Characterisation of brain disorders and evaluation of therapy by functional and molecular magnetic resonance techniques.

OBJECTIVES: To review advanced functional and molecular magnetic resonance techniques that are currently clinically useful or with potential clinical use in the near future.

DATA SOURCES AND EXTRACTION: Literature search of Medline to December 2007 was conducted. Key words search terms were: 'magnetic resonance imaging', 'magnetic resonance spectroscopy', 'brain', 'functional', 'perfusion', 'diffusion', 'diffusion tensor', 'magnetic transfer', 'molecular imaging', 'superparamagnetic iron oxide'. Relevant original papers and review articles were retrieved.

STUDY SELECTION: A total of 83 original papers and review articles were systematically analysed.

DATA SYNTHESIS: The introduction of modern neuroimaging modalities in recent years has revolutionised investigation of the normal and diseased brain. Among others, magnetic resonance has emerged as the pre-eminent imaging modality, which can produce both high-resolution anatomical images and maps that reflect a variety of physiological parameters relevant to functional assessment and tissue characterisation. Magnetic resonance imaging techniques are now capable of visualising physiological and diseased processes at cellular and molecular levels, including cerebral blood flow, capillary perfusion and permeability, blood oxygenation level-dependent neuronal activation, microscopical motion of water (water diffusion), integrity of axonal fibres, and the molecular transfer of magnetisation within tissues. Magnetic resonance cell trafficking can evaluate the macrophage activity in areas of brain inflammation. Magnetic resonance cell-labelling strategies can be used to monitor the seeding and migration of embryonic stem cells. Magnetic resonance spectroscopy allows the detection of various metabolites that pertain to different biochemical processes in brain tissues. Such metabolites/spectra include: N-acetyl aspartate used as a neuronal marker, choline as a cell membrane metabolism marker, myo-inositol as a glial marker in proton spectrum, and phosphorous whose spectrum provides an in-vivo assessment of the bio-energetic status of tissues. Besides characterisation of brain disorders, magnetic resonance imaging and spectroscopy can improve the planning and monitoring of therapy and contribute to the development of new therapies.

CONCLUSION: Advances in neuroimaging have made a great leap in the morphological, metabolic, and functional assessment of the neurological diseases, enabling better diagnosis and management of patients.