ANISOTROPY OF THE TRANSVERSE-MODE ULTRASONIC PROPERTIES OF FIXED TENDON AND FIXED MYOCARDIUM

This study investigates the influence of the fiber-reinforced nature o f myocardium and tendon on the propagation of transverse mode ultrason ic waves. Formalin fixed specimens of normal human left ventricular ca rdiac muscle and bovine Achilles tendon were prepared for this study i n such away that transverse mode ultrasonic waves could be propagated perpendicular to the fiber axis of the tissue with the polarization or iented either parallel or perpendicular to the fiber. axis. Measuremen ts of velocity and attenuation were made at 3 MHz to assess the degree of anisotropy in these parameters for both tissues, Formalin fixed te ndon exhibited a significant anisotropy whereas formalin fixed myocard ium displayed a similar trend of more modest magnitude. Results of the se measurements were used to compute two elastic stiffness coefficient s for each tissue, yielding c(44) = 37.2 MPa and c(66) = 18.0 MPa for formalin fixed tendon, and c(44) = 8.97 MPa and c(66) = 8.45 MPa for f ormalin fixed myocardium. To-validate this approach, additional studie s were conducted to measure the transverse mode ultrasonic properties of silicone rubber and motor oil. (C) 1996 Acoustical Society of Ameri ca.