ANISOTROPY OF THE SLOPE OF ULTRASONIC-ATTENUATION IN FORMALIN-FIXED HUMAN MYOCARDIUM

Clinical implementation of quantitative ultrasonic tissue characteriza tion is likely to require imaging the heart with sound propagating at varying angles relative to the fibers of the heart. Under these circum stances, the variation of the ultrasonic properties of myocardium with the angle of propagation relative to the myofibers may represent a si gnificant source of potential misinterpretation. In the present study, the systematic approach of assessing the impact of anisotropy on quan titative myocardial tissue characterization is extended by reporting r esults of a recent in vitro study to measure the anisotropy of the slo pe of ultrasonic attenuation in specimens of formalin fixed human myoc ardium. Data obtained from regions of remote infarct are presented and compared to data acquired from regions identified to be free of infar ct. The slope of attenuation for both regions exhibit a sinusoid-like dependence on angle that is approximately doubled for propagation para llel to the fibers as compared to perpendicular. These results are, in turn, compared to an earlier study from the laboratory that examined the effects of myocardial infarction on ultrasonic attenuation and int erstitial collagen content in freshly excised canine hearts. Discussio n regarding the analysis and interpretation of measurements of slope o f attenuation is presented as well as a discussion of the possible inf luence of formalin fixation on our results. (C) 1996 Acoustical Societ y of America.