Tsuyoshi Matsuda1, Ikuko Uwano1, Yuji Iwadate2, and Makoto Sasaki1
1Division of Ultrahigh Field MRI, Institute for Biomedical Sciences, Iwate Medical University, Iwate, Japan, 2Global MR Applications and Workflow, GE Healthcare Japan, Hino, Japan
1Division of Ultrahigh Field MRI, Institute for Biomedical Sciences, Iwate Medical University, Iwate, Japan, 2Global MR Applications and Workflow, GE Healthcare Japan, Hino, Japan
To optimize the nominal
flip angle (FA) value for actual FA imaging (AFI), we detected pixels
representing erroneous FAs by using phase differences between two AFI images. Nominal
FA values of ≥ 60° were observed to be unsuitable for the AFI at 7 T.
Figure 3. FA and error maps of the human head calculated by
the AFI method. Pixels with erroneous, aliased FAs were found in the nominal
FAs of ≥ 60°.
Figure 2. FA, phase difference,
and error maps of the phantom calculated by the AFI method. FA maps determined by
AFI are considerably different from those by the VFA method for nominal FAs of
90 and 130°, and the map is slightly different only at the central area in that
of 50°. Pixels with erroneous FA values due to the aliasing phenomenon are
readily detected by using the phase difference images by applying the threshold
of 1/6 rad.
