VOA标准英语2011--MRI-like Scan May Help Identify Alzheime

MRI-like Scan May Help Identify Alzheimer's

Alzheimer's disease normally gets a definitive¹ diagnosis² only after the patient dies, and an autopsy³ finds certain distinctive⁴ structures in the brain.
Recently, though, scientists have been seeking some sort of biomarker - a characteristic that can be identified while the patient is still alive.
Emerging research on Alzheimer's suggests that the underlying⁵ physical disease begins years - maybe decades - before any symptoms appear. Kejal Kantarci studies Alzheimer's at the Mayo Clinic in Rochester, Minnesota.
"We wanted to investigate whether people who have normal cognitive⁶ function, but in their 70s and 80s, have any signs of Alzheimer's or other dementia-related pathology through imaging," she says.
In a new study, Kantarci and her colleagues put more than 300 older adults through some advanced imaging procedures.
The participants had positron emission⁷ tomography, or PET scans to identify the level of amyloid-beta in the brain that may signal Alzheimer's. About one-third of them had significant amyloid-beta deposits.
They also got a special kind of MRI scan to look for a biomarker that may indicate Alzheimer's. And those with significant amyloid-beta deposits tended to have high levels of the choline/creatine biomarker. They also scored lower on cognitive tests.
"We found that there is a relationship between the biochemical changes in the brain that we measured and the cognitive performance in the individuals," Kantarci says.
The MR spectroscopy, which is the MRI-type scan, identified people who scored lower on various tests of cognitive function, and who may be at risk for developing Alzheimer's.
The researchers caution that MR spectroscopy can not be used to diagnose Alzheimer's. But this work and other research suggests that it may soon be possible to identify people at higher risk of Alzheimer's and other forms of dementia before they show any symptoms.
Kantarci admits that's not going to help patients now, because there are no effective treatments. "But when they come about," she says, "there will be a chance for us to identify those normally functioning individuals who will benefit most from preventive treatment."
In addition, researchers trying to develop treatments may be able to use this biomarker in tests to assess how effective a new drug is.

1 definitive   

adj.确切的，权威性的；最后的，决定性的

参考例句：

• This book is the definitive guide to world cuisine.这本书是世界美食的权威指南。
• No one has come up with a definitive answer as to why this should be so.至于为什么该这样，还没有人给出明确的答复。

2 diagnosis   

n.诊断，诊断结果，调查分析，判断

参考例句：

• His symptoms gave no obvious pointer to a possible diagnosis.他的症状无法作出明确的诊断。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做一次彻底的调查分析。

3 autopsy   

n.尸体解剖；尸检

参考例句：

• They're carrying out an autopsy on the victim.他们正在给受害者验尸。
• A hemorrhagic gut was the predominant lesion at autopsy.尸检的主要发现是肠出血。

4 distinctive   

adj.特别的，有特色的，与众不同的

参考例句：

• She has a very distinctive way of walking.她走路的样子与别人很不相同。
• This bird has several distinctive features.这个鸟具有几种突出的特征。

5 underlying   

adj.在下面的，含蓄的，潜在的

参考例句：

• The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
• This word has its underlying meaning.这个单词有它潜在的含义。

6 cognitive   

adj.认知的，认识的，有感知的

参考例句：

• As children grow older,their cognitive processes become sharper.孩子们越长越大，他们的认知过程变得更为敏锐。
• The cognitive psychologist is like the tinker who wants to know how a clock works.认知心理学者倒很像一个需要通晓钟表如何运转的钟表修理匠。

7 emission   

n.发出物，散发物；发出，散发

参考例句：

• Rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施，降低污染物排放总量。
• Finally,the way to effectively control particulate emission is pointed out.最后，指出有效降低颗粒排放的方向。