Significance of acoustic field for the myocardial opacification by intravenous contrast echocardiography

Abstract

Purpose: Myocardial opacification is not always homogeneous even in a normal heart. The aim of this study is to clarify why myocardial opacification is faint at the lateral side of the field or at the part far from the focus point.Methods: In canine study, videointensity of the opacification at septal and lateral walls of the short axis view was examined by using both electric and mechanical transducers. In in vitro study, acoustic pressure at several points away from the beam direction was measured using a hydrophone in a water tank. In particular, the effect of position of focus point was evaluated with an electronic transducer.Results: In canine experiment, myocardial opacification of the lateral wall was faint with the electronic transducer, however the mechanical one obtained homogeneous opacification. In vitro, using the electronic type the acoustic pressure was low as the beam shifted, laterally, whereas it was almost uniform in the mechanical type. With the electronic type, moreover, the beam width at the near field was not sharp when the focus point was far, resulting in execessive acoustic pressure.Conclusion: To obtain homogeneous opacifiction, a homogeneous acoustic field is indispensable.