<abstract xmlns="http://www.w3.org/1999/xhtml"><p> Cleft lip/palate (CLP) is a relatively common birth defect so dis- figuring that nowadays it is almost always corrected surgically as early as possible. The postnatal surgical correction does not, however, result in a normally growing upper jaw, but instead, owing to scar tissue, one that grows abnormally. It is important to decide if a clinical treatment group is homogeneous. The example involves data from digitally processed lateral X-ray films of 48 boys who have complete unilateral CLP but no other malformation. 22 landmarks were represented by their Procrustes shape coordinates, principal components of matched- pair differences were examined, and the distribution of the 48 shape changes was studied for outliers in the affine and non-affine subspaces of the full Procrustes shape and form space. To separate outliers from inliers we use bagplots. There are no outliers apparent in the affine subspace. In the non-affine subspaces, we found no outliers in the subspace of bending patterns at large scale but four out- liers in the subspace of local changes at small scale. Almost the same outliers were found by form-space PCA. These latter are associated with possible creases of the corresponding thin-plate splines. In those cases we can use the same spline formalism to relax the outlying form to an inlier by optimal relaxation along the curve d´ecolletage that weighs bending energy against Procrustes distance and stop relaxation on the fence. These maneuvers suggest a possibly novel and interesting fusion of the Procrustes-spline toolkit with outlier detection. They also have practical implications for craniofacial management of CLP follow-up as well as suggestive implications for outlier detection in applied craniometrics and anthropometrics more generally.</p></abstract>

Cleft lip/palate (CLP) is a relatively common birth defect so dis- figuring that nowadays it is almost always corrected surgically as early as possible. The postnatal surgical correction does not, however, result in a normally growing upper jaw, but instead, owing to scar tissue, one that grows abnormally. It is important to decide if a clinical treatment group is homogeneous. The example involves data from digitally processed lateral X-ray films of 48 boys who have complete unilateral CLP but no other malformation. 22 landmarks were represented by their Procrustes shape coordinates, principal components of matched- pair differences were examined, and the distribution of the 48 shape changes was studied for outliers in the affine and non-affine subspaces of the full Procrustes shape and form space. To separate outliers from inliers we use bagplots. There are no outliers apparent in the affine subspace. In the non-affine subspaces, we found no outliers in the subspace of bending patterns at large scale but four out- liers in the subspace of local changes at small scale. Almost the same outliers were found by form-space PCA. These latter are associated with possible creases of the corresponding thin-plate splines. In those cases we can use the same spline formalism to relax the outlying form to an inlier by optimal relaxation along the curve d´ecolletage that weighs bending energy against Procrustes distance and stop relaxation on the fence. These maneuvers suggest a possibly novel and interesting fusion of the Procrustes-spline toolkit with outlier detection. They also have practical implications for craniofacial management of CLP follow-up as well as suggestive implications for outlier detection in applied craniometrics and anthropometrics more generally.

 Detection of non-affine shape outliers for matched-pair shape data

School of Mathematics and Statistics The University of Glasgow University Gardens G12 8QW Glasgow SCOTLAND, UK

Department of Applied Mathematics and Statistics Comenius University Mlynsk´a dolina SK–842-48 Bratislava SLOVAKIA

Tatra Mountains Mathematical Publications

{"article-title":"Detection of non-affine shape outliers for matched-pair shape data"}

Cleft lip/palate (CLP) is a relatively common birth defect so dis- figuring that nowadays it is almost always corrected surgically as early as possible. The...

Detection of non-affine shape outliers for matched-pair shape data

Publié en ligne: 13 nov. 2012

Pages: 83 - 90

DOI: https://doi.org/10.2478/v10127-012-0009-9

Mots clés
shape outliers, relative warp analysis, matched-pair shape differences, bagplots, thin-plate splines, cleft lip/palate.

This content is open access.

Detection of non-affine shape outliers for matched-pair shape data

Publié en ligne: 13 nov. 2012

Pages: 83 - 90

DOI: https://doi.org/10.2478/v10127-012-0009-9

Mots clésshape outliers, relative warp analysis, matched-pair shape differences, bagplots, thin-plate splines, cleft lip/palate.

This content is open access.

Mots clés
shape outliers, relative warp analysis, matched-pair shape differences, bagplots, thin-plate splines, cleft lip/palate.