Fig. 2　A: Initial axial T1-weighted post-contrast MRI showing a left vestibular schwannoma with tumor volume of 3.260 cc. B, C: The tumor was treated with GKS with a prescribed peripheral dose of 12 Gray (Gy), 53% isodose line, and covering 96%. The yellow line indicates the 12 Gy isodose curve and the green lines indicate the 5 Gy, 10 Gy and 15 Gy from the outside to the inside, respectively.