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Every year, tens of thousands of people
world-wide have brain surgery
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without a single incision:
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there’s no scalpel, no operating table,
and the patient loses no blood.
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Instead, this procedure takes place in a
shielded room
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with a large machine that emits invisible
beams of light
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at a precise target inside the brain.
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This treatment is called stereotactic
radiosurgery,
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and those light beams are
beams of radiation:
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their task is to destroy tumors by
gradually scrubbing away malignant cells.
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For patients, the process begins with
a CT-scan,
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a series of x-rays that produce a
three-dimensional map of the head.
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This reveals the precise location, size,
and shape of the tumor within.
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The CT-scans also help to calculate
something called ‘Hounsfield Units’,
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which show the densities
of different tissues.
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This offers information about how
radiation
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will propagate through the brain,
to better optimize its effects.
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Doctors might also use magnetic resonance
imaging, or “MRI’s,”
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that produce finer images of soft tissue,
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to assist in better outlining a
tumor’s shape and location.
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Mapping its precise position and size is
crucial
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because of the high doses of radiation
needed to treat tumors.
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Radiosurgery depends on the use
of multiple beams.
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Individually, each delivers a low dose
of radiation.
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But, like several stage lights converging
on the same point
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to create a bright and inescapable
spotlight, when combined,
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the rays of radiation collectively
produce enough power to destroy tumors.
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In addition to enabling doctors to target
tumors in the brain
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while leaving the surrounding healthy
tissue relatively unharmed,
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the use of multiple beams also
gives doctors flexibility.
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They can optimize the best angles and
routes through brain tissue
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to reach the target and adjust the
intensity within each beam as necessary.
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This helps spare critical structures
within the brain.
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But what exactly does this ingenious
approach do to the tumors in question?
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When several beams of radiation intersect
to strike a mass of cancerous cells,
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their combined force essentially
shears the cells’ DNA,
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causing a breakdown
in the cells’ structure.
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Over time, this process cascades into
destroying the whole tumor.
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Indirectly, the rays also damage the area
immediately surrounding the DNA,
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creating unstable particles
called free radicals.
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This generates a hazardous
microenvironment
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that’s inhospitable to the tumor,
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as well as some healthy cells
in the immediate vicinity.
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The risk of harming non-cancerous tissue
is reduced
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by keeping the radiation beam coverage
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as close to the exact shape
of the tumor as possible.
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Once radiosurgery treatment has destroyed
the tumor’s cells,
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the body’s natural cleaning
mechanism kicks in.
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The immune system rapidly sweeps
up the husks of dead cells
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to flush them out of the body, while
other cells transform into scar tissue.
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Despite its innovations, radiosurgery
isn’t always the primary choice
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for all brain cancer treatments.
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For starters, it’s typically reserved for
smaller tumors.
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Radiation also has a cumulative effect,
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meaning that earlier doses can overlap
with those delivered later on.
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So patients with recurrent tumors
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may have limitations with future
radiosurgery treatments.
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But these disadvantages weigh up
against some much larger benefits.
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For several types of brain tumors,
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radiosurgery can be as successful as
traditional brain surgery
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at destroying cancerous cells.
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In tumors called meningiomas,
recurrence is found to be equal, or lower,
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when the patient undergoes radiosurgery.
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And compared to traditional surgery––
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often a painful experience with
a long recovery period––
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radiosurgery is generally pain-free,
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and often requires little
to no recovery time.
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Brain tumors aren’t the only target for
this type of treatment:
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its concepts have been put to use on
tumors of the lungs, liver, and pancreas.
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Meanwhile, doctors are experimenting
with using it to treat conditions
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such as Parkinson’s disease, epilepsy,
and obsessive compulsive disorder.
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The pain of a cancer diagnosis can be
devastating,
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but advancements in these non-invasive
procedures
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are paving a pathway
for a more gentle cure.