ON THE EFFECT OF LUNG FILTERING AND CARDIAC PRESSURE ON THE STANDARD PROPERTIES OF ULTRASOUND CONTRAST AGENT

The goal standard of contrast echocardiography is the absolute measure of myocardial perfusion using a contrast agent. Actually, several con trast agents are developed. All these agents show left ventricular opa cification after intravenous injection. However, none of these agents shows an acceptable enhancement of the myocardium yet using convention al imaging techniques. The explanation of this phenomenon should be ea sy by measuring the acoustic characteristics of the contrast agent and then making a comparison of these characteristics with those of the m yocardium. In this study we present definitions of standard acoustic p arameters of ultrasound contrast agent, the backscatter coefficient B- s and the scattering-to-attenuation ratio STAR. Afterwards, considerin g an intravenous injection of the contrast agent, and taking into acco unt the effects of lung filtering and cardiac pressure, the standard p roperties of contrast agents are determined in different sites: right ventricle (before lung passage), left ventricle (after lung passage an d taking into account the pressure effect) and in the coronary system. Calculations showed that the acoustic properties are considerably inf luenced by these two effects: lung filtering and cardiac pressure. Com parison of these properties with the tissue properties (myocardium) is then performed. This determines the contribution of the contrast agen t to the enhancement of the tissue visualization. The simulations are performed on Albunex microspheres. The results reveal that the differe nce between scattering of the myocardium and scattering of intravenous ly injected Albunex is too slight to be visible on an echographic imag e. (C) 1998 Elsevier Science B.V.