A common problem in the elaboration of biomechanical models is determining the properties and characteristics (measures) of the physical behavior of in vivo tissues in the human body. Correct estimates must be made of the tissue's physical properties and its surroundings. We suggest a method to compute the constitutive modeling of venous tissue, for every specific patient, from clinically registered ultrasounds images. The vein is modeled as a hyperelastic, incompressible, thin-walled cylinder and the membrane stresses are computed using strain energy. The approach is based on a strain-energy function suggested by Holzapfel capturing the characteristic nonlinear anisotropic responses of femoral veins with its collagen fibers.