Physical factors influencing quantitation of two-dimensional contrast echo amplitudes.

Measurement errors that may interfere with quantitation by the new myocardial contrast two-dimensional echocardiographic technique were examined in a simplified in vitro model consisting of a 50 cc blood-filled balloon with supplemental controlled injection of 0.2 to 2.6 cc of sonicated dextrose 70%. The blood-contrast mixture in the balloon volume was imaged with two-dimensional echocardiography and discrete regions were studied for both magnitude and time course of echo intensities. Preliminary evidence indicates that a regional contrast echo intensity measurement is significantly modified by contrast-related ultrasound attenuation in intervening regions and by the amount and mode of contrast material injection. Thus, injection of 1.2 cc contrast material resulted in substantially higher peak echo intensity and a more rapid decay than injection of 0.8 or 0.6 cc. These measurements were also found to be influenced by the echographic system signal processing and time-gain compensation which contribute to nonlinear and unevenly compensated image distribution of echo amplitudes. Other factors are discussed, including transducer-related image resolution and image texture, contrast agent bubble size and persistence and computer methods for standardized selection of region of interest and analysis of the regional contrast intensity decay curve.