Optical coherence tomography allows for the reliable identification of laryngeal epithelial dysplasia and for precise biopsy: a clinicopathological study of 61 patients undergoing microlaryngoscopy

An overview of the current clinical status of optical imaging in head and neck cancer with a focus on Narrow Band imaging and fluorescence optical imaging

Early and accurate identification of head and neck squamous cell carcinoma (HNSCC) is important to improve treatment outcomes and prognosis. New optical imaging techniques may assist in both the diagnostic process as well as in the operative setting by real-time visualization and delineation of tumor. Narrow Band Imaging (NBI) is an endoscopic technique that uses blue and green light to enhance mucosal and submucosal blood vessels, leading to better detection of (pre)malignant lesions showing aberrant blood vessel patterns. Fluorescence optical imaging makes use of near-infrared fluorescent agents to visualize and delineate HNSCC, resulting in fewer positive surgical margins. Targeted fluorescent agents, such as fluorophores conjugated to antibodies, show the most promising results. The aim of this review is: (1) to provide the clinical head and neck surgeon an overview of the current clinical status of various optical imaging techniques in head and neck cancer; (2) to provide an in-depth review of NBI and fluorescence optical imaging, as these techniques have the highest potential for clinical implementation; and (3) to describe future improvements and developments within the field of these two techniques.

Optical Biopsy of the Upper GI Tract Using Fluorescence Lifetime and Spectra

Screening and surveillance for gastrointestinal (GI) cancers by endoscope guided biopsy is invasive, time consuming, and has the potential for sampling error. Tissue endogenous fluorescence spectra contain biochemical and physiological information, which may enable real-time, objective diagnosis. We first briefly reviewed optical biopsy modalities for GI cancer diagnosis with a focus on fluorescence-based techniques. In an ex vivo pilot clinical study, we measured fluorescence spectra and lifetime on fresh biopsy specimens obtained during routine upper GI screening procedures. Our results demonstrated the feasibility of rapid acquisition of time-resolved fluorescence (TRF) spectra from fresh GI mucosal specimens. We also identified spectroscopic signatures that can differentiate between normal mucosal samples obtained from the esophagus, stomach, and duodenum.

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.

Euclidean distances of laryngopharyngeal structures obtained from CT data for preclinical development of laryngoscopic devices

PURPOSE

This study aims to determine Euclidean distances between landmark structures in the larynx and pharynx to optimize endoscope shaft designs with regard to gentle and patient-oriented handling.

METHODS

Four Euclidean distances between landmarks in the larynx and pharynx were analyzed based on CT data of 66 patients. Distance (1): labium inferius oris-posterior pharyngeal wall at the cervical vertebra C1 (atlas), anterior edge of the tuberculum anterius atlantis. Distance (2): posterior pharyngeal wall adjacent to C1-entrance of pyriform sinus. Distance (3): inferior edge of the uvula-superior edge of the epiglottis. Distance (4): base of the vallecula-posterior pharyngeal wall. The minimum angular field of view α required to observe the glottis with a rigid transoral laryngoscope was derived trigonometrically from distances (2) and (4).

RESULTS

Average Euclidean distances measured: Distance (1): 90.7 mm ± 6.9 mm in men and 86.9 mm ± 5.9 mm in women. (2): 73.7 mm ± 13.4 mm and 56.2 mm ± 7.6 mm. (3): 25.2 mm ± 8.6 mm and 18.5 mm ± 6.8 mm. (4): 20.8 mm ± 4.6 mm and 16.5 mm ± 3.4 mm. α: 16.0° ± 3.9° and 16.6 ± 4.3°.

CONCLUSIONS

As expected, statistically significant sex-related differences could be observed for distances (1)-(4). The results indicate that the length of transoral laryngoscopes should not be below 110 mm and that a minimum angular field of view of α = 17° is required to fully observe the laryngeal inlet.

Computational analysis of six optical coherence tomography systems for vocal fold imaging: A comparison study

OBJECTIVES

There have been many advancements in laryngeal imaging using optical coherence tomography (OCT), with varying system design and probes for use in research, office, and operating room settings. We evaluated the performance of six distinct OCT systems in imaging porcine vocal folds (cords) using computational image processing and segmentation.

METHODS

Porcine vocal folds were scanned using six OCT systems. Imaging system and probe performance were quantitatively assessed for signal penetration, layer differentiation, and epithelium (EP) measurement. Fitted exponential decay curves with corresponding α constant and intensity thresholding segmentation were utilized to quantify the aforementioned parameters.

