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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

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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.