Radiology, Vol 132, 205-209, Copyright © 1979 by Radiological Society of North America
Relative biological effectiveness of low- and high-LET radiotherapy beams for jejunal crypt cell survival at low doses per fraction
KK Fu, TL Phillips, DC Heilbron, G Ross and LJ Kane
In order to determine the relative biological effectiveness (RBE) of
various low- and high-LET radiotherapy beams of low coses, LAF1 mice were
exposed to one dose and 10 equally fractionated doses of 60Co gamma rays,
137Cs gamma rays, 4-MeV x rays, 300-kVp x rays, helium ions in the plateau
and Bragg-peak region, and 15-MeV neutrons; survival of jejunal crypt cells
with the microcolony assay of Withers and Elkind was determined using 60Co
as the standard. RBE values for the survival of 10 cells/circumference for
10 fractionated exposures (2.4 Gy [240 rad] per fraction of 60Co) were:
1.07 for 137Cs, 1.06 for 4-MeV x rays, 1.16 for 300-kVp x rays, 1.10 for
helium ions in the plateau, 1.29 for helium ions in the peak, and 3.02 for
15-MeV neutrons. As LET increased, RBE increased with decrease of
dose/fraction.
