease and speed of acquisition of CFM images together with the resolution and resemblance of the CFM images to hematoxylin-eosin sections suggest that the CFM platform has excellent potential for use in surgical pathology practice.

Focus defect and dispersion mismatch in full-field optical coherence microscopy

Full-field optical coherence microscopy (FFOCM) is an optical technique, based on low-coherence interference microscopy, for tomographic imaging of semi-transparent samples with micrometer-scale spatial resolution. The differences in refractive index between the sample and the immersion medium of the microscope objectives may degrade the FFOCM image quality because of focus defect and optical dispersion mismatch. These phenomena and their consequences are discussed in this theoretical paper. Experimental methods that have been implemented in FFOCM to minimize the adverse effects of these phenomena are summarized and compared.

Review of intraoperative optical coherence tomography: technology and applications [Invited]

During microsurgery, en face imaging of the surgical field through the operating microscope limits the surgeon's depth perception and visualization of instruments and sub-surface anatomy. Surgical procedures outside microsurgery, such as breast tumor resections, may also benefit from visualization of the sub-surface tissue structures. The widespread clinical adoption of optical coherence tomography (OCT) in ophthalmology and its growing prominence in other fields, such as cancer imaging, has motivated the development of intraoperative OCT for real-time tomographic visualization of surgical interventions. This article reviews key technological developments in intraoperative OCT and their applications in human surgery. We focus on handheld OCT probes, microscope-integrated OCT systems, and OCT-guided laser treatment platforms designed for intraoperative use. Moreover, we discuss intraoperative OCT adjuncts and processing techniques currently under development to optimize the surgical feedback derivable from OCT data. Lastly, we survey salient clinical studies of intraoperative OCT for human surgery.