Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
2001-07-26
2003-06-10
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S497000, C219S492000, C607S102000
Reexamination Certificate
active
06576875
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process and device for controlling selective application of heat into a material, preferably into biological tissue, having an ultrasonic-wave-generating unit which couples ultrasonic waves into the material, an ultrasonic-wave-detecting unit which detects the ultrasonic waves emerging from the material and an evaluation unit which generates information-providing parameters relating to the thermal and structural changes inside the material on the basis of the detected ultrasonic waves.
STATE OF THE ART
Processes of the aforementioned class can be used in material research and material processing in general, in particular with material structures which thermal influence may alter structurally. Of particular interest here are also thermotherapy processes, which are employed in selective hyperthermy of confined areas of tissue, in particular in treating tumors and metastases.
Such types of thermotherapy processes applied today can be divided into two groups:
1. Moderate heating to 43° C. from the outside by means of fields:
So-called hyperthermy refers to heating regions of tissue inside the body by means of external energy input. It is used in oncology for treating tumors, e.g. to supplement radiation or chemotherapy. Energy input occurs by means of electrical alternating fields or by means of high energy ultrasound. The therapeutically desired increases in temperature are usually about 6° C. above the internal body temperature, which is usually obtained with treatment periods from 20 to 30 minutes.
2. Generating thermal necrosis at temperatures from 45° C. to 200° C. by intracavitary or minimal-invasive processes:
Confined local thermal tissue damage is a widespread procedure in minimal-invasive surgery and endosurgery in treating pathological changes in tissue, such as tumors and metastases. The most common intracavitary or minimal-invasive methods consist of using infrared-range laser light (LITT: laser-induced thermotherapy), high-frequency coagulator and high-energy ultrasound (HIFU:
high-intensity focused ultrasound). In these applications, essentially the following tissue reactions occur: solely heating, tissue expansion, denaturation (coagulation), gas bubble formation. Subsequent carbonization is therapeutically undesirable. Examples of the diverse applications are treating liver metastases, mammary carcinoma, prostate tumors and brain tumors. Sometimes, for instance in the treatment of liver metastases, structural damage is achieved by using cold (cryotherapy) or alcohol. In the treatment of the prostrate, hot water may also be applied to the target region instead of laser light or ultrasound.
In endosurgery in the gastrointestinal tract, laser applicators or HF applicators are utilized, e.g. for esophageal varices or for widening stenoses.
The overall therapeutic goal of these methods of therapy is maximum damage to the malignant tissue while preserving the surrounding benign tissue regions, which may consist of extremely sensitive structures depending on the nature of their function.
A special case is using infrared laser light for treating glaucoma. Glaucoma is the main cause of blindness in the western countries. The end of a laser fiber is placed from the exterior onto the sclera and the chamber-water producing structures below are coagulated (transscleral cyklophoto coagulation). Too high laser temperatures result in undesirable total damage (disruption) of the irradiated ciliar part of the body. With treatment times of two seconds, switching-off criteria for the laser would be of help provided coagulation is good.
Efficiency and further gaining ground of these methods of treatment are therefore closely tied to the availability of a non-invasive procedure, which informs the surgeon in real time about the current therapeutic effect, respectively provides the control parameter or control signals for back coupling to the heat-generating system.
As these effects generally are dependent on the temporal temperature gradients, solely indicating the attained tissue temperature is insufficient for monitoring the therapy. Particularly in view of the individual, tissue-specific and tumor-specific differences, evidence of structural tissue changes is more precise and informative regarding the current, achieved therapeutical effect than the attained tissue temperature.
Hitherto, there are no inexpensive methods of non-invasive or minimal invasive realtime control for these therapy procedures.
Previous approaches at utilizing diagnostic ultrasound for therapy control have aimed solely at giving the attained tissue temperatures. The pertinent literature proposes, i.e., processes to achieve thermometry by measuring the temperature-dependent velocity of sound propagation. See:
Seip. E. S. Ebbini, “Noninvasive Estimation of Tissue Temperature Response to Heating Fields Using Diagnostic Ultrasound,” IEEE Trans. Biomed. Eng., vol. 42; August 1995.
Seip, P. VanBaren, C. Simon, E. S. Ebbini, “Non-Invasive Saptio-Temporal Temperature Estimation Using Diagnostic Ultrasound,” IEEE Ultrasonics Symposium Proceeding, 1995.
Seip, P. VanBaren, C. A. Cain, E. S. Ebbini, “Noninvasive Real-Time Multipoint Temperature Control for Ultrasound Phased Array Treatments”, IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 43, November 1996.
C. Simon, P. VanBaren, E. S. Ebbini, “Quantitative Analysis and Applications of Noninvasive Temperature Estimation Using Diagnostic Ultrasound” IEEE Ultrasonics Symposium Proceeding, October 1997.
C. Simon,. P. VanBaren, E. S. Ebbini, “Two-Dimensional Temperature Estimation Using Diagnostic Ultrasound,” IEEE Trans. Ultrason., Ferroelect., Freq.Contr., vol 45, July 1998.
DE 195 06 363 A1 describes a process for non-invasive thermometry in organs under hyperthermic and coagulation conditions. In order to obtain data about structural changes, in this process the to-be-heated tissue is bombarded with ultrasonic waves. The amplitude reflection factor of the tissue is measured in the form of a signal. Then, on the basis of the obtained amplitude reflection factors, the sum is determined from the temperature-dependent and structure-dependent changes in the tissue exposed to the heat.
When applied to thermal material treatment for selective internal structural changes in materials, in general, for example the transition from crystalline to amorphous or a chemical change, there are also no known reliable processes for when and in which regions structural changes occur. The preceding known processes for determining the temperature in the path of the applied thermotherapy and hyperthermy are not suited for precise determination of the structural change and the current spatial extent and of the structural change occurring inside a material.
DESCRIPTION OF THE INVENTION
The present invention improves a process and is a device for controlling selective application of heat into a material, preferably biological tissue, having an ultrasonic-wave-generating unit which couples the ultrasonic waves into the material, an ultrasonic-wave-detecting unit which detects the ultrasonic waves emerging from the material and an evaluation unit which generates information providing parameters for the thermal and structural changes inside the material based on the detected ultrasonic waves, in such a manner that an unequivocal statement can be made about the type and extent of structural change inside the material due to the heat input. Furthermore, the present invention makes possible controlling the heat input into the material in such a manner that the desired goal of the treatment inside the material can be achieved without causing undesired structural changes. Finally the invention is a device for performing this process.
An element of the present invention is a process in which the ultrasonic waves emerging from the material are detected time-resolved and site-resolved, with the detected ultrasonic waves being time-resolved in the evaluation unit and being examined for their change of propagation time relative to the ultrasonic-wave si
Kleffner Bernard
Lemor Robert
Antonelli Terry Stout & Kraus LLP
Fraunhofer-Gesellschaft zur Forderung der Angewandten Forschung
Paschall Mark
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