Intracochlear Imaging Using IVUS and OFDI: A Cadaveric Feasibility Study

Abstract

Objective: This study evaluates the feasibility of optical frequency domain imaging (OFDI) and intravascular ultrasound (IVUS) for intracochlear imaging in human cadaveric specimens. We compare their resolution, depth penetration, and ability to identify key cochlear structures and pathological conditions.

Methods: Human cadaveric temporal bones were prepared, and OFDI and IVUS probes were inserted through the round window into the scala tympani. OFDI imaging was performed using the LUNAWAVE system (Terumo, Tokyo, Japan), while IVUS imaging was conducted using the VISICUBE system (Terumo, Tokyo, Japan) with 60 and 40 MHz probes. The probe tips were trimmed to optimize insertion and imaging. Imaging results were compared with histological sections.

Results: OFDI provided high-resolution visualization of the cochlear basal turn, allowing clear identification of the basilar membrane, Reissner's membrane, scala media, and the organ of Corti. IVUS exhibited lower resolution than OFDI but allowed for deeper tissue penetration. The 60 MHz IVUS probe provided higher resolution than the 40 MHz probe, while the 40 MHz probe offered a wider field of view due to greater penetration depth and lower attenuation. Both OFDI and IVUS successfully detected basilar membrane disruptions, a known complication in cochlear implant surgery.

Conclusion: OFDI and IVUS demonstrated feasibility for intracochlear imaging, with OFDI offering superior resolution and IVUS providing greater penetration. This is the first study to apply IVUS for intracochlear imaging, supporting its potential role in intraoperative monitoring and cochlear pathology assessment.

Level of evidence: N/A.

Keywords: cochlear imaging; cochlear implant surgery; intravascular ultrasound (IVUS); optical coherence tomography (OCT); optical frequency domain imaging (OFDI).

FIGURE 1

(A) Insertion of a 40 MHz IVUS probe through the round window of the right ear in a cadaveric specimen. The tympanic membrane has been removed, and the round window is enlarged. (B) Tip of the OFDI probe, showing the location of the rotating scanning mechanism after modification by trimming the tip. (C) Tip of the 60 MHz IVUS probe, showing the location of the ultrasound transducer after modification by trimming the tip. (D) Tip of the 40 MHz IVUS probe, showing the location of the ultrasound transducer after modification by trimming the tip. Triangle, IVUS probe; M, malleus; I, incus; St, stapes; P, promontory. Arrow, imaging component (rotating scanning mechanism for OFDI, transducer for IVUS). OFDI, optical frequency domain imaging; IVUS, intravascular ultrasound. Scale bar: 5 mm.

FIGURE 2

(A) Histological section of the human cochlea (H&E staining). (B) Cross‐section of the cochlear duct. (C) Imaging of the cochlear duct using OFDI, clearly visualizing the basilar membrane, Reissner's membrane, and the organ of Corti with high resolution. (D) Imaging of the cochlear duct using a 60 MHz IVUS probe (AltaView), where the basilar membrane and spiral ligament are identifiable. (E) Imaging of the cochlear duct using a 40 MHz IVUS probe (AnteOwl WR). Although the resolution is lower compared to the 60 MHz probe, a wider area is captured, and the basilar membrane and spiral ligament are still identifiable. RW: Round window, red triangle: Basilar membrane, blue triangle: Organ of Corti, green triangle: Reissner's membrane, red arrow: Spiral ligament, *: Scala media, SV: Scala vestibuli, ST: Scala tympani, P: OFDI or IVUS probe, OFDI: Optical frequency domain imaging, IVUS: Intravascular ultrasound. Scale bar: 1 mm.

FIGURE 3

Imaging of basilar membrane disruption. (A) Imaging of the cochlear duct using OFDI. (B) Imaging of the cochlear duct using a 60 MHz IVUS probe (AltaView). (C) Imaging of the cochlear duct using a 40 MHz IVUS probe (AnteOwl WR). Red triangle: Basilar membrane, green triangle: Reissner's membrane, red arrow: Spiral ligament, SV: Scala vestibuli, ST: Scala tympani, P: OFDI or IVUS probe, OFDI: Optical frequency domain imaging, IVUS: Intravascular ultrasound. Scale bar: 1 mm.