Abstract
Background
Coronary artery calcium is an important marker of coronary artery disease. Myocardial perfusion imaging (MPI) using PET-CT technology requires a CT scan for attenuation correction (CTAC) but is not used routinely to measure coronary calcium burden. This study aimed to determine if a low-dose CTAC scan can also accurately quantify coronary artery calcium.
Methods
Twenty-three patients underwent both a traditional coronary artery calcium scan on a dedicated cardiac CT scanner (CAC-CT) and a myocardial perfusion scan on a hybrid PET-CT scanner. The standard MPI protocol includes rest and stress-matched PET and CTAC scans. The post-stress CTAC scan was modified to approximate the CAC-CT scan protocol while maintaining ~0.5 mSv dose. Coronary artery calcium scores were compared between the Ca-CTAC and CAC-CT scans.
Results
The modified Ca-CTAC scan showed a trend toward slight decreases in segmental stress perfusion of 2-3.5% in the anterior wall segments (P < 0.05). Correlation and agreement between the proposed Ca-CTAC and standard CAC-CT calcium scores at the optimal threshold of 110 HU were also excellent (r 2 = 0.99, κ = 1.0). There was a small difference in the regression slope vs unity: Ca-CTAC = 0.96 × CAC (P < 0.05), but the categorical classification of calcium was accurate in all twenty-three patients (κ = 1.0).
Conclusion
A single low-dose rest CTAC scan can be used for accurate attenuation correction of rest and stress PET perfusion images, thus allowing a post-stress CTAC scan to be optimized for improved quantification of coronary artery calcium without increasing radiation dose vs standard protocols.
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Acknowledgment
This work was supported by an operating grant from the Canadian Institute of Health Research (CIHR) for the RbARMI trial (Grant MIS-100935). The study was also supported in part by the Molecular Function and Imaging (MFI) Program Grant from the Heart and Stroke Foundation of Ontario (Grant #PRG6242). R.S.B. is a Career Investigator supported by the HSFO. T.K. was supported in part by the University of Ottawa Undergraduate Research Opportunities Program.
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Disclosure
RSB and RdK are consultants with Jubilant DRAXimage and have received grant funding from a government/industry program (partners: GE Healthcare, Nordion, Lantheus Medical Imaging, DRAXimage). RdK receives revenues from rubidium generator technology licensed to Jubilant DRAXimage. RSB is a consultant for Lantheus Medical Imaging.
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See related editorial, doi: 10.1007/s12350-014-0029-8.
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Kaster, T.S., Dwivedi, G., Susser, L. et al. Single low-dose CT scan optimized for rest-stress PET attenuation correction and quantification of coronary artery calcium. J. Nucl. Cardiol. 22, 419–428 (2015). https://doi.org/10.1007/s12350-014-0026-y
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DOI: https://doi.org/10.1007/s12350-014-0026-y