The Gamma Knife is actually not a knife at all. It is a technologically advanced tool that allows neurosurgeons to operate on brain tumours, lesions, arteriovenous malformations, trigeminal neuralgia and other specific indications of the brain - without making a single incision. The Gamma Knife uses a single dose of radiation directed by means of 201 very narrow beams to a specific target within the head. Unlike conventional radiation therapy, the Gamma Knife is so exact that it can target abnormal tissue while leaving adjacent normal tissue relatively untouched.

The conditions treated by The London Gamma Knife Centre at Barts include some which could not be treated safely or effectively by conventional surgery and often where surgical treatment would not have been an option at all.

The Gamma Knife uses no moving parts during treatment. This provides enhanced accuracy, reliability and reproducibility. Because of its accuracy, doctors can treat some tumours previously considered inoperable, including those near vital structures such as the brainstem, cranial nerves and optic apparatus. Patients are nearly always treated and discharged within 24 hours.

As with any other radiation treatment, Gamma Knife results are not instantaneous. Treatment is usual aimed at arresting tumour growth, for which success rates are often in the region of 95% or more.