A transducer subassembly with combined imaging and therapeutic capabilities is disclosed. The subassembly includes heat sinks that are configured to maintain the transducer at a low operating temperature so that the transducer operates at high efficiency and also can handle a wider range of frequencies. The subassembly is also configured to allow cooling fluid to flow past the transducer element. One heat sink in the subassembly also acts as an acoustic matching layer and another heat sink acts as a backing. Alternatively, the second heat sink which acts as a backing is optional. The transducer is configured to transmit at one power level for imaging, and at a second power level for ablating. The transducer may comprise sub-elements transmitting at different power levels. The subassembly may be operated at one power level for imaging and a second power level for ablating.