Safety Limits for Human-Size Magnetic Particle Imaging Systems

Current small-animal-sized MPI scanners operate at 1-25 kHz frequency range with 0.1-20 mT peak amplitude, neither of which is optimized. SAR and especially dB/dt safety limits will determine the optimum excitation field, and will impact the optimum scanning speed, field-of-view (FOV) and signal-to-noise ratio (SNR). In this work, we describe the first human-subject safety limit experiments for MPI. Our results indicate that the magnetostimulation threshold monotonically decreases with increasing frequency and is inversely correlated to the body-part size.

[1]  Brian K Rutt,et al.  Peripheral nerve stimulation properties of head and body gradient coils of various sizes , 2003, Magnetic resonance in medicine.

[2]  P A Bottomley,et al.  Power deposition in whole-body NMR imaging. , 1981, Medical physics.

[3]  J D Bourland,et al.  Review of Patient Safety in Time‐Varying Gradient Fields , 2000, Journal of magnetic resonance imaging : JMRI.

[4]  J. Schenck.  Safety of Strong, Static Magnetic Fields , 2000, Journal of magnetic resonance imaging : JMRI.

[5]  J. Reilly.  Peripheral nerve stimulation by induced electric currents: Exposure to time-varying magnetic fields , 1989, Medical and Biological Engineering and Computing.

[6]  Patrick W. Goodwill,et al.  Multidimensional X-Space Magnetic Particle Imaging , 2011, IEEE Transactions on Medical Imaging.

[7]  Bernhard Gleich,et al.  Tomographic imaging using the nonlinear response of magnetic particles , 2005, Nature.

[8]  W Irnich,et al.  Magnetostimulation in MRI , 1995, Magnetic resonance in medicine.

[9]  Patrick W. Goodwill,et al.  The X-Space Formulation of the Magnetic Particle Imaging Process: 1-D Signal, Resolution, Bandwidth, SNR, SAR, and Magnetostimulation , 2010, IEEE Transactions on Medical Imaging.

[10]  J.P. Reilly.  Maximum pulsed electromagnetic field limits based on peripheral nerve stimulation: application to IEEE/ANSI C95.1 electromagnetic field standards , 1998, IEEE Transactions on Biomedical Engineering.

[11]  Olaf Dössel,et al.  Optimizing Coil Currents for reduced SAR in Magnetic Particle Imaging , 2009 .