Gjmj. Vandenaardweg et al., THE RADIATION RESPONSE OF THE CERVICAL SPINAL-CORD OF THE PIG - EFFECTS OF CHANGING THE IRRADIATED VOLUME, International journal of radiation oncology, biology, physics, 31(1), 1995, pp. 51-55
Citations number
21
Categorie Soggetti
Oncology,"Radiology,Nuclear Medicine & Medical Imaging
Purpose: An investigation of the field size effect for the cervical sp
inal cord of the pig after single doses of gamma-rays. In this study,
clinically relevant volumes of the spinal cord were irradiated. Method
s and Materials: The effects of the local irradiation of different len
gths of the spinal cord (2. 5 cm, 5.0 cm, and 10.0 cm) have been evalu
ated in mature pigs (37-43 weeks). Single doses of 25-31 Gy were given
using a Co-60 gamma-source, at a dose rate of 0.21-0.30 Gy/min. The i
ncidence of radiation-induced paralysis was used as the endpoint. The
data were analyzed using probit analysis and a normal tissue complicat
ion probability (NTCP)-model. Results: Twenty-five animals out of a to
tal of 53 developed paralysis, with histological evidence of parenchym
al and vascular changes in their white matter. The slope of the dose-r
esponse curves decreased with the decrease in field size; however, the
re was no significant difference at the radiation dose associated with
a 50% incidence of paralysis (ED(50)) irrespective of the method of a
nalysis. The ED(50) values +/- standard errors (+/- SE) were 27.02 +/-
0.36 Gy, 27.68 +/- 0.57 Gy, and 28.28 +/- 0.78 Gy for field lengths o
f 10, 5, and 2.5 cm, respectively. Analysis of the data with a normal
tissue complication probability (NCTP) model gave similar results. The
latent period for paralysis was 7.5-16.5 weeks with no significant di
fferences between dose and field size. Conclusion: No significant fiel
d size-related differences in response were detectable in the cervical
spinal cord of mature pigs after single dose irradiations, specifical
ly at a clinically relevant level of effect (< ED(10)).