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Free keywords:
Electrons; Human; Models, Biological; Patient Care Planning; Radiometry; Radiotherapy Dosage; Radiotherapy, High-Energy
Abstract:
Inhomogeneities in matter irradiated with fast electrons are sometimes considered to present remarkable difficulties in dose distribution, so that electron therapy should not be applied for deeply situated tumors. In previous publications, easy methods for computing dose distributions in the presence of inhomogeneities are proposed, and a good agreement with measurements in phantoms or in patients is stated to be a good reason for application of fast electrons in such a situation. These different opinions reflect the quite different influence of an inhomogeneity on the dose distribution of fast electrons. Without a quantitative characterization of the type of inhomogeneity, therefore, no such general statement can or should be made.
In the present paper, such a classification of different types of inhomogeneities will be tried, and approximative, easy methods for dose calculation in these cases will be proposed. Some other types of inhomogeneities, in which up to now no easy calculation method can be used, must be excluded. In such cases, quite careful measurements in patient equivalent phantoms or in the patient himself are necessary. In some of these cases, however, other types of radiation - for example, high - energy photons-should then be preferred.
