Single low-dose CT scan optimized for rest-stress PET attenuation correction and quantification of coronary artery calcium
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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.
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.
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).
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.
KeywordsPET/CT imaging coronary artery calcium rubidium
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.
Conflict of interest
No conflict of interest to report.
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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