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. 2022 Jun;29(3):1119-1128.
doi: 10.1007/s12350-020-02408-6. Epub 2020 Nov 4.

Effect of PET-CT misalignment on the quantitative accuracy of cardiac 15O-water PET

Jonny Nordström  1   2   3 , Hendrik J Harms  4   5   6 , Tanja Kero  4   7 , Maryam Ebrahimi  4   5 , Jens Sörensen  4   5   7   6 , Mark Lubberink  4   8   5   6
Affiliations

Effect of PET-CT misalignment on the quantitative accuracy of cardiac 15O-water PET

Jonny Nordström et al. J Nucl Cardiol. 2022 Jun.

Abstract

Background: Quantification of myocardial blood flow (MBF) with PET requires accurate attenuation correction, which is performed using a separate CT. Misalignment between PET and CT scans has been reported to be a common problem. The purpose of the present study was to assess the effect of PET CT misalignment on the quantitative accuracy of cardiac 15O-water PET.

Methods: Ten clinical patients referred for evaluation of ischemia and assessment of MBF with 15O-water were included in the study. Eleven different misalignments between PET and CT were induced in 6 different directions with 10 and 20 mm amplitudes: caudal (+Z), cranial (- Z), lateral (±X), anterior (+Y), and anterior combined with cranial (+ Y and - Z). Blood flow was quantified from rates of washout (MBF) and uptake (transmural MBF, MBFt) for the whole left ventricle and the three coronary territories. The results from all misalignments were compared to the original scan without misalignment.

Results: MBF was only minorly affected by misalignments, but larger effects were seen in MBFt. On the global level, average absolute deviation across all misalignments for MBF was 1.7% ± 1.4% and for MBFt 5.4% ± 3.2 Largest deviation for MBF was - 4.8% ± 5.8% (LCX, X + 20) and for MBFt - 19.3% ± 9.6% (LCX, X + 20). In general, larger effects were seen in LAD and LCX compared to in RCA.

Conclusion: The quantitative accuracy of MBF from 15O-water PET, based on the washout of the tracer, is only to a minor extent affected by misalignment between PET and CT.

Keywords: PET; image analysis; myocardial blood flow; perfusion agents.

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Figures

Figure 1
Figure 1
Polar plots of a patient showing only minor effects on myocardial blood flow (MBF) by misalignment X + 20 in B compared to the original scan without misalignment in A. On the other hand in D, transmural MBF is clearly affected in the left circumflex territory (LCX) with a decrease of 23% compared to the original scan in C
Figure 2
Figure 2
Linear regression and intra class correlation (ICC) in A, B, and Bland–Altman analysis in C-D of myocardial blood flow (MBF) and transmural MBF (MBFt) in the left circumflex territory (LCX) for 20 mm misalignment in the right lateral direction (X − 20). The solid lines in A-B are line of best fits and dashed lines are line of identity. In C-D the solid lines are mean bias and dashed lines are limits of agreement
Figure 3
Figure 3
Scatter dot plots showing relative deviation of myocardial blood flow (MBF) in all misalignments compared to the original scan without misalignment for left ventricle (A), left anterior descending (B), right coronary artery (C), and left circumflex (D). Intra, intra-observer variability; Inter, inter-observer variability
Figure 4
Figure 4
Scatter dot plots showing relative deviation of transmural myocardial blood flow (MBFt) in all misalignments compared to the original scan without misalignment for left ventricle (A), left anterior descending (B), right coronary artery (C), and left circumflex (D). Intra, intra-observer variability; Inter, inter-observer variability. * Deviation of 35.3% at one point in Z − 20
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