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

Diagnostic Assessment (Imaging) and Staging of Laryngeal Cancer

Diagnosis of larynx cancer relies on a detailed history and physical and objective assessment with endoscopy and imaging. Endoscopy is needed to assess for vocal fold function that directly affects staging. Computed tomography and MRI can be used to assess for tumor extent in relation to intra- and extra-laryngeal structures, especially paraglottic and pre-epiglottic space involvement as well as cartilage invasion. Accurate staging is critical for subsequent treatment decision-making regarding larynx preservation.

Intraoperative In Vivo Imaging Modalities in Head and Neck Cancer Surgical Margin Delineation: A Systematic Review

Surgical margin status is one of the strongest prognosticators in predicting patient outcomes in head and neck cancer, yet head and neck surgeons continue to face challenges in the accurate detection of these margins with the current standard of care. Novel intraoperative imaging modalities have demonstrated great promise for potentially increasing the accuracy and efficiency in surgical margin delineation. In this current study, we collated and analyzed various intraoperative imaging modalities utilized in head and neck cancer to evaluate their use in discriminating malignant from healthy tissues. The authors conducted a systematic database search through PubMed/Medline, Web of Science, and EBSCOhost (CINAHL). Study screening and data extraction were performed and verified by the authors, and more studies were added through handsearching. Here, intraoperative imaging modalities are described, including optical coherence tomography, narrow band imaging, autofluorescence, and fluorescent-tagged probe techniques. Available sensitivities and specificities in delineating cancerous from healthy tissues ranged from 83.0% to 100.0% and 79.2% to 100.0%, respectively, across the different imaging modalities. Many of these initial studies are in small sample sizes, with methodological differences that preclude more extensive quantitative comparison. Thus, there is impetus for future larger studies examining and comparing the efficacy of these intraoperative imaging technologies.

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.

Surface kinematic and depth-resolved analysis of human vocal folds in vivo during phonation using optical coherence tomography

SIGNIFICANCE

The human vocal fold (VF) oscillates in multiple vectors and consists of distinct layers with varying viscoelastic properties that contribute to the mucosal wave. Office-based and operative laryngeal endoscopy are limited to diagnostic evaluation of the VF epithelial surface only and are restricted to axial-plane characterization of the horizontal mucosal wave. As such, understanding of the biomechanics of human VF motion remains limited.

AIM

Optical coherence tomography (OCT) is a micrometer-resolution, high-speed endoscopic imaging modality which acquires cross-sectional images of tissue. Our study aimed to leverage OCT technology and develop quantitative methods for analyzing the anatomy and kinematics of in vivo VF motion in the coronal plane.

APPROACH

A custom handheld laryngeal stage was used to capture OCT images with 800 A-lines at 250 Hz. Automated image postprocessing and analytical methods were developed.

RESULTS

Novel kinematic analysis of in vivo, long-range OCT imaging of the vibrating VF in awake human subjects is reported. Cross-sectional, coronal-plane panoramic videos of the larynx during phonation are presented with three-dimensional videokymographic and space-time velocity analysis of VF motion.

CONCLUSIONS

Long-range OCT with automated computational methods allows for cross-sectional dynamic laryngeal imaging and has the potential to broaden our understanding of human VF biomechanics and sound production.

Current Intraoperative Imaging Techniques to Improve Surgical Resection of Laryngeal Cancer: A Systematic Review

Simple Summary

Laryngeal cancer is a prevalent head and neck malignancy, with poor prognosis and low survival rates for patients with advanced disease. The recurrence rate for advanced laryngeal cancer is between 25 and 50%. In order to improve surgical resection of laryngeal cancer and reduce local recurrence rates, various intraoperative optical imaging techniques have been investigated. In this systematic review we identify these technologies, evaluating the current state and future directions of optical imaging for this indication. Evidently, the investigated imaging modalities are generally unsuitable for deep margin assessment, and, therefore, inadequate to guide resection in advanced laryngeal disease. We discuss two optical imaging techniques that can overcome these limitations and suggest how they can be used to achieve adequate margins in laryngeal cancer at all stages.