RESULTS

The smallest average α constant and deepest signal penetration was of the SS-OCT 1700 nm 90 kHz microscope system (α = -1.74), followed by the SS-OCT 1310 nm 200 kHz VCSEL microscope system (α = -1.99), and SS-OCT 1310 nm 50 kHz rigid forward viewing endoscope system (α = -2.23). The EP was not readily visualized for three out of six systems, but was detected using automated segmentation. Average EP thickness (mean ± SD) was calculated as 55.79 ± 31.86 μm which agrees favorably with previous literature.

CONCLUSION

Comparisons of OCT systems are challenging, as they encompass different probe design, optical path, and lasers, depending on application. Practical evaluation of different systems using computer based quantitative image processing and segmentation revealed basic, constructive information, such as EP measurements. To further validate the comparisons of system performance with clinical usability, in vivo human laryngeal imaging will be conducted. Further development of automated image processing and segmentation can be useful in rapid analysis of information. Lasers Surg. Med. 51:412-422, 2019. © 2019 Wiley Periodicals, Inc.

Intraoperative assessment of laryngeal pathologies with optical coherence tomography integrated into a surgical microscope

OBJECTIVE

Endoscopic examination followed by tissue biopsy is the gold standard in the evaluation of lesions of the upper aerodigestive tract. However, it can be difficult to distinguish between healthy mucosa, dysplasia, and invasive carcinoma. Optical coherence tomography (OCT) is a non-invasive technique which acquires high-resolution, cross-sectional images of tissue in vivo. Integrated into a surgical microscope, it allows the intraoperative evaluation of lesions simultaneously with microscopic visualization.

STUDY DESIGN

In a prospective case series, we evaluated the use of OCT integrated into a surgical microscope during microlaryngoscopy to help differentiating various laryngeal pathologies.

METHODS

33 patients with laryngeal pathologies were examined with an OCT- microscope (OPMedT iOCT-camera, HS Hi-R 1000G-microscope, Haag-Streit Surgical GmbH, Wedel, Germany) during microlaryngoscopy. The suspected intraoperative diagnoses were compared to the histopathological reports of subsequent tissue biopsies.

RESULTS

Hands-free non-contact OCT revealed high-resolution images of the larynx with a varying penetration depth of up to 1.2 mm and an average of 0.6 mm. Picture quality was variable. OCT showed disorders of horizontal tissue layering in dysplasias with a disruption of the basement membrane in carcinomas. When comparing the suspected diagnosis during OCT-supported microlaryngoscopy with histology, 79% of the laryngeal lesions could be correctly identified. Premalignant lesions were difficult to diagnose and falsely classified as carcinoma.

CONCLUSION

OCT integrated into a surgical microscope seems to be a promising adjunct tool to discriminate pathologies of the upper aerodigestive tract intraoperatively. However, picture quality and penetration depth were variable. Although premalignant lesions were difficult to diagnose, the system proved overall helpful for the intraoperative discrimination of benign and malignant tumors. Further studies will be necessary to define its value in the future. Lasers Surg. Med. 49:490-497, 2017. © 2017 Wiley Periodicals, Inc.

Effect of saline inhalation on vocal fold epithelial morphology evaluated by optical coherence tomography

OBJECTIVES/HYPOTHESIS

Examination of tissue structures by optical coherence tomography (OCT) has been shown to be useful on mucous membranes of the vocal folds, but so far its application to the human larynx has been limited because it is technically cumbersome and usually needs to be performed with sedation. Here a newly developed, noninvasive combined laryngoscopy and OCT procedure is described and its suitability for ambulatory OCT studies evaluated. Because inhalation therapies utilizing saline solutions are commonly used as a treatment option for disorders of the airways, and vocal fold epithelium is most likely to be affected due to its superficial positioning, epithelial thickness was chosen as a relevant test parameter and evaluated before and after saline inhalation.

METHODS

Seven vocally healthy participants performed a 10-minute inhalation of saline solution and underwent a combined laryngoscopy and OCT before and after the inhalation therapy. Endoscopy was performed using a newly developed combined laryngoscopy and OCT device. The OCT images were used to estimate the epithelial thickness of the vocal folds.

RESULTS

Epithelial thickness measured in all participants before treatment was comparable in size reported in previous studies. Statistical differences before and after inhalation were not detected.

