Elegant radiotherapy comes of age

This article discusses the use of stereotoxic radiosurgery in the treatment of hemorrhaged arteriovenous malformation. Surgical removal, the more routine approach, was unthinkable given its location. Instead, the patient was referred to the University of California, San Francisco, and the UC-Berkeley Donner Laboratory, located in the Berkeley hills high above San Francisco Bay. Radiosurgery uses a narrow beam of single protons, deuterons (one proton and one neutron), or alpha particles (a helium atom stripped of its electrons). Because of their physical properties, those charged particles travel only a specific distance through tissue, a phenomenon known as the Bragg peak. Almost no radiation passes beyond the Bragg peak point. In addition, charged particles deposit more energy at the end of their trail, so they are more damaging to the cells in the area where they stop than to cells in the intervening tissue. Exactly how much more energy depends on the type of particle