Glossary U to Z

Ultracet

See Tramacet.

Ultram

See Tramadol.

Ventricles

Ventricle means chamber or cavity. The two lower chambers of the heart are called ventricles. The ventricular system in the brain is a set of structures continuous with the central canal of the spinal cord, comprising 4 ventricles: the right and left lateral ventricles; the third ventricle; and the fourth ventricle. Cerebrospinal fluid produced in the ventricles surrounds various parts of the brain and the inside of the spinal cord.

Voxel

The smallest unit of three-dimensional space in a computer image, equivalent to a three-dimensional pixel. Used when talking about images from MRI scans for example.

Wax and wane

Increase and decrease.