Technique of high-frequency endolaryngeal ultrasound

Abstract

Objective: We describe in detail the technique of in vivo endolaryngeal ultrasound during microlaryngoscopy, offering a number of practical suggestions which may be of use, especially to the otolaryngologist.Methods: Endosonography is a non-invasive imaging technology usually applied for the assessment of local tumour growth and regional lymph node metastases in the digestive tract.Conclusions: Due to a penetrating depth of up to 25 mm and a high tissue resolution, endosonography also qualifies for use in the larynx. The technique may have a potentially important role in the intra-and post-operative investigation of laryngeal lesions bigger than 3 mm.Key words: Ultrasound; Imaging; Larynx Neoplasm; Laryngology; Laryngoscopy Introduction High-frequency ultrasound is a common imaging modality used to examine the thyroid, salivary glands, lymph nodes, and soft tissues in the head and neck. 1 However, a transcervical approach does not generally allow complete sonographic evaluation of the larynx, due to ossification and intraluminal air. 2 For this reason, computed tomography (CT) and magnetic resonance imaging (MRI) are used to supplement microlaryngoscopy as additional diagnostic tools in the investigation of more extensive laryngeal lesions. 3 Endoscopic versions of ultrasound technology have been developed and successfully applied in the fields of cardiology and gastroenterology. 4,5 Recent investigations of laryngeal endosonography have demonstrated a penetrating depth of 10 to 25 mm (depending on the applied frequency) and a high tissue resolution. 6 -9 Therefore, endolaryngeal ultrasound may be able to predict the exact extension of a laryngeal tumour before surgery is performed, and to assist in finding the best therapeutic solution for the patient. 3 Thus, this non-invasive method could represent an additional diagnostic tool in the field of laryngology.There is currently no precise description in the literature of how to perform in vivo endolaryngeal ultrasound imaging of the larynx. Therefore, the objective of the present study was to fill this gap, and also to offer a number of practical suggestions on the use of this technology.

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“…The surgeon positions and holds the probe steady in the center of the laryngeal lumen, while the assistant starts and stops the scanning process, saves data, and labels the recorded images. Good communication between the 2 examiners results in a rapid acquisition of data, generally requiring <10 minutes of additional operating time 4…”

“…During microlaryngoscopy, endosonography was carried out in accord with the following technique: all equipment was placed on a single table to avoid damage to the sensitive probe. A special applicator was used to insert the miniprobe, which remarkably facilitated its positioning 4…”

“…To evaluate lesions located in the posterior larynx, the orotracheal tube was loaded up by the Lindholm laryngoscope. Finally, the assistant evaluated the sonograms and communicated his results to the surgeon, while the latter carefully removed the instilled saline from the upper aerodigestive tract, continuing the operation 4, 7, 9…”

“…In contrast, endolaryngeal ultrasound (EUS) can easily reach critical regions such as the preepiglottic and paraglottic space. Although providing a higher resolution than that of CT and MRI, this technique is not as yet validated in laryngology 4–7. In the past we demonstrated normal sonoanatomy of the larynx, established anatomical landmarks for endosonography, and correlated them to horizontal whole‐organ sections of the scanned specimens 8…”

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“…The probes have penetrating depths of 10 to 25 mm and a high tissue resolution. 107 Endosonography produces horizontal slice images comparable to CT or MRI but with higher resolution. Kraft and colleagues 108 compared endosonography of laryngeal tumors with CT and MRI and found that endosonography had the highest accuracy for the staging of laryngeal cancer (89% vs 77% for both CT and MRI).…”