1. An ultrasonic diagnostic imaging system for the qualitative or quantitative analysis of tissue perfusion comprising: an array transducer adapted to transmit and receive scanlines over a volumetric region containing tissue which may have a perfusion defect; a beamformer, coupled to the array transducer, which acts to produce image data of a plurality of elevationally distinct slices of the volumetric region; a slice memory, coupled to the beamformer, which stores slice image data; a combiner, coupled to the slice memory, which combines slice image data in the elevation direction; a perfusion detector which operates on the combined slice image data to qualitatively depict perfusion by the concentration of microbubbles in tissue or to produce a quantified perfusion parameter for a region of tissue; and a display responsive to the perfusion detector for displaying at least one of a tissue image with perfusion depicted by color or brightness, or a quantified perfusion parameter for a region of tissue.