Optical Biopsy of Lymph Node Morphology using Optical Coherence Tomography

Compressed sensing of human breast optical coherence 3-D image volume data using predictive coding

There are clinical needs for optical coherence tomography (OCT) of large areas within a short period of time, such as imaging resected breast tissue for the evaluation of cancer. We report on the use of denoising predictive coding (DN-PC), a novel compressed sensing (CS) algorithm for reconstruction of OCT volumes of human normal breast and breast cancer tissue. The DN-PC algorithm has been rewritten to allow for computational parallelization and efficient memory transfer, resulting in a net reduction of computation time by a factor of 20. We compress image volumes at decreasing A-line sampling rates to evaluate a relation between reconstruction behavior and image features of breast tissue.

Diagnostic accuracy of optical coherence tomography for margin assessment in breast-conserving surgery: A systematic review and meta-analysis

BACKGROUND

Breast cancer is the most common malignant tumor among women, and its incidence is increasing annually. At present, the results of the study on whether optical coherence tomography (OCT) can be used as an intraoperative margin assessment method for breast-conserving surgery (BCS) are inconsistent. We herein conducted this systematic review and meta-analysis to assess the diagnostic value of OCT in BCS.

METHODS

PubMed, Web of Science, Cochrane Library, and Embase were used to search relevant studies published up to September 15, 2022. We used Review Manager 5.4, Meta-Disc 1.4, and STATA 16.0 for statistical analysis.

RESULTS

The results displayed 18 studies with 782 patients included according to the inclusion and exclusion criteria. Meta-analysis showed the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and the area under the curve (AUC) of OCT in the margin assessment of BCS were 0.91 (95% CI 0.88-0.93), 0.88 (95% CI 0.83-0.92), 7.53 (95% CI 5.19-10.93), 0.11(95% CI 0.08-0.14), 70.37 (95% CI 39.78-124.47), and 0.94 (95% CI 0.92-0.96), respectively.

CONCLUSIONS

OCT is a promising technique in intraoperative margin assessment of breast cancer patients.

Feasibility of Breast Cancer Metastasis Assessment of Ex Vivo Sentinel Lymph Nodes through a p-H&E Optical Coherence Microscopic Imaging System

Frozen-sectioned hematoxylin-eosin (H&E) image evaluation is the current method for intraoperative breast cancer metastasis assessment through ex vivo sentinel lymph nodes (SLNs). After frozen sectioning, the sliced fatty region of the frozen-sectioned specimen is easily dropped because of different freezing points for fatty tissues and other tissues. Optical-sectioned H&E images provide a nondestructive method for obtaining the insight en face image near the attached surface of the dissected specimen, preventing the freezing problem of fatty tissue. Specimens from 29 patients at Wanfang Hospital were collected after excision and were analyzed at the pathology laboratory, and a fluorescence-in-built optical coherence microscopic imaging system (OCMIS) was then used to visualize the pseudo-H&E (p-H&E) images of the SLNs for intraoperative breast cancer metastasis assessment, and the specificity, sensitivity, and accuracy were 100%, 88.9%, and 98.8% (n = 83), respectively. Compared with gold-standard paraffin-sectioned H&E images, the specificity, sensitivity, and accuracy obtained with the frozen-sectioned H&E images (n = 85) of the specimens were the same as those obtained with the p-H&E images (n = 95). Thus, OCMIS is a useful noninvasive image-assisted tool for breast cancer metastasis assessment based on SLN images.

Classifying breast cancer in ultrahigh-resolution optical coherence tomography images using convolutional neural networks

Optical coherence tomography (OCT) is being investigated in breast cancer diagnostics as a real-time histology evaluation tool. We present a customized deep convolutional neural network (CNN) for classification of breast tissues in OCT B-scans. Images of human breast samples from mastectomies and breast reductions were acquired using a custom ultrahigh-resolution OCT system with 2.72 µm axial resolution and 5.52 µm lateral resolution. The network achieved 96.7% accuracy, 92% sensitivity, and 99.7% specificity on a dataset of 23 patients. The usage of deep learning will be important for the practical integration of OCT into clinical practice.

Intra-operative assessment of sentinel lymph nodes for breast cancer surgery: An update

Lymph node (LN) involvement is the strongest prognostic factor in operable breast cancer (BC). Therefore, accurate assessment of LN status is essential for management of BC patients. The introduction of sentinel LN approach reduced the need for extensive axillary surgery to achieve accurate staging. However, positive sentinel LN as determined on postoperative histological examination often leads to a second axillary operation to ensure an accurate staging and that positive non-sentinel LNs are removed. Although preoperative assessment of LN has improved significantly, its accuracy remains insufficient to avoid further axillary surgery and is not sufficient to predict the status of the LN. Therefore, intraoperative evaluation of the sentinel LN to determine the need for completing lymph node dissection in case of metastasis can provide an important approach to guide BC management decision making. This article reviews the techniques available and under development for intraoperative detection of sentinel LN metastasis in BC surgery. The key features of each technique are described in detail, emphasising the benefits offered by label-free optical techniques: minimal sample preparation, high spatial resolution, and immediate on-site implementation. Optical techniques have the potential to provide a cost-effective and accurate intraoperative platform for the assessment of SLN within the operating theatre.

Fully Automated Postlumpectomy Breast Margin Assessment Utilizing Convolutional Neural Network Based Optical Coherence Tomography Image Classification Method

BACKGROUND

The purpose of this study was to develop a deep learning classification approach to distinguish cancerous from noncancerous regions within optical coherence tomography (OCT) images of breast tissue for potential use in an intraoperative setting for margin assessment.

METHODS

A custom ultrahigh-resolution OCT (UHR-OCT) system with an axial resolution of 2.7 μm and a lateral resolution of 5.5 μm was used in this study. The algorithm used an A-scan-based classification scheme and the convolutional neural network (CNN) was implemented using an 11-layer architecture consisting of serial 3 × 3 convolution kernels. Four tissue types were classified, including adipose, stroma, ductal carcinoma in situ, and invasive ductal carcinoma.

