As phase encoding steps increase, spatial resolution will increase due to which of the following?

• A. Increased echo times
• B. Increased voxel size
• C. Decreased voxel size
• D. Increased slice thickness

Answer: (C)

In magnetic resonance imaging, spatial resolution refers to the ability to distinguish between two points in an image. As the number of phase encoding steps increases, the system samples more data in the phase encoding direction. This increased sampling allows for a finer grid of data points to be reconstructed into an image, resulting in enhanced spatial resolution.

The correct answer highlights that an increase in phase encoding steps leads to a decrease in voxel size. Voxel size is a critical aspect of spatial resolution; smaller voxels allow for more accurate representation of structures within the body. When the voxel size is smaller, the imaging system can delineate finer details, thus improving the clarity and resolution of the resultant image.

In contrast, increasing echo times or slice thickness, or increasing voxel size would not enhance spatial resolution. Echo time influences contrast rather than resolution, while larger voxel sizes and greater slice thickness can result in loss of detail, as they encompass more tissue and potentially mix signals from different structures. Thus, reducing voxel size through increased phase encoding steps directly correlates with improved spatial resolution in MRI.