Abstract: The invention relates to a method for ultrasonic imaging of an organ in a patient's body through a part of the patient's respiratory tract, including: arranging an ultrasonic imaging device in or on the patient's body; introducing a flexible catheter carrying at least one inflatable member into the respiratory tract; positioning the inflatable member at a predetermined location in the respiratory tract; filling the inflatable member with an ultrasonic transmission fluid through the flexible catheter; and transmitting ultrasonic waves from the imaging device through the transmission fluid in the inflatable member to the organ to be imaged. The inflatable member is positioned in the respiratory tract by manipulating guide means that are attached to or integrated with the flexible catheter. The invention further relates to an ultrasonic imaging system for carrying out this method and to an assembly means for use in such an ultrasonic imaging system.