Toward quantitative assessment of deformational plagiocephaly and brachycephaly at the point-of-care

Abstract

Purpose: Develop and validate algorithms that can enable a novice user to quantitatively measure the head shape parameters associated with deformational plagiocephaly and brachycephaly (DPB) using 2D rendered images. Approach: First, the head contour is extracted semi-automatically using the intelligent scissors method. We then automatically compute two indices used in the clinical determination of the DPB from the head shape parameters: the cranial index (CI) and the cranial vault asymmetry index (CVAI). We also present methods to quantify and compensate for the user variability, including camera angle and distance from the head using 2D rendered images. We compared the results of our technology with ground-truth (GT) measurements from 53 infants with DPB and normal cranial parameters. Results: The Spearman correlation coefficient between the new 2D rendered method and the 3D GT was 0.94 ( $p<0.001$ ) and 0.96 ( $p<0.001$ ) for CI and CVAI, respectively. Different simulated camera angles and distances from the head resulted in variation in CI and CVAI in the range of $[-2.0,6.0]$ and $[-4.0,4.0]$ units, respectively. The limits of agreement of the Bland-Altman test were reduced from $[-3.6,5.3]$ and $[-3.6,4.2]$ to $[-0.5,3.0]$ and $[-1.3,1.6]$ for CI and CVAI, respectively, by combining results from different camera angles and positions in our method. The overall accuracy of the proposed technology for DPB detection was 100%. Conclusions: The 2D rendered images of the head can be accurately analyzed to assess DPB. Further study on 2D photos taken from human subjects is warranted.

Keywords: head deformity; pediatrics; point of care; quantitative imaging; smartphone.