What causes the partial volume effect in imaging?

The partial volume effect occurs when a single voxel—the smallest distinguishable cube-shaped unit of a three-dimensional space in imaging—contains more than one type of tissue. Since a voxel can encompass multiple tissues of varying densities and compositions, the imaging system averages the signals from each tissue type present within that voxel. This averaging can lead to a loss of detail and create misleading appearances in the final image, as it may not accurately represent any of the individual tissues' characteristics.

For example, if a voxel contains both fat and muscle tissue, the imaging system may deliver a value that does not appropriately reflect either tissue type, thereby blurring the distinction between them. This effect is particularly pronounced in areas where structures or tissues are adjacent to each other with differing densities, leading to potential misinterpretation in diagnostic imaging.

While motion artifacts, insufficient image resolution, and high radiation exposure can all impact imaging quality, they do not specifically relate to the phenomenon of partial volume averaging that results from multiple tissue types being represented in a single voxel.