Structural MRI as a tool for the study of neurotoxicity and neurodegenerative disorders.

High-resolution magnetic resonance (MR) imaging affords an unprecedented opportunity to study the severity and distribution of neurodegenerative changes in the human brain. By selecting specific MR sequence parameters (i.e., TE and TR), different MR signals can be received from different tissue types, such as gray and white matter. Through optimization of the contrast between different tissue types, the surfaces and internal structures of brain structures of special interest can be visualized and quantitated. Metrics such as two-dimensional areas, three-dimensional volumes, and three-dimensional shape characteristics have proven to be highly useful for quantitating the effects of toxins on the human brain. Among toxins, the effects of alcohol on the human brain have been most intensively studied using structural MR imaging. Volume losses in the cerebral cortex and other brain regions of interest have been carefully quantitated. However, because exposure to alcohol is almost always repeated over many years, the effects of normal aging must be carefully considered when making comparisons between diseased and healthy populations. In contrast to the literature on alcohol, structural MR imaging has been relatively underutilized in the study of drugs and other chemicals such as MPTP and other drugs of abuse that are toxic to special populations of neurons. However, as the resolution of structural MR continues to improve, the structural characteristics of such neuron populations will be visualized and quantitated, and successful use of structural MR imaging for the study of such toxins will become possible.