Lack of evidence for increased tolerance of rat spinal cord with decreasing fraction doses below 2 Gy

Journal Article · Mon Dec 31 23:00:00 EST 1984 · Int. J. Radiat. Oncol., Biol. Phys.; (United States)

DOI:https://doi.org/10.1016/0360-3016(85)90368-2· OSTI ID:5751625

Ang, K K; van der Kogel, A J; van der Schueren, E

The radiation tolerance of the spinal cord, both in man and in rats, has been shown to depend strongly on the size of the dose per fraction. With fraction doses down to about 2 Gy, the spinal cord tolerance can be predicted by a modified Ellis formula. More recently alternative isoeffect formulas were based on the linear-quadratic (LQ) model of cell survival where the effect of dose fractionation is characterized by the ratio ..cap alpha../..beta.. which varies from tissue to tissue. For the spinal cord, as well as for other late responding tissues, the ratio ..cap alpha../..beta.. is small, in contrast to most acutely responding tissues. Both the Ellis-type formula, and to a lesser extent the LQ-model, predict a continuously increasing tolerance dose with decreasing fraction size. From previous experiments on the rat cervical spinal cord with doses per fraction down to about 2 Gy, the ratio ..cap alpha../..beta.. was determined to be 1.7 Gy, and the LQ-model would predict a rise in tolerance with a reduction in fraction size to far below 2 Gy. Based on these predictions clinical studies have been initiated assuming a significantly increased tolerance by reduction of fraction size to about 1 Gy. However, in the present experiments no evidence was found for such an increase in tolerance with fraction sizes below 2 Gy.

• Research Organization: Univ. Hospital St. Rafaeol, Leuven, Belgium
• OSTI ID: 5751625
• Journal Information: Int. J. Radiat. Oncol., Biol. Phys.; (United States), Journal Name: Int. J. Radiat. Oncol., Biol. Phys.; (United States) Vol. 11:1; ISSN IOBPD
• Country of Publication: United States
• Language: English

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62 RADIOLOGY AND NUCLEAR MEDICINE
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
CENTRAL NERVOUS SYSTEM
DISEASES
DOSES
ELECTROMAGNETIC RADIATION
FRACTIONATED IRRADIATION
HARD X RADIATION
IONIZING RADIATIONS
IRRADIATION
MAMMALS
NECROSIS
NERVOUS SYSTEM
PATHOLOGICAL CHANGES
RADIATION DOSES
RADIATIONS
RADIOINDUCTION
RADIOSENSITIVITY
RATS
RODENTS
SKIN DISEASES
SPINAL CORD
TELANGIECTASIS
VASCULAR DISEASES
VERTEBRATES
X RADIATION