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.

Contenu

1 Thermometry in Therapeutic Hyperthermia.- 1.1 Introduction.- 1.2 Clinical Considerations.- 1.2.1 Practical Applications.- 1.2.2 Temperature Control.- 1.3 Available Technologies.- 1.3.1 Thermocouple Thermometry.- 1.3.2 Electrical Resistance Thermometry.- 1.3.3 Gallium Arsenide Optical Thermometry.- 1.3.4 Photoluminescent Thermometry.- 1.4 Measurement Errors and Artifacts.- 1.4.1 Calibration and Drift.- 1.4.2 Thermal Smearing.- 1.4.3 Electromagnetic Artifacts.- 1.4.4 Ultrasound Artifacts.- 1.5 Future Developments.- 1.5.1 Noninvasive Thermometers.- 1.5.2 Mathematical Modeling.- 1.6 Summary.- References.- 2 Noninvasive Control of Hyperthermia.- 2.1 Introduction.- 2.2 General Considerations Regarding Imaging Technique Performances.- 2.2.1 Presentation.- 2.2.2 Expected Performances for Noninvasive Control of Hyperthermia.- 2.2.3 Classification of Imaging Modalities.- 2.2.4 Analysis of Image Content.- 2.2.5 Usual Criteria of Image Quality.- 2.2.6 Temperature Dependence of Images.- 2.2.7 Other Practical Considerations.- 2.2.8 Optimization of Performances.- 2.3 Electromagnetic Radiometric Techniques.- 2.3.1 Presentation.- 2.3.2 Natural Limitations.- 2.3.3 Recent Developments.- 2.3.4 Discussion.- 2.4 X-Ray Tomodensitometry.- 2.4.1 Presentation.- 2.4.2 Fundamentals.- 2.4.3 Image Quality.- 2.4.4 Temperature Dependence of CT Numbers.- 2.4.5 Some Results.- 2.4.6 Discussion.- 2.5 NMR Tomography.- 2.5.1 Fundamentals.- 2.5.2 Image Quality.- 2.5.3 Temperature Dependence of NMR Imaging Parameters.- 2.5.4 Some Results.- 2.5.5 Discussion.- 2.6 Imaging of Dielectric Properties.- 2.6.1 Presentation.- 2.6.2 Fundamentals.- 2.6.3 Salient Features of Dielectric Properties of Living Tissues.- 2.6.4 Electrical Impedance Tomography.- 2.6.5 Microwave Imaging.- 2.6.6 Radiofrequency Inverse Scattering Techniques.- 2.6.7 Conclusion.- 2.7 Ultrasonic Techniques.- 2.7.1 Presentation.- 2.7.2 Sensitivity of Living Tissue Characteristics to Temperature.- 2.7.3 Active Modalities.- 2.7.4 Ultrasound Radiometry.- 2.7.5 Thermo-induced Acoustic Imaging.- 2.7.6 Discussion.- 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.- 3.2.1 Physical Principles: The Black Body Radiation.- 3.2.2 Thermal Power Collected by an Antenna: Nyquist's Formula.- 3.2.3 Thickness of Medium and Radiometric Measurement.- 3.2.4 Reflection Effects at the Air-Medium Interface.- 3.2.5 Characteristics of the Radiometric Method for Temperature Measurement.- 3.3 Microwave Radiometric Systems.- 3.3.1 The Dicke Radiometer: Principle and Limitations.- 3.3.2 The Modified Radiometer.- 3.3.3 Description and Performances of the Radiometer Used for Medical Applications; Performances of the Applicator Antenna.- 3.4 Control of Hyperthermia by Microwave Radiometry.- 3.4.1 Principles and Problems.- 3.4.2 Design of the Microwave Systems.- 3.4.3 Performances and Possibilities: Examples of Experiments on Phantoms, Animals, and Patients.- 3.4.4 Use of Microwave Radiometry to Control Radiofrequency Hyperthermia.- 3.5 Thermal Dosimetry for Microwave Hyperthermia Based on Microwave Radiometry.- 3.5.1 Principles of the Method.- 3.5.2 Computation of the Radiometric Signal.- 3.5.3 Computation of Thermal Profile Using the Bioheat Transfer Equation.- 3.5.4 The Inverse Process.- 3.5.5 Examples of Results Obtained with These Programs: Theory-Experiment Comparisons.- 3.6 Conclusion.- References.