Radiation tolerance of the spinal cord : Dependence on fractionation and extended overall times
conference paper
The cervical region of the rat spinal cord was irradiated with single and fractionated doses of 300kV X-rays. The isoeffect curve for 50% incidence of paralysis in relation to the number of fractions at daily intervals has a slope of 0.44 on a double logarithmic scale diagram. In split-dose experiments with intervals between successive courses of radiotherapy of up to 8 weeks, no further increase in tolerance was observed. However, with a longer interval of 16 weeks, significant additional recovery occurred. The results fit an isoeffect formula (Ellis type) DαNsup(0.44) for the first 8 weeks of treatment, and DαNsup(0.44)(T-56)sup(0.03) for periods between 8 and 16 weeks. The additional recovery starting between 8 and 16 weeks after irradiation is attributed to repopulation by cells with a slow turnover under normal conditions.
Topics
Biological radiation effectsBiological recoveryFractionated irradiationHard X radiationRatsSpinal cordSublethal irradiationTime dependenceAnimalsBiological effectsCentral nervous systemElectromagnetic radiationIonizing radiationsIrradiationMammalsNervous systemRadiation effectsRadiationsRodentsVertebratesX radiation
TNO Identifier
355668
ISBN
92-0-010377-4
Publisher
International Atomic Energy Agency (IAEA)
Article nr.
IAEA-SM-212/33
Source title
International symposium on the radiobiological research needed for the improvement of radiotherapy, 22-26 Nov 1976, Vienna, Austria
Place of publication
Vienna
Pages
85-91
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