1. A method for ultrasonically measuring a volume of a heart in real time comprising: repetitively acquiring ultrasonic images of the heart during a heart cycle in two intersecting image planes which extend through the heart in different directions at substantially the same time with an ultrasound probe; using an automated processor to define corresponding object borders in the ultrasonic images during the heart cycle; producing a plurality of quantified measures of the volume of the heart during the heart cycle from the defined object borders in the different directions; and displaying measures of a continuous change in the heart volume as the heart beats.