1. An ultrasound imaging catheter, comprising: a catheter body having proximal and distal ends and a diameter limited in size to less than about 10 French (3.3 mm); an acoustic window portion coupled to the distal end of the catheter body, the acoustic window portion having an interior surface; a phased array ultrasound transducer housed within the acoustic window portion, the phased array transducer comprising a long axis and configured so that a gap exists between the phased array ultrasound transducer and the interior surface of the acoustic window; an acoustic coupling fluid filling the gap between the transducer array and the interior surface of the acoustic window; and a rotor portion of an electric drive motor positioned within a sealed thin walled portion of the proximal end of the catheter body and mechanically configured and coupled to the phased array ultrasound transducer so as to rotate the phased array ultrasound transducer about a long axis of the distal end of the catheter body, wherein the sealed thin walled portion of the proximal end of the catheter body is configured to removably slip into an opening of a separate reusable structure, wherein the opening is configured within a reusable stator portion of the electric drive motor positioned within the reusable structure.