RESULTS

The binary classification of cancer versus noncancer with the proposed CNN achieved 94% accuracy, 96% sensitivity, and 92% specificity. The mean five-fold validation F1 score was highest for invasive ductal carcinoma (mean standard deviation, 0.89 ± 0.09) and adipose (0.79 ± 0.17), followed by stroma (0.74 ± 0.18), and ductal carcinoma in situ (0.65 ± 0.15).

CONCLUSION

It is feasible to use CNN based algorithm to accurately distinguish cancerous regions in OCT images. This fully automated method can overcome limitations of manual interpretation including interobserver variability and speed of interpretation and may enable real-time intraoperative margin assessment.

Near-infrared imaging and optical coherence tomography for intraoperative visualization of tumors

Surgical excision is the foundation of treatment for early-stage solid tumors in man and companion animals. Complete excision with appropriate margins of surrounding tumor-free tissue is crucial to survival. Intraoperative imaging allows real-time visualization of tumors, assessment of surgical margins, and, potentially, lymph nodes and satellite metastatic lesions, allowing surgeons to perform complete tumor resections while sparing surrounding vital anatomic structures. This Review will focus on the use of near-infrared imaging and optical coherence tomography for intraoperative tumor visualization.

Needle-based Optical Coherence Tomography to Guide Transbronchial Lymph Node Biopsy

BACKGROUND

Transbronchial needle aspiration (TBNA), often used to sample lymph nodes for lung cancer staging, is subject to sampling error even when performed with endobronchial ultrasound. Optical coherence tomography (OCT) is a high-resolution imaging modality that rapidly generates helical cross-sectional images. We aim to determine if needle-based OCT can provide microstructural information in lymph nodes that may be used to guide TBNA, and improve sampling error.

METHODS

We performed ex vivo needle-based OCT on thoracic lymph nodes from patients with and without known lung cancer. OCT imaging features were compared against matched histology.

RESULTS

OCT imaging was performed in 26 thoracic lymph nodes, including 6 lymph nodes containing metastatic carcinoma. OCT visualized lymphoid follicles, adipose tissue, pigment-laden histiocytes, and blood vessels. OCT features of metastatic carcinoma were distinct from benign lymph nodes, with microarchitectural features that reflected the morphology of the carcinoma subtype. OCT was also able to distinguish lymph node from adjacent airway wall.

CONCLUSIONS

Our results demonstrate that OCT provides critical microstructural information that may be useful to guide TBNA lymph node sampling, as a complement to endobronchial ultrasound. In vivo studies are needed to further evaluate the clinical utility of OCT in thoracic lymph node assessment.

Simultaneous measurements of lymphatic vessel contraction, flow and valve dynamics in multiple lymphangions using optical coherence tomography

Lymphatic dysfunction is involved in many diseases including lymphedema, hypertension, autoimmune responses, graft rejection, atherosclerosis, microbial infections, cancer and cancer metastasis. Expanding our knowledge of lymphatic system function can lead to a better understanding of these disease processes and improve treatment options. Here, optical coherence tomography (OCT) methods were used to reveal intraluminal valve dynamics in 3 dimensions, and measure lymph flow and vessel contraction simultaneously in 3 neighboring lymphangions of the afferent collecting lymphatic vessels to the popliteal lymph node in mice. Flow measurements were based on Doppler OCT techniques in combination with exogenous lymph labeling by Intralipid. Through these imaging methods, it is possible to study lymphatic function and pumping more comprehensively. These capabilities can lead to a better understanding of the regulation and dysregulation of lymphatic vessels in health and disease. The image depicts the dynamic measurements of lymphatic valves, lymphatic vessels cross-sectional area and lymph velocity simultaneously measured in vivo with optical coherence tomography.

Review of optical coherence tomography in oncology

The application of optical coherence tomography (OCT) in the field of oncology has been prospering over the past decade. OCT imaging has been used to image a broad spectrum of malignancies, including those arising in the breast, brain, bladder, the gastrointestinal, respiratory, and reproductive tracts, the skin, and oral cavity, among others. OCT imaging has initially been applied for guiding biopsies, for intraoperatively evaluating tumor margins and lymph nodes, and for the early detection of small lesions that would often not be visible on gross examination, tasks that align well with the clinical emphasis on early detection and intervention. Recently, OCT imaging has been explored for imaging tumor cells and their dynamics, and for the monitoring of tumor responses to treatments. This paper reviews the evolution of OCT technologies for the clinical application of OCT in surgical and noninvasive interventional oncology procedures and concludes with a discussion of the future directions for OCT technologies, with particular emphasis on their applications in oncology.

Clinical translation of handheld optical coherence tomography: practical considerations and recent advancements

Since the inception of optical coherence tomography (OCT), advancements in imaging system design and handheld probes have allowed for numerous advancements in disease diagnostics and characterization of the structural and optical properties of tissue. OCT system developers continue to reduce form factor and cost, while improving imaging performance (speed, resolution, etc.) and flexibility for applicability in a broad range of fields, and nearly every clinical specialty. An extensive array of components to construct customized systems has also become available, with a range of commercial entities that produce high-quality products, from single components to full systems, for clinical and research use. Many advancements in the development of these miniaturized and portable systems can be linked back to a specific challenge in academic research, or a clinical need in medicine or surgery. Handheld OCT systems are discussed and explored for various applications. Handheld systems are discussed in terms of their relative level of portability and form factor, with mention of the supporting technologies and surrounding ecosystem that bolstered their development. Additional insight from our efforts to implement systems in several clinical environments is provided. The trend toward well-designed, efficient, and compact handheld systems paves the way for more widespread adoption of OCT into point-of-care or point-of-procedure applications in both clinical and commercial settings.

