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Mapping morphologic change in the external ear


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Grenness, MJ 1999 , 'Mapping morphologic change in the external ear', Research Master thesis, University of Tasmania.

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The movement of the external ear canal, associated with jaw motion,
relative to the concha region of the pinna has been studied. This issue is
most relevant to the fitting and function of In-The-Ear hearing-aids.
Pairs of open-jaw and closed-jaw silicone impressions were taken of 14
ears from 10 subjects. 3D coordinate data was obtained from the concha
region and the anterior surface of the canal using a reflex microscope.
The canal regions were plotted via an optical flat mirror. Proprietary
area-based matching software was used to verify the stability of the
concha region and evaluate distortion of the canal during jaw motion.
The canal data from each pair was placed into the same coordinate
system with their respective concha regions aligned using the areamatching
software. Contour and difference maps of the canal data
were used to demonstrate the amount of anterior-posterior (A-P),
superior-inferior (S-I), and medial-lateral (M-L) movement that
occurred between the open and closed-jaw impressions. Rotations were
also evaluated.
Analysis confirmed that the concha regions did not undergo significant
deformation during jaw movement. The canal regions underwent
varying amounts of internal deformation with the majority of canals
conforming within an RMS of 400 pm across the entire surface. The
majority of canals underwent significant morphologic change relative to
the concha. Movement of the canal in the M-L plane ranged from 0 to
3.8 mm with a mean of 1.4 mm; 8 canals moved laterally, 5 canals
moved medially and 2 ears did not move in the M-L plane. Movement
in the S-I plane ranged from 0 to 3.7 mm with a mean of 1.3 mm; 9
canals moved inferiorly, 2 canals moved superiorly and 3 canals did not
moved in the S-I plane. Movement in the A-P plane ranged between
+3.5 mm and -3 mm, with 5 canals moving anteriorly, 3 ears moved
posteriorly, and 4 ears moving in a mixed fashion. The geometry of the external ear has created difficulties in acquiring
accurate surface maps for analysis. The study has focused on the key
areas of the pinna and canal previously reported to undergo significant
This study does not support previous reports that suggest that the ear
canal only widens with jaw opening. This study gives insights into the
variability in the movements of the ear canal relative to the concha
region of the pinna and will be of interest to clinicians involved in the
fitting of hearing-aids.

Item Type: Thesis - Research Master
Authors/Creators:Grenness, MJ
Keywords: Hearing aids, Ear canal
Copyright Holders: The Author
Copyright Information:

Copyright 1999 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Med.Sc.)--University of Tasmania, 1999.

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