Magnetic Resonance Imaging (MRI) Practice Test

Which pulse sequence is best for demonstrating magnetic susceptibility effects during a hemorrhagic infarct?

1. Spin echo

2. Gradient echo

3. Fast recovery

4. Inversion recovery

The correct answer is: Gradient echo

The gradient echo pulse sequence is particularly effective for demonstrating magnetic susceptibility effects, especially in cases of hemorrhagic infarcts. This is because gradient echo sequences are sensitive to magnetic field variations caused by the presence of deoxyhemoglobin and other paramagnetic substances associated with blood products. In the case of hemorrhagic infarcts, the accumulated blood can create localized magnetic susceptibility differences, which result in signal loss or variations in signal intensity. The gradient echo technique capitalizes on these variations, resulting in a more pronounced appearance of the hemorrhage compared to other pulse sequences. Spin echo sequences, on the other hand, are less sensitive to these susceptibility effects because they use a 180-degree refocusing pulse that mitigates the impact of field inhomogeneities. Fast recovery and inversion recovery sequences may offer contrast in specific circumstances, but they are not specifically tailored for highlighting the magnetic susceptibility effects as effectively as gradient echo. Hence, when assessing for hemorrhagic infarcts, the gradient echo pulse sequence stands out as the best choice.