Case I: normal ear (L) - sagittal view

Case description

A 57-year-old male, with normal hearing in his left ear was selected as a healthy control for OCT/CT image fusion. Otoscopic examination of the left tympanic membrane (TM) showed it to be intact and healthy. In the otoscopic image, the malleus (M) is visible from the umbo (U) to the short process, and the incudostapedial joint (ISJ) can be seen posteriorly through the TM. The coronal CT image shows a broad external ear auditory canal (EAC) and an aerated middle ear space with intact scutum (Sc) and ossicles. The TM is not visible in the CT image due to its thinness and low radiopacity. The corresponding OCT image shows the TM and proximal surfaces of the cochlear promontory (CP), incus (I) and umbo (U).

Diagnostic imaging

(click image to enlarge)

otoscopic image
audiogram
CT (sagittal view)
OCT (3D view)
case1-axial
click to axial view
case1-coronal
click to coronal view
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case 1 sagittal CT/OCT fused

Clinical findings

As compared to the CT image, the most striking difference is the high visibility of soft tissue structures in the OCT image, especially the tympanic membrane (TM) and tensor fold (TF). Also noteworthy is the inability of OCT to resolve the distal edge of the incus due to the limited penetration of OCT into bone, the shadowing of the portion of the cochlear promontory (CP) lying distal to the ubmo (U) and image artefacts running axially from bright features on the TM. Feature edges appear better resolved in the OCT image than the CT image owing to the higher resolution of OCT (~50μm) as compared CT (~300μm). The limited field of view of the OCT image can be seen in the abrupt termination of the inferior aspect of the TM and the inability to observe structure superior and medial to the scutum (SC) in the epitympanum.