Bulk modulus and volume variation measurement of the liver and the kidneys in vivo using abdominal kinetics during free breathing.

This article presents a method of predictive simulation, patient-dependant, in real time of the abdominal organ positions during free breathing. The method, that considers both influence of the abdominal breathing and thoracic breathing, needs a tracking of the patient skin and a model of the patient-specific modification of the diaphragm shape. From a measurement of the abdomen viscera kinematic during free breathing, we evaluate through a finite element analysis, the stress field sustained by the organs for a hyperelastic mechanical behaviour using large strain theory. From this analysis, we deduce an in vivo Poisson's ratio and a homogeneous bulk modulus of the liver and kidneys, and compare it to the ones in vitro available in the literature.