Murine chronic lymph node window for longitudinal intravital lymph node imaging

Chronic imaging windows in mice have been developed to allow intravital microscopy of many different organs and have proven to be of paramount importance in advancing our knowledge of normal and disease processes. A model system that allows long-term intravital imaging of lymph nodes would facilitate the study of cell behavior in lymph nodes during the generation of immune responses in a variety of disease settings and during the formation of metastatic lesions in cancer-bearing mice. We describe a chronic lymph node window (CLNW) surgical preparation that allows intravital imaging of the inguinal lymph node in mice. The CLNW is custom-made from titanium and incorporates a standard coverslip. It allows stable longitudinal imaging without the need for serial surgeries while preserving lymph node blood and lymph flow. We also describe how to build and use an imaging stage specifically designed for the CLNW to prevent (large) rotational changes as well as respiratory movement during imaging. The entire procedure takes approximately half an hour per mouse, and subsequently allows for longitudinal intravital imaging of the murine lymph node and surrounding structures for up to 14 d. Small-animal surgery experience is required to successfully carry out the protocol.

In Vivo Molecular Optical Coherence Tomography of Lymphatic Vessel Endothelial Hyaluronan Receptors

Optical Coherence Tomography (OCT) imaging of living subjects offers increased depth of penetration while maintaining high spatial resolution when compared to other optical microscopy techniques. However, since most protein biomarkers do not exhibit inherent contrast detectable by OCT, exogenous contrast agents must be employed for imaging specific cellular biomarkers of interest. While a number of OCT contrast agents have been previously studied, demonstrations of molecular targeting with such agents in live animals have been historically challenging and notably limited in success. Here we demonstrate for the first time that microbeads (µBs) can be used as contrast agents to target cellular biomarkers in lymphatic vessels and can be detected by OCT using a phase variance algorithm. This molecular OCT method enables in vivo imaging of the expression profiles of lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), a biomarker that plays crucial roles in inflammation and tumor metastasis. In vivo OCT imaging of LVYE-1 showed that the biomarker was significantly down-regulated during inflammation induced by acute contact hypersensitivity (CHS). Our work demonstrated a powerful molecular imaging tool that can be used for high resolution studies of lymphatic function and dynamics in models of inflammation, tumor development, and other lymphatic diseases.

Investigation of optical coherence micro-elastography as a method to visualize micro-architecture in human axillary lymph nodes

Background

Evaluation of lymph node involvement is an important factor in detecting metastasis and deciding whether to perform axillary lymph node dissection (ALND) in breast cancer surgery. As ALND is associated with potentially severe long term morbidity, the accuracy of lymph node assessment is imperative in avoiding unnecessary ALND. The mechanical properties of malignant lymph nodes are often distinct from those of normal nodes. A method to image the micro-scale mechanical properties of lymph nodes could, thus, provide diagnostic information to aid in the assessment of lymph node involvement in metastatic cancer. In this study, we scan axillary lymph nodes, freshly excised from breast cancer patients, with optical coherence micro-elastography (OCME), a method of imaging micro-scale mechanical strain, to assess its potential for the intraoperative assessment of lymph node involvement.

Methods

Twenty-six fresh, unstained lymph nodes were imaged from 15 patients undergoing mastectomy or breast-conserving surgery with axillary clearance. Lymph node specimens were bisected to allow imaging of the internal face of each node. Co-located OCME and optical coherence tomography (OCT) scans were taken of each sample, and the results compared to standard post-operative hematoxylin-and-eosin-stained histology.

Results

The optical backscattering signal provided by OCT alone may not provide reliable differentiation by inspection between benign and malignant lymphoid tissue. Alternatively, OCME highlights local changes in tissue strain that correspond to malignancy and are distinct from strain patterns in benign lymphoid tissue. The mechanical contrast provided by OCME complements the optical contrast provided by OCT and aids in the differentiation of malignant tumor from uninvolved lymphoid tissue.

Conclusion

The combination of OCME and OCT images represents a promising method for the identification of malignant lymphoid tissue. This method shows potential to provide intraoperative assessment of lymph node involvement, thus, preventing unnecessary removal of uninvolved tissues and improving patient outcomes.

In vivo label-free measurement of lymph flow velocity and volumetric flow rates using Doppler optical coherence tomography

Direct in vivo imaging of lymph flow is key to understanding lymphatic system function in normal and disease states. Optical microscopy techniques provide the resolution required for these measurements, but existing optical techniques for measuring lymph flow require complex protocols and provide limited temporal resolution. Here, we describe a Doppler optical coherence tomography platform that allows direct, label-free quantification of lymph velocity and volumetric flow rates. We overcome the challenge of very low scattering by employing a Doppler algorithm that operates on low signal-to-noise measurements. We show that this technique can measure lymph velocity at sufficiently high temporal resolution to resolve the dynamic pulsatile flow in collecting lymphatic vessels.

Intraoperative optical coherence tomography for assessing human lymph nodes for metastatic cancer

Background

Evaluation of lymph node (LN) status is an important factor for detecting metastasis and thereby staging breast cancer. Currently utilized clinical techniques involve the surgical disruption and resection of lymphatic structure, whether nodes or axillary contents, for histological examination. While reasonably effective at detection of macrometastasis, the majority of the resected lymph nodes are histologically negative. Improvements need to be made to better detect micrometastasis, minimize or eliminate lymphatic disruption complications, and provide immediate and accurate intraoperative feedback for in vivo cancer staging to better guide surgery.

Methods

We evaluated the use of optical coherence tomography (OCT), a high-resolution, real-time, label-free imaging modality for the intraoperative assessment of human LNs for metastatic disease in patients with breast cancer. We assessed the sensitivity and specificity of double-blinded trained readers who analyzed intraoperative OCT LN images for presence of metastatic disease, using co-registered post-operative histopathology as the gold standard.

