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The user’s choice of the Background Region of Interest can artificially elevate the calculated EF, so take high and low areas of activity under careful consideration.The numbers used to calculate EF and generate the volume curve should be counts in each frame from the blood pool within the ventricle.This method is subjective, very dependent upon the visual determination of a border by the operator.The ROI generated for each frame of the cardiac cycle should include all of the left ventricle.
Ejection fraction (%) = [ED (net) – ES (net)] ÷ ED x 100 This is defined as the fraction of the left ventricular end-diastolic volume expelled during contraction.
For an accurate EF and volume curve, background activity must be subtracted from the total counts of each ventricle ROI.
A contoured background region several pixels wide should be drawn along the lateral side of the LV edge.
A background-corrected time-activity curve is then generated.
Counts detected in the LV are proportional to volume, and the change from end-systolic counts (ESC) to end-diastolic counts (EDC) of the LV can be used for the calculation of left ventricular ejection fraction.