A method of operating an ultrasound catheter includes providing an elongate catheter body having at least a first lumen； providing a housing coupled with a proximal end of the elongate catheter body, the housing having an inner cavity； providing a fluid inlet in fluid communication with at least one of the first lumen and the inner cavity； providing a sonic connector coupled to a proximal portion of an ultrasound transmission member； providing vibration absorption O-rings disposed in the inner cavity around at least a portion of the ultrasound transmission member, the plurality of vibration absorption O-rings being located distal to the sonic connector； and delivering fluid to the fluid inlet to supply the fluid at least distally into the first lumen of the elongate catheter body to dissipate heat received from the ultrasound transmission member in the first lumen of the elongate catheter body.
