Gated Myocardial Perfusion SPECT: Algorithm-Specific Influence of Reorientation on Calculation of Left Ventricular Volumes and Ejection Fraction
Daniela Knollmann 1*,
Oliver H. Winz 1,
Philipp T. Meyer 1,
Mardjan Raptis 1,
Thomas Krohn 1,
Karl-Christian Koch 2,
and
Wolfgang M. Schaefer 1
1 Department of Nuclear Medicine, University Hospital, Aachen University of Technology, Aachen, Germany
2 Medical Clinic I (Cardiology), University Hospital, Aachen University of Technology, Aachen, Germany
* To whom correspondence should be addressed. E-mail: dknollmann{at}ukaachen.de.
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Abstract |
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Gated myocardial perfusion SPECT allows calculation of end-diastolic and end-systolic volumes (EDV and ESV, respectively) and left ventricular ejection fraction (LVEF). The quantification algorithms QGS (quantitative gated SPECT), 4D-MSPECT, and CARE heart show a good correlation with cardiac MRI. Nevertheless, differences in contour finding suggest algorithm-specific effects if heart axes vary. The effect of tilting heart axes on gated SPECT was quantified as a possible source of error. Methods: Sixty men underwent gated SPECT (450 MBq of 99mTc-tetrofosmin or sestamibi, 8 gates/cycle). After correct reorientation (R0), datasets were tilted by 5°, 10°, 15°, 20°, 30°, and 45° along both long axes (R5, R10, R15, R20, R30, and R45, respectively). EDV, ESV, and LVEF were calculated using QGS, 4D-MSPECT, and CARE heart. Because a 15° tilt could be a maximum possible misreorientation in routine, R0 and R15 results were analyzed in detail. Absolute-difference values between results of tilted and correctly reoriented datasets were calculated for all tilts and algorithms. Results: QGS and CARE heart succeeded for R0 and R15 in all cases, whereas 4D-MSPECT failed to find the basal plane in 1 case (patient B). R2 values between paired R15/R0 results were 0.992 (QGS), 0.796 (4D-MSPECT; R2 = 0.919 in n = 59 after exclusion of the failed case), and 0.916 (CARE heart) for EDV; 0.994 (QGS), 0.852 (4D-MSPECT; R2 = 0.906 in n = 59), and 0.899 (CARE heart) for ESV; and 0.988 (QGS), 0.814 (4D-MSPECT; R2 = 0.810 in n = 59), and 0.746 (CARE heart) for LVEF. Concerning all levels of misreorientation, 1 patient was excluded for all algorithms because of multiple problems in contour finding; additionally for 4D-MSPECT patient B was excluded. In the 45° group, QGS succeeded in 58 of 59 cases, 4D-MSPECT in 58 of 58, and CARE heart in 33 of 59. Mean absolute differences for EDV ranged from 5.1 ± 4.1 to 12.8 ± 10.5 mL for QGS, from 6.7 ± 6.3 to 34.2 ± 20.7 mL for 4D-MSPECT, and from 5.4 ± 5.6 to 25.2 ± 16.1 mL for CARE heart (tilts between 5° and 45°). Mean absolute differences for ESV ranged from 4.1 ± 3.7 to 8.0 ± 9.4 mL for QGS, from 5.6 ± 8.0 to 10.0 ± 10.5 mL for 4D-MSPECT, and from 5.4 ± 5.6 to 25.5 ± 16.1 mL for CARE heart. Mean absolute differences for LVEF ranged from 1.1% ± 1.0% to 2.2% ± 1.8% for QGS, from 4.0% ± 3.5% to 8.0% ± 7.1% for 4D-MSPECT, and from 3.4% ± 2.9% to 9.2% ± 6.0% for CARE heart. Conclusion: Despite tilted heart axes, QGS showed stable results even when using tilts up to 45°. 4D-MSPECT and CARE heart results varied with reorientation of the heart axis, implying that published validation results apply to correctly reoriented data only.
Key Words:
gated SPECT, QGS, 4D-MSPECT, CARE heart, reorientation
