A Novel Imaging Method for the Cartilaginous Eustachian Tube Lumen: Computerized Tomography During the Forced Response Test

Objectives: In vivo imaging of the open cartilaginous Eustachian tube (ET) lumen by computed tomography (CT) scan during ET function (ETF) testing to establish new methodology. Methods: Five adults underwent unilateral ETF testing of an ear with a nonintact tympanic membrane using the forced response test (FRT) to measure the opening pressure (PO), steady state pressure (PS), and flow conductance (CS). Then at baseline and during the PS phase of the FRT, a temporal-bone CT scan with continuous 0.625 mm thickness was obtained. Multiplanar oblique reformats along the axis of the ET were created, and point value and region of interest (ROI) Hounsfield unit measurements were recorded from the location of the ET lumen. Results: At the FRT flow rate of 11 ml/min, the average PO, PS, and CS were 370.5 daPa, 119.6 daPa, and 0.16 ml/min/daPa, respectively. For flow rates of 23 and 46 ml/min, these values were 236.2, 204.2, 0.12 and 385.5, 321.1, 0.18, respectively. Although areas with lower attenuation were suggestive of air density, a distinct air-filled cartilaginous ET lumen could not be confirmed. Conclusions: While the current imaging parameters failed to resolve the air-soft tissue interface throughout the open cartilaginous ET, further advances in imaging may obviate this limitation.