Advances in perfusion magnetic resonance imaging in Alzheimer's disease.

Recent research has demonstrated that brain circulation abnormalities, either during task-induced neural activity or at rest, are more commonly associated with Alzheimer's disease (AD) than was previously thought. This is consistent with the increasing attention to the early involvement of vascular risk factors in the development of AD, in addition to the dominating neurodegenerative pathology. Early detection of cerebral perfusion changes could help advance diagnosis and intervention therapies. The present article reviews advances in perfusion magnetic resonance imaging in the study of AD. In general, there are consistent accounts of cerebral hypoperfusion in the temporal and parietal lobes in people with clinically diagnosed AD. In the early stages of the disease, transient hyperperfusion may occur particularly in the prefrontal cortex, possibly as a compensatory effect. Nevertheless, significant variability in the details of perfusion patterns is present in the early phases, making the use of these methods in early diagnosis difficult. Noninvasive perfusion-weighted magnetic resonance imaging methods have advantages over nuclear medicine imaging, especially for safe usage in long-term follow-up studies. Optimization of perfusion-weighted imaging techniques is crucial for any future clinical application. Additional studies are needed with optimization likely to come with 3T and higher field strength magnets.