Lithotripsy in the common bile duct using ultrasound. Preliminary in vitro experiments

In patients with an increased surgical risk, common bile duct stones can be removed with the aid of endoscopic papillotomy. Most stones are either passed spontaneously, or can be drawn out with the Dormia basket. Excessively large stones can first be smashed with the mechanical lithotripter. Some 20% of the stones presenting are, however, too hard to be smashed in this way. A technique was accordingly developed for smashing such bile duct stones using ultrasound. A prerequisite for this technique was the development of an acoustic wave guide that would conduct ultrasound energy even when bent. With this procedure, it will soon be possible to destroy bile duct stones in situ.

Transfer function analysis of a quasioptical ultrasonic imaging system

The imaging properties of lenses have been well analyzed in the optical regime. However, most of these analyses have been confined to two cases: illumination of the object with ideal coherent or ideal incoherent light. In ultrasonics, imaging systems with lenses also are known. But in contrast to the optical case, the object can be easily insonified with waves of variable frequency or with a noise source of adjustable bandwidth. In this paper, the influence of the broad frequency bandwidth in an ultrasonic imaging system is emphasized. A so called "imaging channel transfer function" (ICTF) is introduced to describe all nonelectrical system properties. It is shown that the ICTF is part of a temporal frequency transfer function. This transfer function has a frequency dependence which is not readily attainable with well-known active or passive RLC-networks. Finally, it is demonstrated how to use the ICTF for calculating the image response in a wideband imaging system with ultrasonic sources emitting either deterministic or stochastic signals of a certain bandwidth.

[Ultrasound computer tomography--new image-producing possibilities]

A new technique using ultrasound computed tomography is explained. Reconstruction of pictures follows basically the algorithm of radiology CT in one plane. The computed data of several scan planes with different angles of the same subject are used for image reconstruction. In this manner, poor lateral resolution of reflections is eliminated. The improved quality of the CT ultrasound images is shown.