title: In vitro tympanic membrane position identification with a co-axial fiber-optic otoscope.
abstract: 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.
authors.affiliation: Linköping University, Department of Biomedical Engineering, Linkoping 58185, SwedenLinköping University, Department of Oto-Rhino-Laryngology, Linkoping 58185, Sweden. miksu@cesu.se
authors.forename: Mikael
authors.initials: M
authors.lastname: Sundberg
authors.forename: Markus
authors.initials: M
authors.lastname: Peebo
authors.forename: Tomas
authors.initials: T
authors.lastname: Strömberg
mesh_terms: D005336:Fiber Optic Technology / Q000295:instrumentation*; D006801:Humans; D016018:Least-Squares Analysis; D008954:Models, Biological; D010033:Otitis Media / Q000473:pathology; D019720:Otoscopes; D038781:Otoscopy / Q000379:methods*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D014432:Tympanic Membrane / Q000033:anatomy & histology*