Results

Our results suggest that intraoperative OCT examination of LNs is an appropriate real-time, label-free, non-destructive alternative to frozen-section analysis, potentially offering faster interpretation and results to empower superior intraoperative decision-making.

Conclusions

Intraoperative OCT has strong potential to supplement current post-operative histopathology with real-time in situ assessment of LNs to preserve both non-cancerous nodes and their lymphatic vessels, and thus reduce the associated risks and complications from surgical disruption of lymphoid structures following biopsy.

Investigation of Optical Coherence Microelastography as a Method to Visualize Cancers in Human Breast Tissue

An accurate intraoperative identification of malignant tissue is a challenge in the surgical management of breast cancer. Imaging techniques that help address this challenge could contribute to more complete and accurate tumor excision, and thereby help reduce the current high reexcision rates without resorting to the removal of excess healthy tissue. Optical coherence microelastography (OCME) is a three-dimensional, high-resolution imaging technique that is sensitive to microscale variations of the mechanical properties of tissue. As the tumor modifies the mechanical properties of breast tissue, OCME has the potential to identify, on the microscale, involved regions of fresh, unstained tissue. OCME is based on the use of optical coherence tomography (OCT) to measure tissue deformation in response to applied mechanical compression. In this feasibility study on 58 ex vivo samples from patients undergoing mastectomy or wide local excision, we demonstrate the performance of OCME as a means to visualize tissue microarchitecture in benign and malignant human breast tissues. Through a comparison with corresponding histology and OCT images, OCME is shown to enable ready visualization of features such as ducts, lobules, microcysts, blood vessels, and arterioles and to identify invasive tumor through distinctive patterns in OCME images, often with enhanced contrast compared with OCT. These results lay the foundation for future intraoperative studies. Cancer Res; 75(16); 3236-45. ©2015 AACR.

Assessment of Sentinel Node Biopsies With Full-Field Optical Coherence Tomography

Current techniques for the intraoperative analysis of sentinel lymph nodes during breast cancer surgery present drawbacks such as time and tissue consumption. Full-field optical coherence tomography is a novel noninvasive, high-resolution, fast imaging technique. This study investigated the use of full-field optical coherence tomography as an alternative technique for the intraoperative analysis of sentinel lymph nodes. Seventy-one axillary lymph nodes from 38 patients at Tenon Hospital were imaged minutes after excision with full-field optical coherence tomography in the pathology laboratory, before being handled for histological analysis. A pathologist performed a blind diagnosis (benign/malignant), based on the full-field optical coherence tomography images alone, which resulted in a sensitivity of 92% and a specificity of 83% (n = 65 samples). Regular feedback was given during the blind diagnosis, with thorough analysis of the images, such that features of normal and suspect nodes were identified in the images and compared with histology. A nonmedically trained imaging expert also performed a blind diagnosis aided by the reading criteria defined by the pathologist, which resulted in 85% sensitivity and 90% specificity (n = 71 samples). The number of false positives of the pathologist was reduced by 3 in a second blind reading a few months later. These results indicate that following adequate training, full-field optical coherence tomography can be an effective noninvasive diagnostic tool for extemporaneous sentinel node biopsy qualification.

A review of optical coherence tomography in breast cancer

Optical coherence tomography (OCT) is a medical imaging modality that opens up new opportunities for imaging in breast cancer. It provides two- and three-dimensional micro-scale images of tissue structure from bulk tissue,

Optical techniques for the intraoperative assessment of nodal status

The lymphatic system is an important pathway in the metastatic spread of many malignancies and a key prognostic indicator. Nondestructive assessment of the nodal status during surgery could limit the amount of lymph nodes that need to be resected and allow for immediate regional lymphadenectomy during sentinel lymph node biopsy procedures. This review looks into the possibilities of conventional medical imaging methods that are capable of intraoperative nodal assessment and discusses multiple newly developed optical techniques. The physical background behind these techniques is reviewed and a concise overview of their main advantages and disadvantages is provided. These recent innovations show that while the application of optical modalities for intraoperative nodal staging is not yet applied routinely, there is reason enough to expect their introduction in the near future.

Large field, high resolution full-field optical coherence tomography: a pre-clinical study of human breast tissue and cancer assessment

We present a benchmark pilot study in which high-resolution Full-Field Optical Coherence Tomography (FF-OCT) was used to image human breast tissue and is evaluated to assess its ability to aid the pathologist’s management of intra-operative diagnoses. FF-OCT imaging safety was investigated and agreement between FF-OCT and routinely prepared histopathological images was evaluated. The compact setup used for this study provides 1 µm³ resolution and 200 µm imaging depth, and a 2.25 cm² specimen is scanned in about 7 minutes. 75 breast specimens were imaged from 22 patients (21 women, 1 man) with a mean age of 58 (range: 25-83). Pathologists blind diagnosed normal/benign or malignant tissue based on FF-OCT images alone, diagnosis from histopathology followed for comparison. The contrast in the FF-OCT images is generated by intrinsic tissue scattering properties, meaning that no tissue staining or preparation is required. Major architectural features and tissue structures of benign breast tissue, including adipocytes, fibrous stroma, lobules and ducts were characterized. Subsequently, features resulting from pathological modification were characterized and a diagnosis decision tree was developed. Using FF-OCT images, two breast pathologists were able to distinguish normal/benign tissue from lesional with a sensitivity of 94% and 90%, and specificity of 75% and 79% respectively.

Imaging of non-tumorous and tumorous human brain tissues with full-field optical coherence tomography

A prospective study was performed on neurosurgical samples from 18 patients to evaluate the use of full-field optical coherence tomography (FF-OCT) in brain tumor diagnosis.

FF-OCT captures en face slices of tissue samples at 1 μm resolution in 3D to a penetration depth of around 200 μm. A 1 cm² specimen is scanned at a single depth and processed in about 5 min. This rapid imaging process is non-invasive and requires neither contrast agent injection nor tissue preparation, which makes it particularly well suited to medical imaging applications.

