Methods of Hyperthermia Control

The enormous potential that hyperthermia has for benefiting patients with cancer is impressively indicated by biological studies, both in vitro and in vivo, and by comparative clinical studies whenever the heat has been appro priate to the size of the tumor. But hyperthermia, as with any other technologically based medical procedures, requires an extensive develop ment of sophisticated instrumentation and techniques to offer routine clinical benefit. We probably erred in starting clinical trials so soon. We had hoped that by showing the clinical benefits on some superficial tumors quickly, financial support would be stimulated for the required technolog ical developments. Unfortunately, treating superficial disease adequately was more difficult than we had supposed and regional treatments were less successful than we had wished. The physical reasons are clear and were apparent from the beginning, although in our enthusiasm we ignored them. Circumstances are different now. We have to treat a wide range of tumors in various sites, but the systems and techniques required are only available in a few laboratories and clinics where they still are undergoing refinement.

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This book deals with the major problem of hyperthermia control - which has not yet been optimally solved - by considering the invasive techniques of thermometry as well as the noninvasive methods of radiothermometry and thermal imaging. The various techniques of thermometry as currently practiced in clinical settings using implanted probes are reviewed and discussed extensively, emphasis being placed upon the procedures for locating probes in tissue. The possible methodological approaches to noninvasive control of hyperthermia based upon different principles of radiometry and imaging (X-ray, NMR, ultrasound, microwave, electric impedance) are reviewed, addressing questions such as the compromise of sensitivities (thermal, spatial, temporal), the problem of noise rejection, the space constraint (heater and imager targeted at the same volume), and the sensitivity of the thermometric parameter to other physiological veriables. To exemplify the potentials of noninvasive control, the development and practical implementation of a system integrating microwave heating and radiometry into a totally engineered package are described.

Contenu
1 Thermometry in Therapeutic Hyperthermia.- 1.1 Introduction.- 1.2 Clinical Considerations.- 1.3 Available Technologies.- 1.4 Measurement Errors and Artifacts.- 1.5 Future Developments.- 1.6 Summary.- References.- 2 Noninvasive Control of Hyperthermia.- 2.1 Introduction.- 2.2 General Considerations Regarding Imaging Technique Performances.- 2.3 Electromagnetic Radiometric Techniques.- 2.4 X-Ray Tomodensitometry.- 2.5 NMR Tomography.- 2.6 Imaging of Dielectric Properties.- 2.7 Ultrasonic Techniques.- 2.8 Discussion, Synthesis, and Prospects.- References.- 3 Use of Microwave Radiometry for Hyperthermia Monitoring and as a Basis for Thermal Dosimetry.- 3.1 Introduction.- 3.2 Measurement of Thermal Radiation.- 3.3 Microwave Radiometric Systems.- 3.4 Control of Hyperthermia by Microwave Radiometry.- 3.5 Thermal Dosimetry for Microwave Hyperthermia Based on Microwave Radiometry.- 3.6 Conclusion.- References.