A parameter calculating unit calculates a parameter value at each time through an interpolation process based on a parameter value at a telediastole stored in a telediastole memory and a parameter value at a telesystole stored in a telesystole memory. An interpolation coefficient memory stores an interpolation coefficient which is used for the interpolation process. When the parameter calculating unit calculates, for each parameter, parameter values of the times from telediastole to the telesystole, a region-of-interest setting unit sets, for each time, a three-dimensional region of interest in the three-dimensional data space based on the plurality of parameters. With this process, a three-dimensional region of interest which dynamically changes from the telediastole to the telesystole is set in the three-dimensional data space.
