Gamma Knife — Targeted Stereotactic Radiosurgery

Technically classified as stereotactic radiosurgery (SRS), the Gamma Knife utilizes multiple cobalt-60 radiation sources arranged in a circular configuration. Each individual beam carries a relatively low dose of energy that passes safely through healthy brain tissue, cranial bones, and scalp without causing substantial cellular disruption along its entry path.

At the focal point where all beams converge—known as the isocentre—the cumulative radiation dose is intensely concentrated. This concentrated energy destroys the DNA of targeted tumour cells, arresting their reproductive capacity and inducing vascular obliteration over time. Advanced stereotactic head frames or custom-moulded thermoplastic immobilization masks are used alongside high-resolution neuroimaging to maintain spatial precision within fractions of a millimetre.

For patients with deep, surgically inaccessible brain tumours or medical conditions that make traditional open craniotomy hazardous, Gamma Knife offers a vital, incision-free alternative. The treatment is usually completed in a single outpatient session or over a few fractionated visits, eliminating the prolonged recovery times, infection risks, and general anaesthesia associated with open brain surgery. Most individuals return to their normal daily activities within twenty-four to forty-eight hours. It also provides an effective local salvage option if brain tumours recur after prior whole-brain radiation therapy.

Gamma Knife treatment does not depend on a specific laboratory biomarker; rather, patient selection relies entirely on high-resolution neuroimaging. Thin-slice, contrast-enhanced magnetic resonance imaging (MRI) and computed tomography (CT) scans are acquired immediately before the procedure. Radiation oncologists, neurosurgeons, and medical physicists import these three-dimensional scans into specialized computer planning software to delineate tumour margins precisely and establish strict safety boundaries around delicate structures like the optic chiasm and brainstem.

Gamma Knife is most frequently employed to manage secondary brain metastases originating from primary cancers such as lung cancer, breast cancer, melanoma, renal cell carcinoma, and colorectal cancer. It is also a primary treatment modality for benign intracranial lesions, including vestibular schwannomas (acoustic neuromas), meningiomas, and pituitary adenomas. Selected cases of primary glial tumours, such as glioblastomas, may also receive Gamma Knife treatment.

Because Gamma Knife provides extreme spatial precision, it has largely replaced whole-brain radiation therapy for patients with limited brain metastases, successfully preserving long-term neurocognitive function. It can be combined sequentially with systemic therapies, including targeted small-molecule inhibitors and immune checkpoint inhibitors, which can cross the blood-brain barrier. Tumours do not disappear instantly after radiosurgery; instead, they gradually stabilize, shrink, or form inert scar tissue over several months, tracked via surveillance MRI scans.