A Methodological Comparison between Ultrasound and X-ray Evaluations of Bone Age

The most conventional method of skeletal age assessment in children and adolescents uses CHN standards to evaluate the left hand radiograph.But a newly developed ultrasound device(BonAge System,made by Sunlight Medical Ltd.,Israel) has been widely put in use of skeletal growth evaluation.Objective: to compare the accuracy of the ultrasound method with the standard radiographic method.Participants: 322 children and adolescents aged 5-17 years,127 girls,195 boys.Materials and methods: 1)An repeated ultrasound examination of 93 participants' distal radial and ulna epiphysis was made to evaluate the new device's repeatability and stability.2) 229 participants underwent radiography of the left hand,followed by ultrasound measurement of the same hand using BonAge system.This system evaluates the relationship between the velocity of sound passing thorough the distal radial and ulna epiphysis and growth.Two experienced experts,blinded to each other and to the chronological age and BonAge result,analyzed the radiograph and gave out their own judgment of bone age according to CHN standards.The correlation between BonAge result and averaged specialists' judgments was analyzed.Results: 1)There was high correlation and no significant difference between the average of two repeated BonAge results.The device was quite stable in use.2) There were great systematic error and random error between the average values of ultrasound and radiograph bone ages not only in gender groups but in age groups as well.The error was enlarged with age older.The univariate analysis for one dependent variable by multi-factors showed that bone age results were mainly influenced by such factors as evaluation methods and age,but were not significantly related to gender.The results by two methods were also not highly correlatted especially for those older participants,so we cannot built a good linear regression relationship between the evaluation outcomes of two methods.Conclusion: There were great methodological differences between the principles of the BonAge and radiograph.The two methods can not be replaced each other.