Published online by Cambridge University Press: 04 August 2010
Since its introduction for human study in the early 1980s, magnetic resonance (MR) has proven itself an extremely versatile technique for evaluation of many different parameters of anatomic, physiologic, and metabolic interest. The number of phenomena amenable to analysis using magnetic resonance (MR) techniques is increasing every year. This versatility arises from the many different sources of magnetic contrast that can be generated using either endogenous or exogenous contrast, from the versatility of the techniques for manipulation of the nuclear spins that generate the observed signals, and from the extremely safe nature of MR that lends itself well to longitudinal studies and large patient populations.
MR techniques can now evaluate tissue parameters relevant to TCA cycle metabolism, anaerobic glycolysis, ATP levels, blood–brain barrier permeability, macrophage infiltration, cytotoxic edema, spreading depression, cerebral blood flow and volume, and neurotransmitter function. The paramagnetic nature of certain oxidation states of iron leads to the ability to map out brain function using deoxyhemoglobin as an endogenous contrast agent, and also allows for mapping of local tissue iron concentrations. In addition to these metabolic parameters, the number of ways to generate anatomic contrast using MR is also expanding, and in addition to conventional anatomic scans, mapping of axonal fiber tracts can also be performed using the anisotropy of water diffusion. A selective, non-exhaustive, summary of the various parameters of relevance to neurodegeneration (ND) that can be measured using MR techniques is presented in Table 21.1.