LEKSELL GAMMA KNIFE - PAST, PRESENT AND FUTURE

Abstract

The first prototype of the Leksell Gamma Knife was installed in 1968 at Sophiahemmet Hospital in Stockholm, Sweden. Since that this system underwent significant improvement affecting quality and safety of patient’s treatment. Initial Leksell Gamma Knife systems called U and B were later on replaced by models C and 4C. Finally, the newest system called Leksell Gamma Knife Perfexion was introduced in 2006. The first and currently only gamma knife unit in the Czech Republic was installed in Prague in 1992. Initial Leksell Gamma Knife model B was later upgraded to the Leksell Gamma Knife model C which was finally replaced by the latest Leksell Gamma Knife Perfexion installed at Na Homolce Hospital in December 2009. The source of radiation in the Leksell Gamma Knife is 60Co. Half life of 60Co is 5.26 years. Two energies of gamma photons are emitted with energy of 1.17 MeV and 1.33 MeV. High number of multiple 60Co beams directed in one focus point are used. This geometry leads to a high dose in focus point and very low dose to surrounding tissue. There are 201 60Co beams in the case of Leksell Gamma Knife models U, B, C and 4C and 192 60Co beams in the case of Perfexion, respectively. Radiosurgical treatment is done in one single fraction. Leksell stereotactic frame which is attached to patient’s head is used for exact imaging and targeting. The whole procedure involves typically only one single fraction of radiation and is done in one treatment day. Main diagnosis involve following intracranial lesions: arteriovenous malformations, meningiomas, acoustic neuromas, pituitary adenomas, single and multiple metastasis, glial tumors and functional radiosurgery such as trigeminal neuralgia. This review article describes how this system evolved since the first prototype, provides technical specifications of different Leksell Gamma Knife systems and makes comparison between different systems.