[Imaging diagnostics of the pharynx and larynx]

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.

Shear Wave Elastography to Assess False Vocal Folds in Healthy Adults: A Feasibility Study

OBJECTIVES

The aim of the study was to investigate the feasibility of using ultrasound shear wave elastography to quantify mechanical properties and movement symmetry of false vocal folds positioned in adduction and abduction.

METHODS

We prospectively measured the shear wave velocity (SWV) within the bilateral false vocal folds in 10 healthy adults using acoustic radiation force impulse imaging. From a transcutaneous approach at the level of thyroid cartilage, 5 SWV measurements were obtained within each side of the false vocal folds twice in adduction and again in abduction for each participant. Configuration-related differences in the SWV within false vocal folds were compared between adduction and abduction, in addition to differences between the right and left false vocal folds and between men and women, by a paired t test. We developed an SWV index [(SWV_greater - SWV_lesser )/SWV_greater ] to assess movement symmetry between the right and left false vocal folds. Intraobserver agreement on repeated measures was examined by the intraclass correlation coefficient.

RESULTS

The 10 participants included 5 men and 5 women. We observed that the SWV within false vocal folds was significantly higher in adduction than in abduction (P < .001). The SWV within false vocal folds in adduction was also significantly higher in women compared to men (P < .001). There was no significant difference in the SWV between the right and left false vocal folds in adduction or in abduction or between men and women in abduction (P > .05). The mean SWV index was 0.05 (range, 0.03-0.07). The intraclass correlation coefficient for intraobserver agreement was 0.89 (P < .001).

CONCLUSIONS

Shear wave elastography seems to be feasible to quantify mechanical properties and evaluate the symmetry of false vocal folds in healthy adults.

Ultrasound imaging of the larynx and vocal folds: recent applications and developments

PURPOSE OF REVIEW

This article reviews recent clinical applications of ultrasound imaging in laryngeal examinations and new developments in imaging techniques for laryngeal tissue characterization.

RECENT FINDINGS

The B-mode image has become a popular tool for identifying masses, lesions, and nodules at the vocal folds, and combining the B-scan with Doppler imaging makes it possible to also evaluate their functionality. The B-mode image has been used to diagnose lesions and paralysis in vocal folds in children, and to evaluate nerve function by visualizing the structure of the larynx and the movement of the bilateral vocal folds. Ultrasound Nakagami imaging based on the statistics of backscattered signals is a new parametric imaging method that complements the conventional B-scan for tissue characterization. Nakagami imaging is a functional ultrasound imaging tool for visualizing the relative concentrations of collagen and elastic fibers, which are key factors influencing the biomechanical properties of the vocal folds.

SUMMARY

Future clinical applications could combine conventional B-mode and Nakagami images to allow physicians to simultaneously evaluate the morphology and scatterer properties of laryngeal tissues.

[Imaging in carcinoma of the upper respiratory tract. TNM classification of neoplastic lesions]

Computer tomography (CT) and magnetic resonance (MRI) imaging are instrumental in cancer staging in carcinoma of the upper respiratory tract in that they are able to identify local spread and tumor invasion, which can often be only insufficiently evaluated by clinical and endoscopic examination alone. These additional radiologic findings, in conjunction with the clinical examination, aid in choosing the most appropriate therapeutic approach. The evaluation of CT and MRI findings is challenging due to the complex anatomy of the head and neck area. This article reviews the most important anatomical structures for the evaluation of cancer invasion and therapeutic decision-making.

Different imaging techniques in the head and neck: Assets and drawbacks

In this review, the gold standard imaging techniques for the head and neck and the latest upcoming techniques are presented, by comparing computed tomography (CT), magnetic resonance imaging and positron emission tomography-CT, as well as ultrasound, depending on the examined area. The advantages and disadvantages of each examination protocol are presented. This article illustrates the connection between the imaging technique and the examined area. Therefore, the head and neck area is divided into different sections such as bony structures, nervous system, mucous membranes and squamous epithelium, glandular tissue, and lymphatic tissue and vessels. Finally, the latest techniques in the field of head and neck imaging such as multidetector CT, dual-energy CT, flash CT, magnetic resonance angiography, spectroscopy, and diffusion tensor tractography using 3 tesla magnetic resonance are discussed.

Developing a 3D model of the laryngeal cartilages using HRCT data and MIMICS's segmentation software

Discussions relating to the biomechanics of the larynx are still generally controversial. The purpose of this study is to develop a 3D model of the larynx based on high-resolution computer tomography (HRCT) data identifying and visualizing anatomical landmarks and structures of the larynx. We examined four fresh cadaver larynges with HRCT. The DICOM (Digital Imaging and Communication in Medicine) data were post-processed with the software package MIMICS for three-dimensional visualization. All relevant structures of the laryngeal cartilages could be identified on HRCT and visualized in a 3D model. We conclude that 1) HRCT provides excellent data for three-dimensional visualization of the laryngeal anatomy, and 2) the combined technology of HRCT and MIMICS is useful to study the biomechanics on 3D images and for preoperative planning of laryngeal framework surgery.

