voxel

Syllable breakdown

Dictionary meaning

a three-dimensional picture element — the volumetric equivalent of a pixel (picture element) in two-dimensional imaging — representing a single value in a three-dimensional data grid; the word voxel is a portmanteau of volumetric and pixel; in medical imaging each voxel in a CT, MRI, or PET dataset represents a discrete cubic or rectangular volume of tissue and contains a number representing the imaging signal from that tissue volume — in CT the number is a Hounsfield unit representing X-ray attenuation; voxel dimensions determine spatial resolution: smaller voxels capture finer anatomical detail but require more data storage and longer acquisition times; a typical brain MRI might consist of 200 slices each with 256 × 256 voxels — approximately 13 million voxels total; in MRI voxel size is determined by field of view, matrix size, and slice thickness; in CT it is determined by reconstruction kernel and slice thickness; isotropic voxels — equal dimensions in all three spatial directions — enable high-quality reconstructions in any plane

Examples

• The high-resolution MRI acquired isotropic voxels of 0.5 mm in each dimension, enabling detailed visualisation of hippocampal subfields.
• Each voxel in the PET image represents the average radiotracer uptake in a 4 × 4 × 4 mm cube of tissue.

Synonyms: volume element, 3D pixel, volume pixel