Temporal chronic epileptic parenchyma and brain tumors such as meningiomas, low-grade and high-grade gliomas, and choroid plexus papilloma were imaged. A subpopulation of neurons, myelin fibers and CNS vasculature were clearly identified. Cortex could be discriminated from white matter, but individual glial cells such as astrocytes (normal or reactive) or oligodendrocytes were not observable.

This study reports for the first time on the feasibility of using FF-OCT in a real-time manner as a label-free non-invasive imaging technique in an intraoperative neurosurgical clinical setting to assess tumorous glial and epileptic margins.

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Demonstration of full-field optical coherence tomography imaging of human brain samples

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Potential as an intraoperative tool for determining tissue architecture and content in minutes

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Myelin fibers, neurons, microcalcifications, tumor cells, microcysts, and vessels identified

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Good correspondence with histological slides, allowing clinical use for tissue selection

SEGMENTATION AND CORRELATION OF OPTICAL COHERENCE TOMOGRAPHY AND X-RAY IMAGES FOR BREAST CANCER DIAGNOSTICS

Pre-operative X-ray mammography and intraoperative X-ray specimen radiography are routinely used to identify breast cancer pathology. Recent advances in optical coherence tomography (OCT) have enabled its use for the intraoperative assessment of surgical margins during breast cancer surgery. While each modality offers distinct contrast of normal and pathological features, there is an essential need to correlate image-based features between the two modalities to take advantage of the diagnostic capabilities of each technique. We compare OCT to X-ray images of resected human breast tissue and correlate different tissue features between modalities for future use in real-time intraoperative OCT imaging. X-ray imaging (specimen radiography) is currently used during surgical breast cancer procedures to verify tumor margins, but cannot image tissue in situ. OCT has the potential to solve this problem by providing intraoperative imaging of the resected specimen as well as the in situ tumor cavity. OCT and micro-CT (X-ray) images are automatically segmented using different computational approaches, and quantitatively compared to determine the ability of these algorithms to automatically differentiate regions of adipose tissue from tumor. Furthermore, two-dimensional (2D) and three-dimensional (3D) results are compared. These correlations, combined with real-time intraoperative OCT, have the potential to identify possible regions of tumor within breast tissue which correlate to tumor regions identified previously on X-ray imaging (mammography or specimen radiography).

Optical imaging techniques for point-of-care diagnostics

Improving access to effective and affordable healthcare has long been a global endeavor. In this quest, the development of cost-effective and easy-to-use medical testing equipment that enables rapid and accurate diagnosis is essential to reduce the time and costs associated with healthcare services. To this end, point-of-care (POC) diagnostics plays a crucial role in healthcare delivery in both developed and developing countries by bringing medical testing to patients, or to sites near patients. As the diagnosis of a wide range of diseases, including various types of cancers and many endemics, relies on optical techniques, numerous compact and cost-effective optical imaging platforms have been developed in recent years for use at the POC. Here, we review the state-of-the-art optical imaging techniques that can have a significant impact on global health by facilitating effective and affordable POC diagnostics.

Real-time speckle variance swept-source optical coherence tomography using a graphics processing unit

Advances in swept source laser technology continues to increase the imaging speed of swept-source optical coherence tomography (SS-OCT) systems. These fast imaging speeds are ideal for microvascular detection schemes, such as speckle variance (SV), where interframe motion can cause severe imaging artifacts and loss of vascular contrast. However, full utilization of the laser scan speed has been hindered by the computationally intensive signal processing required by SS-OCT and SV calculations. Using a commercial graphics processing unit that has been optimized for parallel data processing, we report a complete high-speed SS-OCT platform capable of real-time data acquisition, processing, display, and saving at 108,000 lines per second. Subpixel image registration of structural images was performed in real-time prior to SV calculations in order to reduce decorrelation from stationary structures induced by the bulk tissue motion. The viability of the system was successfully demonstrated in a high bulk tissue motion scenario of human fingernail root imaging where SV images (512 × 512 pixels, n = 4) were displayed at 54 frames per second.

Three-dimensional optical coherence tomography for optical biopsy of lymph nodes and assessment of metastatic disease

BACKGROUND

Numerous techniques have been developed for localizing lymph nodes before surgical resection and for their histological assessment. Nondestructive high-resolution transcapsule optical imaging of lymph nodes offers the potential for in situ assessment of metastatic involvement, potentially during surgical procedures.

METHODS

Three-dimensional optical coherence tomography (3-D OCT) was used for imaging and assessing resected popliteal lymph nodes from a preclinical rat metastatic tumor model over a 9-day time-course study after tumor induction. The spectral-domain OCT system utilized a center wavelength of 800 nm, provided axial and transverse resolutions of 3 and 12 μm, respectively, and performed imaging at 10,000 axial scans per second.

RESULTS

OCT is capable of providing high-resolution label-free images of intact lymph node microstructure based on intrinsic optical scattering properties with penetration depths of ~1-2 mm. The results demonstrate that OCT is capable of differentiating normal, reactive, and metastatic lymph nodes based on microstructural changes. The optical scattering and structural changes revealed by OCT from day 3 to day 9 after the injection of tumor cells into the lymphatic system correlate with inflammatory and immunological changes observed in the capsule, precortical regions, follicles, and germination centers found during histopathology.

CONCLUSIONS

We report for the first time a longitudinal study of 3-D transcapsule OCT imaging of intact lymph nodes demonstrating microstructural changes during metastatic infiltration. These results demonstrate the potential of OCT as a technique for intraoperative, real-time in situ 3-D optical biopsy of lymph nodes for the intraoperative staging of cancer.

