Stereotactic Radiosurgery (SRS
Despite its name, stereotactic radiosurgery is a non-surgical procedure that delivers precisely-targeted radiation at much higher doses than traditional radiation therapy while sparing healthy tissue organs nearby.
SRS is a technique that is most commonly used for tumors in the brain or spinal column. Unlike IMRT, SRS is typically delivered in a maximum of 5 sessions. Despite the use of the word "surgery" in its name, it does not involve removing the tumor with a surgical blade. Instead, a focused high-intensity beam of radiation is used to target the tumor.
Stereotactic radiosurgery, also called stereotactic radiotherapy, is a highly precise form of radiation therapy initially used to treat tumors and other abnormalities of the brain. Now radiosurgery is also being used to treat cancer in other parts of the body in a procedure called stereotactic body radiotherapy (SBRT).
Stereotactic radiosurgery relies on several technologies:
- three-dimensional imaging that determines the exact coordinates of the target within the body
- systems to immobilize and carefully position the patient
- highly focused gamma-ray or x-ray beams that converge on a tumor or abnormality radiation
- in some cases, image-guided radiation therapy (IGRT),which uses medical imaging to confirm the location of a tumor immediately before or during the delivery of
radiation to further improve the precision and accuracy of the treatment
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 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.
Although stereotactic radiosurgery is often completed in a one-day session, physicians sometimes recommend multiple treatments, especially for tumors larger than one inch in diameter.
Stereotactic Body Radiation Therapy (SBRT)
SBRT is a very similar technique to SRS but is used for targets that are outside the brain and the spine. SBRT is most commonly used for targets in the lung, liver, pancreas and kidney, and is typically delivered in a maximum of 5 sessions.
Framed Stereotactic RadioSurgery (SRS)
It is a technique that is carried out in cooperation with the department of neurosurgery. In this case, a head frame is attached to the skull under local anesthesia to ensure sub-millimeter precision and treatments are delivered in one session. SRS has almost equivalent efficacy to removing the tumor using surgery. This technique is highly effective in treating brain and spinal cord tumors and cancers.
Frameless Stereotactic Radiotherapy (FSRT)
It is a minimally invasive computer-aided procedure—used to treat patients with brain cancer—which delivers a highly concentrated dose of radiation with millimeter precision. The dose is delivered in multiple fractions (3-30 treatments). By selectively targeting a precise region, there is a minimal effect on the surrounding normal areas of the body. This technique is highly effective in some brain cancers, lung cancers, liver, pancreatic, bone and prostate cancers.
There is an exciting new option for treating lung cancer - respiration-gated radiation therapy. Historically the lungs have presented a challenge to radiation oncologists. The target tumor, like the lung itself, is constantly moving during treatment. For treatment to be effective, a larger area of the lung (and more healthy tissue) is irradiated, to ensure that the tumor is always within the radiation beam. With respiration-gated radiation therapy, the radiation beam is targeted - in real time with the breath - to a specific point in the cycle of respiration. Radiation gating reduces the amount of healthy lung receiving radiation, so a higher dose of radiation-double if not more-can be used. It can also reduce the time of treatment, in some cases from as many as six weeks to only two.
Ultimately, radiation-gating allows us to offer hope to people previously considered to be "untreatable." atients too sick to have surgery or traditional radiation therapy may be able to receive treatment with respiration-gated radiation therapy.
The new HD120 MLC multileaf collimator enables clinicians to deliver extremely precise radiosurgical treatments, including intensity-modulated radiosurgery (IMRS). A multileaf collimator is a device with many computer-controlled mechanical "leaves" or "slats" that continually shape the treatment beam as the radiation is delivered from different angles around the patient. HD MLC also offers improved dose delivery characteristics, including a steeper dose fall-off gradient, so that the amount of dose delivered decreases rapidly outside the targeted area, protecting healthy tissues more effectively than is possible with earlier beam shaping devices. The HD120 MLC is designed for durability, so that it can be relied upon during