A tissue-ablation method and apparatus are disclosed. The apparatus includes a plurality of RF ablation electrodes, and a plurality of sensor elements, each movable from retracted to deployed positions in a tissue to be ablated. A control device in the apparatus is operatively connected to the electrodes for supplying an RF power to the electrodes, to produce tissue ablation that advances from individual-electrode ablation regions to fill a combined-electrode ablation volume. The control device is operatively connected to the sensor elements for determining the extent of ablation in the regions of the sensor elements. The supply of RF power to the electrodes can thus be regulated to control the level and extent of tissue ablation throughout the combined-electrode volume. The electrodes are preferably hollow-needle electrodes through which liquid can be infused into the tissue, also under the control of the control unit, to modulate and optimize tissue ablation.