Shahrokh Abbasi-Rad1, Martijn Cloos1,2, Jin Jin3, Kieran O'Brien3, and Markus Barth1,2,4
1Centre for Advanced Imaging, University of Queensland, Brisbane, Australia, 2ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, 3Siemens Healthcare Pty Ltd, Brisbane, Australia, 4School of Electrical Engineering and Information Technology, The University of Queensland, Brisbane, Australia
1Centre for Advanced Imaging, University of Queensland, Brisbane, Australia, 2ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, 3Siemens Healthcare Pty Ltd, Brisbane, Australia, 4School of Electrical Engineering and Information Technology, The University of Queensland, Brisbane, Australia
We showed that the use of two
adiabatic refocusing pulses (TR-FOCI) could mitigate the B1+
inhomogeneity problem commonly observed at 7T in a twice-refocussed spin echo
diffusion weighted images.
Figure
4. Shows the comparison of b0
images acquired by SLR versus adiabatic refocusing pulses. The B1+
insensitivity of the adiabatic TR-FOCI pulse mitigates the B1+
inhomogeneity leading to retrieval of spin-echo signal at the temporal lobe and
cerebellum. The first column shows the relative FA map indicating the
low B1+ areas and the last column shows the relative SNR map. The SNR map
indicates that in the B1+ starved areas of the
brain SNR is improved up to 10 times. The TR value (30000 ms) was kept
identical between the two measurements so that signal intensities could be
comparable.
Figure
3. (a) shows the localizer
view of the phantom with the location of the acquired slice. (b) shows the slice
profile images of the SLR refocusing pulse versus TR-FOCI refocusing pulse with
different scale factors for the power of the pulse. With the scale factor of
one, the pulse is applied with the power of 9 T, which is derived from the simulations as the minimum value
required for the adiabaticity of the pulse. (c), (d), and (e)
show the slice profile across the superior, center, and the inferior regions of
the slice.