Multimodality treatment for cerebral arteriovenous malformations: complementary role of proton beam radiotherapy, Nakai Y, Ito Y,Sato M,Nakamura K,Shiigai M,Takigawa T,Suzuki K,Ikeda G,Ihara S,Okumura T,Mizumoto M,Tsuboi K,Matsumura A, Neurol Med Chir (Tokyo), 52(12), 859-864, 2012