A1235
Title: Asymmetry analysis of bilateral shapes
Authors: Xiangyu Wu - University of Leeds (United Kingdom) [presenting]
Kanti Mardia - Leeds University (United Kingdom)
John Kent - University of Leeds (United Kingdom)
Balvinder Khambay - University of Birmingham (United Kingdom)
Colin Goodall - University of Leeds (United Kingdom)
Abstract: Many biological objects possess approximate bilateral symmetry about a midplane. The landmark-based methods are used to measure departures from bilateral symmetry. A vector of unsigned elementary features is constructed to describe the asymmetry of each object based on these landmarks. Two approaches are proposed to compare the level of asymmetry between two groups of objects. In the first approach the elementary features are combined into a scalar composite asymmetry score for each object; then standard univariate tests are used on the composite asymmetry score to assess asymmetry. In the second approach a univariate test statistic is constructed for each elementary feature; then the maximum of these statistics is used for a union-intersection test. The methodology is illustrated on two data sets collected to assess the success of two types of surgery: (1) cleft lip surgery, where the level of asymmetry is compared between a group of cleft lip subjects and a group of normal subjects; and (2) orthognathic surgery, where for each patient, the level of asymmetry after surgery is compared to that before surgery.
