A catheter apparatus for obtaining an image of internal surface characteristics of a vascular vessel is provided. The catheter apparatus comprises an tubular element adapted for insertion into the vascular vessel, a non-rotating acoustic waveguide disposed within the tubular element and coupled to a source of an ultrasonic signal located external to the vascular vessel, and an acoustically driven turbine. The turbine is responsive to the ultrasonic signal for directing the ultrasonic signal in a rotating pattern from a distal end of the acoustic waveguide through the tubular element at an angle relative to an axis of the vascular vessel. The ultrasonic signal includes a low frequency ultrasonic signal and a high frequency ultrasonic signal. The low frequency ultrasonic signal drives the acoustically driven turbine to direct the high frequency ultrasonic signal in the rotating pattern. The acoustically driven turbine comprises a plurality of turbine blades, and either an acoustic reflecting surface or an acoustic refracting lens. At least one transducer disposed external to the vascular vessel provides the source of the high and the low frequency ultrasonic signals. The tubular element may further be provided with a lumen for carrying a guidewire.