1. A medical image diagnostic system comprising: a medical imaging apparatus for acquiring a radiation image of an object to be inspected projected on a projection surface by applying radiation to the object, acquiring an ultrasonic slice image of the object along a slice surface substantially orthogonal to said projection surface by transmitting ultrasonic waves toward the object and receiving ultrasonic echoes reflected by the object, and generating first image data representing plural ultrasonic slice images along plural slice surfaces, second image data representing at least one radiation image, and location data representing locations of said plural slice surfaces on said projection surface; a medical image storage apparatus for correlating and storing the first image data, the second image data, and the location data generated by said medical imaging apparatus; and a medical image display apparatus for displaying at least one ultrasonic slice image along at least one slice surface based on the first image data loaded from said medical image storage apparatus, and displaying at least one radiation image, on which a marker indicating a location of said at least one slice surface on said projection surface is shown, based on the second image data and the location data loaded from said medical image storage apparatus.