Accuracy of Cranial Shape Measurements Using Smartphones: A Prospective Study.

OBJECTIVE: Prospectively validate the accuracy of smartphone-based digital cranial measurements for the diagnosis and treatment of deformational plagiocephaly and/or brachycephaly (DPB), compared with calipers used in the standard of care. DESIGN/METHODS: Bird's-eye-view head photos were captured via smartphone, and their heads were measured with hand calipers by an expert user. CI/CVAI/CVA were calculated from photos and caliper measurements, and from 3D photogrammetry of the head as ground truth. Digital and caliper measurements were compared against 3D-based ground truth using mean absolute error, Spearman correlation coefficient, and Bland-Altman method. Statistical significance between methods was assessed using Wilcoxon Rank-Sum test. PARTICIPANTS: 71 infants aged 2-11 months (20 female, 51 male) with DPB. RESULTS: The mean absolute errors for CI, CVAI, CVA were 1.63 ± 1.44, 1.45 ± 1.29, 2.38 ± 1.86 mm for smartphone, and 2.60 ± 1.96, 1.43 ± 1.22, 2.04 ± 1.81 mm for calipers, respectively. The correlation coefficients for CI, CVAI, CVA between smartphone and ground truth were 0.90, 0.94, 0.80 (p < 0.001), and 0.87, 0.93, 0.84 (p < 0.001) between calipers and ground truth, respectively. Bland-Altman results were (0.08, [-4.18, 4.34]), (-0.05, [-3.85, 3.76]), (-0.82, [-6.52, 4.87]) for smartphone, and (1.41, [-4.34, 7.15]), (0.28, [-3.37, 3.94]), (0.16, [-5.18, 5.49]) for caliper measurements respectively. Digital and caliper measurements were similar (p = 0.12) except for CI, where digital measurements were more accurate (p = 0.04). CONCLUSION: Smartphone-based cranial measurements have very high correlation with 3D-based ground truth, and they are comparable or superior to caliper measurements. Digital measurements can be performed in pediatric offices or from home to help with the early detection and treatment of DPB.

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

[This corrects the article DOI: 10.1117/1.JMI.8.2.024504.].

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

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.