Manuel Murbach1, Thomas Doering2, and Gregor Schaefers2,3
1Murbach EMConsulting, Zurich, Switzerland, 2MR:comp GmbH, Gelsenkirchen, Germany, 3MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany
1Murbach EMConsulting, Zurich, Switzerland, 2MR:comp GmbH, Gelsenkirchen, Germany, 3MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany
This
study shows that our alternative method (Tier 2.5) may be suitable to estimate
realistic in vivo E-fields at short implant locations without being overly
conservative. The standard Tier 2 method may result in implant labels to be
>3 times more restrictive than in current practice.
Figure 3: Comparison of the
ViP model FATS with the ASTM test-field. E10g maximum intensity projection
(MIP) for all imaging positions at 1.5T, normalized to normal operating mode.
Maximum E10g in FATS is up to >4 times higher than the ASTM test field of
120 V/m, resulting in a factor >18 in power (red box). For the complete
assessment, other models, MR coils, and field strengths have to be considered.
Figure 2: Comparison of
the different Tiers: Tier 2, where the total E-field of the passive implant is
averaged on 10g cubes. Proposed Tier 2.5, where the tangential E-field along
representative trajectories over the 3D volume of the passive implant are
averaged. Tier 3, where the 1D tangential E-field is extracted and used as
input for the transfer function.
