without a single incision:

每年，全世界有數萬人接受

there's no scalpel, no operating table, and the patient loses no blood.

沒有任何切口的腦部手術：

Instead, this procedure takes place in a shielded room

沒有解剖刀，沒有手術台，

with a large machine that emits invisible beams of light

病人也不會失血。

at a precise target inside the brain.

這項醫療程序改在隔離室進行，

This treatment is called stereotactic radiosurgery,

裡面有一台大型機器， 發射看不見的光束，

and those light beams are beams of radiation:

精準射向大腦中的目標點。

their task is to destroy tumors by gradually scrubbing away malignant cells.

這項治療方式稱為立體定向手術，

For patients, the process begins with a CT-scan,

那些光束則是放射線射束：

a series of x-rays that produce a three-dimensional map of the head.

任務是漸漸除掉惡性細胞，

This reveals the precise location, size, and shape of the tumor within.

以摧毀腫瘤。

The CT-scans also help to calculate something called "Hounsfield Units,"

對病人而言，流程 始於電腦斷層掃瞄，

which show the densities of different tissues.

透過一連串 X 光， 產生出頭部的三維圖像，

This offers information about how radiation

呈現顱內腫瘤的 精確位置、大小，和形狀。

will propagate through the brain, to better optimize its effects.

電腦斷層掃瞄也能協助計算

Doctors might also use magnetic resonance imaging, or MRI's,

所謂的「韓森費爾德單位」，

that produce finer images of soft tissue,

這個值代表不同組織的密度。

to assist in better outlining a tumor's shape and location.

這些資訊能協助判斷放射線

Mapping its precise position and size is crucial

如何穿過大腦才會有最佳的效果。

because of the high doses of radiation needed to treat tumors.

醫生也可能使用磁振造影（MRI），

Radiosurgery depends on the use of multiple beams.

產生出更精細的軟組織影像，

Individually, each delivers a low dose of radiation.

協助將腫瘤的形狀 和位置描繪得更清楚。

But, like several stage lights converging on the same point

精確描繪腫瘤的位置和大小極其重要，

to create a bright and inescapable spotlight, when combined,

因為要用高劑量的 放射線來治療腫瘤。

the rays of radiation collectively produce enough power to destroy tumors.

放射手術需要使用多條射束，

In addition to enabling doctors to target tumors in the brain

每一條各是低劑量的放射線束。

while leaving the surrounding healthy tissue relatively unharmed,

但就如同舞台上的多重光源 聚焦於同一個點，

the use of multiple beams also gives doctors flexibility.

以產生出明亮、不亂竄的聚光燈，

They can optimize the best angles and routes through brain tissue

放射線通通加疊在一起

to reach the target and adjust the intensity within each beam

共同產生足以摧毀腫瘤的力量。

as necessary.

除了能讓醫生在相對不傷害

This helps spare critical structures within the brain.

周圍健康組織的情況下 對付腦中的腫瘤之外，

But what exactly does this ingenious approach do to the tumors in question?

多重射束的使用也讓醫生保有彈性，

When several beams of radiation intersect to strike a mass of cancerous cells,

他們可以找出放射線穿過腦部組織

their combined force essentially shears the cells' DNA,

抵達目標的最佳角度和路線，

causing a breakdown in the cells' structure.

並根據需求調整每條射束的強度，

Over time, this process cascades into destroying the whole tumor.

這麼做便能避免傷害 腦部的重要結構。

Indirectly, the rays also damage the area immediately surrounding the DNA,

但這種巧妙的方法 對目標腫瘤到底有什麼作用？

creating unstable particles called free radicals.

當數條放射線射束交會

This generates a hazardous microenvironment

攻擊癌細胞聚集處時，

that's inhospitable to the tumor,

它們結合起來的力量 基本上會切斷細胞的 DNA，

as well as some healthy cells in the immediate vicinity.

造成細胞的結構受損。

The risk of harming non-cancerous tissue is reduced

隨時間重覆這個流程， 會漸漸將整個腫瘤摧毀。

by keeping the radiation beam coverage

射線也會間接傷害到 和目標 DNA 相鄰接的區域，

as close to the exact shape of the tumor as possible.

創造出不穩定的粒子，稱為自由基。

Once radiosurgery treatment has destroyed the tumor's cells,

這會產生出一個有害的微環境，

the body's natural cleaning mechanism kicks in.

不適合腫瘤生長，

The immune system rapidly sweeps up the husks of dead cells

也不適合鄰接區域中的 一些健康細胞生長。

to flush them out of the body, while other cells transform into scar tissue.

傷害非癌症組織的風險 之所以能被降低，

Despite its innovations, radiosurgery isn't always the primary choice

是因為放射線射束的覆蓋範圍

for all brain cancer treatments.

被控制在盡可能 和腫瘤的形狀完全一樣。

For starters, it's typically reserved for smaller tumors.

一旦放射手術治療 將腫瘤細胞摧毀之後，

Radiation also has a cumulative effect,

身體的自然清理機制就會啟動。

meaning that earlier doses can overlap with those delivered later on.

免疫系統馬上就會 將死亡細胞的屍體清掉，

So patients with recurrent tumors

並排出體外，而其他細胞 則會轉變成疤痕組織。

may have limitations with future radiosurgery treatments.

儘管放射手術十分創新，

But these disadvantages weigh up against some much larger benefits.

卻不見得是所有 腦部癌症治療的首選。

For several types of brain tumors,

首先，放射手術會用來 治療較小的腫瘤。

radiosurgery can be as successful as traditional brain surgery

放射線也會有累加效應，

at destroying cancerous cells.

意即，先前的劑量可能會 和後來施予的劑量加疊。

In tumors called meningiomas, recurrence is found to be equal, or lower,

所以，對於腫瘤復發的病人，

when the patient undergoes radiosurgery.

未來的放射手術治療就可能會受限。

And compared to traditional surgery—

但這些弊處要拿來 和更重要的益處相比較。

often a painful experience with a long recovery period—

針對數種腦瘤，

radiosurgery is generally pain-free,

放射手術都有可能 和傳統腦部手術一樣

and often requires little to no recovery time.

能成功摧毀癌症細胞。

Brain tumors aren't the only target for this type of treatment:

就腦膜瘤而言，

its concepts have been put to use on tumors of the lungs, liver, and pancreas.

若病人接受放射手術，

Meanwhile, doctors are experimenting with using it to treat conditions

復發的機率和傳統一樣或更低。

such as Parkinson's disease, epilepsy, and obsessive compulsive disorder.

和傳統手術相比——

The pain of a cancer diagnosis can be devastating,

傳統手術通常是痛苦的經驗， 且時間復原很長——

but advancements in these non-invasive procedures

放射手術一般來說是無痛的，

are paving a pathway for a more gentle cure.

且需要的復原時間很短， 甚至可以立即復原。