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The concept of thermal dose.
1MRC Cyclotron Unit, Hammersmith Hospital, London, Great Britain.
Summary
Calculating biologically equivalent thermal dose is crucial for variable hyperthermia treatments. The Dewey formula offers a feasible method for integrating biological effects over treatment duration, accounting for temperature variations.
Area of Science:
- Oncology
- Radiation Oncology
- Biophysics
Background:
- Hyperthermia treatment effectiveness is often described by thermal dose.
- Ideal thermal dose calculations assume constant temperature, which is not realistic.
- Variable temperatures during hyperthermia necessitate biologically equivalent thermal dose calculations.
Purpose of the Study:
- To evaluate methods for calculating biologically equivalent thermal dose in hyperthermia.
- To assess the feasibility and limitations of the Dewey formula for thermal dose integration.
Main Methods:
- Integration of the biological isoeffect relationship (Dewey formula) over the entire treatment duration.
- Analysis of thermal dose calculation under conditions of moderate temperature variation.
Main Results:
- The Dewey formula provides a practical method for comparing hyperthermia treatments with moderate temperature variations.
- The formula's accuracy is limited by sudden temperature reductions (step-down sensitization) or prolonged treatments (thermotolerance).
- The formula does not account for inter-tissue sensitivity differences or variations during fractionated treatments.
Conclusions:
- Biologically equivalent thermal dose calculation is essential for variable hyperthermia.
- The Dewey formula is a feasible approach but has limitations for extreme temperature fluctuations and varying tissue sensitivities.
- Further research is needed on the applicability of these formulas when combining hyperthermia with ionizing radiation.