MRI Physics And Clinical Applications Practice Exam

Spatial resolution comes from the size of the voxels, which is basically the field of view divided by how many phase-encoding samples you acquire. If you want finer detail without making the scan take longer, shrink the field of view while keeping the matrix size the same. That makes each voxel smaller, so you see more detail, but the total number of phase-encoding steps—and thus the time to acquire them—stays the same, so the scan time isn’t increased. Just be mindful that a smaller FOV can cause aliasing if anatomy extends outside the FOV, so coverage must match the region of interest or you need anti-aliasing strategies. Rationale for not selecting the other options: increasing the number of excitations boosts signal-to-noise ratio but also increases scan time and does not improve spatial resolution per unit time; decreasing the matrix size enlarges voxels and reduces resolution; increasing the repetition time lengthens the scan, again not improving resolution without changing time.