1. An intravascular ultrasound imaging system, comprising: a catheter having an elongated body having a distal end and an imaging core arranged to be inserted into the elongated body, the imaging core being arranged to transmit ultrasonic energy pulses and to receive reflected ultrasonic energy pulses; and an imaging engine coupled to the imaging core and arranged to provide the imaging core with energy pulses to cause the imaging core to transmit the ultrasonic energy pulses, the energy pulses being arranged in repeated sequences and wherein the energy pulses of each sequence have varying characteristics.