There is strong evidence that the elastic and the viscous properties of a tissue correlate well with the pathological state of the tissue. These properties could be determined using several methods including a creep method. Creep is a slow progressive deformation of a material under constant stress. The purpose of this paper is to present our preliminary investigation on measuring the loss tangent, i.e. the ratio of the loss modulus and the storage modulus, of different parts of a phantom mimicking a tissue, and differentiate a lesion from the background material based on our model-free technique.