Objective: Left ventricular function is prognostically important. Our aim was to validate different algorithms' measurements with rubidium-82 PET, using computed tomography (CT) acquired simultaneously on hybrid imaging.
Methods: Fifty patients (33 men, 17 women, mean age 59 years SD 12) referred for coronary artery disease evaluation underwent rubidium-82 PET myocardial perfusion scintigraphy and 64-slice CT coronary angiography simultaneously on hybrid PET/CT. Left ventricular ejection fraction, end-systolic volume and end-diastolic volume from quantitative gated PET at rest, were calculated using quantitative gated single-photon emission computed tomography (QGS), Emory Cardiac Toolbox (ECT), Myometrix and CardIQ Physio software and then compared with CT. The paired t-test and Bland–Altman plots were used for analysis.
Results: There was no significant difference between CT and both QGS and ECT for calculating ESV. Otherwise there were significant differences (t-test, P<0.05) between CT coronary angiography and all other software algorithms in calculating systolic and diastolic volumes. Bland–Altman analysis revealed a bias towards underestimating end-diastolic volume with mean differences of 32.3, 34.8, 42.6 and 35.7 ml for QGS, ECT, Myometrix and CardIQ Physio, respectively. The limits of agreement (mean bias±1.96 SD) for left ventricular ejection fraction (%) were 8.5±21.0, 12.9±21.0, 3.5±18.9 and 5.6±17.1, for QGS, ECT, Myometrix and CardIQ Physio, respectively.
Conclusion: The systematic error (or mean bias) of the Myometrix algorithm is the smallest, and CardIQ Physio shows the least statistical error (or limits of agreement) when calculating ejection fraction from rubidium-82 myocardial perfusion PET, compared with QGS and ECT. The wide limits of agreement between the different algorithms mean that they are not interchangeable.
Institute of Nuclear Medicine, University College London, UK
Correspondence to Dr Leon J. Menezes, FRCR, Institute of Nuclear Medicine, UCL, 5th Floor Tower, University College London Hospital, 235 Euston Road, London NW1 2BU, UK
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Received 25 November 2008 Revised 30 January 2009 Accepted 4 February 2009