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Dose fractionation, dose rate and iso-effect relationships for normal tissue responses

Journal Article · · Int. J. Radiat. Oncol., Biol. Phys.; (United States)
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. 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. 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. An important feature of the described formalism is that it is directly based on radiobiological insights and it provides a more logical concept to account for the diversity of tissue responses than the assumption of different exponents of N and T in the NSD formula.
Research Organization:
Univ. of Amsterdam, The Netherlands
OSTI ID:
5344851
Journal Information:
Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 8:11; ISSN IOBPD
Country of Publication:
United States
Language:
English

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