Virtual laryngoscopy—preliminary experience

Comparison of diagnostic accuracy of computed tomography virtual endoscopy and flexible fibre-optic laryngoscopy in the evaluation of neck anatomic structures and neoplasms

BACKGROUND AND PURPOSE

Computed tomography virtual endoscopy (CT-VE) is a non-invasive technique which allows visualisation of intraluminal surfaces by tridimensional reconstruction of air/soft tissues. The aim of this study was to compare the diagnostic accuracy of CT-VE and flexible fibre-optic laryngoscopy (FFL) in identifying normal neck anatomic structures and pharyngeal and laryngeal lesions.

METHODS

Forty-two patients with a history of neck cancer were assessed by two ENT surgeons using FFL and by one neuroradiologist using CT-VE in order to evaluate the visualisation of the epiglottis, vallecula, glossoepiglottic folds, pyriform sinuses, vocal cords and mass pathology. The visualisation of the structures in both modalities was assessed according to the following score: 0 = not visualised, 1 = partial visualisation, 2 = complete and clear visualisation. A weighted kappa coefficient was used to evaluate the inter-observer agreement. McNemar's test was performed to compare the two diagnostic tests.

RESULTS

The inter-observer agreement between FFL and CT-VE was fair in the assessment of the vocal cords (k = 0.341); moderate in the assessment of the glossoepiglottic folds (k = 0.418), epiglottis (k = 0.513) and pyriform sinuses (k = 0.477); and substantial in the assessment of the vallecula (k = 0.618) and the tumour (0.740). McNemar's test showed no significant difference between the two tests (p<0.05).

CONCLUSION

CT-VE is a non-invasive technique with a diagnostic accuracy comparable to FFL in terms of visualisation of anatomical structures and pharyngeal and laryngeal lesions.

The effect of virtual endoscopy on diagnostic accuracy and airway management strategies in patients with head and neck pathology: a prospective cohort study

PURPOSE

There is growing evidence to suggest a deficiency in anesthesiologists' diagnosis of airway pathology and subsequent airway management planning, and conventional instruments have not shown increases in safety. Virtual endoscopy (VE) is a tool that can detail intraluminal anatomical "fly-through" information in a format visually similar to the flexible endoscopic views familiar to anesthesiologists. We aimed to determine the effect of VE on diagnostic accuracy and airway management strategies when compared with conventional tools.

METHODS

Clinical scenarios, along with computerized tomography (CT) imaging, were presented to 20 anesthesiologists, and structured questions were asked regarding diagnosis of airway pathology and airway management strategy. Virtual endoscopy videos were then provided and the questions were repeated. Following the CT and VE presentations, the anesthesiologists' responses involving diagnostic accuracy and airway management strategy were compared between the CT and VE techniques. Answers relating to the utility of VE were also sought.

RESULTS

Diagnostic accuracy was 54.1% with CT alone and increased to 67.7% when VE was added (P = 0.007). In 48% of cases, the addition of VE to clinical history and CT led to changes in airway management strategy (P < 0.001), and 90.6% of these changes were deemed more cautious (P < 0.001).

CONCLUSION

Virtual endoscopy improves the accuracy in diagnosis of airway pathology when compared with CT alone. Furthermore, it leads to more conservative and potentially safer airway management strategies in patients with head and neck pathology.

Anatomical education and surgical simulation based on the Chinese Visible Human: a three-dimensional virtual model of the larynx region

Anatomical knowledge of the larynx region is critical for understanding laryngeal disease and performing required interventions. Virtual reality is a useful method for surgical education and simulation. Here, we assembled segmented cross-section slices of the larynx region from the Chinese Visible Human dataset. The laryngeal structures were precisely segmented manually as 2D images, then reconstructed and displayed as 3D images in the virtual reality Dextrobeam system. Using visualization and interaction with the virtual reality modeling language model, a digital laryngeal anatomy instruction was constructed using HTML and JavaScript languages. The volume larynx models can thus display an arbitrary section of the model and provide a virtual dissection function. This networked teaching system of the digital laryngeal anatomy can be read remotely, displayed locally, and manipulated interactively.

Dynamic MRI of the vocal cords using phased-array coils: A feasibility study

OBJECTIVE

Endoscopy for evaluation of hoarseness is an invasive procedure and the result depends, to a large extent, on the patient's cooperation. Successful laryngoscopy can also be hampered by unfavourable anatomic conditions, a severely impaired general condition, or severe coagulopathy. We evaluated the feasibility of doing ultra-fast magnetic resonance imaging (MRI), using a recent dedicated coil design and a sequence with inherently high signal-to-noise ratios (SNR), for the detection of motility disorders of the vocal cords.

MATERIALS AND METHODS

Twelve consecutive patients (eight males and four females) in the age range of 24-80 years (mean age 60 years) with persistent hoarseness and presumed vocal cord palsy were included in this blinded prospective study. Two two-element phased-array carotid coils were used for signal reception. The first coronal real-time steady-state free precession (SSFP) sequence was performed during silence (i.e., with no vocal cord motion) and the second while phonating 'heee.' Qualitative MRI findings were compared with the results of the endoscopic examination.

RESULTS

The examination time for setup, patient instruction and positioning, localization scans, and real-time SSFP scans was less than 10 min. Seven patients with laryngoscopically-confirmed unilateral palsy of the vocal cord were correctly identified with MRI. The five remaining patients had hoarseness due to causes other than vocal cord palsy; they showed normal motion of the vocal cords on MRI and endoscopy.

CONCLUSION

Compared to preceding studies, the image quality in this study is supported by excellent SNR (carotid phased-array coils and SSFP sequence with higher SNR if compared to a spoiled gradient-echo sequence or an EPI sequence). Further studies, with larger groups of patients, are necessary to show if this protocol can serve as an alternative to endoscopy in selected cases.

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.

The Novel Use of Computer-Generated Virtual Imaging to Assess the Difficult Pediatric Airway

In a patient with a known difficult airway, history and examination may be of limited use in formulating a management plan for subsequent tracheal intubation. Further detailed and descriptive review of the airway is necessary. Virtual imaging is a recent advance in radiology that offers noninvasive airway assessment. It creates a movie clip image of the upper airway akin to the view obtained through a fiberscope. We present a patient with Goldenhar syndrome in whom virtual imaging was used to identify the cause of a previous failed tracheal intubation.