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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.
每年，全世界有成千上万的人接受了无创的脑部手术：没有手术刀，没有手术台，病人不会失血。
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.
这种手术是在一个屏蔽室里进行的，里面有一台大型机器，它会向大脑内部的精确目标发射不可见的光束。
This treatment is called stereotactic radiosurgery, and those light beams are beams of radiation:
这种治疗叫做立体定向放射治疗,这些光束是辐射束：
their task is to destroy tumors by gradually scrubbing away malignant cells.
它们会逐渐清除恶性细胞，最终消灭肿瘤。
For patients, the process begins with a CT-scan, a series of x-rays that produce a three-dimensional map of the head.
对于病人来说，这个手术始于CT扫描，就是通过照射一系列的X射线产生头部的三维成像。
This reveals the precise location, size, and shape of the tumor within.
CT扫描能显示出肿瘤的精确位置、大小以及形状。
The CT-scans also help to calculate something called "Hounsfield Units," which show the densities of different tissues.
它还可以计算一种叫做“亨氏单位”的指标，亨氏单位能显示不同组织的密度。
This offers information about how radiation will propagate through the brain, to better optimize its effects.
揭示辐射如何在大脑中传播，以更好地发挥作用。
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.
医生也可以使用磁共振成像，它能产生更清晰的软组织图像，以便于更好地概述肿瘤的形状和位置。
Mapping its precise position and size is crucial because of the high doses of radiation needed to treat tumors.
绘制出肿瘤的精确位置和大小是至关重要的，因为治疗肿瘤需要高剂量的辐射。
Radiosurgery depends on the use of multiple beams. Individually, each delivers a low dose of radiation.
放射治疗依赖于多束射线的作用。每一束都能单独产生低剂量的辐射。
But, like several stage lights converging on the same point to create a bright and inescapable spotlight,
但是，就像几盏舞台灯光汇聚在同一点上会变成一个明亮的、惹眼的聚光灯一样，
when combined, the rays of radiation collectively produce enough power to destroy tumors.
辐射的射线聚集在一起能够产生足够的能量来摧毁肿瘤。
In addition to enabling doctors to target tumors in the brain while leaving the surrounding healthy tissue relatively unharmed,
除了能使医生瞄准大脑中的肿瘤，同时使周围的健康组织相对不受伤害之外，
the use of multiple beams also gives doctors flexibility.
多光束的使用也给了医生提供了灵活性。
They can optimize the best angles and routes through brain tissue to reach the target and adjust the intensity within each beam as necessary.
他们可以优化光束通过脑组织到达目标的最佳角度和路径，并根据需要调整每个光束的强度。
This helps spare critical structures within the brain. But what exactly does this ingenious approach do to the tumors in question?
这有助于避开大脑中的关键结构。但这种独特方法对肿瘤到底有什么作用呢？
When several beams of radiation intersect to strike a mass of cancerous cells,
当几束辐射交汇，并射向一团癌细胞，
their combined force essentially shears the cells' DNA, causing a breakdown in the cells' structure.
它们会合力切断细胞的DNA，导致细胞结构遭到破坏。
Over time, this process cascades into destroying the whole tumor.
随着时间的推移，这一系列连锁的过程会摧毁整个肿瘤。
Indirectly, the rays also damage the area immediately surrounding the DNA, creating unstable particles called free radicals.
射线也会间接破坏DNA周围的区域，产生不稳定的粒子，我们称之为自由基。
This generates a hazardous microenvironment that's inhospitable to the tumor, as well as some healthy cells in the immediate vicinity.
这就产生了一种有害的微环境，这种微环境对肿瘤以及附近的一些健康细胞都是不利的。
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.
通过保持辐射束的覆盖范围尽可能接近肿瘤的确切形状，可以降低伤害非癌组织的风险。
Once radiosurgery treatment has destroyed the tumor's cells, the body's natural cleaning mechanism kicks in.
一旦放射外科治疗摧毁了肿瘤细胞，身体的自然清理机制就会开始发挥作用。
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.
免疫系统开始迅速清理死细胞的外壳，将它们排出体外，而其他细胞则会转化为疤痕组织。
Despite its innovations, radiosurgery isn't always the primary choice for all brain cancer treatments.
尽管放射治疗有其创新之处，但它在所有的脑癌治疗中并非总是首选方案。
For starters, it's typically reserved for smaller tumors.
首先，它通常被用来对付较小的肿瘤。
Radiation also has a cumulative effect, meaning that earlier doses can overlap with those delivered later on.
其次，辐射也具有累积效应，这就意味着，早期的辐射剂量可能与后来的辐射剂量叠加。
So patients with recurrent tumors may have limitations with future radiosurgery treatments.
因此，肿瘤复发的病人在未来的放射外科治疗中可能面临着局限性。
But these disadvantages weigh up against some much larger benefits.
尽管存在着这些缺点，但放射治疗的优势依然非常明显。
For several types of brain tumors, radiosurgery can be as successful as traditional brain surgery at destroying cancerous cells.
对于几种类型的脑瘤，放射治疗也可以和传统的脑部手术一样成功地消灭癌细胞。
In tumors called meningiomas, recurrence is found to be equal, or lower, when the patient undergoes radiosurgery.
在被称为脑膜瘤的肿瘤中，患者接受放射治疗的复发率与手术相当，甚至更低。
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.
和传统手术相比--手术通常是一段需要漫长恢复期的痛苦经历--而放射治疗通常是无痛的，通常几乎不需要恢复时间。
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.
脑瘤并不是放疗的唯一用途：它的概念已经应用于肺、肝和胰腺的肿瘤。
Meanwhile, doctors are experimenting with using it to treat conditions such as Parkinson's disease, epilepsy, and obsessive compulsive disorder.
与此同时，医生们正在试验用它来治疗其他疾病，比如帕金森病、癫痫，还有强迫症。
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.
诊断出癌症带来的痛苦可能是撕心裂肺的，但这些非侵入性治疗技术的进步也为更温和的治疗手段铺平了道路。
