A system employing ultrasound imaging as a method to localize a patient's tissue volume to be treated prior to applying therapeutic levels of ultrasound energy includes a therapy transducer for producing high-intensity fields that cause necrosis and an imaging transducer for producing high-quality ultrasound images. The therapy transducer is a spheroidal piezoelectric element and the imaging transducer is made up of a plurality of piezoelectric elements mounted in fixed relationship to the therapy transducer. The therapy transducer transmits a beam that is focused at a location in the tissue to be treated. The imaging transducer is then steered to produce successive receive beams which scan the tissue, including the tissue at the focal point of the pulsed therapy transducer. The image of the focal point is then superimposed on an image of the tissue to be treated obtained by B-mode imaging using the imaging transducer to transmit and then receive. Proper alignment of the focal point and the tissue to be treated ensures proper positioning of the therapy transducer relative to the patient.