An intravascular Doppler ultrasonic device (100, 200), comprising: - a catheter body, which extends along a longitudinal direction and is shaped for intravascular insertion into a blood vessel of a living being; - a tip region forming a fraction of the catheter body at a distal end thereof, the tip region being bendable in at least one direction perpendicular to the longitudinal direction; - an ultrasound probe in the tip region, which is configured to emit ultrasonic radiation from the distal end of the catheter body in substantially the longitudinal direction and to receive ultrasound echo radiation from substantially the longitudinal direction and provide a probe signal indicative thereof; - a Doppler spectrum determination unit, which is configured to receive the probe signal and to determine therefrom Doppler spectrum data indicative of a Doppler spectrum of the ultrasound echo radiation; - an actuator in the tip region, which is configured to receive actuation drive power provided through the catheter body and to exert to the tip region a bending moment of a controllable amount; - an actuation controller, which is configured to control actuation drive power delivery to the actuator so as to control the amount of the bending moment; - a Doppler spectrum analysis unit, which is configured to receive the Doppler spectrum data and to determine from it a Doppler signal quality measure indicative of a signal quality of the Doppler spectrum; wherein - the actuation controller is further configured - to determine the actuation drive power in dependence on the determined Doppler signal quality measure, namely, - to control a scanning motion of the tip region within a predetermined scanning range by controlling the actuator for consecutively setting a plurality of bending moments; and - to determine the bending moment to be used for operation by selecting that bending moment which is associated with the determined Doppler signal quality measure that fulfils a predetermined Doppler spectrum selection criterion. - a catheter body, which extends along a longitudinal direction and is shaped for intravascular insertion into a blood vessel of a living being; - a tip region forming a fraction of the catheter body at a distal end thereof, the tip region being bendable in at least one direction perpendicular to the longitudinal direction; - an ultrasound probe in the tip region, which is configured to emit ultrasonic radiation from the distal end of the catheter body in substantially the longitudinal direction and to receive ultrasound echo radiation from substantially the longitudinal direction and provide a probe signal indicative thereof; - a Doppler spectrum determination unit, which is configured to receive the probe signal and to determine therefrom Doppler spectrum data indicative of a Doppler spectrum of the ultrasound echo radiation; - an actuator in the tip region, which is configured to receive actuation drive power provided through the catheter body and to exert to the tip region a bending moment of a controllable amount; - an actuation controller, which is configured to control actuation drive power delivery to the actuator so as to control the amount of the bending moment; - a Doppler spectrum analysis unit, which is configured to receive the Doppler spectrum data and to determine from it a Doppler signal quality measure indicative of a signal quality of the Doppler spectrum; wherein - the actuation controller is further configured - to determine the actuation drive power in dependence on the determined Doppler signal quality measure, namely, - to control a scanning motion of the tip region within a predetermined scanning range by controlling the actuator for consecutively setting a plurality of bending moments; and - to determine the bending moment to be used for operation by selecting that bending moment which is associated with the determined Doppler signal quality measure that fulfils a predetermined Doppler spectrum selection criterion. - to determine the actuation drive power in dependence on the determined Doppler signal quality measure, namely, - to control a scanning motion of the tip region within a predetermined scanning range by controlling the actuator for consecutively setting a plurality of bending moments; and - to determine the bending moment to be used for operation by selecting that bending moment which is associated with the determined Doppler signal quality measure that fulfils a predetermined Doppler spectrum selection criterion.