An intravascular ultrasound (IVUS) imaging device comprising: a flexible elongate member configured to be positioned within a lumen of a vessel of a patient, the flexible elongate member comprising a proximal portion and a distal portion; an imaging assembly disposed at the distal portion of the flexible elongate member , the imaging assembly including: a plurality of first ultrasound transducers configured to operate at a first center frequency, the plurality of first ultrasound transducers being disposed in a first arrangement linearly parallel to a longitudinal axis of the flexible elongate member , forming a linear transducer array; and a plurality of second ultrasound transducers configured to operate at a second center frequency different from the first center frequency, the plurality of second transducers being annularly disposed in a second arrangement around the longitudinal axis of the flexible elongate member , forming an annular transducer array; wherein the first ultrasound transducers are configured to generate Doppler ultrasound image data and wherein the second ultrasound transducers are configured to generate grayscale ultrasound image data; wherein the first and second arrangements provide a first field of view and a second field of view respectively, wherein the first field of view is adapted for imaging the blood flowing through the lumen and the second field of view is adapted for imaging the vessel in depth. a flexible elongate member configured to be positioned within a lumen of a vessel of a patient, the flexible elongate member comprising a proximal portion and a distal portion; an imaging assembly disposed at the distal portion of the flexible elongate member , the imaging assembly including: a plurality of first ultrasound transducers configured to operate at a first center frequency, the plurality of first ultrasound transducers being disposed in a first arrangement linearly parallel to a longitudinal axis of the flexible elongate member , forming a linear transducer array; and a plurality of second ultrasound transducers configured to operate at a second center frequency different from the first center frequency, the plurality of second transducers being annularly disposed in a second arrangement around the longitudinal axis of the flexible elongate member , forming an annular transducer array; a plurality of first ultrasound transducers configured to operate at a first center frequency, the plurality of first ultrasound transducers being disposed in a first arrangement linearly parallel to a longitudinal axis of the flexible elongate member , forming a linear transducer array; and a plurality of second ultrasound transducers configured to operate at a second center frequency different from the first center frequency, the plurality of second transducers being annularly disposed in a second arrangement around the longitudinal axis of the flexible elongate member , forming an annular transducer array; wherein the first ultrasound transducers are configured to generate Doppler ultrasound image data and wherein the second ultrasound transducers are configured to generate grayscale ultrasound image data; wherein the first and second arrangements provide a first field of view and a second field of view respectively, wherein the first field of view is adapted for imaging the blood flowing through the lumen and the second field of view is adapted for imaging the vessel in depth. <EOS>