Alix Plumley1, Philip Schmid1, and Emre Kopanoglu1
1Cardiff University Brain Research Imaging Centre, Cardiff, United Kingdom
1Cardiff University Brain Research Imaging Centre, Cardiff, United Kingdom
SAR distributions are sensitive to head motion in pTx, potentially exceeding safety limits when motion occurs. We investigate the effect of pTx coil size on SAR motion-sensitivity, and find that SAR for coil models with larger dimensions is less sensitive to motion than that with smaller coils.
Fig.3 Worst-case
local-SAR following motion for pTx pulses. (i) psSAR for
worst-cases as a factor of psSARcentre (same pulse without motion).
Tissue volume exposed to higher SAR than psSARcentre shown in
orange. (ii) SAR profiles for corresponding worst-cases (bottom
row) compared to their SARcentre (top row). Colour scale shows psSAR as
a factor of psSARcentre (normalised per coil). The number of spokes
in each coil’s worst-case pulse is indicated with asterisks. (iii)
The positions at which these worst-case psSAR were observed. All worst-cases
were observed at slice 1 or 2.
Fig.2 Motion-sensitivity
of (i) peak local-SAR and (ii) whole-head SAR for RF-shim
pulses designed using at the central position, and evaluated at all off-centre positions for each coil model A to
F. Slice 2 shown; slices 2-5 showed similar trends. Y-axes refer to SAR at each
evaluated position (left-right [L-R] and anterior-posterior [A-P] displacements),
as a factor of SAR at the centre position (i.e. without motion). SARcentre
was comparable across coil models (not shown).
