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.
In a previous study, we presented a new technique for representation of the shape of a scattering surface. A sensor based on two parallel fiber arrays yielded a source-detector intensity matrix (SDIM). In that study, it was shown that convex and concave polyacetal plastic (Delrin) surfaces could be accurately distinguished using the proposed technique. A simplified simulation model for calculating the SDIM was used, assuming that backscattered light was generated by Lambertian sources in the illuminated surface. These simulations showed discrepancies compared to measurements, probably due to the absence of light scattering in the model.
Here, we will present an improved model, based on the Monte Carlo technique for light transport in turbid media. The optical properties of the Delrin phantoms were estimated by means of different measurement techniques. The optical properties and the geometry of the Delrin phantoms were implemented in the model along with the spatial distribution of the source and detector fibers of the sensor. The SDIM was extracted from backscattered photons exiting the turbid medium from the curved surface. The SDIM:s obtained with the Monte Carlo model, showed a much closer agreement with the measurements than those obtained with the Lambertian model. The small discrepancies observed are probably due to spatially varying optical properties of the plastic phantoms.
Measurements, using the previously described sensor, of the SDIM from Delrin pieces with convex and concave surfaces, are compared to the SDIM extracted from simulations using the Monte Carlo model.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.