A miniature ultrasound imaging probe that may be delivered through the biopsy channel of an endoscope. The probe includes a probe tip mounted at the distal end of a flexible catheter. The probe tip includes a transducer body mounted on the distal end of a distal actuating rod with the transducer body carrying an ultrasound transducer. The distal actuating rod is mounted on the distal end of a plurality of concentric, springs wound in opposite directions extending concentrically through the catheter and terminating in a proximal actuating rod. A flexible bag filled with an acoustic coupling fluid is mounted at the distal end of the catheter. The bag surrounds the transducer body to isolate it from the external environment and retain the acoustic coupling fluid. When the probe is to be inserted through a narrow passage, the proximal actuating rod is advanced into the catheter to extend the transducer body against the flexible bag. As a result, the bag elongates and its width is reduced. When the probe is to be used for imaging, the proximal actuating rod is retracted to withdraw the transducer body away from the bag and allow the bag to expand radially so that it can conform to a surface through which an image is to be obtained.