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Methods for Quantitative Imaging

Mapping of the water content in the brain is one of the most challenging tasks in quantitative imaging. In our implementations, the necessary intermediate steps towards this aim are mapping of the longitudinal (T1) and transversal (T2*) relaxation times, of the transmit (B1) and receive efficiencies of the coil system and measurement of the temperature of a reference probe. By-products of the same measurements are phase images and field maps. See also the work by the team Quantitative Imaging. Fig. 1 shows a comparison of the results obtained with three different methods for water mapping at 3T: a) TAPIR+QUTE; b) 2D method, long TR; c) 3D method. Depending on experimental requirements of concrete projects (e.g. brain coverage, resolution, measurement time) the optimal method can be chosen.

Based on high-quality quantitative parameters, several properties can be investigated: for example, their distribution, homogeneity of tissue based on the different parameters (link to Fabian’s project), correlation between parameters and changes in their values with the field strength (Fig 2). Such studies are relevant to investigations of macromolecular and iron content in the tissue, changes related to aging or disease, and may also lead to a better segmentation of the brain into microscopically distinct regions.

Methods for Quantitative ImagingFig 1: Water maps (in %) and T1 maps obtained at 3T in vivo by use of three different protocols and two different methods of mapping T1 (Look-Locker-based and 2-point methods)