Time-modified OSEM algorithm for more robust assessment of left ventricular dyssynchrony with phase analysis in ECG-gated myocardial perfusion SPECT

Matti J Kortelainen; Tuomas M Koivumäki; Marko J Vauhkonen; Mikko A Hakulinen

doi:10.1186/s40658-019-0261-z

Time-modified OSEM algorithm for more robust assessment of left ventricular dyssynchrony with phase analysis in ECG-gated myocardial perfusion SPECT

EJNMMI Phys. 2019 Dec 27;6(1):30. doi: 10.1186/s40658-019-0261-z.

Authors

Matti J Kortelainen^{1

2}, Tuomas M Koivumäki³, Marko J Vauhkonen⁴, Mikko A Hakulinen^{4

5}

Affiliations

¹ Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211, Kuopio, Finland. matti.kortelainen@uef.fi.
² Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland. matti.kortelainen@uef.fi.
³ Department of Medical Physics, Central Finland Central Hospital, Jyväskylä, Finland.
⁴ Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211, Kuopio, Finland.
⁵ Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland.

Abstract

Background: In ordered subsets expectation maximization (OSEM) reconstruction of electrocardiography (ECG)-gated myocardial perfusion single-photon emission computed tomography (SPECT), it is often assumed that the image acquisition time is constant for each projection angle and ECG bin. Due to heart rate variability (HRV), this assumption may lead to errors in quantification of left ventricular mechanical dyssynchrony with phase analysis. We hypothesize that a time-modified OSEM (TOSEM) algorithm provides more robust results.

Methods: List-mode data of 44 patients were acquired with a dual-detector SPECT/CT system and binned to eight ECG bins. First, activity ratio (AR)-the ratio of total activity in the last OSEM-reconstructed ECG bin and first five ECG bins-was computed, as well as standard deviation SD_R-R of the accepted R-R intervals; their association was evaluated with Pearson correlation analysis. Subsequently, patients whose AR was higher than 90% were selected, and their list-mode data were rebinned by omitting a part of the acquired counts to yield AR values of 90%, 80%, 70%, 60% and 50%. These data sets were reconstructed with OSEM and TOSEM algorithms, and phase analysis was performed. Reliability of both algorithms was assessed by computing concordance correlation coefficients (CCCs) between the 90% data and data corresponding to lower AR values. Finally, phase analysis results assessed from OSEM- and TOSEM-reconstructed images were compared.

Results: A strong negative correlation (r = -0.749) was found between SD_R-R and AR. As AR decreased, phase analysis parameters obtained from OSEM images decreased significantly. On the contrary, reduction of AR had no significant effect on phase analysis parameters obtained from TOSEM images (CCC > 0.88). The magnitude of difference between OSEM and TOSEM results increased as AR decreased.

Conclusions: TOSEM algorithm minimizes the HRV-related error and can be used to provide more robust phase analysis results.

Keywords: Dyssynchrony; Image reconstruction; Myocardial perfusion imaging; Phase analysis; SPECT.

Abstract

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