Semi-quantitative MCE (contrast perfusion scores)
In much the same way as wall thickening is graded using a numerical score and then divided by the number of segments to yield the Wall Motion Scoring Index (WMSI), the pattern of contrast uptake in myocardial segments can also be numerically scored.
An example of a semi-quantitative scoring system would be:
|0 = minimal / absent contrast opacification|
|1 = reduced / heterogeneous contrast opacification|
|2 = normal / homogenous contrast opacification|
The scores for each segment are summed and then divided by the number of segments to yield a CONTRAST PERFUSION INDEX (CPI).
At rest, this score clearly also is linked to myocardial viability (lack of contrast uptake implies lack of an intact microvasculature which usually implies scar tissue) – a CPI>1.5 has been shown to correlate with a low likelihood of viable myocardium.
If the CPI is calculated at rest and after stress, the difference between the two represents the ISCHAEMIC BURDEN of myocardium.
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