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EFFECTS OF MISPLACED ROI AND BACKGROUND ON FINAL RESULTS CARDIAC.

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Presentation on theme: "EFFECTS OF MISPLACED ROI AND BACKGROUND ON FINAL RESULTS CARDIAC."— Presentation transcript:

1 EFFECTS OF MISPLACED ROI AND BACKGROUND ON FINAL RESULTS CARDIAC

2 Terminology Gross counts the total number of counts acquired with the radiation source present. Gross counts are also referred to as total counts. Net counts The actual counts produced by the radiation source. Net counts = gross counts – background counts Background counts Counts in the body not related to the ROI or organ of interest.

3 end-diastole heart at fullest point of relaxation (dilatation) Represented by the T wave on the electrocardiogram end-systole heart at fullest point of contraction Represented by QRS on the electrocardiogram ROI Area where number counts are determined Terminology

4 EF = net ED-net ES / net ED x 100% ROI area/counts EDESBkg Too LargeEF to HIGHEF to LOWEF to High misplaced area with high counts Too SmallEF to LOWEF to HIGHEF to LOW misplaced area with low counts (outside body margin)

5 EF = net ED-net ES / net ED x 100% ROI counts ED Too LargeEF to HIGH Too SmallEF to LOW Correctly drawn ROI EF = 90,000 counts - 35,000 counts/ 90,000 counts x 100% = 61.1% Too Large ED ROI EF = 110, ,000 counts/ 110,000 x 100% = 68.2% Too Small ED ROI EF = 75, ,000 counts/ 75,000 x 100% = 53.3% ED = 90,555 counts ES = 35,555 counts BKG = 555 counts NET counts net ED = 90,555 counts counts = 90,000 counts net ES = 35,555 counts counts = 35,000 counts ACTUAL counts

6 EF = net ED-net ES / net ED x 100% ROI counts ES Too LargeEF to LOW Too SmallEF to HIGH ED = 90,555 counts ES = 35,555 counts BKG = 555 counts NET counts net ED = 90,555 counts counts = 90,000 counts net ES = 35,555 counts counts = 35,000 counts Correctly drawn ROI EF = 90,000 counts - 35,000 counts/ 90,000 counts x 100% = 61.1% Too Large ES ROI EF = 90,000 counts - 45,000 counts/ 90,000 x 100% = 50% Too Small ES ROI EF = 90,000 counts - 25,000 counts/ 90,000 x 100% = 72.2% ACTUAL counts

7 EF = net ED-net ES / net ED x 100% ROI counts Bkg Too LargeEF to High misplaced area with high counts Too SmallEF to LOW misplaced area with low counts (outside body margin) ACTUAL counts ED = 90,555 counts ES = 35,555 counts BKG = 555 counts NET counts net ED = 90,555 counts counts = 90,000 counts net ES = 35,555 counts counts = 35,000 counts Too Large counts Bkg ROI EF = 89,000 counts - 34,000 counts / 89,000 counts x 100% = 61.8% net ED = 90,555 counts - 1,555 counts = 89,000 net ES = 35,555 counts - 1,555 counts = 34,000 BKG too large = 1,555 counts Too Small counts Bkg ROI EF = 90,550 counts - 35,550 counts/ 90,550 counts x 100% = 60.7 % net ED = 90,555 counts - 5 counts = 90,550 counts net ES = 35,555 counts - 5 counts = 35,550 counts BKG misplaced outside of body margin= 5 counts Correctly drawn ROI EF = 90,000 counts - 35,000 counts/ 90,000 counts x 100% = 61.1%


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