Novel imaging technologies in the assessment of cerebral ageing and vascular dementia

Introduction of magnetic resonance imaging (MRI) has opened new possibilities for detecting age-related brain tissue changes. The majority of these abnormalities consists of hyperintense foci in the deep and subcortical white matter probably related to microvascular disturbances and of signal hyperintensities around the lateral ventricles. It has also been suggested that these abnormalities may contribute to the development of cognitive impairment. The correlation between age-related signal abnormalities on conventional MRI and neuropsychologic dysfunction is limited, however, and a threshold beyond which such a relation may come into existence has not yet been defined. Poor tissue characterisation by conventional MRI may be one explanation. Therefore, new pulse sequences are expected not only to provide a higher lesion contrast such as the fluid attenuated inversion recovery (FLAIR) technique but also to offer new insights concerning the composition of incidental brain lesions. In this context both magnetisation transfer imaging (MTI) and diffusion weighted imaging (DWI) may serve to gain information about the integrity of cell membranes and organelles and the preservation of axons and fibre tracts. We will review the technical background of these recently developed MR sequences and their first applications to age-associated brain abnormalities.