[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.96,0:00:11.92,Default,,0000,0000,0000,,Every year, tens of thousands of people\Nworld-wide have brain surgery
Dialogue: 0,0:00:11.92,0:00:14.20,Default,,0000,0000,0000,,without a single incision:
Dialogue: 0,0:00:14.20,0:00:19.54,Default,,0000,0000,0000,,there’s no scalpel, no operating table, \Nand the patient loses no blood.
Dialogue: 0,0:00:19.54,0:00:23.64,Default,,0000,0000,0000,,Instead, this procedure takes place \Nin a shielded room
Dialogue: 0,0:00:23.64,0:00:28.17,Default,,0000,0000,0000,,with a large machine that emits \Ninvisible beams of light
Dialogue: 0,0:00:28.17,0:00:31.49,Default,,0000,0000,0000,,at a precise target inside the brain.
Dialogue: 0,0:00:31.49,0:00:35.49,Default,,0000,0000,0000,,This treatment is called \Nstereotactic radiosurgery,
Dialogue: 0,0:00:35.49,0:00:39.32,Default,,0000,0000,0000,,and those light beams \Nare beams of radiation:
Dialogue: 0,0:00:39.32,0:00:45.38,Default,,0000,0000,0000,,their task is to destroy tumors by\Ngradually scrubbing away malignant cells.
Dialogue: 0,0:00:45.38,0:00:49.14,Default,,0000,0000,0000,,For patients, the process begins \Nwith a CT-scan,
Dialogue: 0,0:00:49.14,0:00:54.01,Default,,0000,0000,0000,,a series of x-rays that produce \Na three-dimensional map of the head.
Dialogue: 0,0:00:54.01,0:00:59.65,Default,,0000,0000,0000,,This reveals the precise location, size,\Nand shape of the tumor within.
Dialogue: 0,0:00:59.65,0:01:05.05,Default,,0000,0000,0000,,The CT-scans also help to calculate\Nsomething called "Hounsfield Units,"
Dialogue: 0,0:01:05.05,0:01:08.32,Default,,0000,0000,0000,,which show the densities\Nof different tissues.
Dialogue: 0,0:01:08.32,0:01:11.24,Default,,0000,0000,0000,,This offers information \Nabout how radiation
Dialogue: 0,0:01:11.24,0:01:15.40,Default,,0000,0000,0000,,will propagate through the brain,\Nto better optimize its effects.
Dialogue: 0,0:01:15.40,0:01:20.33,Default,,0000,0000,0000,,Doctors might also use \Nmagnetic resonance imaging, or MRI’s,
Dialogue: 0,0:01:20.33,0:01:23.64,Default,,0000,0000,0000,,that produce finer images of soft tissue,
Dialogue: 0,0:01:23.64,0:01:28.25,Default,,0000,0000,0000,,to assist in better outlining \Na tumor’s shape and location.
Dialogue: 0,0:01:28.25,0:01:31.80,Default,,0000,0000,0000,,Mapping its precise position and size \Nis crucial
Dialogue: 0,0:01:31.80,0:01:36.20,Default,,0000,0000,0000,,because of the high doses of radiation\Nneeded to treat tumors.
Dialogue: 0,0:01:36.20,0:01:40.31,Default,,0000,0000,0000,,Radiosurgery depends on the use\Nof multiple beams.
Dialogue: 0,0:01:40.31,0:01:44.04,Default,,0000,0000,0000,,Individually, each delivers a low dose\Nof radiation.
Dialogue: 0,0:01:44.04,0:01:48.36,Default,,0000,0000,0000,,But, like several stage lights converging\Non the same point
Dialogue: 0,0:01:48.36,0:01:53.02,Default,,0000,0000,0000,,to create a bright and inescapable\Nspotlight, when combined,
Dialogue: 0,0:01:53.02,0:01:58.52,Default,,0000,0000,0000,,the rays of radiation collectively\Nproduce enough power to destroy tumors.
Dialogue: 0,0:01:58.52,0:02:02.34,Default,,0000,0000,0000,,In addition to enabling doctors to target\Ntumors in the brain
Dialogue: 0,0:02:02.34,0:02:05.75,Default,,0000,0000,0000,,while leaving the surrounding \Nhealthy tissue relatively unharmed,
Dialogue: 0,0:02:05.75,0:02:09.86,Default,,0000,0000,0000,,the use of multiple beams \Nalso gives doctors flexibility.
Dialogue: 0,0:02:09.86,0:02:14.39,Default,,0000,0000,0000,,They can optimize the best angles \Nand routes through brain tissue
Dialogue: 0,0:02:14.39,0:02:18.44,Default,,0000,0000,0000,,to reach the target and adjust \Nthe intensity within each beam
Dialogue: 0,0:02:18.44,0:02:19.94,Default,,0000,0000,0000,,as necessary.
Dialogue: 0,0:02:19.94,0:02:22.95,Default,,0000,0000,0000,,This helps spare critical structures\Nwithin the brain.
Dialogue: 0,0:02:22.95,0:02:28.12,Default,,0000,0000,0000,,But what exactly does this ingenious\Napproach do to the tumors in question?
Dialogue: 0,0:02:28.12,0:02:33.80,Default,,0000,0000,0000,,When several beams of radiation intersect\Nto strike a mass of cancerous cells,
Dialogue: 0,0:02:33.80,0:02:38.20,Default,,0000,0000,0000,,their combined force essentially\Nshears the cells’ DNA,
Dialogue: 0,0:02:38.20,0:02:41.34,Default,,0000,0000,0000,,causing a breakdown\Nin the cells’ structure.
