A clinical apparatus includes a storage to store strain data, strain rate data, or acceleration data measured in a ROI (region of interest); and a data processor to calculate a stress, a stress tensor, a stress tensor component, an inertia, a mean normal stress, a pressure, a mechanical source, an elastic constant, a visco elastic constant, a viscosity, or a density of an arbitrary point within the ROI. The data processor calculates the stress, the stress tensor, the stress tensor component, the inertia, the mean normal stress, the pressure, or the mechanical source based on an equation representing a relation between (i) the stress, the stress tensor, the stress tensor component, the inertia, the mean normal stress, the pressure, or the mechanical source, (ii) the elastic constant, the visco elastic constant, the viscosity, or the density, and (iii) the measured strain data, the strain rate data, or the acceleration data.