Parametric imaging of the local attenuation coefficient in human axillary lymph nodes assessed using optical coherence tomography

We report the use of optical coherence tomography (OCT) to determine spatially localized optical attenuation coefficients of human axillary lymph nodes and their use to generate parametric images of lymphoid tissue. 3D-OCT images were obtained from excised lymph nodes and optical attenuation coefficients were extracted assuming a single scattering model of OCT. We present the measured attenuation coefficients for several tissue regions in benign and reactive lymph nodes, as identified by histopathology. We show parametric images of the measured attenuation coefficients as well as segmented images of tissue type based on thresholding of the attenuation coefficient values. Comparison to histology demonstrates the enhancement of contrast in parametric images relative to OCT images. This enhancement is a step towards the use of OCT for in situ assessment of lymph nodes.

Three-dimensional high-resolution imaging of gold nanorods uptake in sentinel lymph nodes

In this paper, we demonstrate an application of a noninvasive imaging modality, photothermal optical coherence tomography (PT-OCT), for imaging gold nanorods (GNRs) uptake in sentinel lymph node (SLN) of mice in situ. This application enables us to obtain higher quality images of SLN structures due to the photothermal contrast properties of the GNRs. It is also demonstrated that GNRs accumulate differently within several SLN structures, and this uptake is time dependent. Finally, we determine the average concentration of GNRs within the whole SLN which is used to demonstrate uptake kinetics of the nanoparticles.

Optical coherence tomography: the intraoperative assessment of lymph nodes in breast cancer

During breast-conserving surgeries, axillary lymph nodes draining from the primary tumor site are removed for disease staging. Although a high number of lymph nodes are often resected during sentinel and lymph-node dissections, only a relatively small percentage of nodes are found to be metastatic, a fact that must be weighed against potential complications such as lymphedema. Without a real-time in vivo or in situ intraoperative imaging tool to provide a microscopic assessment of the nodes, postoperative paraffin section histopathological analysis currently remains the gold standard in assessing the status of lymph nodes. This paper investigates the use of optical coherence tomography (OCT), a high-resolution real-time microscopic optical-imaging technique, for the intraoperative ex vivo imaging and assessment of axillary lymph nodes. Normal (13), reactive (1), and metastatic (3) lymph nodes from 17 human patients with breast cancer were imaged intraoperatively with OCT. These preliminary clinical studies have identified scattering changes in the cortex, relative to the capsule, which can be used to differentiate normal from reactive and metastatic nodes. These optical scattering changes are correlated with inflammatory and immunological changes observed in the follicles and germinal centers. These results suggest that intraoperative OCT has the potential to assess the real-time node status in situ, without having to physically resect and histologically process specimens to visualize microscopic features.

Three-dimensional optical imaging of microvascular networks within intact lymph node in vivo

Sentinel lymph nodes (SLNs) are the first lymph nodes to drain wastes originated from cancerous tissue. There is a need for an in vivo imaging method that can image the intact SLN to further our understanding of its normal as well as abnormal functions. We report the use of ultrahigh sensitive optical microangiography (UHS-OMAG) to image functional microvascular and lymphatic vessel networks that innervate the intact lymph node in mice in vivo. The promising results show a potential role of UHS-OMAG in the future understanding and diagnosis of the SLN involvement in cancer development.

Mapping tissue optical attenuation to identify cancer using optical coherence tomography

The lymphatic system is a common route for the spread of cancer and the identification of lymph node metastases is a key task during cancer surgery. This paper demonstrates the use of optical coherence tomography to construct parametric images of lymph nodes. It describes a method to automatically estimate the optical attenuation coefficient of tissue. By mapping the optical attenuation coefficient at each location in the scan, it is possible to construct a parametric image indicating variations in tissue type. The algorithm is applied to ex vivo samples of human axillary lymph nodes and validated against a histological gold standard. Results are shown illustrating the variation in optical properties between cancerous and healthy tissue.

Intraperitoneal virtual biopsy by fibered optical coherence tomography (OCT) at natural orifice transluminal endoscopic surgery (NOTES)

INTRODUCTION

Fibered optical coherence tomography (OCT) in conjunction with natural orifice transluminal endoscopic surgery (NOTES) could provide a facility for rapid, in situ pathological diagnosis of intraperitoneal tissues in a truly minimally invasive fashion.

MATERIALS AND METHODS

A large porcine model was established to test this hypothesis. A standard double channel gastroscope (Olympus) was used to achieve a transgastric access to the peritoneum and initiate the pneumoperitoneum. Magnetic retraction was used to display the sigmoid colon along with its mesentery. A commercially available fibered OCT probe (NIRIS system, Imalux) was inserted via a working channel of the gastroscope and used to assess intraperitoneal tissues. Separately, OCT images of human tissue specimens ex vivo were contrasted with representative standard histopathological slides.

RESULTS

Intraperitoneal OCT provided clear real-time images of both the serosal and muscularis propria mural layers as well as the submucosal-muscularis interface. Examination of mesenteric lymph nodes (including sentinel nodes) allowed visualization of their subcapsular sinus. Comparison of representative cross-sections however failed to evince sufficient resolution for confident diagnosis.

CONCLUSION

This approach is technically feasible and, if the technology is advanced and proven accurate in human patients, could potentially be used to individualize operative extent prior to definitive resection.

Clinical feasibility of microscopically-guided breast needle biopsy using a fiber-optic probe with computer-aided detection

Needle biopsy of small or nonpalpable breast lesions has a high nondiagnostic sampling rate even when needle position is guided by stereotaxis or ultrasound. We assess the feasibility of using a near-infrared fiber optic probe and computer-aided detection for the microscopic guidance of needle breast biopsy procedures. Specimens from nine consented patients undergoing breast-conserving surgery were assessed intraoperatively using a needle device with an integrated fiber-optic probe capable of assessing two physical tissue properties highly correlated to pathology. Immediately following surgical resection, specimens were probed by inserting the optical biopsy needle device into the tissue, simulating the procedure used to position standard biopsy needles. Needle positions were marked and correlated with histology, which verified measurements obtained from 58 needle positions, including 40 in adipose and 18 in tumor tissue. This study yielded tissue classifications based on measurement of optical refractive index and scattering. Confidence-rating schemes yielded combined sensitivity of 89% (16/18) and specificity of 78% (31/40). Refractive index tests alone identified tumor tissue with a sensitivity of 83% (15/18) and specificity of 75% (30/40). Scattering profiles independently identified tumor tissue with a sensitivity of 61% (11/18) and specificity of 60% (24/40). These results show that a biopsy needle with an integrated fiber optic probe can be used to identify breast tumor tissue for sampling. Integration of this probe into current practices offers the potential to reduce nondiagnostic sampling rates by directly evaluating in situ microscopic tissue properties in real-time, before removal.

