<prompt> Gamma knife is used in?RadiotherapyChemotherapyNuclear medicineRadioisotope scan  <response>: ANSWER: A RadiotherapyREF: Practical Radiotherapy physics and equipment Pam Cherry Angela M. Duxbury 2nd Edition page 132, is a medical procedure that allows non-invasive treatment of benign and malignant tumors. It is also known as stereotactic radiotherapy, SRT when used to target lesions in the brain, and stereotactic body radiotherapy SBRT when used to target lesions in the body. Inaddition to cancer, it has also been shown to be beneficial for the treatment of some non-cancerous conditions, including functional disorders such as arteriovenous malformations AVMs and trigeminal neuralgia. 