Partial Volume Effect in medical imaging speaks to the idea that we may not detect signal in small volumes or regions when our resolution is limited. If you are a researcher that is totally crazy about the amygdala, for example, you might worry that the limited resolution of MRI would underestimate your signal in functional data. It also speaks to the idea of losing contrast between two regions (for example, two tissue types within the same voxel) because of such a limited resolution.
I like to think of this second idea, losing contrast between two tissue types because of limited resolution, in the context of multi-ingredient truffles. Presenting, one of my crazy creations:
The ingredients in these amazing truffles include: dried strawberries, blueberries, crunchy cinnamon apples, raisins, peanuts, coconut, almonds, dates, and walnuts, held together with vanilla touched white chocolate. How do these delicious bites of glory represent the problem of partial volume effects? It’s very simple. Each cluster is akin to a voxel, filled with many different ingredients, but we might be forced to represent the entire thing with only one taste. We lose information about the different ingredients (the tissue types) because of the limited resolution of our tongue (the imaging modality).