Normal aging: Brain morphologic, chemical and physiologic changes detected with in vivo MRI

This chapter reviews age-related changes in the brains of healthy elderly subjects as measured with state-of-the-art magnetic resonance imaging (MRI) techniques. The review covers changes in brain structure and volume, water diffusion, biochemical composition of neural tissues, neuronal activity and cerebral blood flow. Imaging older individuals with MRI is associated with unique challenges. Claustrophobia related to the MRI environment was actually found to be lower in subjects over 65 years of age and higher in middle-age individuals, particularly women. The utility of MRI in aging research and clinical practice is improving with the introduction of novel contrast mechanisms to probe the brain tissue. The discussed imaging methods benefit with the emergence of high field MRI scanners, compared to the widely available 1.5T and 3T scanners. A drawback of most of the MRI methods is the difficulty in obtaining quantitative information, unlike imaging schemes such as computed tomography and positron emission tomography.