Leksell model c unit

Patients were evaluated and consented by a radiation oncologist and neurosurgeon before GKRS. Patients were treated with a Leksell model C unit (Elekta, Norcross, GA) before May 2009 and with a Leksell GammaKnife Perfexion unit (Elekta) thereafter. Before undergoing radiosurgery, the patient underwent a 1.5T or 3T high-resolution contrast-enhanced stereotactic MRI and/or CT study of the brain. Treatment planning was performed using the Leksell GammaPlan treatment planning system (Elekta). Dose prescription was determined according to size and volume of the metastasis, and generally following the guidelines published by Shaw et al (12 (link)) for single-fraction radiosurgical treatment of previously irradiated primary brain tumors and brain metastases.

Prior to treatment failure, all patients had been treated with Gamma Knife radiosurgery (Leksell Model C unit prior to May 2009, Leksell Gamma Knife Perfexion unit after May 2009; Elekta AB, Stockholm, Sweden). Prior to radiosurgery, patients underwent a high-resolution contrast-enhanced stereotactic MRI study of the brain. Treatment planning was performed using the Leksell GammaPlan Treatment Planning System (Elekta AB). Dose prescription was determined based on size and volume of each metastasis, generally following the guidelines published by Shaw et al. for single fraction radiosurgical treatment of brain metastases [8 (link)]. The median marginal dose of the previously treated lesion was 18 Gy (range 10– 24 Gy) and the median resected volume at the time of stereotactic radiosurgery failure was 4.9 cc (range 0.2–53 cc).