Optical coherence tomography system requirements for clinical diagnostic middle ear imaging

Abstract

Noninvasive middle ear imaging using optical coherence tomography (OCT) presents some unique challenges for real-time, clinical use in humans. We present results from a two-dimensional/three-dimensional OCT system built to assess the imaging requirements of clinical middle ear imaging, and the technical challenges associated with them. These include the need to work at a low numerical aperture, the deleterious effects of transtympanic imaging on image quality at the ossicles, sensitivity requirements for clinical fidelity of images at real-time rates, and the high dynamic-range requirements of the ear. We validated the system by imaging cadaveric specimens with simulated disorders to show the clinical applicability of the images. We also provide additional insight into the likely role of OCT in clinical otology.

Long-range, wide-field swept-source optical coherence tomography with GPU accelerated digital lock-in Doppler vibrography for real-time, in vivo middle ear diagnostics

“…Translating OCT middle ear imaging to the clinic involves a number of challenges [17]. Given the natural curvature and oblique orientation of the human TM relative to the ear canal, and allowing for normal anatomical variability between patients, a practical system must be capable of imaging over a depth range exceeding 10 mm in order to capture the entire middle ear; a range that has not been achievable with spectral-domain systems used in earlier studies [13,16].…”

Extratympanic Observation of Middle and Inner Ear Structures in Rodents Using Optical Coherence Tomography

“…Therefore, these results showed the accuracy of OCT images and the possibility of utilizing the OCT as measuring the middle and inner ear structures. Utility of OCT have been reported to have the ability to show the structures of the inner ear in the mice [15]. Tona et al [16] reported that OCT could evaluate the gross anatomy of mouse cochlea, including the Reissner's membrane and basilar membrane, with results demonstrating endolymphatic hydrops.…”

“…Because the light used in OCT should pass through the curvature of the external canal, the OCT system combined with a surgical microscope or endoscope was developed for this purpose [5,[16][17][18][19]. Microscope-integrated intraoperative OCT is already commercially available for imaging of ophthalmic surgical maneuvers [15,16,20]. Garcia et al [21] introduced an intraoperative OCT probe used for vocal fold imaging, which could also be applied to ear imaging if modified.…”

“…Therefore, increasing the NA increases the resolution but decreases the depth of focus quadratically, which means we need to choose the appropriate lens according to the target [22]. Therefore, in order to extend the depth of the field, the typical NA of lenses in surgical microscope used in the middle ear should be less than 0.02 [15]. Although the NA of the lens used in this study was 0.056, which was enough for visualizing the middle, inner ears of rodents, the NA of the lens for the application to humans should be considered lessening according to the situation of the combination of the OCT system with the microscope or endoscope.…”

Anti-confocal versus confocal assessment of the middle ear simulated by Monte Carlo methods

“…The properties of the eardrum change from person to person, especially during OME since it can become thicker and a biofilm may become attached to it. A wide range of scattering parameters is simulated in order to cover the whole possible range including values estimated in literature of µ s < 22 mm −1 at 1310 nm [9]. Figure 4 shows the signal and SBR for increased scattering coefficient and changed scattering anisotropy of the eardrum.…”