Karaciğer dokusu kırılma tokluğunun tespiti: deneyler ve doğrulama

In several medical procedures such as catheter insertion, robotic-guided needle placement, suturing, cutting or tearing, and biopsy, fracture toughness of the soft tissue being penetrated, cut, or teared plays a crucial role in force interactions between the surgical tool and the tissue. Although significant amount of experimental work carried out on hard-biomaterials, such as bone and dentin to estimate their fracture toughness, the number of studies on soft tissues is very limited and the estimated values show large variations. In this study, we show that the toughness values estimated in the earlier studies show large variations because the effect of puncturing/cutting tool geometry on the results has been mostly neglected. To prove our argument, needle insertion experiments are performed on 3 bovine livers with 4 custom-made needles having different diameters. A unique value for the fracture toughness of bovine liver is obtained by curve fitting to the toughness values estimated from the insertion experiments for different needle diameters (J = 164 ± 6 J/m2). In order to validate the experimental results, finite element (FE) simulations are performed. For this purpose, we first collect experimental data from the bovine livers via static indentation and ramp and hold experiments to estimate their hyper-viscoelastic material properties through an inverse FE solution. Then, we simulate needle insertion into the FE model of each liver using the energy-based fracture mechanics approach. The force responses obtained through the FE simulations for different needle diameters show an excellent agreement with the ones acquired through the physical experiments.