Some in vivo effects of pi mesons in mice.

The effect of 70 MeV pi mesons was studied to determine the effectivness of such beams aginst normal tissues in vivo. The end points included thymic weight loss, oocyte and bone marrow CFU-S survival and the induction of macroscopid lens opacities. The results indicate that pi mesons are not signifacantly more effective for these end-points than more conventional radiation sources such as 60Co gama rays, 220 kVp X rays, and 14 MeV X rays and electrons. Nor was there any detectable difference in RBE between the peak and plateau regions of the pi meson beam. The significance of these findings is discussed in relation of the the published pi meson RBE values of between 1 therefore 4 and 5 therefore 0.