a few links regarding the gamma knife thang:

http://www.medicine.indiana.edu/

http://www.sciencedaily.com/releases/2002/06/020605073153.htm

http://www.irsa.org/publications/BrainTalkV6_2.pdf

http://www.iupui.edu/~neurosur/GammaKnife.html

http://www.clarian.org/clinical/gammaknife/index.jhtml?print=true