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Optical Methods for Tympanic Membrane Characterisation: Towards Objective Otoscopy in Otitis Media
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Otitis media, which is an upper respiratory tract infection that affect the middle ear, is the second most common disease in childhood, outnumbered in prevalence only by the common cold. Diagnosis of middle ear inflammation is often performed in the primary healthcare where the normal procedure involves anamnesis and physical examination of the tympanic membranes (TM) of the patient, usually be means of otoscopy. The general aim of this thesis was to develop optical methods that enable quantification of TM characteristics associated with otitis media. Diffuse reflectance spectroscopy was applied to quantify TM erythema using previously suggested erythema detection algorithms. Healthy TM:s were significantly distinguished from TM:s with induced erythema (p < 0.01) and from TM:s in ears with mucous middle ear effusion (p < 0.05). A new technique for surface shape assessment based on an on-axis dual fibre array incorporated in an otoscope was developed and evaluated in ear models and on tympanic membranes from harvested temporal bones. The technique utilises the combined effects of source-detector fibre separation and fibre-to-sample distance on the detected light intensity.

Optical phantoms, both polyacetal plastic solids and latex membranes, were utilised to demonstrate the ability of the surface shape assessment technique to differentiate between convex and concave surfaces – as a bulging tympanic membrane is typically associated with acute otitis media whereas a retracted eardrum is associated with otitis media with effusion. Monte Carlo simulations of the surface shape data were performed in order to validate the experimental results with a theoretical model that are consistent with light transport theory. Retracted and bulging tympanic membranes from harvested temporal bones could be separated with a single measurement, given that variations in measurement distance were accounted for and that measurement from normally positioned tympanic membranes were used for signal normalization. In conclusion, the studies implicate that for individual otitis diagnosis, the hyperaemic tympanic membrane was separated from the healthy by application of erythema indices using diffuse reflectance spectroscopy. Moreover, bulging and retracted positions of the tympanic membrane were separable by means of the source-detector intensity matrix. For further clinical studies it is reasonable to assume that data from both methods are needed for diagnosis.

Place, publisher, year, edition, pages
Institutionen för medicinsk teknik , 2008. , 97 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1173
Keyword [en]
Optical Methods, Spectroscopy, Surface Curvature, Monte Carlo, Tympanic Membrane, Otitis Media
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:liu:diva-11246ISBN: 978-91-7393-933-1 (print)OAI: oai:DiVA.org:liu-11246DiVA: diva2:17662
Public defence
2008-04-11, Berzeliussalen, Ingång 65, plan 9, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Opponent
Supervisors
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2009-05-14
List of papers
1. Fibre-optic array for curvature assessment: application in otitis diagnosis
Open this publication in new window or tab >>Fibre-optic array for curvature assessment: application in otitis diagnosis
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2004 (English)In: Medical & Biological Engineering & Computing, ISSN 0140-0118, Vol. 42, no 2, 245-252 p.Article in journal (Refereed) Published
Abstract [en]

A contact-free sensor consisting of two parallel optical-fibre arrays was designed to assess surface shapes of diffusely scattering media. By sequentially illuminating objects using one fibre array and detecting the diffusely back-scattered photons by the other, a source-detector intensity matrix was formed, where the matrix element (i, j) was the intensity at detector j when light source i was excited. Experimental data from convex and concave polyacetal plastic surfaces were recorded. A mathematical model was used for simulating source-detector intensity matrices for the surfaces analysed in the experiments. Experimental results from the system were compared with the theoretically expected results provided by the mathematical model. The shape and relative amplitude showed similar behaviour in the experiments and simulations. A convex/concave discriminator index D, representing the detected intensity difference between two source-detector separations, was defined. The relative dynamic range of D, defined as the difference between the maximum and the minimum divided by the mean of the index, was 1.37 for convex surfaces and 0.68 for concave surfaces, at a measuring distance of 4.5mm. The index D was positive for convex surfaces and negative for concave surfaces, which showed that the system could distinguish between convex and concave surfaces, an important result for the diagnosis of otitis media.

Keyword
Diffuse reflection, Optical imaging, Otitis media, Surface shape identification
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-13008 (URN)10.1007/BF02344638 (DOI)
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2014-10-08
2. Diffuse reflectance spectroscopy of the human tympanic membrane in otitis media
Open this publication in new window or tab >>Diffuse reflectance spectroscopy of the human tympanic membrane in otitis media
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2004 (English)In: Physiological Measurement, ISSN 0967-3334, Vol. 25, no 6, 1473-1483 p.Article in journal (Refereed) Published
Abstract [en]

We have investigated if features in the diffuse reflectance spectra from in vivo spectroscopic measurements of the tympanic membrane could aid the diagnosis of otitis media in children. Diffuse reflectance spectroscopy, in the visible wavelength range, was used in 15 ears from children with otitis media with effusion before and after myringotomy and in 15 healthy ears as a reference. Two previously published erythema detection algorithms yielded numerical quantities of haemoglobin content. With a combination of the algorithms, induced erythema (after myringotomy) was distinguished from healthy ears using Student's t-test (p < 0.01). Otitis media with mucous effusion was distinguished from (1) otitis media with serous effusion, (2) induced erythema and (3) healthy ears, (p < 0.05) using Student's t-test for independent groups and the paired t-test for dependent groups. Our results imply that reflectance spectroscopy is a promising technique to be used for the diagnosis of otitis media.

