FACTORS AFFECTING THE ULTRASONIC PROPERTIES OF EQUINE DIGITAL FLEXOR TENDONS

The velocity, attenuation and apparent backscattering coefficient of 6 -11-MHz ultrasound were measured in three orthogonal directions in equ ine deep digital flexor (DDF) and superficial digital flexor (SDF) ten dons at 0 degrees C. Ultrasonic measurements were examined for correla tion with tendon water, collagen, DNA and glycosaminoglycans contents, determined by chemical analyses and with structure observed by scanni ng electron microscopy. The SDF tendon contained more water, more DNA (i.e., more cells), less collagen and less glycosaminoglycans and exhi bited lower velocities and attenuations than the DDF tendon. Velocitie s were governed primarily by the adiabatic bulk modulus and density, p erturbed by a highly direction-dependent rigidity. Ultrasound propagat ing across tendon generated frequency-independent backscattering which appeared to derive from the large interfaces between the fascicles, w hile along the fibres backscattering varied as f(3.62 +/- 0.88) and ap peared to derive from small structures such as collagen fibres. The me chanisms by which ultrasound is attenuated by tendon remain unknown.