Head and neck computed tomography virtual endoscopy: evaluation of a new imaging technique

Development of a Machine Learning-Enabled Virtual Reality Tool for Preoperative Planning of Functional Endoscopic Sinus Surgery

Objectives  Virtual reality (VR) is an increasingly valuable teaching tool, but current simulators are not typically clinically scalable due to their reliance on inefficient manual segmentation. The objective of this project was to leverage a high-throughput and accurate machine learning method to automate data preparation for a patient-specific VR simulator used to explore preoperative sinus anatomy. Methods  An endoscopic VR simulator was designed in Unity to enable interactive exploration of sinus anatomy. The Saak transform, a data-efficient machine learning method, was adapted to accurately segment sinus computed tomography (CT) scans using minimal training data, and the resulting data were reconstructed into three-dimensional (3D) patient-specific models that could be explored in the simulator. Results  Using minimal training data, the Saak transform-based machine learning method offers accurate soft-tissue segmentation. When explored with an endoscope in the VR simulator, the anatomical models generated by the algorithm accurately capture key sinus structures and showcase patient-specific variability in anatomy. Conclusion  By offering an automatic means of preparing VR models from a patient's raw CT scans, this pipeline takes a key step toward clinical scalability. In addition to preoperative planning, this system also enables virtual endoscopy-a tool that is particularly useful in the COVID-19 era. As VR technology inevitably continues to develop, such a foundation will help ensure that future innovations remain clinically accessible.

Glottic configuration changes and outcomes of endoscopic arytenoid abduction lateropexy

INTRODUCTION

Endoscopic arytenoid abduction lateropexy (EAAL) is an effective glottis enlarging procedure for the treatment of bilateral vocal cord palsy (BVCP). The postoperative glottic configuration changes can be evaluated by modern, high-resolution, 3D image reconstructions. Functional results are described by spirometry as well as objective and subjective phoniatric tests.

METHODS

Unilateral EAAL was performed in ten malignant thyroid gland tumor patients (eight women, two men), who had BVCP after thyroid surgery. Slicer 3D^® software was used for morphometric analysis. Pre- and postoperative peak inspiratory flow (PIF) and standard phoniatric parameters were compared.

RESULTS

The glottic gap improved significantly (+ 60%). Significant improvement of PIF was found in all cases. Phoniatric tests revealed better quality of voice and patient satisfaction. Their voices changed from a severely impaired to a socially acceptable, almost normal, quality.

CONCLUSION

The results support our clinical observations that the ideal position of the lateralization sutures is the one which provides a physiological abduction position of the arytenoid cartilage. Considering these good results, the surgical indications for minimally invasive endoscopic arytenoid lateropexy may be extended.

Virtual endoscopy of laryngeal carcinoma: Is it useful?

OBJECTIVE: To compare virtual endoscopy (VE) with flexible endoscopy in patients with cancer of the larynx.

STUDY DESIGN AND SETTINGS: This prospective study includes 24 patients with proven cancer of the larynx. Patients underwent spiral CT according to our standard protocol for upper airway imaging. This same set of axial scans was transferred to a dedicated workstation to obtain VE images. Results of VE were compared with the findings of flexible endoscopy.

RESULTS: Quality of the examination was good in 96% of the patients. VE identified all exophytic lesions. Two small flat lesions could be observed as slightly enhanced plaques only on the axial scans. Subglottic extension was correctly demonstrated in all cases by associating VE to the axial scans.

CONCLUSION: VE shows high sensitivity in the identification of exophytic lesions of the larynx and can establish relationships between cancer and nearby structures. It can be performed in the presence of severe stenosis and does not require sedation and additional scanning. On the other hand, VE show limits in the identification of flat lesions and does not allow biopsies and functional imaging to be performed.

SIGNIFICANCE: VE is a useful tool for staging and presurgery treatment of cancer of the larynx.

Correlative anatomy for thoracic inlet; glottis and subglottis; trachea, carina, and main bronchi; lobes, fissures, and segments; hilum and pulmonary vascular system; bronchial arteries and lymphatics

Because it is relatively inexpensive and universally available, standard radiographs of the thorax should still be viewed as the primary screening technique to look at the anatomy of intrathoracic structures and to investigate airway or pulmonary disorders. Modern trained thoracic surgeons must be able to correlate surgical anatomy with what is seen on more advanced imaging techniques, however, such as CT or MRI. More importantly, they must be able to recognize the indications, capabilities, limitations, and pitfalls of these imaging methods.

