Transcutaneous ultrasonography is an established procedure for diagnosis and therapy in gastroenterology. However, ultrasonic images can often be hampered by pulmonary and intestinal gas and by bony and adipose tissue. In 1956 Wild and Reid reported the first results of transrectal ultrasound of the prostate 1]. In 1976 Lutz introduced an A-mode ultrasonic probe which could be introduced via the biopsy channel of an endoscope 2]. In 1978 and 1980 Hisanaga performed echocardiography using an ultrasonic transducer attached to the tip of a flexible instrument 3, 4]. In animal studies and...