Contrast and Spatial Resolution Practice Test

Partial volume effect happens when a voxel contains more than one tissue type, so the measured signal is a blend of those tissues. This blends become most noticeable when the structure you’re trying to resolve is small and approaches the size of a voxel, because many voxels at the boundary will contain a mixture rather than a single tissue. As a result, edges blur and the true intensity or size of the structure is misrepresented. If the structure is large compared with the voxel, each voxel largely contains one tissue type, so the mixture is reduced and the partial volume effect diminishes. It isn’t about how dense the tissue is; it’s about how much of the voxel is occupied by different tissues. Reducing voxel size (higher resolution) helps mitigate this effect.