High-Resolution OCT Imaging Improves Ear Disease Diagnosis

A portable device that integrates optical coherence tomography (OCT) with traditional otoscopy can provide clinicians in hearing clinics with images of the interior of the tympanic membrane, or eardrum, and the middle ear, in addition to standard otoscopic images of the ear. By combining otoscopic views with high-resolution imaging, the OCT otoscope can offer a more comprehensive picture of ear health and help improve diagnostic accuracy.

The device was developed by researchers at the University of Southern California (USC), who aimed to construct a device that can be easily used in a hearing clinic to provide clinically relevant information that is not available through traditional otoscopy.

Routine otoscopic imaging yields information about the surface of the tympanic membrane, but it does not provide depth perception because it allows only a monocular view of the eardrum. Images from a traditional otoscope may not catch pathologies that pose a significant risk of hearing loss and other complications, especially in cases where the eardrum has become opaque due to disease.

With the integrated OCT otoscope, a clinician can correlate the otoscopic view with the OCT view and improve disease management based on the additional details furnished by the OCT images.

The handheld OCT otoscope features a field of view that is 7.4 mm in diameter, with lateral and axial resolutions of 38 μm and 33.4 μm, respectively. The wide field of view makes it possible to image nearly the entire tympanic membrane and middle ear down to the cochlear promontory. The integrated fiber optic interferometer demonstrates sub-nanometer sensitivity to vibration.

Otoscope and OCT image acquired from normal ear. (a) A snapshot from the otoscopic video camera. Dashed colored lines indicate the positions where the linear scans are shown in panels (c) and (d). (b) Image generated from an OCT volume. (c) Scan extracted along the green-colored dashed line from the OCT volumetric image. (d) B-scan extracted along the red-colored dashed line from the OCT volume. (e) 3D volume rendering of the ear. Abbreviations: MA, malleus; CT, chorda tympani; TM, tympanic membrane; IN, incus; UM, umbo; CL, cone of light; P, promontory. Courtesy of W. Kim et al., doi 10.1117/1.JBO.29.8.086005.

To enhance image clarity and ensure reliable results, the researchers developed algorithms that resample the images in Cartesian coordinates after collection in spherical polar coordinates and correct aberrations.

The researchers tested the OCT otoscope on over 100 patients in a clinical study held at the hearing clinic at USC Keck Hospital. The results demonstrated the ability of the integrated device to characterize a variety of middle ear pathologies in a large population of clinic patients. In addition, the results showed that the device can provide clinically relevant information not discernible using traditional imaging techniques.

For example, in one case, abnormal buildup of scar-like tissue and the lack of classical signs of myringitis made diagnosis difficult from visualization with just a standard otoscope. The OCT volumetric images revealed that the abnormal tissue was attached to the eardrum and not just laying on top of the eardrum. Removing the tissue by debridement could have resulted in tearing of the eardrum, producing a perforation.

The user-friendly design of the OCT otoscope makes it easy to integrate into existing clinical workflows. It can be operated by one person using a foot pedal to control image acquisition. A single person can collect a set of images from a patient in seconds to minutes. The imaging speed and wide field of view further aid in the collection of images.

Compared with traditional imaging modalities such as MRI and computed tomography, OCT is less expensive, more portable, and has better resolution, making it advantageous as a diagnostic imaging tool for middle ear pathologies in a busy clinical setting.

The hand-held OCT otoscope could enhance the precision of ear examinations and potentially lead to better outcomes for patients suffering from hearing loss due to ear diseases. As the technology becomes more widely available, it could transform the way ear health is assessed and treated, offering hope for more accurate diagnoses and improved patient care.

The research was published in the Journal of Biomedical Optics (www.doi.org/10.1117/1.JBO.29.8.086005).