Abstract

Laryngeal cancer is a prevalent head and neck malignancy, with poor prognosis and low survival rates for patients with advanced disease. Treatment consists of unimodal therapy through surgery or radiotherapy in early staged tumors, while advanced stage tumors are generally treated with multimodal chemoradiotherapy or (total) laryngectomy followed by radiotherapy. Still, the recurrence rate for advanced laryngeal cancer is between 25 and 50%. In order to improve surgical resection of laryngeal cancer and reduce local recurrence rates, various intraoperative optical imaging techniques have been investigated. In this systematic review, we identify these technologies, evaluating the current state and future directions of optical imaging for this indication. Narrow-band imaging (NBI) and autofluorescence (AF) are established tools for early detection of laryngeal cancer. Nonetheless, their intraoperative utility is limited by an intrinsic inability to image beyond the (sub-)mucosa. Likewise, contact endoscopy (CE) and optical coherence tomography (OCT) are technically cumbersome and only useful for mucosal margin assessment. Research on fluorescence imaging (FLI) for this application is sparse, dealing solely with nonspecific fluorescent agents. Evidently, the imaging modalities that have been investigated thus far are generally unsuitable for deep margin assessment. We discuss two optical imaging techniques that can overcome these limitations and suggest how they can be used to achieve adequate margins in laryngeal cancer at all stages.

Imaging the Vocal Folds: A Feasibility Study on Strain Imaging and Elastography of Porcine Vocal Folds

Vocal folds are an essential part of human voice production. The biomechanical properties are a good indicator for pathological changes. In particular, as an oscillation system, changes in the biomechanical properties have an impact on the vibration behavior. Subsequently, those changes could lead to voice-related disturbances. However, no existing examination combines biomechanical properties and spatial imaging. Therefore, we propose an image registration-based approach, using ultrasound in order to gain this information synchronously. We used a quasi-static load to compress the tissue and measured the displacement by image registration. The strain distribution was directly calculated from the displacement field, whereas the elastic properties were estimated by a finite element model. In order to show the feasibility and reliability of the algorithm, we tested it on gelatin phantoms. Further, by examining ex vivo porcine vocal folds, we were able to show the practicability of the approach. We displayed the strain distribution in the tissue and the elastic properties of the vocal folds. The results were superimposed on the corresponding ultrasound images. The findings are promising and show the feasibility of the suggested approach. Possible applications are in improved diagnosis of voice disorders, by measuring the biomechanical properties of the vocal folds with ultrasound. The transducer will be placed on the vocal folds of the anesthetized patient, and the elastic properties will be measured. Further, the understanding of the vocal folds’ biomechanics and the voice forming process could benefit from it.

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.

Air Injection and Transillumination in Phonosurgery: A Novel Technique

OBJECTIVES/HYPOTHESIS

The goal of this study was to introduce two novel techniques in phonomicrosurgery, air injection (AIR), and transillumination (TI), to improve the diagnosis and surgical excision of pathological tissue in vocal folds during suspension laryngoscopy while preserving the healthy tissue as much as possible.

STUDY DESIGN

Prospective clinical case series.

METHODS

Thirty-four patients with benign vocal cord lesions who underwent phonomicrosurgery between January 2016 and May 2017 were evaluated. Pre- and intraoperative recordings were evaluated by three experienced laryngologists. Stroboscopic video images taken during the preoperative diagnosis and interoperative video recordings made before and after AIR and TI were performed were reviewed and compared. During the preoperative evaluation, the surgeons declared their surgical plans and noted changes while observing the intraoperative evaluation during AIR and TI.

RESULTS

Sixty-eight vocal folds were evaluated. The initial diagnosis was found to be consistent with the final diagnosis in only 10 patients (29.4%). The diagnoses of 29 vocal folds (42.6%) and the surgical plans changed after AIR and TI. In six cases, submucosal bands, additional morphological structures in the vicinity of the primary pathology, were observed; these could only be visualized with AIR and TI. AIR and TI revealed new pathologies in four vocal folds that were noted to be normal in the preoperative evaluation.

CONCLUSION

AIR and TI are useful and promising techniques to identify undiagnosed lesions in vocal folds and to increase the success of minimally invasive phonosurgery.

