Ultrasound endoscope having ultrasound probe in combination with endoscopic observation system

An ultrasound endoscope system, comprising:

• an endoscope having a rotatable fore end section forward of a rigid non-rotatable section of an endoscopic insertion rod, said rotatable fore end section having an observation window and being rotatable about a longitudinal axis of said insertion rod to turn said endoscopic observation window at the distal end thereof;
• an ultrasound probe to be introduced into a body cavity through said endoscopic insertion rod and into said fore end section, and having an ultrasound transducer at the distal end thereof for making radial scans independently of rotational movements of said movable fore end section of said endoscopic insertion rod:
• an angle detection means for detecting a rotational angle of said rotatable fore end section of said endoscopic insertion rod with respect to said non-rotatable section when the rotatable fore end section is operated to turn view field of said endoscopic observation window and generating a signal representative of said angle;
• and
• an ultrasound image rotating means for turning a view field of a radial scan ultrasound image provided by said transducer on a monitor screen through an angle commensurate with a rotational angle of said rotatable fore end section of said endoscopic insertion rod on the basis of said signal from said angle detection means.