Background: Bone age (BA) assessment is a routine procedure in paediatric radiology, for which the Greulich and Pyle (GP) atlas is mostly used. There is rater variability, but the advent of automatic BA determination eliminates this. Objective: To validate the BoneXpert method for automatic determination of skeletal maturity of healthy children against manual GP BA ratings. Materials and methods: Two observers determined GP BA with knowledge of the chronological age (CA). A total of 226 boys with a BA of 3-17 years and 179 girls with a BA of 3-15 years were included in the study. BoneXpert's estimate of GP BA was calibrated to agree on average with the manual ratings based on several studies, including the present study. Results: Seven subjects showed a deviation between manual and automatic BA in excess of 1.9 years. They were re-rated blindly by two raters. After correcting these seven ratings, the root mean square error between manual and automatic rating in the 405 subjects was 0.71 years (range 0.66-0.76 years, 95% CI). BoneXpert's GP BA is on average 0.28 and 0.20 years behind the CA for boys and girls, respectively. Conclusion: BoneXpert is a robust method for automatic determination of BA.

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Pediatric Radiology: roentgenology, nuclear medicine, ultrasonics, CT, MRI
Erasmus MC: University Medical Center Rotterdam

van Rijn, R.R, Leguin, M, & Thodberg, H.H. (2009). Automatic determination of Greulich and Pyle bone age in healthy Dutch children. Pediatric Radiology: roentgenology, nuclear medicine, ultrasonics, CT, MRI, 39(6), 591–597. doi:10.1007/s00247-008-1090-8