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
To compare the quantitative results with those provided by the usual visual interpretation, the left ventricular boundary is divided into 5 anatomical regions, denoted:
Example of Centerline Wall Motion Template usage.
|Node||Code Meaning of Concept Name||Code Meaning or Example Value||TID|
|X.X.1||Procedure Reported||Centerline Wall Motion Analysis||3208|
|X.X.2||Contour Realignment||Center of Gravity||3208|
|X.X.3||Normalized Chord Length||5.0 %||300|
|X.X.4||Normalized Chord Length||5.1 %||300|
|X.X.5||Normalized Chord Length||5.3 %||300|
|X.X.102||Normalized Chord Length||4.5 %||300|
|X.X.104.1||Cardiac Wall Motion||Hypokinetic||3208|
|X.X.104.2||Circumferential Extend||LAD Region||3208|
|X.X.104.3||First Chord of Abnormal Region||66||3208|
|X.X.104.4||Last Chord of Abnormal Region||76||3208|
|X.X.104.5||Cardiac Wall Motion||Hypokinetic||3208|
|X.X.104.6||Circumferential Extend||RCA Region||3208|
|X.X.104.7||First Chord of Abnormal Region||66||3208|
|X.X.104.8||Last Chord of Abnormal Region||76||3208|
|X.X.104.9||Cardiac Wall Motion||Hyperkinetic||3208|
|X.X.104.10||Circumferential Extend||LAD Region||3208|
|X.X.104.11||First Chord of Abnormal Region||14||3208|
|X.X.104.12||Last Chord of Abnormal Region||48||3208|
|X.X.104.13||Cardiac Wall Motion||Hyperkinetic||3208|
|X.X.104.14||Circumferential Extend||RCA Region||3208|
|X.X.104.15||First Chord of Abnormal Region||25||3208|
|X.X.104.16||Last Chord of Abnormal Region||48||3208|
|X.X.104.17||Cardiac Wall Motion||Akinetic||3208|
|X.X.104.18||Circumferential Extend||LAD Region||3208|
|X.X.104.19||First Chord of Abnormal Region||69||3208|
|X.X.104.20||Last Chord of Abnormal Region||71||3208|
|X.X.104.21||Cardiac Wall Motion||Akinetic||3208|
|X.X.104.22||Circumferential Extend||RCA Region||3208|
|X.X.104.23||First Chord of Abnormal Region||69||3208|
|X.X.104.24||Last Chord of Abnormal Region||71||3208|
|X.X.105||Regional Abnormal Wall Motion||3208|
|X.X.105.1||Finding Site||Single LAD Region in RAO Projection||3208|
|X.X.105.2||Territory Region Severity||6.6||300|
|X.X.105.2.1||Cardiac Wall Motion||Hypokinetic||300|
|X.X.105.3||Opposite Region Severity||3.1||300|
|X.X.105.3.1||Cardiac Wall Motion||Hyperkinetic||300|
|X.X.105.4||Finding Site||Single RCA Region in RAO Projection||3208|
|X.X.105.5||Territory Region Severity||2.6||300|
|X.X.105.5.1||Cardiac Wall Motion||Hyperkinetic||300|
|X.X.105.6||Opposite Region Severity||7.6||300|
|X.X.105.6.1||Cardiac Wall Motion||Hypokinetic||300|
|X.X.105.7||Finding Site||Multiple LAD Region in RAO Projection||3208|
|X.X.105.8||Territory Region Severity||7.1||300|
|X.X.105.8.1||Cardiac Wall Motion||Hyperkinetic||300|
|X.X.105.9||Opposite Region Severity||2.9||300|
|X.X.105.9.1||Cardiac Wall Motion||Hyperkinetic||300|
|X.X.105.10||Finding Site||Multiple RCA in Region RAO Projection||3208|
|X.X.105.11||Territory Region Severity||2.9||300|
|X.X.105.11.1||Cardiac Wall Motion||Hypokinetic||300|
|X.X.105.12||Opposite Region Severity||7.1||300|
|X.X.105.12.1||Cardiac Wall Motion||Hyperkinetic||300|
Computer Calculated Reference
Interpolated Local Reference
Mean Local Reference
The computer-defined obstruction analysis calculates the reconstruction diameter based on the diameters outside the stenotic segment. This method is completely automated and user independent. The reconstructed diameter represents the diameters of the artery had the obstruction not been present.
The proximal and distal borders of the stenotic segment are automatically calculated.
The difference between the detected contour and the reconstructed contour inside the reconstructed diameter contour is considered to be the plaque.
Based on the reconstruction diameter at the Minimum Luminal Diameter (MLD) position a reference diameter for the obstruction is defined.
The interpolated reference obstruction analysis calculates a reconstruction diameter for each position in the analyzed artery. This reconstructed diameter represents the diameters of the artery when no disease would be present. The reconstruction diameter is a line fitted through at least two user-defined reference markers by linear interpolation.
By default two references are used at the positions of the reference markers are automatically positioned at 5% and 95% of the artery length.
To calculate a percentage diameter stenosis the reference diameter for the obstruction is defined as the reconstructed diameter at the position of the MLD.
In cases where the proximal and distal part of the analyzed artery have a stable diameter during the treatment and long-term follow-up, this method will produce a stable reference diameter for all positions in the artery.
In case of mean local reference obstruction the reference diameter will be an average of the diameters at the position of one or more the reference markers.
This method is particularly appropriate for the analysis of bifurcated arteries.
A vessel segment length as seen in the image is not always indicated as the same X-axis difference in the graph.
The X-axis of the graph is based on pixel positions on the midline and these points are not necessarily equidistant. This is caused by the fact that vessels do not only run perfectly horizontally or vertically, but also at angles.
When a vessel midline is covering a number of pixel positions perfectly horizontal or vertical, it will cover less space in mm compared to a vessel that covers the same number of pixel positions under an angle. When a segment runs perfectly horizontal or vertical, the segment length is equal to the amount of midline pixel points times the pixel separation (each point of the midline is separated exactly the pixel spacing in mm) and the points on the X-axis also represent exactly one pixel space. This is not the case when the vessel runs under an angle. For example an artery that is positioned at a 45 angle, the distance between two points on the midline is 0.7 times the pixel spacing.
As example, the artery consists of 10 elements (n =10); each has a length of 1mm(pixel size). If the MLD was exactly in the center of the artery you would expect the length from 0 to the MLD would be 5 sub segments long, thus 5 mm. This is true if the artery runs horizontal or vertically (assumed aspect ratio is 1).
If the artery is positioned in a 45º angle then the length of each element is √2 times the pixel size compared to the previous example. Thus the length depends on the angle of the artery.