Implication of using MRI co-registered with CT in Leksell Gamma Knife® dose planning for patients with vestibular schwannoma.

• Dose-planning can be performed using MRI, CT or a combination of these techniques.
• There are potential benefits of using stereotactic CT in the dose-planning process.
• Addition of CT to the MRI based plan generates shifts in the individual iso-centers.
• This gives changes in the dose distributions. Clinical implications are yet unknown.