Sentinel node biopsy for the individualization of surgical strategy for cure of early-stage colon cancer

INTRODUCTION

The requirement for nodal analysis currently confounds the oncological propriety of focused purely endoscopic resection for early-stage colon cancer and complicates the evolution of innovative alternatives such as natural orifice transluminal endoscopic surgery (NOTES) and its hybrids. Adjunctive sentinel node biopsy (SNB) deserves consideration as a means of addressing this shortfall.

METHODS

Data from two prospectively maintained databases established for multicentric studies of SNB in colon cancer that employed similar methodologies were pooled to establish technique potency selectively in T1/T2 disease (both overall and under optimized conditions) and to project potential clinical impact.

RESULTS

Of 891 patients with T1-4, M0 intraperitoneal colon cancer, 225 had T1/T2 disease. Sentinel nodes were either not found or were falsely negative in 18 patients with T1/T2 cancers (8%) as compared with 17% (112/646) in those with T3/T4 disease (P = 0.001). Negative predictive value (NPV) in the former exceeded 95%, while sensitivity [including immunohistochemistry (IHC)] was 81%. In the 193 patients with T1/T2 disease recruited from those centers contributing >22 patients, sensitivity was 89% and NPV 97%. Thus, in this cohort, SNB could have correctly prompted localized resection (obviating en bloc mesenteric dissection) in 75% (144) of patients, including 59 with T1 lesions potentially amenable to intraluminal resection alone as their definitive treatment. Forty-four patients (23.4%) would still have conventional resection, leaving three patients (1.6% overall) understaged (11% false-negative rate).

CONCLUSION

These findings support the further investigation of SNB as oncological augment for localized resective techniques. Specific prospective study should pursue this goal.

Supplementation of endoscopic submucosal dissection with sentinel node biopsy performed by natural orifice transluminal endoscopic surgery (NOTES) (with video)

BACKGROUND

Endoscopic submucosal dissection (ESD) is proving to be effective for the resection of selected early gastric and colon cancers. Its application and appropriateness could be extended if a means of determining lymphatic dissemination without recourse to a conventional operation could be provided.

OBJECTIVE

To demonstrate the feasibility of companion sentinel node biopsy (SNB) by natural orifice transluminal endoscopic surgery (NOTES) concurrent with intraluminal ESD in both the sigmoid colon and stomach.

DESIGN

Acute porcine model.

INTERVENTION

Arbitrarily selected mucosal foci were targeted for combined NOTES-SNB and ESD in the sigmoid and stomach of 2 separate anesthetized animals. NOTES peritoneal access was obtained either transgastrically or transvaginally. A second intraluminal endoscope was passed either orally or rectally, as appropriate, to perform submucosal injection for lymphatic mapping under direct vision of the NOTES endoscope. This endoscope then identified the first-order draining (sentinel) nodes and allowed their excisional biopsy. The sigmoid was retracted by magnetic assistance as required, while torque of an intraluminal gastroscope manipulated the stomach. After retrieval of the nodes, 1-cm and 1.5-cm specimens were resected from the sigmoid and stomach, respectively, by conventional ESD. At procedure end, necropsy was performed.

RESULTS

All sentinel nodes were identified, underwent biopsy, and were retrieved intact. ESD was subsequently readily performed without complication. SNB completeness and ESD quality were confirmed postprocedure.

LIMITATIONS

Experimental model with limited sample size.

CONCLUSIONS

Although not yet appropriate for human use, this proposal merits serious consideration as a potential means of augmenting the effectiveness and appropriateness of ESD techniques for GI neoplasia.

Regional nodal staging for early stage colon cancer in the era of endoscopic resection and N.O.T.E.S

Advanced endoscopic technologies and techniques capable of providing localized resection of colonic primaries are entering clinical practice. As much as Natural Orifice Transluminal Endoscopic Surgery (N.O.T.E.S.) may ultimately provide for transmural resection with narrow margins, intraluminal techniques such as endoscopic submucosal resection can now effect excision of early stage tumors from within the colon. However, the limit on the application of these approaches is oncological providence as current staging requires en bloc mesenteric resection in every case to ensure that adequate nodal assessment is assured. Furthermore, this requirement is also a limiting factor on the advance of innovative procedures such as Single-Incision Laparoscopic Surgery and N.O.T.E.S.-hybrid techniques as these approaches, while likely adept at the definitive management of the primary, have limitations regarding their ability to provide full base mesenteric resection (due mostly to constraints on retraction capacity as well as operating field space and exposure). Therefore a means to accurately and efficiently identify those patients who are truly node negative (and so in whom radical mesenteric lymphadenectomy could be avoided) would allow all of these techniques to advance with a clear focus on address of the primary. This review analyses the current state of the art of regional staging in the colonic mesentery in place of formal lymphadenectomy. It includes deliberation of both preoperative non-invasive testing as well as novel means of employing N.O.T.E.S. approaches to allow direct determination of lymph node status (in particular that of sentinel nodes) by either rapid histopathological examination or by emerging technologies such as Optical Coherence Tomography that may provide optical or 'virtual' biopsy.

