How is spatial resolution defined in MRI?

• A. Field of view size
• B. Voxel size
• C. Slice thickness
• D. Gradient strength

Answer: (B)

Spatial resolution in MRI is primarily defined by voxel size. Voxel size is a three-dimensional representation of a pixel, being essentially a volume element that combines the dimensions of the image's height, width, and depth. Smaller voxel sizes can enhance spatial resolution, allowing for the differentiation of smaller structures within the imaging field.

In MRI, improving spatial resolution is critical for accurately depicting anatomical details and pathologies. The size of the voxel is determined by several factors, such as the field of view, matrix size, and slice thickness. While slice thickness and field of view can influence the effective voxel size, they are not direct measures of spatial resolution themselves in the way that voxel size is. Gradient strength affects the speed and efficiency of image acquisition but does not directly characterize spatial resolution.

Thus, voxel size is the most fundamental determinant of spatial resolution in MRI, making it the correct choice.