Clinical Utility of Intraoperative Tympanomastoidectomy Assessment Using a Surgical Microscope Integrated with an Optical Coherence Tomography

Significant technical and optical advances are required for intraoperative optical coherence tomography (OCT) to be utilized during otological surgeries. Integrating OCT with surgical microscopy makes it possible to evaluate soft tissue in real-time and at a high resolution. Herein, we describe an augmented-reality, intraoperative OCT/microscope system with an extended working distance of 280 mm, providing more space for surgical manipulation than conventional techniques. We initially performed ex vivo experiments to evaluate system performance. In addition, we validated the system by performing preliminary clinical assessments of tympanomastoidectomy outcomes in six patients with chronic otitis media. The system evaluated residual inflammation in the region-of-interest of the mastoid bone. Most importantly, the system intraoperatively revealed the connection between the graft and the remnant tympanic membrane. The extended working distance allows otological surgeons to evaluate the status of both the mastoid bone and tympanic membrane during manipulation, affording full intraoperative imaging.

A morphological classification for vocal fold leukoplakia

Introduction

There is still no general method for discriminating between benign and malignant leukoplakia and identifying vocal fold leukoplakia.

Objective

To evaluate the reliability of a morphological classification and the correlation between morphological types and pathological grades of vocal fold leukoplakia.

Methods

A total of 375 patients with vocal fold leukoplakia between 2009 and 2015 were retrospectively reviewed. Two observers divided the vocal fold leukoplakia into flat and smooth, elevated and smooth, and rough type on the basis of morphological appearance. The inter-observer reliability was evaluated and the results of classification from both observers were compared with final pathological grades. Clinical characteristics between low risk and high risk group were also analyzed.

Results

The percentage inter-observer agreement of the morphological classification was 78.7% (κ = 0.615, p < 0.001). In the results from both observers, the morphological types were significantly correlated with the pathological grades (p₁ < 0.001, p₂ < 0.001, Kruskal–Wallis test; r₁ = 0.646, p₁ < 0.001, r₂ = 0.539, p₂ < 0.001, Spearman Correlation Analysis). Multivariate analysis showed patient's age (p = 0.018), the size of lesion (p < 0.001), and morphological type (p < 0.001) were significantly different between low risk group and high risk group. Combined receiver operating characteristic curve analysis of significant parameters revealed an area under the receiver operating characteristic curve of 0.863 (95% CI 0.823–0.903, p < 0.001).

Conclusions

The proposed morphological classification of vocal fold leukoplakia was consistent between observers and morphological types correlated with pathological grades. Patient's age, the size of lesion, and morphological type might enable risk stratification and provide treatment guidelines for vocal fold leukoplakia.

Primary and salvage laser surgery of 341 glottic cancers-Comparison of treatment outcomes between University Head Neck Tertiary Referral Center and Local Head Neck Department

OBJECTIVE

The main goal was to compare the clinical data of patients with T1 and T2 glottic cancer treated with CO₂ transoral laser microlaryngoscopy (TLM) in the Tertiary Referral University Department of Otolaryngology, Head Neck Surgery, Poznan and the local Department of Otolaryngology, Oncology and Maxillofacial Surgery, Bydgoszcz.

MATERIAL AND METHODS

Unified databases for the 7-year period January 2005-December 2011 were created to compare these two cohorts. The database contained 341 patients: 231 from the tertiary center and 110 from the local department, of which 298 (87%) were men, and 43 (13%) were women.

RESULTS

Cordectomy type I-IV was performed in 250 (73%) patients, cordectomy type V-VI in 84 (25%) patients, and cordectomy enlarged to epiglottic petiole in 7 (2%) patients. Local recurrence was observed in 96 (28%) cases. Among these cases, 81 (87.5%) patients had salvage surgery: 43 re-cordectomy, 10 open partial laryngectomy, and 28 total laryngectomy. The outcomes for the whole cohort, Tertiary Referral Center and Local Department respectively were as follows: larynx preservation rate was 91.8%, 93.6%, and 88%; 3-year disease specific survival was 97.4%, 97.9%, and 93.3%; 3-year overall survival was 93.5%, 96.6%, and 85.5%; 5-year disease specific survival was 95.2%, 95.2%, and 96.3%; and 5-year overall survival was 84.5%, 88.7%, and 76%, respectively.

CONCLUSION

Comparison of the cohorts showed that outcomes of primary treatment were similar but there were noticeable differences in salvage treatment efficacy, favoring patients from the Tertiary Referral Center. Lasers Surg. Med. 50:311-318, 2018. © 2017 Wiley Periodicals, Inc.