Mayo Clinic Finds Multiple Imaging Methods Each Provide Important Details about Cognitive Impairment

Saturday, July 26, 2008

Two new Mayo Clinic studies found that imaging methods like magnetic resonance imaging (MRI), magnetic resonance (MR) spectroscopy, and 11C Pittsburgh Compound B (11C-PIB) each provide independently valuable information about cognitive function. By using all of these imaging methods together, the researchers say physicians can better predict the likelihood of a patients' progression to Alzheimer's disease. These studies will be presented at the Alzheimer's Association International Conference on Alzheimer's Disease meeting in Chicago on July 26.

MRI illustrates the death of neurons in the brain. Neurons are responsible for cognition, and neuron deterioration is an effect of Alzheimer's disease. MR spectroscopy uses MRI to detect abnormal chemicals in the brain. A positron emission technology (PET)-based imaging method, 11C-PIB identifies amyloid plaques in the brain, a central marker for Alzheimer's disease.

"These studies show that there is not complete overlap in the information provided by these imaging methods," says Clifford Jack Jr., M.D., a Mayo Clinic radiologist and director of the Mayo Clinic Aging and Imaging Research laboratory. "So, the use of multiple imaging modalities will provide the most comprehensive view of a patient's disease progression. This information is useful in predicting whether a patient will progress to Alzheimer's disease or other dementias, as well as provide guidance about the most effective treatment plan to pursue.

The first study, led by Dr. Jack, included 17 patients with mild cognitive impairment, 20 patients who were cognitively normal, and eight patients with probable Alzheimer's disease. Each patient received both 11C-PIB and MRI scans. Based on the imaging, Dr. Jack and a team of Mayo Clinic researchers expect that patients with positive PIB and MRI scans showing neuron deterioration in the hippocampus will likely progress most rapidly to Alzheimer's disease. In contrast, the team expects that patients with negative PIB scans and neuron deterioration in the hippocampus will likely progress to non-Alzheimer's disease dementias (i.e., frontotemporal dementia, Lewy body dementia).

The second study was led by Kejal Kantarci, M.D., a Mayo Clinic radiologist. Dr. Kantarci and her team studied 126 individuals with mild cognitive impairment who received both MRI and MR spectroscopy scans annually from 1998 to 2005. Of these individuals, 54 progressed to dementia (41 with Alzheimer's disease, 10 with Lewy body dementia, and three with other dementia). An abnormal MRI indicated a 41 percent chance that an individual would progress to Alzheimer's disease within three years. If MRI and MR spectroscopy both were abnormal, that likelihood increased to 56 percent. Additionally, an abnormal MRI, abnormal MR spectroscopy, and evidence of stroke on MRI raised the likelihood to 85 percent.

Other members of the Mayo Clinic research teams included Stephen Weigand, Maria Shiung, Val Lowe, M.D.; Matthew Senjem, Bradley Kemp, Ph.D.; Jennifer Whitwell, Ph.D.; Selamawit Nagash, Ph.D.; Robert Ivnik, Ph.D.; Glenn Smith, Ph.D.; Peter O'Brien, Ph.D.; David Knopman, M.D.; Bradley Boeve, M.D., and Ronald Petersen, M.D., Ph.D.

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