Influence of bright intramural echoes on estimates of ultrasonic attenuation from backscattered ultrasound in excised myocardium

The purpose of this study was to quantitate the influence of bright intramural echoes on estimates of myocardial attenuation from analyses of backscattered ultrasound. To achieve this, M-mode image-based measurements of the inherent anisotropic properties of myocardial attenuation were performed on rotating myocardial specimens. The approach was to use a commercially-available ultrasonic imaging system to acquire M-mode images of 24 excised cylindrical specimens from six formalin-fixed lamb hearts for data analysis using a video signal analysis technique. As a control, through-transmission rf-based measurements were performed concurrently using a pair of focused, single-element ultrasonic transducers. We devised an objective approach to compensate M-mode results for the presence of bright intramural echoes that makes use of the rotational symmetry of the measurements. A comparison of the uncompensated and compensated estimates of attenuation shows that the effect of bright intramural echoes under the conditions of this study increases the average error in M-mode results by approximately 240% compared with that observed when such effects are minimized by compensation. For both uncompensated and compensated M-mode results, increased temporal averaging shows only a modest reduction in average error. These data suggest that for measurements of attenuation from backscattered ultrasound using M-mode images, the effects of bright intramural echoes can be a significant source of error despite increased temporal averaging and therefore may require compensation.