Diagnostic contribution of virtual endoscopy in diseases of the upper airways

PURPOSE

Virtual endoscopy (VE) is a new diagnostic tool that generates 3-dimensional (3D) views of a lumen by exploiting cross-sectional images. The purpose of this study was to evaluate the usefulness of VE as a diagnostic tool in the diseases of the larynx and pharynx.

MATERIALS AND METHODS

Twenty-two patients with a mean age of 57 years were included in the study. The patients underwent larynx examination, optical endoscopy (OE), and computed tomography (CT) of the larynx. Later, VE was produced from the CT images.

RESULTS

Eight patients had larynx carcinoma, a 5-year-old patient had a laryngeal web, a 43-year-old man had fish bone stuck in his submucosal layer, 10 patients were normal, and the remaining two patients were under follow-up for treated nasopharynx carcinoma and had no evidence for recurrence. VE showed the laryngeal tumor in seven patients and the laryngeal web in one patient, but failed to show a plaquelike tumor and the fishbone within the submucosa.

CONCLUSIONS

Our findings suggest that VE is a useful and complimentary method of 3D imaging in the diseases compromising the laryngeal lumen. Furthermore, it may be superior to OE in severe stenosis or obstructions where the endoscope cannot be passed through.

CT and virtual endoscopy findings in congenital laryngeal web

Laryngeal web is a rare lesion resulting from incomplete recanalization of the primitive larynx. Because the extent of airway involvement affects surgical management, patients should be studied thoroughly before treatment. Although the diagnosis is based on the endoscopy findings in most of the cases, laryngoscopy may fail to show the subglottic extension of the disease. Virtual endoscopy may provide the information needed for surgery in such cases. Here, we report the computed tomography and virtual endoscopy findings in a 5-year-old child with a laryngeal web.

Virtual laryngoscopy—preliminary experience

PURPOSE

Computed tomographic virtual laryngoscopy is a non-invasive radiological technique that allows visualisation of intra-luminal surfaces by three-dimensional reconstruction of air/soft tissue interfaces. It is particularly useful when the patient cannot tolerate clinical examination, when infection, neoplasm or congenital defects compromise the lumen and for assessment of the sub-glottic region. We have performed virtual laryngoscopy on patients referred because of upper airway symptoms, and compared the findings with those at conventional laryngoscopy.

MATERIALS AND METHODS

Axial scans were obtained using a Toshiba Xpress helical scanner. Virtual laryngoscopy was then performed on a workstation using Toshiba "Fly-thru" software and was completed within 5 min.

RESULTS

Pathology included vocal cord nodules, laryngeal cysts, Reinke's oedema, laryngeal neoplasms and leukoplakia.

CONCLUSIONS

Virtual laryngoscopy displays anatomical detail comparable to conventional endoscopy. Impassable obstructions are no hindrance and all viewing directions are possible. It is especially useful for providing views of the larynx from below.

Clinical usefulness of 3-dimensional computed tomography laryngography in laryngeal and hypopharyngeal cancer

This study was designed to evaluate the clinical usefulness of 3-dimensional computed tomography (CT) laryngography for the determination of subglottic extension in laryngeal cancer and for the involvement of the pyriform sinus apex in hypopharyngeal cancer. Twenty-one patients with laryngeal cancer and 19 patients with hypopharyngeal cancer underwent spiral CT during quiet breathing, /E/ phonation, Valsalva's maneuver, and modified Valsalva's maneuver. Three-dimensional volume rendering with CT data was performed on a workstation. Three-dimensional CT laryngography was compared to laryngoscopy, axial CT, endoscopy, and/or histopathologic findings. Three-dimensional CT laryngography was useful for showing subglottic extension in laryngeal cancer and involvement of pyriform sinus apex in hypopharyngeal cancer. Three-dimensional CT laryngography with quiet breathing was most informative for the determination of subglottic extension, whereas 3-dimensional CT laryngography with modified Valsalva's maneuver was most informative for the diagnosis of pyriform sinus apex involvement. In patients with vocal cord palsy, the contour of the vocal cord was the same during all 4 maneuvers. Three-dimensional CT laryngography during quiet breathing, /E/ phonation, Valsalva's maneuver, and modified Valsalva's maneuver may be useful in assessing laryngeal and hypopharyngeal cancers. This technique may provide important information not provided by conventional CT images.