CONCLUSION

The newly developed combined laryngoscopy and OCT procedure enables rapid investigation of the vocal fold epithelium. Inhalation of saline solution did not appear to affect the thickness of the epithelium of the vocal folds in vocally healthy subjects, as evaluated by OCT.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 126:E332-E336, 2016.

Automated working distance adjustment enables optical coherence tomography of the human larynx in awake patients

Optical coherence tomography (OCT) provides structural information of laryngeal tissue which is comparable to histopathological analysis of biopsies taken under general anesthesia. In awake patients, movements impede clinically useful OCT acquisition. Therefore, an automatic compensation of movements was implemented into a swept source OCT-laryngoscope. Video and OCT beam path were combined in one tube of 10-mm diameter. Segmented OCT images served as distance sensor and a feedback control adjusted the working distance between 33 and 70 mm by synchronously translating the reference mirror and focusing lens. With this motion compensation, the tissue was properly visible in up to 88% of the acquisition time. During quiet respiration, OCT contrasted epithelium and lamina propria. Mean epithelial thickness was measured to be 109 and [Formula: see text] in female and male, respectively. Furthermore, OCT of mucosal wave movements during phonation enabled estimation of the oscillation frequency and amplitude. Regarding clinical issues, the OCT-laryngoscope with automated working distance adjustment may support the estimation of the depth extent of epithelial lesions and contribute to establish an indication for a biopsy. Moreover, OCT of the vibrating vocal folds provides functional information, possibly giving further insight into mucosal behavior during the vibratory cycle.

Intra-operative application of confocal endomicroscopy using a rigid endoscope

Objective:

To introduce the application of confocal endomicroscopy during microlaryngoscopy, to enable intra-operative evaluation of human laryngeal epithelium.

Methods:

A rigid endoscope was connected to the scanner head of a Heidelberg Retina Tomograph II confocal laser scanning system via an adapter. The endoscope was gently placed on the surface of a vocal fold through a laryngoscope during microlaryngoscopy.

Results:

The application of confocal endomicroscopy using a rigid endoscope enabled technical improvements (i.e. improved image quality, automatic volume scan, and reduced tissue pressure due to the presence of a perforation plate with central hole at the end of the endoscope) which permitted greater sensitivity and improved handling. Confocal endomicroscopy provided good quality, in vivo, en-face images and enabled an assessment of laryngeal epithelium volume.

Conclusion:

This method enables the surgeon to monitor epithelial changes in pre-malignant lesions. The combination of confocal endomicroscopy together with optical coherence tomography (as a complementary technique that provides optical cross-sections) should be further explored in a formal clinicopathological study.

Optical coherence tomography in conjunction with bronchoscopy

OBJECTIVE

To evaluate the feasibility of and the potential for using optical coherence tomography in conjunction with conventional bronchoscopy in the evaluation of the airways.

METHODS

This was a pilot study based on an ex vivo experimental model involving three animals: one adult New Zealand rabbit and two Landrace pigs. An optical coherence tomography imaging catheter was inserted through the working channel of a flexible bronchoscope in order to reach the distal trachea of the animals. Images of the walls of the trachea were systematically taken along its entire length, from the distal to the proximal portion.

RESULTS

The imaging catheter was easily adapted to the working channel of the bronchoscope. High-resolution images of cross sections of the trachea were taken in real time, precisely delineating microstructures, such as the epithelium, submucosa, and cartilage, as well as the adventitia of the anterior and lateral tracheal walls. The corresponding layers of the epithelium, mucosa, and cartilage were clearly differentiated. The mucosa, submucosa, and trachealis muscle were clearly identified in the posterior wall.

CONCLUSIONS

It is feasible to use an optical coherence tomography imaging catheter in combination with a flexible bronchoscope. Optical coherence tomography produces high-resolution images that reveal the microanatomy of the trachea, including structures that are typically seen only on images produced by conventional histology.

[Advances in endoscopic diagnosis of dysplasia and carcinoma of the larynx]

To improve the preoperative and intraoperative diagnosis of laryngeal cancer and its precursors, various endoscopic imaging techniques have been developed in recent years. These techniques differ markedly in their specific applications and goals. Precisely distinguishing among normal mucosa, dysplasia and invasive carcinoma with these procedures is necessary. Furthermore, the exact identification of tumor margins should be possible. The long-term goal is the development of optical biopsy. Since so far there have only been small studies regarding the evaluation of the presented methods, it is necessary to establish multi-center trials with large sample sizes to accurately estimate the value of these endoscopic imaging techniques.

