Neutron RBE for primate spinal cord treated with clinical regimens.
The RBEs of high-energy neutrons given in 9 or 12 fractions for cervical spinal cord injury in rhesus monkeys was determined using photons at 2.2 Gy per fraction as the reference radiation. Because the dose-response functions were not parallel, the RBE was not constant but rather increased with dose or, equivalently, with the probability of myelopathy. This required the development of a novel method of determining the RBE versus level of response. The RBE is presented as a function of probability of myelopathy from 0.1 to 99%. At a 50% incidence of myelopathy, the RBE (+/- 1 SE) was 5.22 +/- 0.15. A difference in the histopathology of lesions induced by photon and neutron treatments was observed.
Schultheiss
T E
TE
Division of Radiotherapy, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Stephens
L C
LC
Ang
K K
KK
Jardine
J H
JH
Peters
L J
LJ
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005214:Fast Neutrons; D008253:Macaca mulatta; D011882:Radiotherapy, High-Energy / Q000009:adverse effects; D012062:Relative Biological Effectiveness; D013118:Spinal Cord Diseases / Q000209:etiology; D013119:Spinal Cord Injuries / Q000532:radiotherapy*