ObjectiveTo compare the diagnostic efficiency of 18F- FDG coincidence SPECT/CT and 99Tcm- MDP whole body bone scan (WBBS) in detecting malignancy.MethodsA total of 71 cases (male 45,female 26,mean age 59.2 ± 15.4 years) with clinically confirmed malignancy underwent both 99TcmMDP WBBS and 18F-FDG coincidence imaging within three weeks.The sensitivity,specificity,accuracy,positive and negative prediction value of these two imaging methods in detecting bone metastases were compared based on the results from pathology or clinical follow-up.x2test was used for data analysis.ResultsA total of 350 lesions (including primary,second malignancy and benign disease) in 71 patients were eval-uated.81.7％ (286/350) malignant lesions were identified by either 99Tcm-MDP WBBS (209/350,59.7％ ) or 18F-FDG coincidence imaging ( 141/350,40.3％ ) (x2 =25.65,P ＜ 0.01 ).The imaging findings of osteoblastic,osteolytic,mixed types of bone metastases by99Tcm-MDP WBBS and 18F-FDG coincidence imaging were significantly different (x2 =20.78,2.89 and 9.94,all P ＜ 0.05 ).The sensitivity,specificity,accuracy,false-positive,false-negative,positive and negative predictive values for detecting bone metastases by 18 F-FDG coincidence study and 99Tcm-MDP WBBS were as follows:11.72％ ( 15/128),91.67％(22/24),24.34％ (37/152),8.33％ (2/24),88.28％ (113/128),88.24％ (15/17),16.30％ (22/135) ; and 53.91％ (69/128),75.00％ ( 18/24),57.24％ (87/152),25.00％ (6/24),46.09％ (59/128),92.00％ (69/75),23.38％ ( 18/77 ).The sensitivity,accuracy,false-negative,positive-predicting value of the two methods had been significant different (x2 =32.70- 46.21,all P ＜ 0.01 ).When two methods were combined,the diagnostic efficiency could been improved.ConclusionThe 99Tcm-MDP WBBS and 18F-FDG coincidence imaging has a complementary role in detecting bone metastases.