Contribution of virtual endoscopy to the investigation of laryngotracheal pathological conditions

Three-dimensional CT scan imaging obtained by using helicoidal CT scan provides the basis for an endoscopic exam said to be virtual since no invasive procedure is actually performed. Compared to optical endoscopy this easily accessible exam offers additional information especially for the analysis of the infraglottic and tracheal areas, which are two anatomically rigid segments. This property facilitates their three-dimensional reconstruction. Our study encompassed 6 patients presenting with a stenosis of the laryngotracheal tract. In 5 of them it was possible to correlate optical and virtual endoscopic imaging. Coupling both exams significantly improved the diagnostic investigation and facilitated the management of the disease. However, the real contribution of virtual endoscopy to the exploration of tumoral conditions still remains to be determined given the low degree of tissue resolution. As a consequence parietal and extraparietal lesional spreading is more accurately assessed by axial scan imaging.

Virtual laryngotracheal endoscopy based on geometric surface modeling using spiral computed tomography data

This prospective study describes the clinical utility of virtual endoscopy based on geometric surface modeling of the laryngotracheal lumen. Eighteen children with dyspnea related to either subglottic angioma (n = 5) or laryngotracheal stenosis (n = 13) were included. All patients underwent video-recorded operative endoscopy, spiral computed tomography, and 3-dimensional reconstruction of the laryngotracheal lumen. Modeling was achieved by contour detection on spiral computed tomographic images and reconstruction using a geometric shape-recognition algorithm. The generated surface was used for diagnosis and measurement using interactive and automatic tools. Findings of virtual endoscopy and operative endoscopy were compared. Virtual endoscopy confirmed narrowing of the airway in all cases. In 9 cases, high-grade stenosis prevented complete operative endoscopy, but virtual endoscopy allowed accurate assessment and measurement of the stenosis. The findings of operative and virtual endoscopy were concordant in 9 cases. We conclude that surface modeling provides valuable information for preoperative evaluation of laryngotracheal narrowing. The ability to assess extraluminal anatomy provides a clearer picture of overall disease involvement. In the future, virtual endoscopy will probably be used in conjunction with operative endoscopy for therapeutic decision-making. Noninvasive virtual endoscopy could become an alternative to traditional endoscopy under general anesthesia for therapeutic follow-up.

Virtual endoscopic evaluation of labyrinthine fistulae resulting from cholesteatoma

OBJECTIVES/HYPOTHESIS

Fistulae of the otic capsule occur in approximately 10% of cholesteatoma cases. Preoperative imaging of this complication is valuable in limiting intraoperative morbidity. Three-dimensional virtual endoscopic imaging provides a new method for analysis of conventional computed tomography (CT) imaging data. The purpose of the study was to examine the feasibility and efficacy of this technique in detecting labyrinthine fistulae caused by cholesteatoma.

STUDY DESIGN

Retrospective case study.

METHODS

Fifteen patients with surgically confirmed lateral semicircular canal fistula and preoperative CT scan were included. Scans meeting inclusion criteria were imported into a software program for production of virtual endoscopic images. Dehiscent and normal lateral semicircular canals were navigated while varying threshold values for surrounding bone. Changes in threshold values produce the effect of thickening or thinning the bone enveloping the semicircular canal. Threshold parameters that produced easy circumnavigation ("open") and intact inner surface of the lateral canal ("closed") were recorded.

RESULTS

The fistula group demonstrated a significantly lower "closed" threshold level and, consequently, a greater range of navigation between "open" and "closed" thresholds. Intrasubject absolute differences in threshold values between normal and abnormal ears appeared to be the most accurate method for detecting a fistula. The suggested imaging parameters displayed an overall sensitivity for fistula detection of 67% with a specificity of 93%.

CONCLUSIONS

The three-dimensional virtual endoscopic algorithm shows promise as a method for confirmation of otic capsule dehiscences. Sensitivity for detection is suboptimal but can be improved by alterations in image acquisition parameters.