Magnetic Resonance Imaging (MRI) Practice Test

Which MRI sequence is most suitable for assessing cortical lesions?

1. Spin echo

2. Fast spin echo

3. Gradient echo

4. FLAIR

The correct answer is: FLAIR

The choice of FLAIR (Fluid-Attenuated Inversion Recovery) as the most suitable MRI sequence for assessing cortical lesions is grounded in the sequence's ability to suppress cerebrospinal fluid (CSF) signals. FLAIR is particularly effective in highlighting lesions in the cortex and subcortical areas because it nullifies the high signal from CSF, allowing for better visualization of abnormalities that might otherwise be obscured. Cortical lesions, such as those seen in conditions like multiple sclerosis or certain tumors, can be challenging to detect with other sequences due to their proximity to CSF, which often appears much brighter on T2-weighted images. FLAIR reduces this issue by making the CSF signal low or absent, providing a clearer contrast between the lesions and the surrounding brain tissue. Other sequences, while useful in many contexts, may not offer the same level of sensitivity for cortical lesions. For instance, spin echo and fast spin echo techniques provide good anatomical detail but might still be influenced by the strong CSF signal. Gradient echo sequences are typically more sensitive to susceptibility effects and may highlight hemorrhagic changes but are less optimized for detecting subtle cortical lesions compared to FLAIR.