Functional magnetic resonance imaging in neuroradiology

The assessment of cerebral functions has long been the domain of positron-e mission tomography and single photon emission computed tomography. The use of rapid imaging sequences and contrast agents enables physiological and pa thophysiological cerebral processes to be assessed and monitored by magneti c resonance imaging. Both T1- and T2*-weighted contrast-enhanced fast imagi ng sequences can be used to assess tissue perfusion, vascularity, and micro circulation by applying models developed in nuclear medicine. The diffusion of water molecules and hemodynamic aspects of the macrovasculature can als o be monitored. Functional magnetic resonance (MR) imaging enables the visu alization of neuronal function and activity, and MR spectroscopy makes poss ible the metabolic mapping of lesions and surrounding tissue. The advantage s of MR techniques includes their low invasiveness, multiplanar imaging abi lity, and lack of radiation. This contribution discusses the clinical use o f functional MR imaging methods and their role in neuroradiological disease s. Measuring perfusion and diffusion allows detailed insight into the patho physiology of cerebral ischemia and is already being used routinely in acut e ischemic stroke. Dynamic MR angiography enables the hemodynamic assessmen t of vascular malformations. In CNS neoplasms these imaging techniques can improve lesion characterization and the selecting, planning, and monitoring of therapy. Functional MR imaging techniques have also revolutionized the study of psychiatric illness; however,their clinical utility here is still limited. Initial results in patients with dementia and schizophrenia have p rovided insight into the pathophysiological changes of these diseases.