A third fundamental challenge for ultrahigh field MRI arises from the fact that relaxation times change substantially compared to lower field strengths, thus significantly altering image appearance. Bottomley extrapolated data obtained at lower field strengths, and predicted increasing tissue T1 relaxation times with increasing field strength, whereas T2 relaxation times were predicted to remain approximately constant (Bottomley et al., 1984). Because of susceptibility effects, T2* relaxation times are expected to become significantly shorter at ultrahigh field MRI. Since all
Table 3.1. Relaxation time measurements at 8 T.
Frontal WM Motor GM Frontal GM
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