Richard Wolf Gmbh

Rainer Riedlinger

Gunther Kurtze

Marko Liebler

Siegfried Ginter

Friedrich Ueberle

Thomas Dreyer

Local tissue areas should be thermally destroyed when using ultrasound thermotherapy. Traditionally, mono-frequency continuous wave ultrasound signals are used to this end. These lead to a non-optimal distribution of heat or to a non-optimal localization of the heating inside the tissue. In practice, the following dosage problem arises: the prevention of unwanted tissue damage in the tissue located in front of the target area while simultaneously having a sufficiently high damaging effect in the target area. The aim of the invention is to optimize the distribution of heat or to increase the localization of the heating. To these ends, modified transmitted signals (e.g. multi-frequency signals) are used that are adapted to a specific utilization of the non-linear ultrasound propagation and attenuation properties inside the tissue. This enables, while limited to the target area, a non-linear heating yield caused by non-linear ultrasound effects to be achieved that drastically improves the localization of the heating. Due to this optimization, the problem of dosage is substantially eased, and it is possible to thermally destroy even deep-lying tumors without unwanted burning of the tissue located in front of the tumors. This results in both improving the practical usability of ultrasound thermotherapy and in further reducing the side effects thereof.

Method for effecting local increases in temperature inside materials, particularly body tissue

A device for generating sonic signal forms for limiting, preventing or regressing the growth of pathological tissue comprises an ultrasonic transmission system for transmitting sound waves, focussed on the tissue to be treated, by way of a coupling medium. An ultrasonic signal produced at the focus of the system comprises brief pulses having at least one rarefaction phase with a negative sonic pressure amplitude with a value greater than 2.times.10.sup.5 Pa. The ultrasonic signal is radiated with a carrier frequency exceeding 20 kHz, a sonic pulse duration T of less than 100 .mu.s and a pulse recurrence rate of less than 1/(5T). The device produces controlled cavitation in the tissue to be treated.

Ultrasonic treatment of pathological tissue

A piezoelectric transducer in the form of a spheroidal cap comprises a mosaic of individual piezoceramic elements having a height of 3 to 10 mms and a lateral extension that does not substantially exceed the height there being gaps between the piezoceramic elements which are filled with an electrically insulating material having a modulus of elasticity which is smaller by at least one order of magnitude than that of the ceramic material, with the rise of the spheroidal cap amounting to at least 5 cms and the apex angle of the corresponding spherical sector amounting to at least 60.degree..

Piezoelectric transducer for the destruction of concretions within an

A method and apparatus are described for the detection of possible tissue injuries caused by cavitation during the medical application to a patient's body of high sonic energy which is generated extraneously by means of a sonic transducer for destruction of an element--for example a concretion--which is present in a target area. To detect the possible occurrence of cavitation the target area is acted upon by an acoustic test signal and a reception signal is generated from at least an initial reflection of the test signal. This signal is then examined by comparison with the test signal to detect the presence of an impedance jump leading to an attenuated reflection, so that a control signal may be generated upon detection of an impedance jump of this nature. Audible or visible warning signals may be engendered among others, and the sonic transducer may be deactivated if need be, by means of this control signal.

Method for detection of cavitations during medical application of high

A piezoelectric transducer for destruction of concretions inside the body. The transducer essentially comprises a spheroidal cap having piezoelectric ceramic elements situated at its radially inner front side. To prevent overpressure pulses radiated at the front side of the transducer being followed by underpressure pulse reflected from the rear side of the cap, the cap is produced from metal, preferably from a copper alloy. The impact wave resistances of the cap metal and of the ceramic material should largely correspond. Furthermore, the rear-side surface of the rear wall of the cap is so shaped geometrically and/or provided with a coating, that the sonic waves reflected therefrom are no longer focussed.

Piezoelectric transducer for destruction of concretions inside the body

A sound transmitter for generation of transient acoustic pulses, comprising a spatially curved focussing emitter surface which is represented by the area of a single active or passive emitter or by the areas of several emitters matched in respect of their period of operation and amplitude. The pulses occurring in the region of the focus are generated by a substantially unipolar and chronologically limited pressure and/or velocity evolution at the emitter surface. So that a substantially unipolar pressure pulse may equally be generated at the focus of an emitter surface of this nature, the emitter surface deviates in a specified manner from an ideally focussing emitter surface so that as a result of the differences in period of operation caused by a real deviation in the region of the focus, the chronological increase and decrease of the velocity potential in the focal region calculable by means of the Rayleigh integral differ in speed, so that the pressure evolution determined from the substantially unipolar evolution of the velocity potential by derivation based on time has a brief pulse of high amplitude at the beginning or end, which is followed or preceded by a longer pulse of lesser amplitude.

Sonic transmitters

A sonic transmitter has placed in front of it or in its acoustic beam path, an acoustic diode comprising at least two peripherally secured foils in mutual contact, the foils having opposed surfaces with a degree of adhesion and/or cohesion such that they may be pulled apart beyond a threshold value which may be acted upon--of negative sound pressure thus suppressing negative sound pulses, whereas positive sound pressures may be transmitted at almost unaltered levels in view of the existing mechanical contact of the foils.

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Karlsruhe, Germany

Rainer Riedlinger