Abstract: Objective  To explore the imaging features of ultrasound in girls at different developmental stages and their ability to distinguish idiopathic central precocious puberty from premature thelarche. 
Methods  We performed a retrospective study with a sample of 124 girls, who underwent ultrasound for evaluation development. We evaluated breast ultrasound grade, breast and pelvic ultrasound, and clinical characteristics including age and body mass index. Among the 124 girls, 52 were up to 9 years old with early breast development. We divided them into idiopathic central precocious puberty(16 cases), and premature thelarche groups(38 cases) and evaluated the clinicoradiologic findings for each group. 
Results  A total 124 girls were graded by breast ultrasound grade, including 34 cases of grade A(27.4%), 49 cases of grade B(39.5%), 18 cases of grade C(14.5%), 5 cases of grade D(4%) and 18 cases of grade E(14.5%). There were statistical differences in age, BMI, uterine volume, uterine length diameter, anterior-posterior diameter of uterus/anterior-posterior diameter of cervix(FCR), maximum ovarian volume, endometrial thickness, vaginal wall thickness, number of ≥4 mm follicles, maximum follicular diameter, breast bud diameter and breast bud volume for girls(P＜0.05). There were 16 cases of ICPP and 38 cases of PT. The age, uterine volume, uterine length, endometrial thickness, maximum ovarian volume, ≥4 mm follicle number, maximum follicle diameter, breast bud diameter and breast bud volume of girls between ICPP and PT groups were statistically different(P＜0.05), while BMI, FCR value and vaginal wall thickness were not statistically different(P＞0.05). The breast ultrasound grade of 16 ICPP subjects were as follows: grade A in 1 case(6.3%), B in 13 cases and （81.2%), C in 2 cases(12.5%); breast ultrasound grade in 38 PT subjects was grade A in 18 cases(47.4%), B in 18 cases(47.4%), C in 2 cases(5.2%). There was statistical difference in breast ultrasound grading between two groups(P＜0.05). 
Conclusion  〖JP2〗It was shown that the ultrasonographic staging of breast development could provide more accurate and objective data.Ultrasound has the ability to distinguish idiopathic central precocious puberty from premature thelarche. 〖JP〗

Key words:  , mammary glands, human； ultrasonography； puberty, precocious