时差N小时 扫描有风险?

Dear Yael and Don: I know that imaging tests like CT scans and MRI and nuclear imaging are great tools because they allow doctors to see inside the body. But don't they also expose people to radiation? And if so, isn't this a bad thing?

亲爱的雅艾尔和唐：我知道像CT扫描和核磁共振成像等影像学检查是很好的医疗设备，因为它们能协助医生看见身体内部。但它们不会让人受到辐射吗？如果是，这难道不是件坏事？

Yael: Yes. And no. Some imaging tests do expose people to radiation. But just to be clear, MRI, which stands for magnetic resonance¹ imaging, does not use radiation. So if you have an MRI, there's no risk of exposure.

雅艾尔：是，也不是。有些影像学检查确实对人体有辐射作用。但你要清楚，MRI扫描，也就是核磁共振成像却并不涉及到辐射。因此如果你做MRI扫描，并不会有接触辐射的风险。

Don: But other types of imaging tests do use risk of exposure. Like nuclear imaging, which is used to look for heart disease. And CT, or CAT scans, which use x-rays to take 3D pictures inside the body. And, unfortunately, over time these tests do sometimes expose people to dangerously high levels of radiation. High enough to cause cancer, in some cases.

唐：但其它类型的影像学检查确实有辐射，比如用来检查心脏病的核成像，CT或CAT扫描，利用X光线拍摄人体内部的3D影像。但不幸的是，时间长了这些扫描确实会让人们暴露在高水平的、危险的辐射中去。在某些情况下，辐射的水平高到足以致癌。

Yael: But why would doctors order tests that put people at risk for getting cancer?

雅艾尔：但为什么医生还要求病人冒着患上癌症的风险做检查呢？

Don: Well, mainly because the tests are often very useful. For example, mammography is the best way to look for early signs of breast cancer. But it's not as clear that other tests, such as nuclear imaging, are as useful for detecting heart disease. It may be, but there's not enough hard evidence to be certain.

唐：好吧，主要原因是这些检查非常有用。例如，乳房X光检查是寻找乳腺癌早期症状的最佳方法。但其他的一些检查却不明确，比如核成像是否对检测心脏病有用。或许有用，但没有足够的证据来证明。

Yael: So, the risks of radiation exposure from a CT scan or a nuclear imaging may outway the benefits.

雅艾尔：那么，进行CT扫描或者核成像的益处可能要超过它所带来的辐射风险。

Don: Right. It's not that people should always avoid these imaging tests. But they should be aware of the risks.

唐：对。人们不应该总是去回避影像学检查，不过也应该意识到它的风险。

1 resonance   

n.洪亮；共鸣；共振

参考例句：

• Playing the piano sets up resonance in those glass ornaments.一弹钢琴那些玻璃饰物就会产生共振。
• The areas under the two resonance envelopes are unequal.两个共振峰下面的面积是不相等的。