Magnetic Resonance Imaging (MRI) Practice Test

What type of imaging sequence would you use to enhance the visibility of fluid in a gradient echo acquisition?

1. Short Tau Inversion Recovery

2. Incoherent gradient echo

3. Coherent gradient echo

4. Echo Planar Imaging

The correct answer is: Coherent gradient echo

Using a coherent gradient echo sequence enhances the visibility of fluid in MRI images due to its sensitivity to T2* relaxation effects. This type of sequence averages the signal from the flowing fluid while maintaining the phase coherence of the magnetic moments of the spins in the region of interest. As a result, coherent gradient echo techniques are particularly effective for visualizing areas with high fluid content, such as cysts or edema, by providing a better contrast that highlights these features against surrounding tissues. In contrast, other imaging sequences may not emphasize fluid as effectively. For instance, short tau inversion recovery (STIR) is primarily designed to suppress fat signals and could lead to reduced visibility of fluid in certain contexts. Incoherent gradient echo sequences introduce random phase variations that can diminish the signal clarity of fluid. Echo Planar Imaging, although rapid, is not specialized for emphasizing fluid compared to coherent gradient echo sequences, which specifically enhance fluid signal through the manipulation of phase coherence. Thus, coherent gradient echo is the optimal choice for maximizing fluid visibility in MRI gradient echo acquisitions.