 The brown amyloid plaques are linked to Alzheimer's. Pic: UCLA |
A team at the University of California, Los Angeles, says it has found a way to highlight distinctive brain changes linked to Alzheimer's.
Although the disease can be diagnosed by assessing mental decline, physical changes within the brain can usually be confirmed only by a post-mortem.
The study appears in the New England Journal of Medicine.
The UCLA team says its technique might be effective long before disabling symptoms emerge.
This might allow drugs and other therapies to be employed at an earlier stage to slow the progression of the illness, although no cure for Alzheimer's exists.
Marking the spot
Alzheimer's disease is strongly linked to the appearance of abnormal areas called 'amyloid plaques' and 'tangles', although the precise role of these is not fully understood.
However, they do not show up using conventional MRI or CT scanning, and are visible only during an autopsy.
This imaging technology may also allow us to test novel drug therapies and manage disease progression over time 
The UCLA team has invented a chemical which not only shows up on scans, but will bind to plaques and tangles.
Using 'Positron Emitting Tomography' (PET), another type of scanner, damaged areas show up clearly.
However, more evidence was needed that the scan results could be linked to the progression of other symptoms in the disease.
More than 80 people volunteered for the research, some of them healthy, some with 'mild cognitive impairments' such as memory loss, and 25 of whom had received a diagnosis of Alzheimer's because their symptoms were more advanced.
After being injected with the chemical, they were scanned to see if there were any differences between the groups.
The levels of the chemical appearing on the scans were much higher among the Alzheimer's patients compared with the others, and the technique also highlighted more subtle differences between the healthy volunteers and those with the mild symptoms.
In severely affected patients, concentrations of the chemical appeared highest in parts of the brain usually affected by Alzheimer's plaques and tangles.
The researchers then waited two years before scanning the same patients again - and found that those who had worsened during that period, showed clear increases in the levels of the chemical in their brain.
Results confirmed
In addition, when one of the trial patients died 14 months after the first scan, an autopsy confirmed the appearance of amyloid plaques and tangles in exactly the locations the scan had suggested.
Dr Gary Small, who led the study, said: "This suggests that we may now have a new diagnostic tool for detecting pre-Alzheimer's conditions to help us identify those at risk, perhaps years before symptoms become obvious. The ability to diagnose at the earliest possible stage is of huge importance to people with Alzheimer's disease
"This imaging technology may also allow us to test novel drug therapies and manage disease progression over time, possibly protecting the brain before damage occurs."
Professor Dorothy Auer, from Nottingham University, is also working to develop techniques to spot the telltale amyloid plaques using conventional scanners.
She told BBC News Online that any method which could highlight both tangles and plaques was 'exciting'.
"It would be extremely useful to have an accurate method of diagnosis for Alzheimer's disease - however, it is early days for these techniques."
Professor Clive Ballard, director of research at the Alzheimer's Society, said: "This new research could prove significant in the early diagnosis of Alzheimer's disease.
"The ability to diagnose at the earliest possible stage is of huge importance to people with Alzheimer's disease."
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