CT Colormaps

Computed tomography (CT, also known as computed axial tomography) produces images with calibrated voxel intensities, unlike magnetic resonance imaging (MRI), where most sequences yield relative signal intensities. CT scans use Hounsfield units (HU): air is approximately -1000 HU, water is 0 HU, and dense bone can exceed +1000 HU. Most soft tissues (e.g., gray matter, white matter, muscle) fall within a narrow range of 0 to 40 HU. Intravenous contrast agents can temporarily increase the brightness of blood and enhance soft tissue contrast.

Because CT brightness values are standardized, NiiVue includes a set of colormaps specifically optimized to emphasize different tissue types. Use the pull-down menu below to explore how these colormaps affect visualization.