Magnetic Resonance Imaging (MRI) Practice Test

Which gradient echo sequences are NOT characterized by requiring high signal from fluid?

1. Coherent gradient echo

2. Incoherent gradient echo

3. Dynamic gradient echo

4. Standard gradient echo

The correct answer is: Incoherent gradient echo

Incoherent gradient echo sequences are distinguished by their mechanism of signal generation, which does not necessitate high signal from fluid. This approach uses dephasing and rephasing of spins in a way that is less reliant on the presence of fluid as a strong signal source. The incoherent gradient echo primarily depends on spontaneous phase differences among spins, which allows for imaging in situations where fluid may not provide a significant signal. On the other hand, coherent gradient echo sequences, dynamic gradient echo sequences, and standard gradient echo sequences typically emphasize high fluid signal. These sequences often benefit from the T2*-weighted contrast that fluid provides, making them especially useful for evaluating structures containing liquid or for enhancing contrast between tissues. This is particularly important in applications, such as assessing vascular structures or in dynamic studies where fluid dynamics are critical to the imaging process.