Abstract： Objective To study feasibility of differentiation of benign and malignant by using eccentric rate of calcification in pulmonary spherical lesions.Methods Two hundred and forty cases with pulmonary spherical lesions(malignant in 170 and benign in 70) confirmed by pathology or clinical follow-up were collected in this study.All cases were underwent chest CT examinations.Nodule CAD software was used to demarcation of pulmonary spherical lesions and internal calcification.Calcification was defined as an area more than 3 pixel with calcification density(CT value＞120 HU).Furthermore,the ratio of calcification center distanceand calcification edge distance was calculated as Ecc.Mann-Whitney U test was used to compare the eccentric calcification rates between the malignant and the benign pulmonary spherical lesions.Taking pathological results as golden standard,the diagnostic efficacy of Ecc was analyzed using ROC curves.Results In 240 lesions,65 calcifications were detected,of which 18 were malignant calcification distributed in 10 lesions,and 47 were benign calcifications distributed in 16 lesions.The median of Ecc in benign and in malignant lesions were 0.80(0.28-1.29) and 3.01(1.52-4.47).The Ecc of calcification in benign lesions were lower than those in malignant lesions (U=183.000,P＜0.01).Under the cut-off value of 1.00,benign calcifications were more likely to lie inner 1/2 part of lesion [61.70％(29/47)],while malignant calcifications were more likely to lie outer 1/2 part of lesion [77.78％(14/18)].The difference was statistically significant(x2=8.117,P＜0.01).Under the cut-off value of 1.72,the resultant sensitivity,specificity,accurate rate were 83.1％,77.8％,81.5％ respectively.The area under the ROC was 0.804.Conclusions Ecc exhibits the location characteristics of calcification and may be an ideal parameter in quantitative diagnostic modeling for providing evidence of quantitative diagnosis.