A Comparison between Methods Used to Extract Maximum and Minimum Myocardial Velocities by Spectral Pulsed-TDI

Background: Tissue Doppler imaging is an echocardiographic usefulmethod in the assessment of left ventricularmyocardial function in the clinical condition. Pulsed Doppler interrogationmeasures the instantaneousvelocities of the myocardium which passes through the sample volume during thecardiac cycle.Objective: The present study attempts to verify a computerized method todetermine myocardial maximum andminimum velocities throughout the cardiac cycles using spectral pulsed-tissueDoppler imaging. The data ofcurves might be used to calculate myocardial physical and mechanical parametersthroughout the cardiac cycle.Methods: Spectral pulsed-TDI was performed to evaluate longitudinalfunction in 23 healthy volunteers by usinga sample volume placed in 170 left ventricular segments. The velocities wereextracted automatically basedon four common edge detection algorithms using Matlab software. Labeling ofconnected components in boundaryof spectrum allowed comparing the methods. In addition to analysis of varianceand t-test, linear correlationand Bland-Altman analysis were calculated to assess the relationships andagreements between the systolic anddiastolic results of measurements before and after using the computed program.Results: Comparison of the means of the four edge detection methodsshowed that there are statistically signifi-cant differences between methods (number of labels were 12 3 for Canny, 20 4 forRoberts, 31 4 for Sobel and39 5 for Prewitt respectively, P<0.05). There were not significant differencesbetween measured velocities in thesegments; before and after application of the Canny method. There wassignificant correlations (r=0.99 andr=0.96, P=0.01) at the base and mid segments, respectively with Bland-Altmananalysis significant agreementsbetween the measurements.Conclusion: It is concluded that the proposed method automaticallyextracts myocardial velocities using spectralpulsed images. Canny method showed relatively favorable results and seems to bea preferable option toextract velocities from the spectral images. Correlation study and Bland-Altmananalysis confirmed a goodagreement between the measurements.