Impression technique for the assessment of oedema: comparison with a new tactile sensor that measures physical properties of tissue

To measure tissue oedema, the impression technique and a new tactile sensor technique are compared and evaluated in a silicone rubber model and in an in vivo rat testis model. The principles of the two techniques differ in that the impression technique evaluates interstitial fluid flow FT and peak force F(0) when tissue is compressed, whereas the tactile sensor evaluates the hardness/softness or change in resonance frequency Δf when a vibrating rod is attached to tissue. Both techniques can detect changes in silicone hardness/softness or in hormone-induced changes of testes, interstitial fluid. Although both F(0) and FT are significantly correlated to Δf in the experiments, it is concluded that F(0) is the most promising impression parameter to give valuable information about the hardness of living tissue as compared with Δf. The comparison indicates that the impression technique in the most easy, to interpret, non-invasive tool to assess tissue oedema so far developed.