Effects of Voxel Anisotropy in MR Imaging

Figure 10.20(a) shows the effects of sheet normal orientation 0 and voxel anisotropy Az on measured thickness T. The relations between measured thickness T and sheet normal orientation 0 for six values of true thickness t (1, 2, 3, 4, 5, 6) were plotted when three different values of voxel anisotropy Az (1, 2, 4) were used. The relations were regarded as ideal when T = t for any 0, which is the horizontal in the plots of Fig. 10.20(a). When Az = 1, the relations were highly close to the ideal for t > 2. When Az = 2 and Az = 4, significant deviations from the ideal were observed for 0 > 15° and 0 > 30°, respectively.

Figure 10.20(b) shows the plots of the maximum 0 at which error magnitude !E\ is guaranteed to satisfy !E\ < 0.1, \E\ < 0.2, and !E\ < 0.4 for t = 2 with varied voxel anisotropy Az. These plots clarify the range of 0 where the deviation from the ideal is sufficiently small. There was no significant difference between the plots for t = 2 and different values of t (for t > 2).

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