Stereotactic radiosurgery - Gamma Knife


Stereotactic radiosurgery (SRS) is a form of radiation therapy that focuses high-power energy on a small area of the body.

Despite its name, radiosurgery is a treatment, not a surgical procedure. Incisions (cuts) are not made on your body.

More than one system is used to perform radiosurgery. This article is about Gamma Knife radiosurgery.

Alternative Names

Stereotactic radiotherapy; Stereotactic radiosurgery; SRT; Fractionated stereotactic radiotherapy; SRS; Gamma Knife; Gamma Knife radiosurgery; Non-invasive neurosugery; Epilepsy - Gamma Knife


Gamma Knife radiosurgery is done only for tumors and other medical problems of the head. For tumors and problems elsewhere in the body, other radiosurgery systems may be used.

Before treatment, you are fitted with a head frame. The frame is attached to your scalp. This is done using 4 small pins or anchors that go through your skin to the surface of your skull. Medicine is first given to numb the areas where the pins or anchors attach.

The frame keeps your head steady during treatment. It also helps your doctors ensure the energy beams are aimed at the exact spot in your head that needs treatment.

After the frame is attached to your head, imaging tests such as CT, MRI, or angiogram are done. The images show the exact location, size, and shape of your tumor or problem area.

During treatment:

Each treatment takes a few minutes to 2 hours. You may receive more than one treatment session. Most often, no more than five sessions are needed.

Why the Procedure Is Performed

SRS targets and treats an abnormal area. This minimizes damage to nearby healthy tissue.

Gamma Knife radiosurgery is used to treat the following types of brain tumors:

Gamma Knife is also used to treat other problems of the brain:


Radiosurgery may damage tissue around the area being treated. As compared to other types of radiation therapy, Gamma Knife treatment is much less likely to damage nearby healthy tissue.

Brain swelling may occur. Swelling usually goes away without treatment. Some people need medicine to control this swelling. In rare cases, surgery with incisions (open surgery) is needed to treat the brain swelling caused by the radiation.

The spots where the head frame is attached to your scalp may be red and sensitive after treatment. This should go away with time.

Before the Procedure

The day before your procedure:

The day of your procedure:

After the Procedure

Often, you can go home the day of treatment. Arrange ahead of time for someone to drive you home. You can go back to your regular activities the next day if there are no complications such as swelling. If you have complications, you may need to stay in the hospital overnight for monitoring.

Follow instructions for how to care for yourself at home.

Outlook (Prognosis)

The effects of Gamma Knife radiosurgery may take weeks or months to be seen. The prognosis depends on the condition being treated. Your provider will monitor your progress using imaging tests such as MRI and CT scans.


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Brown PD, Jaeckle K, Ballman KV, et al. Effect of radiosurgery alone vs radiosurgery with whole brain radiation therapy on cognitive function in patients with 1 to 3 brain metastases: a randomized clinical trial. JAMA. 2016;316(4):401-409. PMID: 27458945

Elekta AB. Gamma Knife radiosurgery patient resource center. 2015. Accessed August 9, 2016.

Romanelli P, Morris DE, Adler JR Jr, Ewend MG. Image-guided robotic radiosurgery. In: Winn RH, ed. Youmans Neurological Surgery. 6th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 257.

Welling DB, Spear SA, Packer MD. Stereotactic radiation treatment of benign tumors of the cranial base. In: Flint PW, Haughey BH, Lund V, Niparko JK, Robbins KT, eds. Cummings Otolaryngology: Head & Neck Surgery. 6th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 179.