Optical coherence tomography: a review of clinical development from bench to bedside

Since its introduction, optical coherence tomography (OCT) technology has advanced from the laboratory bench to the clinic and back again. Arising from the fields of low coherence interferometry and optical time- and frequency-domain reflectometry, OCT was initially demonstrated for retinal imaging and followed a unique path to commercialization for clinical use. Concurrently, significant technological advances were brought about from within the research community, including improved laser sources, beam delivery instruments, and detection schemes. While many of these technologies improved retinal imaging, they also allowed for the application of OCT to many new clinical areas. As a result, OCT has been clinically demonstrated in a diverse set of medical and surgical specialties, including gastroenterology, dermatology, cardiology, and oncology, among others. The lessons learned in the clinic are currently spurring a new set of advances in the laboratory that will again expand the clinical use of OCT by adding molecular sensitivity, improving image quality, and increasing acquisition speeds. This continuous cycle of laboratory development and clinical application has allowed the OCT technology to grow at a rapid rate and represents a unique model for the translation of biomedical optics to the patient bedside. This work presents a brief history of OCT development, reviews current clinical applications, discusses some clinical translation challenges, and reviews laboratory developments poised for future clinical application.

Benign and malignant lesions in the human breast depicted with ultrahigh resolution and three-dimensional optical coherence tomography

Institutional review board approval at the participating institutions was obtained. Informed consent was waived for this HIPAA-compliant study. The study purpose was to establish the correspondence of optical coherence tomographic (OCT) image findings with histopathologic findings to understand which features characteristic of breast lesions can be visualized with OCT. Imaging was performed in 119 specimens from 35 women aged 29-81 years with 3.5-microm axial resolution and 6-microm transverse resolution at 1.1-microm wavelength on freshly excised specimens of human breast tissue. Three-dimensional imaging was performed in 43 specimens from 23 patients. Microstructure of normal breast parenchyma, including glands, lobules, and lactiferous ducts, and stromal changes associated with infiltrating cancer were visible. Fibrocystic changes and benign fibroadenomas were identified. Imaging of ductal carcinoma in situ, infiltrating cancer, and microcalcifications correlated with corresponding histopathologic findings. OCT is potentially useful for visualization of breast lesions at a resolution greater than that of currently available clinical imaging methods.

Early chloroplastic alterations analysed by optical coherence tomography during a harpin-induced hypersensitive response

The hypersensitive response has been mostly studied by molecular and biochemical methods after sample destruction. The development of imaging techniques allows the monitoring of physiological changes before any signs of cell death. Here, we follow the early steps of a hypersensitive-like response induced by the bacterial elicitor harpin in Nicotiana sp. We describe cytological modifications after inoculation of the harpin protein, using confocal fluorescence microscopy (CFM) and optical coherence tomography (OCT), an interferometric-based microscopy. The changes detected by CFM occurred 5 h after harpin infiltration and corresponded to a redistribution of the chloroplasts from the upper to the inner regions of the palisade mesophyll cells which could be related to a perturbation in the microtubule network. Using OCT, we were able to detect a decrease in chloroplast backscattered signal as early as 30 min after harpin infiltration. A simple physical model, which accounted for the structure and distribution of thylakoid membranes, suggested that this loss of scattering could be associated with a modification in the refractive index of the thylakoid membranes. Our OCT observations were correlated with a decrease in photosynthesis, emphasizing changes in chloroplast structure as one of the earliest hallmarks of plant hypersensitive cell death.

In vivo cancer diagnosis with optical spectroscopy and acoustically induced blood stasis using a murine MCa35 model

Ultrasound-induced blood stasis has been observed for more than 30 years. Most of the literature has been focused on the health risks associated with this phenomenon and methods employed to prevent stasis from occurring during ultrasound imaging. To date, experimental observations have been either in vitro or invasive. The current work demonstrates ultrasound-induced blood stasis in murine normal leg muscle versus tumor-bearing legs, observed through noninvasive measurements of optical spectroscopy, and discusses possible diagnostic uses for this previously undesirable effect of ultrasound. We demonstrate that, using optical spectroscopy, effects of ultrasound can be used to differentiate tumor from normal leg muscle tissue in mice. Finally, we propose a novel diagnostic algorithm that quantitatively differentiates tumor from nontumor with maximum specificity 0.83, maximum sensitivity 0.79, and area under receiver-operating-characteristics curve 0.90.

Computational methods for analysis of human breast tumor tissue in optical coherence tomography images

Optical coherence tomography (OCT) has been demonstrated as a promising means of identifying the boundaries between normal and diseased breast tissue. This capability has yielded promise for the development of OCT techniques for biopsy guidance, surgical margin assessment, and minimally invasive evaluation of disease states. We present methods for the assessment of human breast tissue based on spatial and Fourier-domain analysis. Derived from preliminary OCT data, these methods are aimed at the development of automated diagnostic tools that will aid in the translation of this technology into the clinical environment.

Refractive index of carcinogen-induced rat mammary tumours

Near-infrared optical techniques for clinical breast cancer screening in humans are rapidly advancing. Based on the computational inversion of the photon diffusion process through the breast, these techniques rely on optical tissue models for accurate image reconstruction. Recent interest has surfaced regarding the effect of refractive index variations on these reconstructions. Although many data exist regarding the scattering and absorption properties of normal and diseased tissue, no measurements of refractive index appear in the literature. In this paper, we present near-infrared refractive index data acquired from N-methyl-N-nitrosourea-induced rat mammary tumours, which are similar in pathology and disease progression to human ductal carcinoma. Eight animals, including one control, were employed in this study, yielding data from 32 tumours as well as adjacent adipose and connective tissues.

Optical imaging of lymph nodes

Optical imaging or near infrared fluorescence (NIRF) imaging using enzymatically activatable smart probes is an exiting new imaging modality that can also be used for lymph node visualization and detection. This review intends to briefly summarize general aspects of optical imaging and its capabilities for lymph node imaging.