Magnetic Resonance Imaging (MRI) Practice Test

Magnetic susceptibility artifacts are more prominent with which types of sequences?

1. Spin Echo

2. Fast Spin Echo

3. Gradient Echo

4. Short Tau Inversion Recovery

The correct answer is: Gradient Echo

Magnetic susceptibility artifacts are more prominent with Gradient Echo sequences due to the underlying mechanism of how these sequences acquire images. Gradient Echo sequences utilize variations in the magnetic field to create images, which can result in greater sensitivity to magnetic field inhomogeneities and differences in magnetic susceptibility between tissues. In Gradient Echo imaging, the presence of dephasing caused by variations in the local magnetic field can lead to increased signal loss and geometric distortion near interfaces of different tissues, such as air and fat or bone and soft tissue. This is because the frequency of the precessing spins differs in areas where there are changes in magnetic susceptibility, leading to a loss of coherence among the spins during the read-out process. In contrast, Spin Echo and Fast Spin Echo sequences utilize a rephrasing mechanism that compensates for some of the magnetic field inhomogeneities, thus minimizing susceptibility effects. Short Tau Inversion Recovery (STIR) sequences, specifically designed to suppress fat signals, also tend to have reduced susceptibility artifacts compared to Gradient Echo due to their different imaging approach. Hence, Gradient Echo sequences are more prone to these artifacts, making them the correct choice in this context.