Objective To measure the dangerous depth and the effective safe depth of needling at acupoints of kidney regions based on MRI imaging

and to provide the imaging support for clinical practice.Methods The abdominal enhanced T1 MRI imaging of horizontal plane of 61 healthy subjects was included

the anatomical structure of bilateral Weishu（BL 21）

Sanjiaoshu（BL 22）

Shenshu（BL 23）

Weicang（BL 50）

Huangmen（BL 51） and Zhishi（BL 52） was analyzed

and the dangerous depth and effective safe depth of perpendicular and oblique needling were measured between the left and right sides and subjects with different body sizes.Results There were no significant differences between dangerous depth and effective safe depth of perpendicular and oblique needling at bilateral acupoints of kidney region（P>0.05）.The dangerous depth and effective safe depth of perpendicular and oblique needling at bilateral acupoints of kidney region in the moderate group were larger than the underweight group（P<0.05）

while those in the overweight group were larger than the moderate group and the underweight group（P<0.05）.Conclusion The safe depth of needling at acupoints of kidney region is related to body size

for moderate weight and overweight patients

the needling depth could be increased for better efficacy

while for underweight patients

the recommend direction and depth of needling should be restricted to avoid acupuncture accident.