VOA标准英语2010年-Airport Body Scanners Called Safe If P

"Compared to the dose level of a medical chest x-ray, a backscatter scan is thousands of times lower."

Since the Christmas Day attempted bombing of a U.S. airliner¹, airports are looking for ways to tighten² security.  One method being adopted by some and considered by others is the full body scanner.  A Johns Hopkins university professor says the scanners can be used safely and protect privacy at the same time. 

A young Nigerian – Umar Farouk Abdulmutallab – pleaded not guilty early this year to charges he smuggled³ explosives aboard an airliner by hiding them in his underwear.  He was traveling on a Northwest Airlines flight from Amsterdam to Detroit.  There were 300 people on board.

Many say a full body scanner would have detected the explosives before he boarded the plane.

However, the scanners have raised questions about safety and privacy.  For example, would the scanners give passengers large doses of x-rays?
   
Mahadevappa Mahesh says no. He’s chief physicist⁴ at Johns Hopkins Hospital in Baltimore, Maryland, and associate professor of radiology and medicine at the Johns Hopkins School of Medicine. 

He says two technologies are currently being used in the scanners.  One is Millimeter Wave Technology, the other is Backscatter Technology.

“The Millimeter Radio Wave Technology does not does not use x-rays.  The radio waves are similar to the radio waves produced by cell phones and so forth⁵.  The second one, the Backscatter system, uses x-rays to scan,” he says.

The backscatter system, he says, provides good images.  But some worry about the dose of radiation a person might get by standing⁶ in front of a full body scanner.

“The x-rays are not strong (enough) to penetrate⁷ the body.  They just reflect off the body.  X-rays are captured by a detector⁸ and the detector creates an image,” he says.

But just how safe is it?

“The radiation dose levels in these body scanners are quite low.  Let me compare it to a medical chest x-ray.  Compared to the dose level of a medical chest x-ray, a backscatter scan is thousands of times lower.  The other way to put it in perspective is one has to undergo nearly a thousand to two thousand of the backscatter scans before they get a dose equaling the one chest x-ray,” he says.

The Johns Hopkins physicist says everyone is exposed to radiation everyday and at much higher doses than those emitted by the backscatter scan.

“There’s cosmic radiation, radiation from the earth and so forth.  Compared to that, we need really 100 to 200 scans to be equal to one day of background radiation,” he says.

And he says from take-off to landing, you’re being dosed with enough radiation equal to 40 to 80 backscatter scans. 

Privacy

Mahesh says because the radiation emitted is so low, the security benefits far outweigh⁹ the risks.

 
AFP
This file combination of images taken on October 13, 2009 shows an airport staff member (L) demonstrating a full body scan at Manchester Airport in Manchester, England

“Typically, they are installing two of them. So, simultaneously¹⁰ they can take the front and back image.  So, anything taped onto the surface of the body should show up on the image.  That’s the idea,” he says.

It’s those images that have raised concerns about privacy.  In other words, who sees them?  Professor Mahesh believes these concerns can be addressed.

“In the airport, they’re trying to keep these viewing stations far away from the scanners.  So the same security guy who’s asking a person to go through the scan is not the one who’s seeing the images.  Therefore, it is remotely seen somewhere in a controlled area where the guys who are watching these images are seeing nothing but these images all day,” he says.

And, he says, the images can be adjusted somewhat to enhance privacy without losing the security benefits.

“Some of the images I have seen are more like a ghost image, with anything taped on the surface (of the body) highlighting.  That way it will negate¹¹ some of the revealing details of the body.  These manufacturers are also guaranteeing that the systems do not have a long-term saving mechanism¹².  So the images are not saved and they’re supposed to be purged¹³ then and there, once the screening is done,” he says.

The Johns Hopkins University professor does warn, however, that the scanners must be properly maintained to ensure radiation emissions¹⁴ remain low.

“For example, if the scanners are installed in some African country and after two years it breaks down and somebody comes and does the repair, it needs to be verified by a third party so that radiation dose levels are within standards,” he says.

Mahesh has published his findings on airport full-body scanners in the British Medical Journal.
 

1 airliner   

n.客机，班机

参考例句：

• The pilot landed the airliner safely.驾驶员使客机安全着陆。
• The passengers were shepherded across the tarmac to the airliner.旅客们被引导走过跑道去上飞机。

2 tighten   

v.(使)变紧；(使)绷紧

参考例句：

• Turn the screw to the right to tighten it.向右转动螺钉把它拧紧。
• Some countries tighten monetary policy to avoid inflation.一些国家实行紧缩银根的货币政策，以避免通货膨胀。

3 smuggled   

水货

参考例句：

• The customs officer confiscated the smuggled goods. 海关官员没收了走私品。 来自《现代汉英综合大词典》
• Those smuggled goods have been detained by the port office. 那些走私货物被港务局扣押了。 来自互联网

4 physicist   

n.物理学家，研究物理学的人

参考例句：

• He is a physicist of the first rank.他是一流的物理学家。
• The successful physicist never puts on airs.这位卓有成就的物理学家从不摆架子。

5 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

6 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

7 penetrate   

v.透(渗)入；刺入，刺穿；洞察，了解

参考例句：

• Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
• The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。

8 detector   

n.发觉者，探测器

参考例句：

• The detector is housed in a streamlined cylindrical container.探测器安装在流线型圆柱形容器内。
• Please walk through the metal detector.请走过金属检测器。

9 outweigh   

vt.比...更重，...更重要

参考例句：

• The merits of your plan outweigh the defects.你制定的计划其优点胜过缺点。
• One's merits outweigh one's short-comings.功大于过。

10 simultaneously   

adv.同时发生地，同时进行地

参考例句：

• The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
• The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。

11 negate   

vt.否定，否认；取消，使无效

参考例句：

• Our actions often negate our principles.我们的行为时常与我们所信奉的原则背道而弛。
• Mass advertising could negate the classical theory of supply and demand.大宗广告可以否定古典经济学的供求理论。

12 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

13 purged   

清除（政敌等）( purge的过去式和过去分词 )； 涤除（罪恶等）； 净化（心灵、风气等）； 消除（错事等）的不良影响

参考例句：

• He purged his enemies from the Party. 他把他的敌人从党内清洗出去。
• The iron in the chemical compound must be purged. 化学混合物中的铁必须清除。

14 emissions   

排放物( emission的名词复数 )； 散发物（尤指气体）

参考例句：

• Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
• Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。