Disclosed are an imaging system (10) or an interventional tool, such as a catheter (20), having a first ultrasound transducer array (23) and a second ultrasound transducer array (21) spaced by a fixed distance (D) from each other; wherein both arrays may be used to generate diagnostic images; and a processing arrangement (31, 32) to process a first sensor signal indicative of the first array imaging a reference location (X) at a first point in time, and to process a second sensor signal indicative of the second array imaging the reference location at a second point in time; and determine a translation (pullback) speed of the catheter from the set distance and the difference between the first point in time and the second point in time. Alternatively, a catheter may be provided comprising an ultrasound transducer array at a distal end of the catheter, and two pressure sensors for determining the translation speed.