Advances in laryngeal imaging

Imaging and image analysis became an important issue in laryngeal diagnostics. Various techniques, such as videostroboscopy, videokymography, digital kymography, or ultrasonography are available and are used in research and clinical practice. This paper reviews recent advances in imaging for laryngeal diagnostics.

[Pathological changes of the hypopharynx in the focus of imaging]

The spectrum of pathological changes in anatomical sections of the hypopharynx ranges from benign pathologies to hypopharyngeal carcinoma. Beside the clinical status and the endoscopic evaluation performed by ear, nose and throat specialists, imaging techniques play an important role in pre-therapeutic and post-therapeutic diagnostics and in the follow-up of pharyngeal disease patterns, especially for malignant lesions. A conventional x-ray swallow examination, contrast-enhanced multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI), as well as positron emission tomography (PET) and positron emission tomography computed tomography (PET-CT) are applied depending on the medical question and disease. Especially in radiological oncology, it is extremely important in regions which are clinically difficult to assess to determine the exact localization and extent of hypopharyngeal pathologies to plan the optimal therapy for the patient. This article demonstrates the radiological appearance of pathological changes of the hypopharynx and discusses in particular the hypopharynx carcinoma in the focus of pre-therapeutic and post-therapeutic imaging.

[Radiological normal anatomy of the larynx and pharynx and imaging techniques]

The larynx and the pharynx represent anatomically as well as functionally a very complex organ which serves as an airway and a nutrition channel. Knowledge of anatomy and anatomical topography is therefore a fundamental basis for the evaluation of any pathological process. Beside the clinical examination and endoscopy performed by ear, nose and throat specialists, imaging techniques play a crucial role in pre-therapeutic and post-therapeutic diagnostics. The radiologist employs a conventional x-ray swallow examination, as well as contrast-enhanced multidetector computed tomography (MDCT), magnetic resonance imaging (MRI), positron emission tomography (PET) and positron emission tomography-computed tomography (PET-CT), depending on the medical problem in question. The following article demonstrates the functional and especially the structural anatomy of the larynx and the pharynx. Furthermore, the broad range of imaging techniques in clinical use is discussed.

[Diagnosis of laryngeal carcinoma]

DIAGNOSTICAL PROBLEMS OF LARYNGEAL CARCINOMA: Carcinoma of the larynx is still a prognostic serious disease associated with high mortality. Survival rates for these tumors vary and depend on the presence of early symptoms, anatomic accessibility and lymphatic supply. Despite advances in therapy and novel surgical and non-surgical approaches, early diagnosis remains the best predictor of survival.

STRATEGY AND NOVEL DIAGNOSTICAL PROCEDURES

This article reviews the diagnosis for laryngeal carcinoma in an effort to heighten the clinical and endoscopic recognition of these lesions, providing also global overview of clinical conventional and recent endoscopic diagnostic tools for squamous cell type of carcinoma of the larynx. Screening of asymptomatic individuals would detect tumors at an early enough stage to patients' benefit.

CONCLUSION

The progress in the elucidation of the molecular genetic changes in these tumors should soon bring novel diagnostic procedures into the clinical practise. The review higlights the important advances of endoscopic, radilogical and molecular methods in detection of the tumor which may help clinicians to diagnose tumors as early as possible. TNM staging, biopsy and histopathological grading remain the gold standard for diagnosis of laryngeal carcinoma. A great number of novel endoscopical methods are only supplementary tools to microlaryngoscopy. Some of the most significant biological markers might be integrated with the evaluation of behavioural factors, clinical and histopathological examinations for a new clinicomolecular approach to laryngeal cancer.

Using the patient's questionnaire data to screen laryngeal disorders

This paper is concerned with soft computing techniques for screening laryngeal disorders based on patient's questionnaire data. By applying the genetic search, the most important questionnaire statements are determined and a support vector machine (SVM) classifier is designed for categorizing the questionnaire data into the healthy, nodular and diffuse classes. To explore the obtained automated decisions, the curvilinear component analysis (CCA) in the space of decisions as well as questionnaire statements is applied. When testing the developed tools on the set of data collected from 180 patients, the classification accuracy of 85.0% was obtained. Bearing in mind the subjective nature of the data, the obtained classification accuracy is rather encouraging. The CCA allows obtaining ordered two-dimensional maps of the data in various spaces and facilitates the exploration of automated decisions provided by the system and determination of relevant groups of patients for various comparisons.

Multiple feature sets based categorization of laryngeal images

This paper is concerned with an automated analysis of laryngeal images aiming to categorize the images into three decision classes, namely healthy, nodular, and diffuse. The problem is treated as an image analysis and classification task. Aiming to obtain a comprehensive description of laryngeal images, multiple feature sets exploiting information on image colour, texture, geometry, image intensity gradient direction, and frequency content are extracted. A separate support vector machine (SVM) is used to categorize features of each type into the decision classes. The final image categorization is then obtained based on the decisions provided by a committee of support vector machines. Bearing in mind a high similarity of the decision classes, the correct classification rate of over 94% obtained when testing the system on 785 laryngeal images recorded at the Department of Otolaryngology, Kaunas University of Medicine is rather promising.