Figure1

a Axial CT (left) and CISS images showing the volume of vestibule (red arrow, orange line). The blue arrows indicate cochlea, semi-circular canals and internal auditory canal. CT computed tomography, CISS constructive interference in steady-state. b Axial, sagittal and coronal CISS MR and CT images showing the volume of the cochlea (blue arrow) and vestibule (green arrow) with the different isodose lines from a treatment plan for Cyberknife. A dose of 12 Gy in a single fraction was prescribed to 80% isodose line and no dose constraints were given to the vestibule during treatment plan optimization. It is evident that cochlea is very well spared by giving it priority during plan optimization, while 70% (10.5 Gy) to 30% (4.5 Gy) isodose lines cover the vestibular volume