Window, level, and LUT

Window and level map raw intensities to display gray. Width is the range you show. Center is the midpoint. A wider window shows more anatomy with less contrast between tissues. A narrow window boosts contrast in a small intensity band. A LUT recolors grayscale. Use color sparingly in clinical work. It is better for emphasis and teaching than for everyday reads.

How this looks on a CT

Lung parenchyma likes a wide window and a lower center so tiny nodules stand out against air. Soft tissue sits mid-width around water density for solid organs and nodes. Bone wants a very wide, high window so cortex and trabeculae stay visible together.

Presets in Prism

Modality-aware auto is a starting point when you first open a stack. Always verify it for the finding you care about. Named CT presets such as soft tissue, lung, bone, and brain are shortcuts into width and center patterns that match those jobs.

A common CAP pass starts soft for the abdomen, jumps to lung for a lung window pass, then returns to soft for nodes. A missed fracture query starts on bone for cortical break lines. Soft-tissue questions on MR use that modality’s own VOI tools, not the CT bone preset.

Color LUTs

Grayscale is the default for most diagnostic viewing. Inverted is sometimes preferred for a CXR-like look. Hot, HSV, and rainbow help conspicuity in teaching or when intensity bands overlap, but they can hide true attenuation differences if you lean on them too hard. PET-CT fusion in some products keeps CT grayscale and puts a hot look on PET. Functional CTP maps delivered as secondary captures may look rainbow for education. That is not a substitute for numeric perfusion on the workstation that made the map.

How you drive it

Pick the W/L tool in Navigate, then drag in the active viewport. Vertical and horizontal moves map the way most DICOM readers do. Small moves first. Reset if you get lost. When VOI sync is on across panes, one drag can push to the others. That is useful for matched comparison and annoying for mixed-phase reads where each pane needs its own window.