（说明：左侧是正常大脑的PET扫描图，右侧是阿尔茨海默病患者大脑的PET扫描图）

　　关于阿尔茨海默病（Alzheimers disease），目前的观点是：一是仅有通过死后的脑组织病理检查才能够确诊，即生前难以确诊；二是不可治愈，仅可以适度改善。

　　最近有报道（见下文）认为，利用正电子发射计算机显像（PET）技术检查脑组织中或借助生化技术检查外周血液中的beta-淀粉（beta amyloid）将有助于早期发现，甚至预测阿尔茨海默病。研究人员认为，beta-淀粉的含量变化与脑功能特别是认知功能受损害有关。

　　最后应该说明的是，该类研究目前尚处于初级阶段，即是否对阿尔茨海默病之诊治或预防具有革命性的作用仍有待于进一步研究论证。

　　TUESDAY, Jan. 18 (HealthDay News) -- Researchers report promising results for a scanning test that aims to reveal the presence of Alzheimers disease, potentially allowing doctors to try to treat the illness in its early stages. Another study finds that blood tests could indicate higher risks of dementia later in life.

　　But there is a catch: Alzheimers disease is not curable, and existing treatments only have limited effects.

　　Even so, the ability to precisely diagnose Alzheimers disease during life, which is now impossible, could lead to improved research, said memory specialist Dr. Anton P. Porsteinsson, a psychiatry professor at the University of Rochester School of Medicine, who was not involved with the studies.

　　The findings, published Jan. 19 in the Journal of the American Medical Association, "may have much more relevance" in the future, Porsteinsson said. "Basically, this is a step in the process."

Currently, doctors correctly diagnose Alzheimers disease about 85 percent of the time, Porsteinsson said. The illness can be confirmed only through brain analysis after death. Even with existing scanning technology, "we can not see individual cells or what　is going on," he said. "We can not see the functional impairment that happens," he added.

　　In one of the new studies, researchers led by a team from Avid Radiopharmaceuticals reported that they were able to find signs of Alzheimers disease by using PET scanning technology. They had scanned 35 people who appeared to have the disease before their deaths and looked for signs of beta amyloid, a kind of gunk that clogs the brain in people with the illness.

　　The other study attempted to measure levels of beta amyloid in the blood. It linked lower levels -- a sign that the gunk is getting tied up in the brain -- to higher cognitive problems in 997 elderly people over a nine-year period.

　　The researchers also found that people with higher levels of "cognitive reserve" -- such as those with higher levels of education and literacy -- seemed to be buffered against dementia, said the study is lead author, Dr. Kristine Yaffe, a psychiatrist and professor at the University of California, San Francisco.

　　"The fascinating implication is that if you identify those at risk, maybe you could do something like cognitive stimulation to mitigate the risk," she said.

　　For now, though, "the markers reported here are far too unspecific to distinguish between people who will and will not get the disease," said Dr. Monique M.B. Breteler, an epidemiologist with University Medical Center Rotterdam in the Netherlands who wrote an accompanying commentary. "The importance of this paper is that it shows that there are detectable signals in blood that are related to the later development of the disease."

　　As for cost, Porsteinsson said the expense of the blood tests may go down. As to the other study, "the cost for the PET scans will always be pretty high because you have got to have such expensive tools."