Stereotactic Radiosurgery

Stereotactic Radiosurgery

UC San Diego Health is equipped with some of the world’s most advanced technology for the treatment of brain tumors and neurospinal disorders, including the Varian Trilogy linear accelerator for stereotactic radiosurgery (SRS).

Stereotactic radiosurgery is a form of radiation therapy that concentrates high doses of radiation on very precise areas. Unlike other forms of radiation therapy, stereotactic radiosurgery better focuses the radiation beams on abnormal cells, limiting damage to of nearby healthy tissue. This is particularly important in the brain.

Depending on the case, treatment may be delivered in a single treatment or a limited number of treatment sessions.

Varian Trilogy technology uses an optically-based infrared camera system to guide the radiation beams. This limits the need to use a special frame connected to the skull to stabilize the head.

The Varian Trilogy performs the complete range of radiotherapy techniques, including intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT) and planar and cone-beam CT imaging for in-treatment imaging and progress evaluation. This flexibility allows our radiation oncologists to determine the treatment approach most appropriate for each patient. Read more about SRS, including IMRT and IGRT, below, or see Types of Radiation Therapy.


When the therapeutic value of X-rays was discovered in the late 19th century, radiotherapy, as it was called, was used for a wide variety of cancers. An important limitation, however, was the X-ray machines’ inability to produce high-energy, deeply penetrating beams. Patients receiving early forms of radiotherapy would risk damage to the skin and tissues surrounding the abnormal cells being treated.


In the 1960s, a megavoltage treatment machine was developed, known as a linear accelerator, or linac. The linac significantly advanced the ability of radiation oncologists to effectively treat tumors deep in the body without excessive damage to the skin and other healthy tissue.


In the 1980’s, a revolutionary advancement occurred in the field of radiotherapy. Intensity-modulated radiation therapy (IMRT) delivers the prescription dose of radiation in the three dimensional shape of the tumor. IMRT also controls the intensity of the radiation beam – allowing higher radiation doses to be focused on areas inside the tumor, while minimizing the dose on the edges, near healthy tissue. That means the radiation exposure is substantially reduced to the healthy surrounding tissue and the abnormal tissue is receives precision treatment. Unlike conventional stereotactic radiosurgery approaches, which require several hours to deliver, IMRT stereotactic radiosurgery can be used to treat patients with multiple brain metastases in a single session.


Advances continue in radiation oncology. Today, UC San Diego Health specialists are using image-guided radiation therapy (IGRT) to more precisely identify changes in the abnormal cells each time a patient is on the treatment table. IGRT is made possible by on-board imaging (OBI) with the Varian Trilogy. OBI enables patients to receive highly sophisticated images of their tumor in real time during treatment. It is known that tumors shrink during radiation therapy. IGRT means tiny adjustments can be made in position and set-up during treatment to account for these changes, and improve treatment delivery.