A method of in-vitro measurement of the cross-sectional area of soft tissues, using ultrasonography

Accurate measurement of the cross-sectional area of tendons and ligaments is essential in determining the mechanical properties of biological specimens. We measured these cross-sectional areas in rabbit specimens in vitro, using ultrasonography, in order to evaluate the usefulness of this method as a noncontact measurement technique. The cross-sectional areas of a rabbit's Achilles tendon, medial collateral ligament (MCL), and anterior cruciate ligament (ACL) were measured by means of ultrasonography, digital calipers, and computerized image analysis. For each of these three soft tissues, there was a high correlation between the values yielded by digital calipers and ultrasonography, and there was no significant difference in the values obtained by these three methods. Ultrasonography can detect the concavities on the surface of a specimen such as the ACL, because the shape of the specimen's transverse sonogram resembles its cross-sectional shape on a photograph. We concluded that the values yielded by ultrasonography were acceptable, and that ultrasonography is a useful noncontact measurement technique.