Dose fractionation, dose rate and iso-effect relationships for normal tissue responses
An analysis is presented of responses of a variety of normal tissues in animals to fractionated irradiations. It is shown that the influence of fractionation can be described on the basis of a simple formula relating the effectiveness for induction of cellular effects to the dose per fraction: F(D) = a/sub 1/D + a/sub 2/D/sup 2/. The ratio a/sub 1//a/sub 2/ is derived as an essential parameter for the description of fractionation effects. It is concluded that the values of a/sub 1//a/sub 2/ for responses of various tissues range widely from 2 to 10 Gy. On the basis of the review of radiobiological data, a formalism is developed for the analysis and prediction of iso-effect relations for tissue tolerance, which can be used as an alternative to the nominal standard dose (NSD) formula of Ellis and its derived equations. An essential characteristic of the formalism is that three groups of tissue responses are distinguished which can be described with respect to fractionation effects by average values of a/sub 1//a/sub 2/ = 10; 5 and 2.5 Gy, respectively. These groups comprise a 1:a.o. skin and intestine; 2:connective tissue; 3:a.o. lung and vascular system. Dose rate effects can be described by a similar formalism. For the calculation of equivalent total doses to be applied in clinical treatments, a concept denoted Extrapolated Tolerance Dose (ETD) or Extrapolated Response Dose (ERD) is introduced. ETD is the tolerance dose for an infinite number of very small fractions. This concept is shown to be useful for the summation of different fractionated schedules and of low dose rate treatments. A number of examples is presented illustrating similarities and differences in comparison with calculations based on the NSD formula.
- Research Organization:
- Univ. of Amsterdam, Netherlands
- OSTI ID:
- 5213822
- Journal Information:
- Int. J. Radiat. Oncol., Biol. Phys.; (United States), Vol. 8:11
- Country of Publication:
- United States
- Language:
- English
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FRACTIONATED IRRADIATION
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TISSUES
TOLERANCE
ANIMALS
DOSE RATES
MATHEMATICAL MODELS
RADIATION DOSES
RADIOBIOLOGY
BIOLOGY
BODY
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IRRADIATION
560154* - Radiation Effects on Animals- Basic Studies- (-1987)