 Gamma Knife
How does it work?
A gamma knife consists of a large, heavily
shielded hemisphere containing 201 cobalt-60 sources. The collimated
beams of radiation emanating from the cobalt-60 sources are positioned
to converge on a single point within the unit, where the procedure takes
place.
The patient is fitted with a stereotactic frame which prevents movement of the head during treatment. With the frame in place, precise
coordinate settings are calculated to determine the exact location of
the tumor. The patient rests on a special couch that moves into
Gamma Knife, positioning the patient’s head for treatment.
The procedure takes 15-40 minutes and is normally
performed with local anesthesia.
The Gamma Knife surgery delivers a single, high
dose of ionizing radiation. At the point where all 201 beams
simultaneously intersect, it delivers enough radiation to treat tumors
or vascular malformations while minimizing dose to surrounding tissue.
A variety of helmet sizes allow for four different beam
sizes with apertures ranging from 4 to 18 millimeters.
Complex lesion shapes can be treated through multiple exposures and by
readjusting the collimator and head position.
Patients experience virtually no discomfort or
immediate side effects. The benefits of treatment manifest themselves
over time. The lesion will dissolve or shrink gradually and eventually
disappear or will exhibit no further growth. The time period varies
with the type, size and location of the lesion.
Gamma Knife surgery is more cost efficient than
conventional neurosurgery. Patient hospital stays are short; patients
are usually admitted the evening before treatment and discharged within
a day of treatment. Gamma Knife provides a clear socio-economic
advantage to the community. Many of the expenses of disability and convalescence
associated with conventional surgery are avoided.
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