William R. Pritchard Veterinary Medical Teaching Hospital

Stereotactic Radiosurgery

What is stereotactic radiosurgery?
Stereotactic radiosurgery is a highly precise form of radiation therapy used primarily to treat tumors and other abnormalities of the brain and pituitary gland. It is a non-surgical procedure that delivers a single high-dose of precisely-targeted radiation using highly focused gamma-ray or x-ray beams that converge on the specific area or areas of the brain or pituitary gland where the tumor resides, minimizing the amount of radiation to healthy surrounding tissue. Although stereotactic radiosurgery is often completed in a one-day session, doctors sometimes recommend multiple treatments, especially for tumors larger than one inch in diameter. The procedure is usually referred to as fractionated stereotactic radiotherapy and is completed in three to five treatments.

Stereotactic radiosurgery is an important alternative to invasive surgery, especially for tumors located deep within or close to vital areas of the brain. Radiosurgery is used to treat many types of brain tumors, either benign or malignant primary or metastatic lesions and either single or multiple tumors.

Stereotactic radiosurgery works in the same way as other forms of radiation treatment. It does not actually remove the tumor; rather it damages the DNA of tumor cells. As a result, these cells lose their ability to reproduce. Following treatment, benign tumors usually shrink over a period of time. Malignant and metastatic tumors may shrink more rapidly, even within a couple of months.

What equipment is used?
Linear accelerator (LINAC) radiosurgery consist of four phases: head frame placement and imaging, computerized dose planning and radiation delivery. The LINAC’s gantry rotates around the patient, delivering radiation beams through multiple arcs. The LINAC is able to use a larger x-ray beam, which enables it to treat larger tumors more uniformly and it can be used for fractionated radiosurgery or stereotactic radiotherapy using a relocatable frame, which is an advantage for larger tumors or particularly critical locations.

Who will be involved in this procedure and who operates the equipment?
The treatment team is comprised of a number of specialized medical professionals, typically including a radiation oncologist, a radiologist, a medical radiation physicist, and several radiation therapists.

  • The radiation oncologist leads the treatment team and oversees the treatment; they outline the targeted area(s) to be treated, decide on the appropriate radiation dose, approve the treatment plan, and interpret the results of radiosurgical procedures.
  • A radiologist interprets brain imaging that identifies the targeted area(s) to be treated.
  • The medical radiation physicist ensures the delivery of the precise dose or radiation.
  • The radiation oncologist along with the physicist uses a specialized computer software program to devise a treatment plan, calculates the exposures and beam configuration to conformally treat the targeted area(s) to the prescribed dose.
  • A highly trained radiation therapist positions the patient on the treatment table and operates the machine from an adjacent protected area. The radiation therapist can observe the patient on a closed circuit monitor.
  • A neurologist or neurosurgeon may participate with the radiation oncologist in the multidisciplinary team that considers various treatment options for individual cases and helps decide who may benefit from radiosurgery.

Is there any special preparation needed for the procedure?
Stereotactic radiosurgery is performed on an outpatient basis. The patient should not eat or drink anything after midnight on the night before imaging or the treatment. The owner should ask the oncologist if it is ok to take medications on the day of the treatment.

What will the patient feel during and after the procedure?
Radiosurgery treatments are similar to having an x-ray. There is no pain or discomfort from the actual treatment. Patients are anesthetized for the procedure as even slight movements can cause the oncologist to miss the tumor. In most cases, the patient can resume all normal activities within one or two days.