Technical realization of ME-OCT

Emerging imgaging technology for hearing diagnostics

Optical coherence tomography (OCT) has emerged as a significant advancement in otology and auditory physiology, offering complementary information for clinical decision-making in the examination of the tympanic membrane (TM), ossicular chain, and inner ear. This non-invasive, depth-resolved imaging technique for hearing diagnostics has many advantages over traditional otoscopes and surgical microscopes, which are the primary tools for otologic point of care imaging.

Pitris et al. first demonstrated the potential of OCT imaging for the TM and middle ear in 2001. However, widespread interest in OCT technology for otology research and clinical applications took nearly a decade to develop due to technological limitations. The introduction of swept-source OCT (SS-OCT) in the 2010s, featuring akinetic all-semiconductor lasers and other highly phase-stable systems, made real-time in vivo middle ear OCT clinically viable.

The heart of ME-OCT developed in our lab is a special type of laser known as the akinetic swept-source laser. This type of laser has no mechanical moving parts and can quickly change the frequency or colour of the light it emits. In this ME-OCT with wavelength-swept laser, the light from a wavelength tunable laser is split into two paths: one directed towards a reference and the other towards the sample being imaged.


As the light reflects back from both paths, it recombines at a beam splitter. Here, we capture an interference signal whose oscillation frequency varies with the depth of the ear structure reflecting the light. Analysing these oscillations allows us to construct a reflectivity profile of the structure being imaged as a function of depth along a single image line. This reflectivity profile is often referred to as the axial line or A-line. This A-line captures the complex scattering amplitude of the sample at specific depths and it forms the basis of a wide range of OCT signal processing and image reconstruction applications. As we move the laser beam laterally, a stack of adjacent image lines can be generated, collected and then assembled into a cross-sectional image. By arranging multiple cross-sectional images from neighbouring planes, one can construct a three-dimensional representation of the middle ear space without introducing any radiation to the patient.

To accelerate the clinical adoption of OCT in otology, several form factors have been explored to address the diverse clinical needs by different resaerch groups. For example, integrating OCT with surgical microscopes has enabled detection of microanatomic changes in TM layers and differentiation of keratin from normal or inflamed middle ear mucosa. Handheld OCT probes, resembling otoscopes or endoscopes, have demonstrated their ability to detect biofilm behind the TM and to identify ossicular fixations. Here you can see the pathway our lab took to bring middle ear OCT system from a benchtop design to a practical clinical solution for ENTs. We developed a handheld, otoscopic form factor that is already familiar to clinicians. This system comprises a desktop console, a tethered hand-piece, and an intuitive user interface. It is designed for single-operator use, allowing for direct patient interaction and simultaneous measurement initiation.