was doing experiments with a cathode tube,

用一支陰極射線管在做實驗

a glass container in which a beam of electrons lights up a fluorescent window.

那是一個玻璃容器，裏面用一串電子束點亮一個螢光屏幕

He had wrapped cardboard around the tube

他用硬紙板包覆整個管子

to keep the fluorescent light from escaping,

以避免螢光逸出

when something peculiar happened.

這時一件奇怪的事情發生了

Another screen outside the tube was glowing.

在管子外面的另一個螢幕發亮了

In other words, invisible rays had passed through the cardboard.

換句話說，有無形的射線穿透了硬紙板

Wilhelm had no idea what those rays were, so he called them X-rays,

威廉不知道那射線是什麼，所以他就稱它為 X-射線

and his discovery eventually won him a Nobel Prize.

而他的發現後來使他獲得了諾貝爾獎

Here's what we now know was happening.

以下就是我們目前所了解它是怎麼發生的

When high energy electrons in the cathode tube hit a metal component,

當在陰極射線管的高能量電子撞擊一個金屬物質時

they either got slowed down and released extra energy,

它們不是減速釋放多餘的能量

or kicked off electrons from the atoms they hit,

就是從被它們碰撞的原子撞出電子

which triggered a reshuffling that again released energy.

這會引發重組而釋出能量

In both cases, the energy was emitted in the form of X-rays,

這兩種情況，被釋放的能量轉為 X-射線

which is a type of electromagnetic radiation

這是一種電磁波

with higher energy than visible light, and lower energy than Gamma rays.

比可見光的能量高，而比伽馬射線能量低

X-rays are powerful enough to fly through many kinds of matter

X-射線強到足以穿透許多物質

as if they are semi-transparent,

就好像這些物質是半透明的一樣

and they're particularly useful for medical applications

它們對於醫學應用特別有用

because they can make images of organs, like bones, without harming them,

因為它們能使諸如骨頭的器官呈現影像，而不會傷害到它們

although they do have a small chance

儘管如此，它們還是有微小機會

of causing mutations in reproductive organs, and tissues like the thyroid,

造成生殖器官或如甲狀腺組織的突變

which is why lead aprons are often used to block them.

這就是為什麼常用鉛衣來阻擋它們的原因

When X-rays interact with matter, they collide with electrons.

當 X-射線與物質相互作用時，它們碰撞電子

Sometimes, the X-ray transfers all of its energy to the matter and gets absorbed.

有時候，X-射線將其能量傳給物質而全部被吸收

Other times, it only transfers some of its energy,

又有時候，它只是傳送部分能量

and the rest is scattered.

而其餘的散射掉

The frequency of these outcomes

這些結果發生的頻率

depends on how many electrons the X-rays are likely to hit.

端視 X-射線可能撞擊電子數目的多寡而定

Collisions are more likely if a material is dense,

假如物質是緻密的，碰撞的機率會比較高

or if it's made of elements with higher atomic numbers,

或物質是由原子數較高的元素所構成

which means more electrons.

意謂有較多的電子 （所以撞擊率也較高）

Bones are dense and full of calcium, which has a relatively high atomic number,

骨頭是緻密且充滿鈣質，具有較高的原子序數

so they absorb X-rays pretty well.

所以它們蠻能夠吸收 X-射線

Soft tissue, on the other hand, isn't as dense,

相反的，軟組織不是那麼緻密

and contains mostly lower atomic number elements,

大部分含有較低原子序數的元素

like carbon, hydrogen, and oxygen,

如碳、氫及氧

so more of the X-rays penetrate tissues like lungs and muscles,

所以比較多的 X-射線能穿透如肺及肌肉組織

darkening the film.

使底片變得較黑

These 2-D pictures are only useful up to a point, though.

不過這些 2D 影像的作用只能達到一定的程度

When X-rays travel through the body,

當 X-射線穿過身體

they can interact with many atoms along the path.

它們在行經途徑中與許多原子相互作用

What is recorded on the film reflects the sum of all those interactions.

這些作用的總和最後反應在底片上

It's like trying to print 100 pages of a novel on a single sheet of paper.

這就如同試著把 100 頁的小說印在一張紙上

To see what's really going on,

為了能夠看到全貌

you would have to take X-ray views from many angles around the body

你必須從身體的許多角度照 X 光片

and use them to construct an internal image.

然後將他們組成一個身體內部的圖像

And that's something doctors do all the time in a procedure

這就是醫生常做的的一種檢查

called a CT, Computed Tomography scan,

稱為 CT ，電腦斷層掃描

another Nobel Prize winning invention.

也是另一個獲得諾貝爾獎的發明

Think of CT like this.

將 CT 想像成這樣子

With just one X-ray,

只憑一張 X 光片，

you might be able to see the density change due to a solid tumor in a patient,

你也許能夠看到因病人體內的腫瘤所導致的密度變化

but you wouldn't know how deep it is beneath the surface.

可是你無法知道它在體表下有多深

However, if you take X-rays from multiple angles,

然而，你若從多重角度照 X 光片，

you should be able to find the tumor's position and shape.

就可以知道腫瘤的位置及形狀

A CT scanner works by sending a fan or cone of X-rays through a patient

電腦斷層掃描是將一個扇形或錐狀 X-射線射出，穿過病人

to an array of detectors.

到一個個排列好的影像接收器

The X-ray beam is rotated around the patient,

X 光射線繞著病人旋轉

and often also moved down the patient's body,

也常往病人下方移動

with the X-ray source tracing a spiral trajectory.

讓 X-射線光源按照螺旋軌跡走

Spiral CT scans produce data that can be processed into cross sections

螺旋電腦斷層掃描產生的數據，可以處理成橫斷面

detailed enough to spot anatomical features, tumors,

精細到足以標記出解剖的特徵、腫瘤、

blood clots, and infections.

血塊及感染

CT scans can even detect

電腦斷層掃描甚至可以偵測出

heart disease and cavities in mummies buried thousands of years ago.

數千年前埋葬的木乃伊的心臟疾病及蛀牙

So what began as Roentgen's happy accident has become a medical marvel.

當初倫琴的巧妙意外如今已變成醫學奇蹟

Hospitals and clinics now conduct over 100 million scans each year worldwide

現在每年，全世界的醫院和診所執行超過一億次的掃描

to treat diseases and save lives.

來治療疾病及拯救性命