Keyword
diffuse reflectance spectroscopy, otitis media, tympanic membrane, erythema
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:liu:diva-13009 (URN)10.1088/0967-3334/25/6/012 (DOI)
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2013-11-13
3. Monte Carlo simulations of backscattered light intensity from convex and concave surfaces with an optical fiber array sensor
Open this publication in new window or tab >>Monte Carlo simulations of backscattered light intensity from convex and concave surfaces with an optical fiber array sensor
2006 (English)In: Proceedings of the SPIE - Optical Interactions with Tissue and Cells XVII, SPIE - International Society for Optical Engineering, 2006, Vol. 6084, 8-18 p.Conference paper, Published paper (Other academic)
Abstract [en]

In a previous study, we presented a new technique for representationof the shape of a scattering surface. A sensor basedon two parallel fiber arrays yielded a source-detector intensity matrix(SDIM). In that study, it was shown that convex andconcave polyacetal plastic (Delrin) surfaces could be accurately distinguished usingthe proposed technique. A simplified simulation model for calculating theSDIM was used, assuming that backscattered light was generated byLambertian sources in the illuminated surface. These simulations showed discrepanciescompared to measurements, probably due to the absence of lightscattering in the model.Here, we will present an improved model,based on the Monte Carlo technique for light transport inturbid media. The optical properties of the Delrin phantoms wereestimated by means of different measurement techniques. The optical propertiesand the geometry of the Delrin phantoms were implemented inthe model along with the spatial distribution of the sourceand detector fibers of the sensor. The SDIM was extractedfrom backscattered photons exiting the turbid medium from the curvedsurface. The SDIM:s obtained with the Monte Carlo model, showeda much closer agreement with the measurements than those obtainedwith the Lambertian model. The small discrepancies observed are probablydue to spatially varying optical properties of the plastic phantoms.Measurements, using the previously described sensor, of the SDIM fromDelrin pieces with convex and concave surfaces, are compared tothe SDIM extracted from simulations using the Monte Carlo model.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2006
Series
Proceedings of SPIE (Progress in biomedical optics and imaging), ISSN 1605-7422 ; 6084
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13010 (URN)10.1117/12.659550 (DOI)000237158300002 ()
Conference
Optical Interactions with Tissue and Cells XVII, 21 January 2006, San Jose, CA, USA
Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2014-01-31Bibliographically approved
4. In vitro tympanic membrane position identification with a co-axial fiber optic otoscope
Open this publication in new window or tab >>In vitro tympanic membrane position identification with a co-axial fiber optic otoscope
2011 (English)In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 16, no 9, 097002- p.Article in journal (Refereed) Published
Abstract [en]

Otitis media diagnosis can be assisted by measuring the shape of the tympanic membrane. We have developed an ear speculum for an otoscope, including spatially distributed source and detector optical fibers, to generate source-detector intensity matrices (SDIMs), representing the curvature of surfaces. The surfaces measured were a model ear with a latex membrane and harvested temporal bones including intact tympanic membranes. The position of the tympanic membrane was shifted from retracted to bulging by air pressure and that of the latex membrane by water displacement. The SDIM was normalized utilizing both external (a sheared flat plastic cylinder) and internal references (neutral position of the membrane). Data was fitted to a two-dimensional Gaussian surface representing the shape by its amplitude and offset. Retracted and bulging surfaces were discriminated for the model ear by the sign of the Gaussian amplitude for both internal and external reference normalization. Tympanic membranes were separated after a two-step normalization: first to an external reference, adjusted for the distance between speculum and the surfaces, and second by comparison with an average normally positioned SDIM from tympanic membranes. In conclusion, we have shown that the modified otoscope can discriminate between bulging and retracted tympanic membranes in a single measurement, given a two-step normalization. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3622486]

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2011
Keyword
otitis media, acute otitis media, tympanic membrane, surface shape
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-13011 (URN)10.1117/1.3622486 (DOI)000296707100033 ()
Note
Funding agencies|Swedish Agency for Innovation Systems (VINNOVA) through the Swedish National Center of Excellence for NonInvasive Medical Measurements (NIMED)||Available from: 2008-03-20 Created: 2008-03-20 Last updated: 2017-12-13

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Sundberg, Mikael

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