摘要BACKGROUND The recently introduced ultrasonic flow ratio(UFR),is a novel fast computational method to derive fraction-al flow reserve(FFR)from intravascular ultrasound(IVUS)images.In the present study,we evaluate the diagnostic performance of UFR in patients with intermediate left main(LM)stenosis.METHODS This is a prospective,single center study enrolling consecutive patients with presence of intermediated LM lesions(diameter stenosis of 30％-80％by visual estimation)underwent IVUS and FFR measurement.An independent core laboratory as-sessed offline UFR and IVUS-derived minimal lumen area(MLA)in a blinded fashion.RESULTS Both UFR and FFR were successfully achieved in 41 LM patients(mean age,62.0±9.9 years,46.3％diabetes).An ac-ceptable correlation between UFR and FFR was identified(r = 0.688,P<0.0001),with an absolute numerical difference of 0.03(standard difference:0.01).The area under the curve(AUC)in diagnosis of physiologically significant coronary stenosis for UFR was 0.94(95％CI:0.87-1.01),which was significantly higher than angiographic identified stenosis>50％(AUC = 0.66,P<0.001)and numerically higher than IVUS-derived MLA(AUC = 0.82;P = 0.09).Patient level diagnostic accuracy,sensitivity and spe-cificity for UFR to identify FFR≤0.80 was 82.9％(95％CI:70.2-95.7),93.1％(95％CI:82.2-100.0),58.3％(95％CI:26.3-90.4),re-spectively.CONCLUSION In patients with intermediate LM diseases,UFR was proved to be associated with acceptable correlation and high accuracy with pressure wire-based FFR as standard reference.The present study supports the use of UFR for functional evaluation of intermediate LM stenosis.