根據一項研究報道，PET掃描使用放射性示蹤劑使用18氟標記的熒光脫氧葡萄糖(FDG)，能夠有效地檢查出現輕度認知障礙的阿爾茨海默病（Alzheimer病，AD）患者。

“使用FDG的PET掃描代表一種最有前景的診斷AD的工具，”該項研究的首席作者、慕尼黑技術大學(Germany; www.tu-muenchen.de)核醫學科高級醫師 Alexander Drzezga說。實際上，使用FDG的PET掃描 “或許是最佳的確定最可能發展味AD的MCI患者的工具。”該研究結果發表在2005年10月的《核醫學會核醫學期刊》之上。

輕度認知障礙(MCI)是一個描述輕度但是能夠測量的認知功能（例如記憶功能）損害的術語。MCI患者還沒有表現出癡呆的特征，但是該疾病是AD的朕兆，根據Drzezga醫生的說法，只需要數年就可能發展成該病。許多MCI患者隨著時間出現思考能力的進行性下降，Alzheimer病是主要的原因。

“MCI發生率很高，將在1年內發展成為Alzheimer病；但是這些患者中的一部分或許永遠不會發展成癡呆，甚至隨著時間癥狀會得以改善，”Drzezga說。絕大多數MCI患者在開始PET檢查顯示出典型AD損害，將在16個月內發展成為癡呆，根據一項30例患者的臨床研究結果顯示。他補充說，在開始PET檢查沒有出現異常的患者病情則保持穩定。

根據Drzezga醫生的研究，患Alzheimer病的患者大腦糖代謝模式出現特異性的異常改變，在病變涉及的區域出現下降。使用FDG的PET掃描能夠對區域性的大腦糖代謝進行評估。Drzezga報道說，研究顯示 “大腦糖代謝的檢查，在分子水平上真實反映了與Alzheimer病相關的病理改變，分子掃描成像方法的PET適合在根據神經生理學檢查診斷Alzheimer病之前，描述MCI患者大腦的細微變化。

研究結果還顯示，使用FDG的PET檢測Alzheimer病的精確性要比使用APOEe4危險因子的基因篩查精確的多。

PET Can Detect Alzheimer’s Disease
 
Positron emission tomography (PET) imaging used with the radiotracer 18F-fluorodeoxyglucose (FDG) appears to be an effective tool in detecting Alzheimer’s disease (AD) in patients who have mild cognitive impairment (MCI), according to new research.

“PET imaging with FDG represents one of the most promising tools for diagnosis of Alzheimer’s,” said Alexander Drzezga, M.D., the lead author of the study and a senior physician with the department of nuclear medicine at the Technical University of Munich (Germany; www.tu-muenchen.de). In fact, using PET imaging with FDG “may be the best indicator for determining which MCI patients are most at risk of developing Alzheimer’s.” The study was published in the October 2005 issue of the Society of Nuclear Medicine’s Journal of Nuclear Medicine.

Mild cognitive impairment (MCI) is a term used to describe a slight but measurable deterioration of cognitive capabilities, such as memory function. Patients with MCI do not yet display the characteristics for the diagnosis of dementia, but the disorder is seen as a precursor to AD, which can take years to develop in an individual, according to Dr. Drzezga. Many patients with MCI develop a progressive decline in their thinking capacities over time, and Alzheimer’s disease is typically the underlying cause.

“A high percentage of MCI patients will develop Alzheimer’s disease within a year; however, some of these patients will never develop dementia and may even improve with time,” said Dr. Drzezga. Most MCI patients who showed abnormalities typical of AD in their original PET scan developed dementia within 16 months, according to results from the 30-patient study. Most patients who did not demonstrate abnormalities in their original PET scan remained stable, he added.

Patients with Alzheimer’s show characteristic alterations of the cerebral glucose metabolic pattern, with a decrease in affected brain regions, according to Dr. Drzezga. PET imaging with FDG provides an assessment of regional cerebral glucose metabolism. The study showed that “the analysis of cerebral glucose metabolism actually reflects ongoing pathological changes associated with Alzheimer’s disease on a molecular level and that the molecular imaging method PET is capable of depicting subtle changes in the brain of MCI patients before a diagnosis of Alzheimer’s based on neuropsychological evaluation is possible,” reported Dr. Drzezga.

The study revealed that PET with FDG has a considerably higher accuracy for detecting Alzheimer’s than genetic screening for the APOEe4-risk factor.