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  • Print publication year: 2011
  • Online publication date: December 2011

18 - The process of drug development and approval in the United States, the European Union, and Asia

from Section II - Clinical trial methodology

Summary

Low magnetization transfer ratio (MTR) indicates a reduced capacity of the molecules in the brain tissue matrix to exchange magnetization with the surrounding (magnetic resonance imaging-visible) water molecules. The first step in the quantitative analysis of MT-MR images is the creation of calculated MT images or MTR maps. Although conventional T2-weighted scans play a major role in the assessment of multiple sclerosis (MS) lesion burden, cross-sectional and longitudinal studies have demonstrated that the magnitude of the correlation between clinical disability and brain T2-weighted lesion load is only modest. In MS, lesions enhancing on MRI scans after gadolinium (Gd) injection represent areas with a damaged blood-brain barrier (BBB) and ongoing inflammation. The vast majority of the enhancing lesions are associated with T2 abnormalities and a significant proportion of them may appear hypointense on T1-weighted scans. Quantitative techniques, such as 1H-MRS and diffusion tensor (DT)-MRI, contribute to the understanding of MS pathophysiology.

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