Statistical Shape Analysis of the Human Ear Canal with Application to In-the-Ear Hearing Aid Design

摘要

This thesis is about the statistical shape analysis of the human ear canal with application to the mechanical design of in-the-ear hearing aids. Initially, it is described how a statistical shape model of the human ear canal is built based on a training set of laser-scanned ear impressions. A thin plate spline based approach creates a dense correspondence between the shapes in training set. In addition, a new flexible, non-rigid registration framework is proposed and used to optimise the correspondence ¯eld. The framework is based on Markov Random Field regularisation and is motivated by prior work on image restoration. It is shown how the method significantly improves the shape model. In the second part of the thesis, the shape model is used in software tools that mimic the skills of the expert hearing aid makers. The first result is that it is possible to learn an algorithm to cut an ear canal in order to produce an optimal in-the-ear hearing aid. Secondly, a framework for component placement using a coupling of stochastic optimisation and the results from the shape model is proposed. It is successfully, used to place the so-called faceplate with associated component on in-the-ear hearing aids. In addition, the idea of one-size-fits-most shells is explored. In Danish: Denne afhandling beskriver brugen af statistisk formanalyse af den menneskelige hørekanal i det mekaniske design af i-øret høreapparater. Først beskrives det hvordan en statistisk formmodel af den menneskelige øre- kanal er lavet på baggrund af et træningssæt af laser-skannede øre aftryk. En Thin Plate Spline baseret metode genererer en kompakt korrespondance mellem formerne i træningssættet. Endvidere er en fleksibel, ikke-rigid registrerings metode foreslået og brugt til at optimere korrespondance feltet. Metoden er baseret på Markov Random Field regulering og er motiveret af tidligere arbejde vedrørende billede opretning. Det er vist hvordan metoden signifikant forbedrer formmodellen. I den anden del af afhandlingen, bruges formmodellen i programmer, der efterligner evnerne hos de bedste af dem der laver høreapparater. Det første resultat er, at det er muligt at lære en algoritme at skære en ørekanal for at producere et optimalt i-øret høreapparat. Dernæst, foreslås en metode til placering af komponenter. Metoden bruger en kombination af stokastisk optimering og resultater fra formmodellen. Den er succesfuldt brugt til at placere den såkaldte faceplate med komponenter på i-øret høreapparater. Derudover er ideen om en skal af en størrelse og form, som passer de fleste forfulgt.