Abstract
Recently developed imaging modalities based on the nonlinear response of contrast agents are dependent upon the local acoustic pressure. Thus, regional variations of acoustic pressure arising from myocardial anisotropy can result in nonuniform ‘‘apparent perfusion’’ in the absence of a perfusion defect. Measurements of regional variation of myocardial attenuation in the septum and lateral walls of excised sheep hearts are reported. Studies were carried out on hearts obtained immediately after slaughter from 8 healthy adult sheep. These measurements of attenuation were carried out in orientations analogous to those encountered in the apical four-chamber view, which is the preferred view for clinical studies of myocardial perfusion using contrast-agent-enhanced echocardiography. The video signal analysis method introduced by the University of Wisconsin group was used to analyze data obtained with a commercially available (ATL) clinical scanner using a linear array (L 7-4) operating in fundamental mode. Tissue mimicking phantoms were imaged under identical conditions. Normalizing sample data by reference data from the phantoms yields quantitative estimates of slope of attenuation. Results of these experimental measurements document significant transmural variations in attenuation that could lead to apparent perfusion anomalies in contrast-agent-mediated estimates of regional myocardial perfusion. [Work supported by NIHHL40302.]
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