Exposure of Infants to Gradient Fields in a Baby MRI Scanner

Abstract

Overview

In pediatric magnetic resonance imaging (MRI), a crucial safety consideration is the exposure of infants to rapid, time-varying gradient magnetic fields. These fields generate electric fields within the infant's body, presenting potential health hazards, such as peripheral nerve stimulation.

Methodology

This numerical study assessed the in situ electric fields in infants induced by gradient coils specifically designed for a 1.5 T MRI scanner optimized for infants. The unique configuration includes small-sized gradient coils to suit a small-bore (baby) MRI scanner.

• Model Specifications: An infant model (8-week-old, 4.3kg) was used.
• Gradient Coils: Enumerated as small x, y, z coils.
• Simulation: Calculations used the scalar potential finite differences method, driven by a 1 kHz sinusoidal and a trapezoidal waveform with a 250 µs rise time.
• Positions Tested: Head area (position I), chest area (position II), and body center (position III).

Findings

Resulting electric fields in most tested tissues exceeded the basic restrictions set forth by the ICNIRP 2010 guidelines under both waveform conditions applied. It was observed that fields within the imaging region exhibited similar intensities across different coil types, whereas outside this region varied considerably.

• Larger Fields: Notably, the y-coil induced significantly larger electric fields compared to the x- and z- coils.

Conclusion

The study underscores the importance of carefully considering the electromagnetic field exposure in infant MRI applications due to the potential for exceeding safety guidelines and the associated health risks.