3D Head Shape Quantification for Infants with and without Deformational Plagiocephaly

28 Objective: We developed and tested three dimensional (3-D) indices for quantifying 29 severity of deformational plagiocephaly (DP). 30 Design: We evaluated the extent to which infants with and without DP (as determined 31 by clinic referral and two experts’ ratings) could be correctly classified. 32 Participants: Infants ages 4-11 months, including 154 with diagnosed DP and 100 infants 33 without a history of DP or other craniofacial condition. After excluding participants with 34 discrepant expert ratings, data from 90 infants with DP and 50 infants without DP were retained. 35 Measurements: Two-dimensional histograms of surface normal vector angles were 36 extracted from 3-D mesh data and used to compute the severity scores below. 37 Outcome measures: Left Posterior Flattening Score (LPFS), Right Posterior Flattening 38 Score (RPFS), Asymmetry Score (AS), Absolute Asymmetry Score (AAS) and an approximation 39 of a previously described 2-D measure, the Oblique Cranial Length Ratio (aOCLR). Two40 dimensional histograms localized the posterior flatness for each participant. 41 Analysis: We fit receiver operating characteristic curves and calculated the area under the 42 curves (AUC) to evaluate the relative accuracy of DP classification using the above measures. 43 Results: The AUC statistics were: AAS=91%; LPFS=97%, RPFS=91%; AS=99%, and 44 aOCLR=79%. 45 Conclusion: Novel 3-D-based plagiocephaly posterior severity scores provided better 46 sensitivity and specificity in the discrimination of plagiocephalic and typical head shapes than 47 the 2-D measurements provided by a close approximation of OCLR. These indices will allow for 48 more precise quantification of the DP phenotype in future studies on the prevalence of this 49 condition, which may lead to improved clinical care. 50