Correlation Of Post-to Pre-stenosis Peak Velocity Ratio From Phase-contrast Magnetic Resonance Imaging With The Luminal Stenosis Severity In Coronaryartery Disease Patients

PART ? Correlation Between The Post-To Pre-Stenosis Peak Velocity Ratio From Phase-Contrast Magnetic Resonance Imaging With The Degree Of Stenosis In A Phantom StudyObjective: To study the correlation of post to pre stenosis peak velocity ratio derived from phase-contrast Magnetic Resonance Imaging(PC-MRI)with the stenotic severity in an in-vitro model.Materials and Methods: Flow rates and velocity measurements were performed in an in-vitro model with 20%,40%,60%,and 80% area occlusions at three constant flow rates(1.5,2,and 2.5ml/s)using PC-MRI at 3.0 Tesla.The flow rate,mean velocity and peak velocity were measured at multiple sections of the in-vitro model(5mm proximal to the stenosis,and 5,10,15,20,25,and 30 mm distal to the stenosis).The flow rates and the mean velocity before the stenosis were compared with the true injecting flow rate and calculated mean velocity.The correlation of Post-to prestenosis peak velocity ratio(PVR)with the stenosis severity was analyzed,and a receiver operating characteristic curve was used to define PVR thresholds for differentiate mild to severe stenosis severity.Results: The flow rates and mean velocities of the pre-stenosis derived from PC-MRI had a high agreement with the true injecting flow rates and calculated mean velocities by setting a constricted region-of-interest with lumen size equal to the ground-truth luminal size.As the stenosis severity became heavier,the PVR also rose,the ratio correlated strongly with the degree of the stenosis for all flow rates at different sections distal to the stenosis.(all r>0.98,P<0.05).The receiver operator characteristic curve(ROC)analysis showed the area under ROC curve(AUCs)were all over0.9 for sections at 25 mm after the stenosis.The cut-off value to determine severe stenosis greater than 20%,40%,60%,and 80% was around1.1,1.5,2.0,and 2.6 at 5mm after the stenosis,respectively.Conclusion: PC-MRI derived PVR correlates well with the degree of stenosis.The PVR at sections close to the stenosis has a strong diagnostic value to differentiate mild to severe stenosis.Part ? Correlation of Post-to Pre-stenosis Peak Velocity Ratio from Phase-Contrast Magnetic Resonance Imaging with the Luminal Stenosis Severity in Coronary Artery Disease PatientsObjective: To measure the flow dynamic parameters in coronary artery disease patients by phase-contrast Magnetic Resonance Imaging(PC-MRI),and study the correlation between changes of these parameters with the stenosis severity.Materials and Methods: Phase contrast MRI was carried out on 10 patients with coronary artery atherosclerosis comfirmed previously by computed tomography angiography along with a control group not having coronary artery atherosclerosis.The measurements were done at proximal and distal to the stenosis,including flow rate,mean velocity and peak velocity.The reproducibility of the PC MRI was analyzed by calculating the intra-class correlation coefficient.Paired rank sum test was used to compare the difference in the flow dynamics between proximal and distal coronary arteries.Finally,use the digital subtraction angiography as reference,compare correlation between the pro to pre velocity ratio with the stenosis severity,and use ROC analysis to study the diagnostic power of PVR in differentiating severe stenosis that need further revascularization therapy.Results: High inter-scan agreement was found for indices describing coronary flow rates and peak velocities(intraclass correlation coefficient>0.7).In the control group,the flow rates,mean velocities andpeak velocities measured at proximal and distal sections of the left anterior descending artery had no difference.In the patients group,the flow rates and mean velocities measured at proximal and distal stenosis had no difference,but the post and pro stenosis peak velocity had statistically difference(p<0.05).The post to pre stenosis peak velocity ratio had a correlation with the stenosis severity using the DSA result as reference.ROC analysis of PVR to differentiate severe stenosis show high diagnostic value(AUC>0.8).Conclusion: PC MRI measurements had a high reproducibility.Post to pre stenosis PVR has statistically difference.The PVR may be an alternative method to detect stenosis in coronary artery atherosclerosis.