Comparison of regional myocardial velocities assessed by quantitative 2-dimensional and M-mode color Doppler tissue imaging: Influence of the signal-to-noise ratio of color Doppler myocardial images on velocity estimators ofthe Doppler tissue imaging system

M-mode color Doppler imaging of the myocardium affords a greater sampling r ate and signal-to-noise (S/N) ratio than 2-dimensional (2D) imaging. In thi s study, we compared myocardial velocities assessed by 2D and ill-mode Dopp ler tissue imaging (DTI) at the same site and evaluated the influence of th e S/N ratio on velocity estimates of the currently used DTI systems. In pat ients with and without impaired regional left ventricular function, myocard ial velocities assessed by 2D DTI were lower than those obtained with M-mod e DTI. The difference between regional velocities derived from both imaging techniques was positively correlated with the extent of the "black zone," which could be considered as indirectly reflecting the S/N ratio for each f rame. Thus in the clinical setting and on currently used echocardiographs, 2D DTI may provide underestimated regional myocardial velocities when compa red with M-mode, mainly because of the influence of the lower sampling rate and S/N ratio on velocity estimators of the imaging system.