Exposure of Infants to Gradient Fields in a Baby MRI Scanner

Abstract

In pediatric magnetic resonance imaging (MRI), infants are exposed to rapid, time‐varying gradient magnetic fields, leading to electric fields induced in the body of infants and potential safety risks (e.g. peripheral nerve stimulation). In this numerical study, the in situ electric fields in infants induced by small‐sized gradient coils for a 1.5 T MRI scanner were evaluated. The gradient coil set was specially designed for the efficient imaging of infants within a small‐bore (baby) scanner. The magnetic flux density and induced electric fields by the small x, y, z gradient coils in an infant model (8‐week‐old with a mass of 4.3 kg) were computed using the scalar potential finite differences method. The gradient coils were driven by a 1 kHz sinusoidal waveform and also a trapezoidal waveform with a 250 µs rise time. The model was placed at different scan positions, including the head area (position I), chest area (position II), and body center (position III). It was found that the induced electric fields in most tissues exceeded the basic restrictions of the ICNIRP 2010 guidelines for both waveforms. The electric fields were similar in the region of interest for all coil types and model positions but different outside the imaging region. The y‐coil induced larger electric fields compared with the x‐ and z‐ coils. Bioelectromagnetics. 43:69–80, 2022. © 2021 Bioelectromagnetics Society.

Uncertainty quantification in the assessment of human exposure to pulsed or multi-frequency fields

“…Each standard and guideline addresses this problem differently proposing solutions that depends on the shape of the waveform (ICNIRP 2003, 2010, Bailey et al 2019. The literature includes several papers using these methods to analyze specific exposure scenarios (Lodato et al 2012, Andreuccetti et al 2013, Fiocchi et al 2015, Canova et al 2016, Paffi et al 2016, Tang et al 2022 and other papers pointing out issues and performances of these methods (De Santis et al 2013, Schmid and Hirtl 2016, Keller 2017, Schmid et al 2019. Most of these methods move the problem from the time domain to the frequency domain by means of the Fourier decomposition of the waveform.…”