Stereotactic Radiosurgery (SRS)
The University of Tennessee Medical Center is now offering Brainlab Stereotactic Radiosurgery as part of our expanding state-of-the-art technologies. Brainlab Stereotactic Radiosurgery in conjunction with our new TrueBeam advanced medical linear accelerator system offers the most advanced radiotherapy and radiosurgery technology similar to CyberKnife and GammaKnife.
Brainlab Stereotactic Radiosurgery is non-invasive radiation therapy that offers our patients new options and hope in the fight against cancer and other abnormalities of the brain and spine.
The new TrueBeam advanced medical linear accelerator technology from Varian Medical Systems was engineered from the ground up to deliver high doses with accuracy in the fractions of millimeters, narrowly targeting tumors and better able to avoid the surrounding healthy tissues and organs.
The Cancer Institute’s addition of this state-of-the-art stereotactic radiosurgery increases access to advanced procedures when you need them most. This rapid and painless outpatient treatment allows you to maintain your regular routines, even while fighting cancer. Talk to your doctor today about Brainlab Stereotactic Radiosurgery.
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What is Stereotactic Radiosurgery (SRS) and how is it used?
SRS is a highly precise form of radiation therapy that was first developed to treat small brain tumors and functional abnormalities of the brain. When doctors use SRS to treat tumors in areas of the body other than the brain,it is called stereotactic body radiotherapy (SBRT).
Unlike conventional cancer treatment methods, SRS/SBRT is delivered from outside the body to destroy tumors or other targeted abnormalities without an incision, so you can avoid hospitalization, lengthy recovery periods, and many of the complications often associated with conventional surgery. This treatment is only possible due to the development of highly advanced radiation technologies that permit maximum dose delivery within the target while minimizing dose to the surrounding healthy tissue.
The goal of SRS/SBRT is to deliver doses that will destroy the tumor and achieve permanent local control.
Although SRS commonly refers to a one-day treatment, physicians sometimes recommend multiple stereotactic delivered treatments. This is important for larger tumors as the surrounding normal tissue exposed to the single high dose of radiation must be respected and limited, and the volume of normal tissue treated increases proportionally to the tumor size. Delivering the radiation in more sessions as opposed to one can improve safety and allow the normal tissue to heal in between treatments.
Consider these key benefits offered by Stereotactic Radiosurgery and Stereotactic Body Radiotherapy:
- Great speed and precision, allowing you to return home the same day of treatment
- Potent combination of a powerful linear accelerator, for treatment delivery, with advanced image guidance planning tools that provide your doctor with detailed information about the precise location and shape of your tumor or lesion
- Framelessradiosurgery that offers a more patient-friendly immobilization alternative
SBRT typically consists of one to five treatment sessions delivered over the course of one to two weeks.
For some technologies, you may be asked to have a fiducial marker placed in or near your tumor for selected cases. A fiducial is a small metal BB/pellet type marker that is easily identifiable on an X-ray image and used for a point of reference. However, for most CT based image-guidance technologies, this step is not needed. If a fiducial is required, depending on the location of your tumor, your radiation oncologist may work with a pulmonologist, gastroenterologist or radiologist to have one to four fiducial markers placed near the tumor. Placement of the fiducial marker is almost always an outpatient procedure. Next, your radiation oncologist will determine the method of aligning your body with the beams from the linear accelerator, which is called a simulation.
Three-dimensional imaging, such as CT, MRI and PET/CT is used to locate the tumor or abnormality within the body and define its exact size and shape. These images also guide the treatment planning—in which beams of radiation are designed to converge on the target area from different angles and planes—as well as the careful positioning of the patient for therapy sessions.
Immobilization devices are often used to align patients very precisely and make sure they remain still during simulation and treatment. Some of these systems may hold you quite tight; therefore you should tell your physician if you suffer from claustrophobia. After an immobilization device is created for you, a CT scan is performed over the area to be treated.
Your physicians may also perform a 4DCT, where the CT scan obtains information on how your tumor moves while you breathe. This is very common for tumors in the lungs or liver. After the scan is completed, you will be sent home.
The third part of the process is planning. The radiation oncologist will work with a radiation dosimetrist and medical physicist to plan the beam arrangement best suited for your tumor. They may incorporate other imaging techniques, such as MRI or PET/CT. Using specialized software, the team will go through hundreds of different combinations of beams to determine which would be best for your situation.
Radiation delivery of SRS and SBRT treatment is done on our TrueBeam linear accelerator. There are normally no restrictions on eating or drinking, though some patients may take an anti-inflammatory, anti-nausea or anti-anxiety medication prior to the treatment. You will be placed in the immobilization device. X-rays or a CT scan will be taken to line up the beams of radiation with the tumor prior to starting the radiation therapy. The radiation therapist will position you with guidance from the radiation oncologist based on these x-rays. The radiation therapist will then deliver the treatment. Sometimes, x-rays or a CT scan will be taken during the treatment to monitor the position of the tumor. Treatment can take up to one hour.
SRS and SBRT rely on several technologies:
- Three-dimensional imaging and localization techniques that determine the exact coordinates of the target within the body
- Immobilization systems to carefully position the patient and maintain the patient position during therapy
- Highly focused x-ray beams that converge on a tumor or abnormality
- Image-guided radiation therapy (IGRT) which uses medical imaging to confirm the location of a tumor immediately before, and in some cases, during the delivery of radiation. IGRT improves the precision and accuracy of the treatment
SRS and SBRT are important alternatives to invasive surgery, especially for patients who are unable to undergo surgery and for tumors and abnormalities that are:
- hard to reach
- located close to vital organs/anatomic regions
- subject to movement within the body
In most cases, radiosurgery and SBRT patients can resume all of their normal activities immediately. The number and severity of side effects you experience will depend on the type of radiation and dosage you receive and the part of your body being treated. You should talk to your doctor and nurse about any side effects you experience so they can help you manage them.
The University of Tennessee Cancer Institute treats the following cancerous and non-cancerous conditions of the brain and body with SRS and SBRT:
• Acoustic neuromas
• Brain metastases/gliomas
• Liver tumors/metastases
• Lung tumors/metastases
• Meningiomas of the skull base
• Pituitary adenomas
• Recurrent brain tumors
• Spine tumors/metastases