Sadeq S Alsharafi^{1}, Haile Baye Kassahun^{1}, Ahmed M Badawi^{1}, and AbdEl-Monem M El-Sharkawy^{1}

^{1}Systems and Biomedical Engineering, Cairo University, Giza, Egypt

Eddy-currents are generated in MRI scanners’ metallic structures due to the rapid switching of gradient coils. They may result in image distortions and induce acoustic-noise particularly for fast/spiral sequences. Transient eddy-currents computations can be used to understand the extent of such effects. In this work, a numerical framework was devised to compute transient eddy-currents induced by an amplitude-modulated sinusoidal pulse for a longitudinal gradient coil configuration. Stream functions representation of eddy-currents, Multilayer Integral Method, and an excitation current with amplitude-modulated sinusoidal function are used to solve the circuit equation and efficiently compute transient eddy-currents generated in the cryostat.

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Fig.1: 3D plot of the configuration used in the
simulation including the cryostat and the z-gradient coil. The cryostat cylinder
is meshed into structured triangular elements.

Fig.2: (a) The excitation spiral current pulse illustrating
10-time
points and (b) the corresponding eddy-current density distribution on the
cryostat.

Fig.3: Eddy current magnitude at
arbitrary points A (Top) and B (Bottom) of the cryostat induced by the
excitation amplitude-modulated sinusoidal waveform S(t).

DOI: https://doi.org/10.58530/2022/3249