However, feasible imaging techniques capable of reflecting the physiologic function of the Eustachian tube are still lacking 2. Various imaging modalities and techniques have been employed to assess the Eustacian tube’s morphology and function, including endoscopy, radiography, computed tomography, ultrasound, and so on 6, 7, 8. As the only non-invasive route to access the Eustachian tube, the nasopharyngeal opening has been used for direct inspection of the Eustachian tube. The dynamic function of the tubal structures has been an issue of interest in the otology fields, but their limited anatomical accessibility has been an obstacle to proper evaluation. Despite the clinical importance of dynamic Eustachian tube evaluation, physical examination of the Eustachian tube is challenging due to its location in the parapharyngeal space of the infratemporal fossa 4.ĭysfunction of the Eustachian tube has been suggested as an etiology of various middle ear pathologies, although the underlying mechanism has remained poorly understood 5. By autonomically controlling the peritubal muscles, the Eustachian tube opens and closes to ventilate and protect the middle ear cavity. The distal two-thirds-the pharyngeal part-consists of a cartilaginous skeleton attached to several tubal muscles capable of dynamic movements 1. The proximal one-third-the osseous portion-is a funnel-shaped bony extension of the middle ear cleft. The Eustachian tube consists of complex structures of intratemporal bone and a fibrous, cartilaginous portion. As the only route for ventilating air spaces in the middle ear and mastoid cavity, the complex valve function of the Eustachian tube plays an important role in maintaining middle ear homeostasis, that is, air pressure equalization between the middle ear cavity and atmosphere, middle ear oxygenation, draining of secretions from the middle ear, and protection of the middle ear from retrograde infections 2, 3. The Eustachian tube is an extended part of the upper respiratory tract, which connects the middle ear space and the nasopharynx 1. Using the OCT technique to assess the Eustachian tube anatomy was shown to be feasible, and the fabricated OCT image catheter was determined to be suitable for Eustachian tube assessment. After balloon dilatation, the expansion of the cross-sectional area could be identified from the OCT images. Cross-sectional images of the tube were successfully obtained, and the margins of the anatomical structures including cartilage, mucosa lining, and fat could be successfully delineated. The histological anatomy of the Eustachian tube was compared with corresponding OCT images, The new, Eustachian OCT catheter was successfully inserted in the tubal lumen without damage. The OCT images were acquired from the superior to the nasopharyngeal opening before and after Eustachian tube balloon dilatation. The imaging catheter was introduced through the nasopharyngeal opening and reached toward the middle ear. Three male swine cadaver heads were used to study OCT image acquisition and for subsequent histologic correlation.

A customized OCT system and an imaging catheter, termed the Eustachian OCT, were developed for visualizing the Eustachian tube. This study fabricated a fiber-based optical coherence tomography (OCT) catheter and investigated its potential for assessing the Eustachian tube anatomy. Imaging the Eustachian tube is challenging because of its complex anatomy and limited accessibility.

Auditory tube cadaver