MRI brain scans perform better than common clinical tests at predicting which people will go on to develop Alzheimer’s disease, according to a study being presented next week at the annual meeting of the Radiological Society of North America (RSNA). Currently, risk of Alzheimer’s disease is assessed through standardized questionnaires and genetic with accuracy rates of about 70%-71%. MRI exams of the brain using diffusion tensor imaging (DTI) offer a promising option for more accurate analysis of dementia risk.
DTI provides different metrics of white matter integrity, including fractional anisotropy (FA), a measure of how well water molecules move along white matter tracts. A higher FA value indicates that water is moving in a more orderly fashion along the tracts, while a lower value means that the tracts are likely damaged.
For the new study, lead author Cyrus Raji, MD, of Washington University’s School of Medicine and colleagues performed brain DTI exams on 61 people and quantified differences in DTI among people who declined from normal cognition or mild cognitive impairment to Alzheimer’s dementia compared to controls who did not develop dementia.
About half of the patients went on to develop Alzheimer’s disease, and DTI identified quantifiable differences in the brains of those patients. People who developed the disease had lower FA compared with those who didn’t, suggesting white matter damage. They also had statistically significant reductions in certain frontal white matter tracts.
“DTI performed very well compared to other clinical measures,” Raji says. “Using FA values and other associated global metrics of white matter integrity, we were able to achieve 89 percent accuracy in predicting who would go onto develop Alzheimer’s disease. The Mini-mental State Examination and APOE4 gene testing have accuracy rates of about 70%-71%.” The researchers conducted a more detailed analysis of the white matter tracts in about 40 of the study participants. Among those patients, the technique achieved 95% accuracy.
While more work is needed before the approach is ready for routine clinical use, the results point to a future role for DTI in the diagnostic workup of people at risk for Alzheimer’s disease. Importantly, MRI measures of white matter integrity could speed interventions that slow the course of the disease or even delay its onset.
