Ladislav Oppl

Technical aspects of microwave thermotherapy

We describe our new technical results dealing with microwave thermotherapy (hyperthermia) in cancer treatment, see Refs. [S.B. Field, C. Franconi (Eds.), Physics and technology of hyperthermia, NATO Seminar Proceedings, Urbino, Italy, 1986; J. Hand, J.R. James (Eds.), Physical Techniques in Clinical Hyperthermia, Wiley, New York, 1986; J. Vrba, M. Lapes, Microwave Applicators for Medical Purposes, CTU Press, 1996, in Czech; J. Vrba, C. Franconi, M. Lapes, Theoretical limits for the penetration depth of the intracavitary applicators, International Journal of Hyperthermia, 12:6 (1996) 737-742; C. Franconi, J. Vrba, F. Montecchia, 27 MHz hybrid evanescent-mode applicators with flexible heating field for deep and safe subcutaneous hyperthermia, International Journal of Hyperthermia, 9:5 (1993) 655-674.]. Our research interest is to develop applicators for deep local heating and for intracavitary cancer and/or prostate treatment as well. Further, a system for 3D SAR distribution measurements in water phantom is explained. Basic evaluation of clinical results is given.

Prospective Applications of Microwaves in Medicine

Medical applications of microwaves (i.e. a possibility to use microwave energy and/or microwave technique and technology for therapeutical purposes) are a quite new and a very rapidly developing field. Microwave thermotherapy is being used in medicine for the cancer treatment and treatment of some other diseases since early eighties. In this contribution we would like to offer general overview of present activities in the Czech Republic, i.e. clinical applications and results, technical aspects of thermotherapeutic equipment and last but not least, prospective diagnostics based on microwave principals ant technology and instrumentation.

Microwave Medical Imaging and Diagnostics

Future trends in medical applications of microwave technique and technology can be seen in development of new diagnostic and imaging methods based on high frequency EM field. A significant importance for the future can be identified for the following methods: Microwave tomography, Microwave radiometry, Measurement of complex permittivity, Imaging in the Terahertz waves band and Microwave diagnostic radars.

Measurement of Dielectric Properties of Moisture Textile

The measurement of dielectric parameters of wet textile materials is very important for the design of microwave drying and heating applicators in textile industry. In this contribution there are presented results of two measurement systems - Six-port measurement system and Agilent Impedance/material analyzer. Dielectric properties generally depend on the frequency of applied electromagnetic field, moisture content, temperature and density of materials. However, the amount of water in the drying materials is mostly a dominant factor.

Waveguide Probes for Complex Permittivity Measurement

Paper deals with the complex permittivity measurement of biological tissues. Application of a waveguide probe for this measurement is shown. A non-destructive and non-invasive method based on reflection coefficient measurement attaching the material under test is used. New types of the probes are under investigation - the section of waveguide with H cross-section, the section of waveguide with the rectangular cross-section and with shorted walls, the section of waveguide with inserted dielectric wedge and finally the section of waveguide filled by the liquid dielectric. Properties of these prototypes are studied in the frequency range from 300 kHz to 3 GHz. The method of finite difference in time domain is utilized for the numerical modeling and simulation of the reflection coefficient. The condition for the input reflection coefficient of the waveguide probe is the range from (0.7 - 0.3) in the broad frequency band. Although the waveguide is a narrowband microwave component, its modifications could have broadband frequency behavior of the reflection coefficient. Results indicate that the most interesting and suitable is the solution with removable dielectric. This liquid dielectric with the low value of permittivity has significant influence on the cut-off frequency of waveguide with dominant mode propagation.

Design and Comparison of Exposure Chambers for Verification of Microwave Influence on Biological Systems

The main aim of our work is to design and simulate an exposure chamber in order to analyze the influence of electromagnetic field on mice which can simulate mobile phone emission patterns. We use two types of structures and compare their properties to find the best design for our future work.

Experiences with Superficial Hyperthermia in the Treatment of Patients with Head and Neck Cancers

In this paper is presented our longstanding experience with combination of teleradiotherapy and superficial hyperthermia in the treatment of patients with head and neck cancers, especially in cases with superficial tumors or lymph node metastases, in the Institute of Radiation Oncology in Prague. Microwave thermotherapy - hyperthermia in combination with other treatment methods (mainly with teleradiotherapy) is currently very effective and important method for cancer treatment. Technical equipment for before-mentioned therapeutic method in this clinical working place is described as well. The treatment results were evaluated after 1-2 month after end of treatment series by various examination methods. They are part of this paper as well.

Design of an Exposure Chamber for Biological Experiments

The main aim of this work is to design and to simulate an exposure chamber which can simulate mobile phone emission patterns in order to analyze the influence of electromagnetic field on small animals. During our previous research we found the most suitable type of an exposure chamber for this purpose. The basic properties such as electromagnetic field distribution and impedance matching of our designed chamber were optimized and verified by the aid of a 3D electromagnetic field simulator. As a result of our effort a cylinder waveguide chamber with a working frequency 900MHz has been designed. In the cylindrical structure a circular polarization is excited in order to even the exposure. The chamber is terminated by matched loads on both lateral sides which serve for preventing a possible resonance between sides and the animal.

Microwave applicators for BPH thermotherapy

Paper deals with new results in the field of intracavitary microwave applicators used for Benign Prostatic Hyperplasia (BPH) treatment.

Hyperthermia Applicator Compatible with "NMR"

Microwave thermotherapy is being used in medicine for the cancer treatment and treatment of some other diseases since early eighties [1,2,3,4]. Until now in temperature monitoring and control there is a lack of non-invasive 3D thermometry system, e. g. either Nuclear Magnetic Resonance (NMR) or ultrasound (US). The goal of this paper is to describe design and experimental evaluation of a new type applicator for microwave thermotherapy, which will be compatible with NMR. The first applicator of this type is just being used for a hyperthermia treatment of the experimentally induced pedicle tumours of the rat.