0:00:06.962,0:00:11.920 Every year, tens of thousands of people[br]world-wide have brain surgery 0:00:11.920,0:00:14.200 without a single incision: 0:00:14.200,0:00:19.540 there’s no scalpel, no operating table, [br]and the patient loses no blood. 0:00:19.540,0:00:23.641 Instead, this procedure takes place [br]in a shielded room 0:00:23.641,0:00:28.173 with a large machine that emits [br]invisible beams of light 0:00:28.173,0:00:31.493 at a precise target inside the brain. 0:00:31.493,0:00:35.493 This treatment is called [br]stereotactic radiosurgery, 0:00:35.493,0:00:39.323 and those light beams [br]are beams of radiation: 0:00:39.323,0:00:45.383 their task is to destroy tumors by[br]gradually scrubbing away malignant cells. 0:00:45.383,0:00:49.143 For patients, the process begins [br]with a CT-scan, 0:00:49.143,0:00:54.013 a series of x-rays that produce [br]a three-dimensional map of the head. 0:00:54.013,0:00:59.654 This reveals the precise location, size,[br]and shape of the tumor within. 0:00:59.654,0:01:05.048 The CT-scans also help to calculate[br]something called "Hounsfield Units," 0:01:05.048,0:01:08.318 which show the densities[br]of different tissues. 0:01:08.318,0:01:11.238 This offers information [br]about how radiation 0:01:11.238,0:01:15.403 will propagate through the brain,[br]to better optimize its effects. 0:01:15.403,0:01:20.331 Doctors might also use [br]magnetic resonance imaging, or MRI’s, 0:01:20.331,0:01:23.641 that produce finer images of soft tissue, 0:01:23.641,0:01:28.248 to assist in better outlining [br]a tumor’s shape and location. 0:01:28.248,0:01:31.798 Mapping its precise position and size [br]is crucial 0:01:31.798,0:01:36.204 because of the high doses of radiation[br]needed to treat tumors. 0:01:36.204,0:01:40.306 Radiosurgery depends on the use[br]of multiple beams. 0:01:40.306,0:01:44.036 Individually, each delivers a low dose[br]of radiation. 0:01:44.036,0:01:48.357 But, like several stage lights converging[br]on the same point 0:01:48.357,0:01:53.015 to create a bright and inescapable[br]spotlight, when combined, 0:01:53.015,0:01:58.523 the rays of radiation collectively[br]produce enough power to destroy tumors. 0:01:58.523,0:02:02.343 In addition to enabling doctors to target[br]tumors in the brain 0:02:02.343,0:02:05.753 while leaving the surrounding [br]healthy tissue relatively unharmed, 0:02:05.753,0:02:09.856 the use of multiple beams [br]also gives doctors flexibility. 0:02:09.856,0:02:14.389 They can optimize the best angles [br]and routes through brain tissue 0:02:14.389,0:02:18.441 to reach the target and adjust [br]the intensity within each beam 0:02:18.441,0:02:19.941 as necessary. 0:02:19.941,0:02:22.951 This helps spare critical structures[br]within the brain. 0:02:22.951,0:02:28.118 But what exactly does this ingenious[br]approach do to the tumors in question? 0:02:28.118,0:02:33.796 When several beams of radiation intersect[br]to strike a mass of cancerous cells, 0:02:33.796,0:02:38.203 their combined force essentially[br]shears the cells’ DNA, 0:02:38.203,0:02:41.343 causing a breakdown[br]in the cells’ structure. 0:02:41.343,0:02:46.198 Over time, this process cascades [br]into destroying the whole tumor. 0:02:46.198,0:02:51.670 Indirectly, the rays also damage the area[br]immediately surrounding the DNA, 0:02:51.670,0:02:55.819 creating unstable particles[br]called free radicals. 0:02:55.819,0:02:58.359 This generates a hazardous [br]microenvironment 0:02:58.359,0:03:00.439 that’s inhospitable to the tumor, 0:03:00.439,0:03:03.839 as well as some healthy cells [br]in the immediate vicinity. 0:03:03.839,0:03:07.279 The risk of harming non-cancerous tissue[br]is reduced 0:03:07.279,0:03:09.699 by keeping the radiation beam coverage 0:03:09.699,0:03:14.110 as close to the exact shape[br]of the tumor as possible. 0:03:14.110,0:03:18.000 Once radiosurgery treatment has destroyed[br]the tumor’s cells, 0:03:18.000,0:03:21.300 the body’s natural cleaning[br]mechanism kicks in. 0:03:21.300,0:03:25.300 The immune system rapidly sweeps[br]up the husks of dead cells 0:03:25.300,0:03:30.492 to flush them out of the body, while[br]other cells transform into scar tissue. 0:03:30.492,0:03:35.304 Despite its innovations, radiosurgery[br]isn’t always the primary choice 0:03:35.304,0:03:37.614 for all brain cancer treatments. 0:03:37.614,0:03:41.744 For starters, it’s typically reserved [br]for smaller tumors. 0:03:41.744,0:03:44.454 Radiation also has a cumulative effect, 0:03:44.454,0:03:49.010 meaning that earlier doses can overlap[br]with those delivered later on. 0:03:49.010,0:03:51.380 So patients with recurrent tumors 0:03:51.380,0:03:55.604 may have limitations with future[br]radiosurgery treatments. 0:03:55.604,0:04:00.667 But these disadvantages weigh up [br]against some much larger benefits. 0:04:00.667,0:04:02.797 For several types of brain tumors, 0:04:02.797,0:04:06.637 radiosurgery can be as successful [br]as traditional brain surgery 0:04:06.637,0:04:08.597 at destroying cancerous cells. 0:04:08.597,0:04:13.829 In tumors called meningiomas, [br]recurrence is found to be equal, or lower, 0:04:13.829,0:04:16.679 when the patient undergoes radiosurgery. 0:04:16.679,0:04:18.639 And compared to traditional surgery— 0:04:18.639,0:04:21.979 often a painful experience [br]with a long recovery period— 0:04:21.979,0:04:24.739 radiosurgery is generally pain-free, 0:04:24.739,0:04:28.479 and often requires [br]little to no recovery time. 0:04:28.479,0:04:32.049 Brain tumors aren’t the only target [br]for this type of treatment: 0:04:32.049,0:04:37.187 its concepts have been put to use on[br]tumors of the lungs, liver, and pancreas. 0:04:37.187,0:04:41.187 Meanwhile, doctors are experimenting[br]with using it to treat conditions 0:04:41.187,0:04:46.583 such as Parkinson’s disease, epilepsy,[br]and obsessive compulsive disorder. 0:04:46.583,0:04:49.693 The pain of a cancer diagnosis [br]can be devastating, 0:04:49.693,0:04:52.733 but advancements in these [br]non-invasive procedures 0:04:52.733,0:04:55.853 are paving a pathway[br]for a more gentle cure.