Leksell gamma knife model b

Radiosurgery was performed on the Leksell Gamma Knife Model B (years 2000–2004), C (2004–2009), and Perfexion (2009–2013) (Elekta AB, Stockholm). High‐resolution contrasted MRI was performed just prior to SRS. Median dose delivered to the tumor margin was 20 Gy (range: 10–24 Gy). Dose was generally prescribed to the 50% isodose line. Dose was prescribed according to guidelines published by Shaw et al. 18.

In all 53 cases, a Leksell stereotactic frame was fixed to the patient’s skull under local anesthesia. High-resolution contrast-enhanced magnetic resonance imaging (MRI) was performed, utilizing a slice thickness of 2 mm for treatment planning. Radiosurgery was performed using the Leksell Gamma Knife model B (Elekta AB) before 2007, the Leksell Gamma Knife model C (Elekta AB) between January 2007 and October 2011, and the Leksell Gamma Knife Perfexion (Elekta AB) thereafter. Multiple dose planning sessions were carried out using the GammaPlan system (Elekta Instruments).
In the cohort evaluated in the present study, the mean prescribed radiation dose was 13.5 Gy (range, 10–16 Gy), for which the equivalent dose in 2-Gy fractions (EQD2; calculated assuming an α/β = 3 for chordomas) ranged from 26 to 60.8 Gy (mean, 44.8 Gy). The mean isodose line was 45.8% (range, 40–50%); the mean maximum dose was 29.4 Gy (range 22–33.3 Gy); and the mean tumor volume was 17.1 cm³ (range, 1.1–62.2 cm³). Some patients had complicated radiotherapy histories, so the average total EQD2 for these patients was 60.3 Gy (range, 26–200 Gy) (Table 1).