Hyperspectral imaging of mucosal surfaces in patients

The aim of this study was to proof applicability of hyperspectral imaging for the analysis and classification of human mucosal surfaces in vivo. The larynx as a prototypical anatomically well-defined surgical test area was analyzed by microlaryngoscopy with a polychromatic lightsource and a synchronous triggered monochromatic CCD-camera. Image stacks (5 benign, 7 malignant tumors) were analyzed by established software (principal component analysis PCA, hyperspectral classification, spectral profiles). Hyperspectral image datacubes were analyzed and classified by conventional software. In PCA, images at 590-680 nm loaded most onto the first PC which typically contained 95% of the total information. Hyperspectral classification clustered the data highlighting altered mucosa. The spectral profiles clearly differed between the different groups. Hyperspectral imaging can be applied to mucosal surfaces. This approach opens the way to analyze spectral characteristics of histologically different lesions in order to build up a spectral library and to allow non-touch optical biopsy.

Evaluating the use of optical coherence tomography for the detection of epithelial cancers in vitro

Optical coherence tomography (OCT) is a noninvasive imaging methodology that is able to image tissue to depths of over 1 mm. Many epithelial conditions, such as melanoma and oral cancers, require an invasive biopsy for diagnosis. A noninvasive, real-time, point of care method of imaging depth-resolved epithelial structure could greatly improve early diagnosis and long-term monitoring in patients. Here, we have used tissue-engineered (TE) models of normal skin and oral mucosa to generate models of melanoma and oral cancer. We have used these to determine the ability of OCT to image epithelial differences in vitro. We report that while in vivo OCT gives reasonable depth information for both skin and oral mucosa, in vitro the information provided is less detailed but still useful. OCT can provide reassurance on the development of TE models of skin and oral mucosa as they develop in vitro. OCT was able to detect the gross alteration in the epithelium of skin and mucosal models generated with malignant cell lines but was less able to detect alteration in the epithelium of TE models that mimicked oral dysplasia or, in models where tumor cells had penetrated into the dermis.

Advances in bio-optical imaging for the diagnosis of early oral cancer

Oral cancer is among the most common malignancies worldwide, therefore early detection and treatment is imperative. The 5-year survival rate has remained at a dismal 50% for the past several decades. The main reason for the poor survival rate is the fact that most of the oral cancers, despite the general accessibility of the oral cavity, are not diagnosed until the advanced stage. Early detection of the oral tumors and its precursor lesions may be the most effective means to improve clinical outcome and cure most patients. One of the emerging technologies is the use of non-invasive in vivo tissue imaging to capture the molecular changes at high-resolution to improve the detection capability of early stage disease. This review will discuss the use of optical probes and highlight the role of optical imaging such as autofluorescence, fluorescence diagnosis (FD), laser confocal endomicroscopy (LCE), surface enhanced Raman spectroscopy (SERS), optical coherence tomography (OCT) and confocal reflectance microscopy (CRM) in early oral cancer detection. FD is a promising method to differentiate cancerous lesions from benign, thus helping in the determination of adequate resolution of surgical resection margin. LCE offers in vivo cellular imaging of tissue structures from surface to subsurface layers and has demonstrated the potential to be used as a minimally invasive optical biopsy technique for early diagnosis of oral cancer lesions. SERS was able to differentiate between normal and oral cancer patients based on the spectra acquired from saliva of patients. OCT has been used to visualize the detailed histological features of the oral lesions with an imaging depth down to 2–3 mm. CRM is an optical tool to noninvasively image tissue with near histological resolution. These comprehensive diagnostic modalities can also be used to define surgical margin and to provide a direct assessment of the therapeutic effectiveness.

[Optical coherence tomography in otolaryngology]

Optical coherence tomography is an imaging technique based on coherence interferometry. It is used in many medical fields due to its non-invasive imaging capabilities with micrometer resolution. The aim of the authors was to review the applicability of the optical coherence tomography in otolaryngology. Literature data and their own studies show that optical coherence tomography is a reliable method for identifying and targeted biopsy of inflammated, pre-malignant or cancer tissue in human laryngeal and pharyngeal mucosa. Another emerging field for optical coherence tomography is diagnosis of middle ear diseases, especially stapes ankylosis and cholesteatoma.