Bath and shower effect in spinal cord: the effect of time interval.
OBJECTIVE
To evaluate the time dependency of the sensitizing effect of a large low-dose field on a small high-dose field in the rat cervical spinal cord.


METHODS
Irradiation experiments with a relatively low dose to a large volume (bath, 2 cm, 4 Gy) were combined with high doses to a small volume (shower, 4.7 mm, 26-43 Gy) at intervals of 8 minutes and 3, 12, and 24 hours. Both a functional score defined as motor impairment and a histologic score characterized as white matter necrosis were used as end points.


RESULTS
Application of the 4-Gy bath dose resulted in a significant decrease in 50% isoeffective dose (ED(50)) from 48.7 Gy (small field) to 40.8 Gy. If the interval was extended, the ED(50) increased to 44.4 (3 hours) and 44.8 Gy (12 hours), whereas a 24-hour interval resulted in a significant increase to 51.9 Gy. If the histologic end point was considered, the ED(50) for all dose-response curves decreased slightly with 0.2 to 2.6 Gy without significantly changing the kinetics.


CONCLUSIONS
The bath effect as applied in the bath-and-shower experiment lasted for at least 12 hours and disappeared in the 24-hour interval. This time scale clearly deviates from the repair kinetics in spinal cord derived from low-dose-rate and fractionated irradiations.
Philippens
Marielle E P
ME
Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegan, The Netherlands.
Pop
Lucas A M
LA
Visser
Andries G
AG
Peeters
Wenny J M
WJ
van der Kogel
Albert J
AJ
D000465:Algorithms; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D007928:Lethal Dose 50; D008297:Male; D009043:Motor Activity / Q000502:physiology / Q000528:radiation effects; D009186:Myelin Sheath / Q000473:pathology / Q000528:radiation effects; D009336:Necrosis; D010243:Paralysis / Q000209:etiology; D011833:Radiation Injuries, Experimental / Q000473:pathology / Q000503:physiopathology*; D011836:Radiation Tolerance / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000473:pathology / Q000528:radiation effects*; D013119:Spinal Cord Injuries; D013997:Time Factors