The preliminary results of the project devoted to the use of optical coherence tomography technique to evaluate the middle ear effusion condition are presented. The method of estimation of the middle ear effusion viscosity using the Fourier analysis of the OCT data is proposed. The method provides the possibility to distinguish areas filled by water and effusion in situ. The data on use of the especially-developed SD OCT system is reported.
Employment of chlorin-based photosensitizers (PSs) provides additional advantages to photodynamic therapy (PDT) due to absorption peak around 405 nm allowing for superficial impact and efficient antimicrobial therapy. We report on the morphological and clinical study of the efficiency of PDT at 405 nm employing chlorin-based PS. Numerical studies demonstrated difference in the distribution of absorbed dose at 405 nm in comparison with traditionally employed wavelength of 660 nm and difference in the in-depth absorbed dose distribution for skin and mucous tissues. Morphological study was performed at the inner surface of rabbit ear with histological examinations at different periods after PDT procedure. Animal study revealed tissue reaction to PDT consisting in edema manifested most in 3 days after the procedure and neoangiogenesis. OCT diagnostics was confirmed by histological examination. Clinical study included antimicrobial PDT of pharynx chronic inflammatory diseases. It revealed no side effects or complications of the PDT procedure. Pharyngoscopy indicated reduction of inflammatory manifestations, and, in particular cases, hypervascularization was observed. Morphological changes were also detected in the course of monitoring, which are in agreement with pharyngoscopy results. Microbiologic study after PDT revealed no pathogenic bacteria; however, in particular cases, saprophytic flora was detected.
The most valuable results for the use of OCT imaging in ENT diagnostics have been shown by Stephen Boppart and his group in Illinois Urbana-Champaign University. In 2016 this group demonstrated the possibility to reconstruct some viscosity properties of the effusion by the use of OCT providing some additional measurements.
Our team have provided the pilot study on the possibility of detection of the effusion using the OCT device in 2014 13. The current work is devoted to improvement of Dr Boppart’s approach to examine the effusion viscosity.
To provide the preliminary investigations we used the time-domain OCT device due to the reason of its clinical approval. This device provides about 200 A-scans per second, which is quite enough to register the Brownian movement of the scatterers in the middle ear effusion.
All investigations were made by the use of thin (2.4 mm diameter) flexible forward-viewing probe 14 pushed through the standard ear mirror. The main disadvantage of the probe is the requirement of the contact between the tip and the tympanic membrane, which may cause some discomfort to the patient. In the order to enhance the image brightness behind the tympanic membrane the immersion was injected in the auditory meatus. The use of immersion also provides the reference level of scatterers mobility while the effusion viscosity was examined.
The conventional OCT image of the eardrum demonstrates the high level of backscattering particles behind the membrane in the case of otitis media with effusion. Following 11, we switch scanning off and recorded images. The obtained image became time-resolved and moving scatterers are presented here as quite short horizontal lines on the image while the steady area is presented by long horizontal lines set.
Dr Monroy used time-correlated analysis to estimate the mobility of particles suspended in the effusion. We propose to use the Fourier analysis of the image, which seems to be more informative.
We implemented the 2D-Fourier transform to the OCT data recorded while the scanning was switched off. One can easily note the differences in the width of the spectrum between areas of eardrum, water immersion and effusion noting the effective spectral width. To numerically estimate the width of the Fourier image we fit every row data with the Gaussian shape. After that the FWHM parameters of the Gaussian shapes were used to obtain the in-depth profile of the particles “mobility. One can see that the obtained by proposed method particles “mobility” is quite different in cases of the water suspension and the effusion.
We have proposed the method of estimation of the middle ear effusion viscosity using the Fourier analysis of the OCT data obtained by the fixed probe beam. The method provides the possibility to distinguish areas filled by water and effusion. We believe this approach to be useful in differentiation the grade of the otitis media with effusion in clinical conditions.
This research was supported by Russian Science Foundation (project No 17-15-01507).
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