Dialogue: 0,0:02:41.34,0:02:46.20,Default,,0000,0000,0000,,Over time, this process cascades \Ninto destroying the whole tumor.
Dialogue: 0,0:02:46.20,0:02:51.67,Default,,0000,0000,0000,,Indirectly, the rays also damage the area\Nimmediately surrounding the DNA,
Dialogue: 0,0:02:51.67,0:02:55.82,Default,,0000,0000,0000,,creating unstable particles\Ncalled free radicals.
Dialogue: 0,0:02:55.82,0:02:58.36,Default,,0000,0000,0000,,This generates a hazardous \Nmicroenvironment
Dialogue: 0,0:02:58.36,0:03:00.44,Default,,0000,0000,0000,,that’s inhospitable to the tumor,
Dialogue: 0,0:03:00.44,0:03:03.84,Default,,0000,0000,0000,,as well as some healthy cells \Nin the immediate vicinity.
Dialogue: 0,0:03:03.84,0:03:07.28,Default,,0000,0000,0000,,The risk of harming non-cancerous tissue\Nis reduced
Dialogue: 0,0:03:07.28,0:03:09.70,Default,,0000,0000,0000,,by keeping the radiation beam coverage
Dialogue: 0,0:03:09.70,0:03:14.11,Default,,0000,0000,0000,,as close to the exact shape\Nof the tumor as possible.
Dialogue: 0,0:03:14.11,0:03:18.00,Default,,0000,0000,0000,,Once radiosurgery treatment has destroyed\Nthe tumor’s cells,
Dialogue: 0,0:03:18.00,0:03:21.30,Default,,0000,0000,0000,,the body’s natural cleaning\Nmechanism kicks in.
Dialogue: 0,0:03:21.30,0:03:25.30,Default,,0000,0000,0000,,The immune system rapidly sweeps\Nup the husks of dead cells
Dialogue: 0,0:03:25.30,0:03:30.49,Default,,0000,0000,0000,,to flush them out of the body, while\Nother cells transform into scar tissue.
Dialogue: 0,0:03:30.49,0:03:35.30,Default,,0000,0000,0000,,Despite its innovations, radiosurgery\Nisn’t always the primary choice
Dialogue: 0,0:03:35.30,0:03:37.61,Default,,0000,0000,0000,,for all brain cancer treatments.
Dialogue: 0,0:03:37.61,0:03:41.74,Default,,0000,0000,0000,,For starters, it’s typically reserved \Nfor smaller tumors.
Dialogue: 0,0:03:41.74,0:03:44.45,Default,,0000,0000,0000,,Radiation also has a cumulative effect,
Dialogue: 0,0:03:44.45,0:03:49.01,Default,,0000,0000,0000,,meaning that earlier doses can overlap\Nwith those delivered later on.
Dialogue: 0,0:03:49.01,0:03:51.38,Default,,0000,0000,0000,,So patients with recurrent tumors
Dialogue: 0,0:03:51.38,0:03:55.60,Default,,0000,0000,0000,,may have limitations with future\Nradiosurgery treatments.
Dialogue: 0,0:03:55.60,0:04:00.67,Default,,0000,0000,0000,,But these disadvantages weigh up \Nagainst some much larger benefits.
Dialogue: 0,0:04:00.67,0:04:02.80,Default,,0000,0000,0000,,For several types of brain tumors,
Dialogue: 0,0:04:02.80,0:04:06.64,Default,,0000,0000,0000,,radiosurgery can be as successful \Nas traditional brain surgery
Dialogue: 0,0:04:06.64,0:04:08.60,Default,,0000,0000,0000,,at destroying cancerous cells.
Dialogue: 0,0:04:08.60,0:04:13.83,Default,,0000,0000,0000,,In tumors called meningiomas, \Nrecurrence is found to be equal, or lower,
Dialogue: 0,0:04:13.83,0:04:16.68,Default,,0000,0000,0000,,when the patient undergoes radiosurgery.
Dialogue: 0,0:04:16.68,0:04:18.64,Default,,0000,0000,0000,,And compared to traditional surgery—
Dialogue: 0,0:04:18.64,0:04:21.98,Default,,0000,0000,0000,,often a painful experience \Nwith a long recovery period—
Dialogue: 0,0:04:21.98,0:04:24.74,Default,,0000,0000,0000,,radiosurgery is generally pain-free,
Dialogue: 0,0:04:24.74,0:04:28.48,Default,,0000,0000,0000,,and often requires \Nlittle to no recovery time.
Dialogue: 0,0:04:28.48,0:04:32.05,Default,,0000,0000,0000,,Brain tumors aren’t the only target \Nfor this type of treatment:
Dialogue: 0,0:04:32.05,0:04:37.19,Default,,0000,0000,0000,,its concepts have been put to use on\Ntumors of the lungs, liver, and pancreas.
Dialogue: 0,0:04:37.19,0:04:41.19,Default,,0000,0000,0000,,Meanwhile, doctors are experimenting\Nwith using it to treat conditions
Dialogue: 0,0:04:41.19,0:04:46.58,Default,,0000,0000,0000,,such as Parkinson’s disease, epilepsy,\Nand obsessive compulsive disorder.
Dialogue: 0,0:04:46.58,0:04:49.69,Default,,0000,0000,0000,,The pain of a cancer diagnosis \Ncan be devastating,
Dialogue: 0,0:04:49.69,0:04:52.73,Default,,0000,0000,0000,,but advancements in these \Nnon-invasive procedures
Dialogue: 0,0:04:52.73,0:04:55.85,Default,,0000,0000,0000,,are paving a pathway\Nfor a more gentle cure.