What happens to voxel size when the field of view (FOV) is increased?

• A. It remains constant
• B. Decreases, improving spatial resolution
• C. Increases, decreasing spatial resolution
• D. Increases, improving spatial resolution

Answer: (C)

When the field of view (FOV) is increased, the voxel size increases, which leads to a decrease in spatial resolution. This relationship is rooted in the principles of MRI imaging.

A voxel, or volumetric pixel, is the three-dimensional equivalent of a pixel in 2D imaging, representing a specific volume of tissue. The FOV refers to the total area that is being imaged. When the FOV is enlarged, the same number of data points (or pixels) must be spread over a larger area. Consequently, each voxel occupies a larger volume, which means that the detail captured within each voxel decreases.

Spatial resolution, which refers to the ability to distinguish small structures within the image, is directly impacted by voxel size. Larger voxels can result in loss of detail and blurring of fine structures, ultimately decreasing the spatial resolution of the image. Thus, an increased FOV allowing for larger voxel sizes reduces the overall spatial resolution of the MRI images.