The Diameter Symmetry of a Stenosis is a parameter determining the symmetry in arterial plaque distribution.

The Symmetry Index is defined by: a / b where a is smaller or equal to than b . a and b are measured in the reconstructed artery at the position of the minimal luminal diameter.

Possible values of symmetry range from 0 to 1, where 0 indicates complete asymmetry and 1 indicates complete symmetry.

Reference: Quantitative coronary arteriography; physiological aspects, page 102-103 in: Reiber and Serruys, Quantitative coronary arteriography, 1991