Original Article
Automated dynamic motion correction improves repeatability and reproducibility of myocardial blood flow quantification with rubidium-82 PET imaging

https://doi.org/10.1007/s12350-022-03134-xGet rights and content

Abstract

Background

Patient motion reduces the accuracy of PET myocardial blood flow (MBF) measurements. This study evaluated the effect of automatic motion correction on test-retest repeatability and inter-observer variability in a clinically relevant population.

Methods

Patients with known or suspected CAD underwent repeat rest 82Rb PET scans within minutes as part of their scheduled rest-stress perfusion study. Two trained observers evaluated the presence of heart motion in each scan. Global LV and per-vessel MBF were computed from the dynamic rest images before and after automatic motion correction. Test-retest and inter-observer variability were assessed using intra-class correlation and Bland-Altman analysis.

Results

140 pairs of test-retest scans were included, with visual motion noted in 18%. Motion correction decreased the global MBF values by 3.5% (0.80 ± 0.24 vs 0.82 ± 0.25 mL⋅min−1⋅g−1; P < 0.001) suggesting that the blood input function was underestimated in cases with patient motion. Test-retest repeatability of global MBF improved by 9.7% (0.25 vs 0.28 mL⋅min−1⋅g−1; P < 0.001) and inter-observer repeatability was improved by 7.1% (0.073 vs 0.079 mL⋅min−1⋅g−1; P = 0.012). There was a marked impact on both test-retest repeatability as well as inter-observer repeatability in the LCX territory, with improvements of 16.5% (0.30 vs 0.36 mL⋅min−1⋅g−1; P < 0.0000) and 18.4% (0.13 vs 0.16 mL⋅min−1⋅g−1; P < 0.001), respectively.

Conclusion

Automatic motion correction improved test-retest repeatability and reduced differences between observers.

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.

References (19)

There are more references available in the full text version of this article.

Cited by (0)

The authors of this article have provided a PowerPoint file, available for download at SpringerLink, which summarizes the contents of the paper and is free for re-use at meetings and presentations. Search for the article DOI on SpringerLink.com.

The authors have also provided an audio summary of the article, which is available to download as ESM, or to listen to via the JNC/ASNC Podcast.

View full text