An intravascular ultrasound device (12) comprising an array (16) of ultrasound transducer elements (18) which extends in a longitudinal (22) and annular (20) direction along and around the device body (14). The device includes control electronics which allow the array to driven either as a set of longitudinally oriented (28) subgroups of elements (e.g. each including one or more rows of the array), or as a set of annularly oriented subgroups (26) of elements (e.g. each including one or more columns of the array). By switching between these two different operation modes, two different functions can be performed using the same single unitary array of elements: either cross-sectional imaging in the longitudinal mode, or blood flow sensing in the annular mode.
