Original ArticleAutomated dynamic motion correction improves repeatability and reproducibility of myocardial blood flow quantification with rubidium-82 PET imaging
Introduction
Myocardial blood flow (MBF) quantification using rubidium-82 PET is a prominent tool used in the diagnostic and prognostic assessment of patients with ischemic heart disease. Quantitative MBF is an invaluable clinical asset, providing improved prognostic value compared to relative myocardial perfusion imaging (MPI) in the assessment of coronary artery disease (CAD).1,2 There are several technical factors which can potentially impact the measured MBF values, notably patient motion. The prevalence of patient motion has been reported in multiple studies, ranging from 20% to 60% of scans.3,4 Several studies have shown that the effect of patient motion on measured MBF is significant, some even reporting mean changes of up to 39%5 and 44%.4
Limited studies have explored the effects of motion correction in rubidium-82 PET. Manual motion correction has been assessed in the context of stress scans, rest scans, and repeat rest scans in healthy and clinical populations.6, 7, 8 Automatic motion correction has also been explored in the context of operator variability.9 However there has been no study exploring the impact of automatic motion correction on test-retest repeatability. The objective of this study was to investigate the effect of an automatic motion correction algorithm on test-retest repeatability as well as inter-observer variability in a clinically relevant population.
Section snippets
Study population
Under the clinical quality improvement program at the University of Ottawa Heart Institute 141 patients with known or suspected coronary artery disease (CAD) underwent a repeat quality assurance rest 82Rb PET scan on the day of their scheduled rest-stress perfusion study between April 2017 and September 2019. All patients completed a routine questionnaire on medical history, cardiac risk factors, medications, and cardiac symptoms. Consecutive patients were included based on their verbal consent
Study population
One patient was excluded due to attenuation correction artifact on the retest scan, leaving a total of 140 patients in the final analysis. The mean injected activity for scan 1 (test) was 800 ± 180 MBq compared to 440 ± 120 MBq for the quality assurance scan 2 (retest). The demographics of the study population are presented in Table 1. The analysis cohort consisted of 96 men and 44 women aged 64 ± 11 years with a high prevalence of cardiac risk factors and symptoms, as expected in patients
Summary of findings
To our knowledge, this is the first study to evaluate the effects of automatic motion correction on the test-retest and inter-observer repeatability of 82Rb dynamic PET scans in a clinically relevant population. The main finding was that both test-retest and inter-observer repeatability of MBF measurements performed at rest were improved significantly following the application of automatic motion correction on the dynamic image series. The impact of automatic motion correction seemed to have a
New knowledge gained
Automatic MC has a beneficial impact on both inter-observer and test-retest repeatabilities of PET MBF measurements at rest. Our results point to automatic motion correction having a significant but relatively small (~ 10%) effect on test-retest repeatability under resting conditions. We also observed a vessel-dependent effect of automatic MC which has yet to be noted in other studies, with the most profound improvements observed in the LCX territory.
Conclusion
Automatic MC significantly improves test-retest and inter-observer repeatability of rest MBF measurements using 82Rb PET. This effect seems to be vessel dependent, with the greatest improvements occurring in the LCX territory. These results support the routine use of automatic MC either alone or as an adjunct to manual MC in clinical practice.
Author contributions
JC was responsible for the conceptualization, data curation, formal analysis, and writing of this article. NM was responsible for data curation as well as review and editing of the manuscript. RD contributed to investigation, conceptualization, as well as writing and editing of the manuscript. RB was responsible for the supervision of the investigation as well as reviewing and editing of the manuscript.
Disclosures
Robert deKemp is consultant for- and receives unrestricted grant funding and royalties from Rubidium-82 generator technologies licensed to Jubilant Radiopharma. Rob Beanlands is consultant for- and has received grant funding from GE Healthcare, Lantheus Medical Imaging, and Jubilant Radiopharma. The other authors declare that they have no conflicts of interest or disclosures.
Funding
Canadian Institutes of Health Research (CIHR) Grant# FRN 133673.
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