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Objectives There are few quantitative studies directly evaluating methods of determining pulmonary embolism.New Computer-Aided Detection(CAD)methods for measuring pulmonary emboli may help in defining the relationship of the pulmonary embolism to right ventricular dysfunction(RVD).We used CAD to investigate the severity degree of pulmonary embolism with a differential geometric approach and we also explored whether the severity degree of pulmonary emboli were associated with the RVD.Methods We used a new method of CAD measurement to assess pulmonary emboli in 557 patients.Automated evaluation of the severity degree of the pulmonary embolism by CAD was conducted using the total embolism area/lumen area.Pulmonary emboli were also evaluated using the vascular obstruction index(VOI),as determined by the Mastora and Qanadli scores,read by two experienced thoracic radiologists.The RVD was defined as the ratio of the diameter of the right ventricle(RV)to the diameter of the left ventricle(LV).A paired t test was used to compare the severity degree of the pulmonary embolism evaluated by Mastora or Qanadli score,to the severity degree determined by CAD.Interobserver variability was determined for both the Mastora and Qanadli scoring systems.Correlation of the severity degree of the pulmonary embolism and RVD was also evaluated by Spearmans rank correlation analysis.Results There was good consistency between observers in evaluating the severity degree of pulmonary embolism by Mastora or Qanadli scores(P >0.05).There was no significant difference(P >0.05)in the severity degree of pulmonary embolism evaluated by Mastora,Qanadli,or CAD.However,there was statistical significance between the severity degrees determined by Mastora and Qanadli(P <0.05).The severity degree of pulmonary embolism evaluated by Mastora,Qanadli,and CAD had significant positive correlation with RVD(R=0.75,P<0.00,R=0.69,P<0.00,R=0.80,P<0.00).Conclusion We propose a fully automated approach to evaluate pulmonary embolism that is simple and reliable.We found strong correlation between the severity degree of pulmonary embolism evaluated by CAD and RVD.