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