The Development of a Low-Cost Laser Reflectance System to Determine the Cross-Sectional Shape and Area of Soft Tissues

Determination of mechanical properties (stress-strain relationships) of ligaments and tendons is dependent on the method used to measure the cross-sectional area for tissue stress calculations. Current methods include the constant pressure area micrometer [1], the “molding technique” [3], and the laser micrometer system [2, 4]. The first two methods require mechanical contact with the specimen. Although the laser micrometer, developed in our laboratory, is a non-contact image reconstruction method, it can introduce errors when the tissue has a complex cross-section that includes concavities. The laser micrometer system also is quite expensive. To overcome these limitations, we developed a system using a laser reflectance transducer to determine the cross-sectional shape and area of geometrically complex soft tissues. This system uses reflected laser radiation for specimen measurements and thus can detect all concavities. This report describes the system, the developed reconstruction algorithm, and the method used to evaluate standard cross-sectional shapes and areas as well as those for the porcine anterior cruciate ligament (ACL).