Current clinical workflow in otology
Existing tools lack the precision for confident diagnoses
Middle ear disorders are typically diagnosed through a variety of methods, each contributing to a comprehensive
understanding of the condition. This complex process typically involves a collaborative, multidisciplinary
effort among audiologists, otolaryngologists, and sometimes radiologists. Their joint expertise is pivotal in
ensuring that patients receive comprehensive evaluations and personalised treatment plans, both of which are
essential for the effective management and improved outcomes of those afflicted with these conditions.
The diagnostic process often begins with an optical examination of the tympanic membrane (TM) using an otoscope
or microscope. This is supplemented by air and bone audiometry, as well as functional tests such as tympanometry
and wide-band ear-canal power reflectance measurements. These functional tests assess the mechanical response of
the middle ear. However, it is important to note that despite their extensive application, these tests offer
limited selectivity and specificity in diagnosing a majority of middle ear disorders, with otitis media being a
notable exception. When imaging is indicated, the primary non-invasive option currently available is computed
tomography (CT). However, CT scans have limitations in resolving middle ear structures like the ossicles at
times, rendering them of limited diagnostic value except for certain specific diseases. This gap in diagnostic
capabilities means that clinicians sometimes face challenges in reaching conclusive diagnosis, not due to a lack
of expertise, but because of the constraints imposed by the current technological tools at their disposal.
Structural imaging
Morphological diagnostic
Our facility is a specialized tertiary care clinic that caters to an adult demographic, primarily receiving
referrals from community ENTs throughout the maritime provinces of Canada. In our practice, we have adopted ME-OCT
as an resaerch tool to supplement diagnostic information where feasible.
Here is how we use the hand-held OCT system in our clinic. The process involves inserting the imaging handpiece
into the patient's ear, akin to using an otoscope, which in this case, is for a healthy volunteer. As we explore
the "patient" 's middle ear, a clear view of the middle ear structures appears on the left with a umbo in the
center, and the tympanic membrane on either side. You can also catch a glimpse of other anatomical landmarks such
as ossicles and supporting ligaments. In the case where 2D image is insufficient to identify the cause of
conductive hearing loss. we can continue our investigation in 3D where more precise measurements can be made with
accurate representation of the anatomical structure.
4D imaging of middle ear (Valsalva)
Capturing middle ear dynamics
One of the benefits of fast scanning is that we can capture dynamic parameters. Some of these influences middle
ear function. Here, OCT can detect pressure change induced displacement of the middle ear as the eardrum produces
a known and repeatable physical response when air forces through the sinuses and Eustachian tube during Valsalva.
OCT Doppler vibrometry (OCT-DV)
Structure specific mobility measurements
OCT-DV introduces a novel approach to capturing the dynamics of ear structures. As mentioned early, the signal of
interest in OCT is called A-line, which contains the vibration signature of a given structure. When we set a
sample into periodic motion by sending pure tone stimulus. The measured vibration signature will change
accordingly. This change can be isolated and decoded by processing the differences in sequential A-lines at each
pixel, allowing for a precise analysis of induced changes at given frequencies. This vibrational information can
be directly displayed on top of the structural image. As shown in this video, OCT captures the sound-induced
velocity change at the umbo by sweeping through a range of pure tones at different frequencies where the screen on
the right shows the otoscopic view of the ear. The blue line indicates the cross-section on the left screen, and
the cross-hair provides the visual confirmation that we are centred at umbo. As we step through different tones,
we can see the resulting A-line shifts slightly due to the stimulus. Following the measurement, we automatically
calculate the stimulus-induced vibration response where we have a normalised pressure velocity on the y-axis and
frequencies of interest on the x-axis.
In conclusion, ME-OCT enables structural and functional analysis of the middle ear space through the TM, providing
high resolution vibrometry information that cannot be obtained from standard auditory testing. Recent studies have
highlighted the advantages of OCT both independently and as a complement to current otology diagnostic tools. Its
various applications, such as stapes fixation detection, otitis media evaluation, antibiotic treatment monitoring,
and effusion classification, could help bridge the gap between the limitations of existing clinical diagnostic
tools and the need for more accurate and precise diagnoses
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