What occurs to voxels when the number of phase encoding steps increases?

• A. Voxels increase in size
• B. Voxels decrease in size
• C. Voxels remain the same size
• D. Voxels become irregular

Answer: (B)

When the number of phase encoding steps increases in magnetic resonance imaging (MRI), the resolution in the phase encoding direction improves. This improvement in resolution results in a decrease in the size of the individual voxels.

Voxels, or volumetric pixels, are the 3D equivalent of 2D pixels in images, representing the smallest distinguishable box-shaped part of a three-dimensional space in an MRI scan. In MRI, the size of a voxel is determined by the matrix size of the image and the field of view (FOV). By increasing the number of phase encoding steps, the matrix size becomes larger while maintaining the same FOV. This reduction in voxel size enables finer detail to be captured in the resulting images, thereby leading to enhanced image quality.

In contrast, if the number of phase encoding steps were decreased, the voxel size would increase, resulting in a loss of detail and resolution in the images produced. Understanding this relationship between phase encoding steps and voxel size is critical in optimizing MRI scans for better diagnostic capabilities.