| How is the Gamma Knife different from radiation therapy?
In a sentence, Gamma Knife is more accurate and takes less time to
deliver than traditional radiation therapy.
Traditional radiation therapy often breaks up (fractionates) delivery of
radiation. This is done because cancer cells differ from healthy cells,
recovering more slowly from radiation exposure and, due to differing mitotic
(cell division and growth cycles) activity, are susceptible to cellular
destruction. Fractions of the 'killing dose' are delivered to the target and
while the healthy tissue recovers more quickly than cancer tissue, the
diseased tissue then is ultimately destroyed. Fractions are often delivered
with daily doses on weekdays over a period of 1 to 8 weeks, depending on the
disease.
Gamma Knife surgery is different from conventional radiation therapy of
the brain because the radiation is precisely directed at the target and
spares the surrounding normal brain tissue and other structures. Because of
this, the 'killing dose' can be delivered to just the targeted tumor in one
session. It is an 'overwhelming' dose that destroys the tumor.
Gamma Knife radiosurgery can be used in conjunction with whole brain
radiation therapy with excellent results. In addition, it can also be used
with conventional surgery as a treatment for tumors that cannot be totally
excised or, in some cases, where the tumor is inoperable.
Single versus multiple visits
Gamma Knife radiosurgery (single dose
treatment) is different than traditional Linear Accelerator (LINAC) based
radiation in that it is a single dose - one time, one day, and you're done,
versus multiple treatments (fractionated). Because the Gamma Knife has 201
sources of radiation, healthy tissue gets only 1/200th of the dose delivered
to the target. For that reason, the Gamma Knife can be used in a single-dose
delivery, eliminating the need to fractionate (break up the total dose into
smaller doses in order to preserve healthy brain tissue).
More accurate
Because the Gamma Knife has a fixed isocenter and fixates
the skull for delivery, its accuracy (and resulting minimal dosing to
healthy tissue) is superior to that of the LINAC.
Ease of treatment for you and the treating physicians
In addition, LINACs, used for stereotactic radiosurgery, usually take longer to treat
than does the Gamma Knife (especially for multiple tumors). Bottom line? You
wait less time with the Gamma Knife.
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