Quantifying coronary artery calcification from a contrast-enhanced cardiac computed tomography angiography study.
OBJECTIVE
We sought to quantify coronary artery calcium (CAC) using a single contrast-enhanced cardiac computed tomography angiography (CCTA) study. CCTA has been successfully used for the assessment of coronary artery stenoses, whereas non-contrast ECG-gated computed tomography (Standard-CAC) is commonly performed to quantify CAC. Thus each scan individually contributes to the total radiation dose.


RESULTS
Patients who underwent both Standard-CAC and CCTA scans were identified. Standard-CAC images were scored using the Agatston method. CCTA scans were scored for CAC (CCTA-CAC), whereby CAC was defined as plaque with attenuation 2 SD above the mean attenuation value of the ascending aorta (HU(aorta)). The correlation between Standard-CAC and CCTA-CAC was determined with the slope used to derive a correction factor for the conversion of CCTA-CAC results to a Standard-CAC Agatston score (AS). To test applicability, the correction factor was assessed in a separate validation cohort of similar demographics. From April 2011 to June 2012, a derivation cohort of 92 patients was identified and analysed. An additional 47 patients were identified for the validation cohort. Correlation between Standard-CAC and CCTA-CAC was excellent (r = 0.96). The slope (y = 2.74 × CCTA-CAC score) derived correction factor from the derivation cohort was used to adjust CCTA-CAC derived scores to an AS (CCTA-CAC(corrected) = 2.74 × CCTA-CAC). The correction factor was applied to the validation cohort CCTA-CAC results with excellent agreement between CCTA-CAC(corrected) and Standard-CAC (kappa = 0.93).


CONCLUSIONS
Quantification of CAC from a single contrast-enhanced CCTA scan is feasible and correlates well with Standard-CAC. Larger, multicentre studies are needed to validate the universal applicability of CAC quantified using CCTA.
Department of Medicine (Cardiology), University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON, Canada K1Y 4W7.
Ilias
I
Mylonas
Mohammed
M
Alam
Noor
N
Amily
Gary
G
Small
Li
L
Chen
Yeung
Y
Yam
Benjamin
B
Hibbert
Benjamin J W
BJ
Chow
D055424:Cardiac-Gated Imaging Techniques; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014283:Triiodobenzoic Acids; D061205:Vascular Calcification / Q000000981:diagnostic imaging*
D003287:Contrast Media; D014283:Triiodobenzoic Acids; C044834:iodixanol
Contrast-enhanced CTA; Coronary artery calcium