A new computer-aided analysis may help detect the earliest signs of cell damage caused by Alzheimer's disease.
Alzheimer's is best treated early
The system is able to analyse the extent of damage in areas of grey matter, where brain cells are tightly packed together.
The researchers say it could lead to earlier diagnosis of a disease that can be treated most effectively in its initial stages.
The University of California, Irvine, study appears in the journal Radiology.
Researcher Dr Min-Ying Su said: "Our methods may aid in earlier diagnosis of Alzheimer's disease, allowing earlier intervention to slow down disease progression."
As Alzheimer's disease progresses, cell membranes in the brain may be damaged, allowing water molecules to move throughout the brain more freely.
Neural processes are disrupted and the brain cells die.
Difficult to measure
This process of cellular damage causes an increase in the apparent diffusion coefficient (ADC) - a measurement used to study the mobility of water in the brain.
However, until now it has proved very difficult to measure ADC levels in areas of grey matter - where damage is most likely to cause Alzheimer's symptoms.
The Irvine team has overcome this problem by developing a computer mapping technique that can be applied to analyse water diffusion images generated by specialised MRI brain scans.
Using it, they were able to measure ADC values in large areas of the brains of 13 elderly patients with mild cognitive impairment (MCI), and compare them with results obtained from a similar number of healthy volunteers.
Dr Su said the new technology could help doctors to develop a comprehensive picture of the typical cellular changes that take place in the early stages of Alzheimer's.
It might also help them to tailor treatments to an individual patient's level of risk.
She said: "Patients with MCI who are very likely to progress to Alzheimer's disease may start early treatment interventions, while patients who may remain stable with MCI can be spared from treatment and the associated side-effects."
Rebecca Wood, of the Alzheimer's Research Trust, said finding a way to diagnose Alzheimer's disease in its early stages was a top priority for researchers.
She said: "While the patients studied in this research have mild cognitive impairment, which puts them at higher risk of developing Alzheimer's, they don't yet seem to have been proven to have the disease, which is crucial if we are to establish whether this technique can spot the disease in the early stages."
Susanne Sorenson, of the Alzheimer's Society, said: "More research will be required, but it is possible that as more scanners become available it could contribute to providing a diagnosis at an earlier stage of the disease."