Dietrich Hassler

Method and apparatus for adaptive focusing in a medical ultrasound imaging apparatus

A sectional plane of the examination subject is first scanned by focused ultrasound transmission beams in an adaptation phase. Disturbing effects from the reflected echo signals which are caused by the inhomogenities in the tissue are thereby measured. In this adaptation phase, correction values for the delay time of the signals of the elemental transducers of the ultrasound array in comparison to the standard focusing are also derived from the measured values. In a following B-image imaging phase, the delay times of the active aperture are then varied dependent on the correction values during the emission and/or during reception. The disturbing effects are thereby compensated. A method and apparatus are disclosed which are especially well-suited for linear array systems and for patients having inhomogeneous tissues.

Shockwave source having a centrally disposed ultrasound locating system

A shockwave source of the type wherein a shockwave is generated by rapid electromagnetic repulsion of a membrane by a rapidly energized coil has a central opening extending through the membrane and the coil. An ultrasound head of an ultrasound transmission and reception system is received in the opening. The ultrasound head is disposed in a mount which is rotatable around its longitudinal axis by a rotary drive. In one embodiment of the shockwave source, the shockwave source also has a focusing device disposed in front of the membrane, and in this embodiment the focusing device also has a central opening in which the ultrasound head is received. The ultrasound head has a distal end in contact with a liquid coupling agent for promoting transmission to, and reception from, a patient to which the shockwave source is coupled. The shockwave source is particularly suited for lithotripsy treatment of gallstones.

Lithotripter with locating system integrated therewith and method for its use

A lithotripter for disintegrating a calculus in the body of a patient has a shock wave source which emits shock wave pulses which are focussed to the calculus by an acoustic lens. As seen in the propagation direction of the shock wave pulses, a semi-transmissive acoustic mirror is disposed in front of the acoustic lens at a fixed angle. An ultrasound transducer, which is part of an ultrasound locating system, such as an ultrasound sector scanner, is disposed laterally with respect to the acoustic mirror, so that ultrasound waves are transmitted by the transducer to the calculus, and the reflected waves are transmitted from the calculus to the transducer, reflected by the acoustic mirror. Shock wave pulses from the shock wave source are only minimally impeded by the mirror, so that the therapy is substantially uninfluenced by the presence of the mirror. The ultrasound signals are used to identify the position of the calculus in the patient, so that the position can be continuously observed, even during the time in which the shock pulses are acting on the calculus. The approach path of the shock wave pulse to the calculus can also be ultrasonically monitored.

Apparatus for generating acoustic rarefaction pulses

An apparatus for generating acoustic rarefaction pulses, i.e., a negative pressure pulse, has a pressure pulse source and reflector having a negative reflection factor, and an acoustic propagation medium filling the space between the pressure pulse source and the reflector. The reflector has a boundary surface facing toward the pressure pulse source, consisting of a medium which is acoustically soft in comparison to the acoustic propagation medium. The boundary surface medium is separated from the acoustic propagation medium by a wall which is impenetrable by the acoustic propagation medium.

Shock wave source having central locating system & disposed in a cavity free of shock waves

A shock wave source for disintegrating a calculus has a centrally disposed cavity in which a locating system for identifying the position of the calculus is disposed. The shock wave source has an emission surface, from which shock waves are emitted into a coupling agent in the shock wave source. The emission surface is angled in the direction of shock wave propagation, so that the shock waves emitted therefrom diverge. A focusing element is provided which focuses the shock waves onto the calculus, the focusing element having a structure which, in addition to focusing the shock waves, compensates for the divergence of the shock waves. Due to the divergence of the shock waves, the central cavity in which the locating system is disposed is maintained free of shock waves.

Adaptive Beamforming for Correction of Velocity Fluctuations Close to the B-Scan-Array

It is well known from the literature1 that velocity fluctuations across the active aperture of a linear array for B-scan-imaging can give rise to image degradation. Various methods have been proposed and tested to compensate for image blurring of this origin. We have investigated a method very similar to the one published by O’Donnel and Flax2 in 1988. Results showing up the merits and limits of our method named “adaptive antenna”3 are to be presented in this report.