Beamforming to image an object (310), such as an interventional tool, is enhanced by initializing the beamformer (308) with the object's location, and optionally its orientation. The initializing uses an estimate of the location/orientation. The estimate is derived from the output of one or more sensors (304, 306). These are disposed external to the imaging array (316) that operates with the beamformer. The estimate is made without the need for a result of any imaging based on data arriving by reflected ultrasound. One or more of the sensors may be attached to the object, which may be elongated, as in the case of a needle or catheter used in medical diagnosis and treatment. In some implementations, one or more of the sensors are attached to the imaging probe (302). The sensors may be, for example, ultrasound, electromagnetic, optical, or shape sensors. Alternatively, ultrasound transmitting transducers may be substituted for the ultrasound sensors.