In vivo quantification of myocardial echo intensity from logarithmically amplified, demodulated radiofrequency signals

Clinical application of echocardiographic tissue characterization necessitates measurements through the chest wall. Different distances between transducer and myocardial region of interest result in variable attenuation effects. Therefore, meaningful comparisons of myocardial echo intensity measurements are difficult with current equipment. The present study aims at the quantification and compensation of depth-dependent attenuation effects. Ten normals, 14 patients with mild (n = 7) or moderate (n = 7) hypertensive left ventricular hypertrophy and 10 transplant candidates were examined. Gain-independent logarithmically amplified, demodulated radiofrequency signals of parasternal long axis cross-sections were digitized. Mean myocardial echo intensities were determined in septal and posterior wall regions of interest. The slope of attenuation was determined from these clinically obtained data by plotting the distances between transducer and regions of interest against myocardial echo intensities. An attenuation coefficient derived from this slope was used for compensation of the depth-dependent losses of myocardial echo intensity. Compared with normals, compensated mean myocardial echo intensities were significantly lower in mild or moderate hypertensive left ventricular hypertrophy, but showed no significant difference in transplant candidates. Despite several limitations, the method employed in this study appears to be a possible approach to in vivo quantification and compensation of attenuation.