A method for coronary artery calcium scoring using contrast-enhanced computed tomography.
BACKGROUND
Limitations to the coronary calcium score include its requirement for noncontrast imaging and radiation exposure that approaches current methods for contrast-enhanced CT angiography.


OBJECTIVE
We sought to derive and validate a method of measuring the coronary artery calcium score (CACS) from standard contrast-enhanced CT, obviating the need for a second non-contrast calcium scan.


METHODS
The volume of intramural calcium of >320 HU in major coronary vessels was measured in 90 contrast-enhanced and traditional non-contrast calcium scan pairs. An empiric conversion factor was derived to convert the small voxel contrast-enhanced calcium volume to an Agatston calcium score. The accuracy of this technique was then prospectively validated in 120 consecutive patients undergoing clinical calcium scans and contrasted-enhanced coronary CT. Eleven patients were excluded from analysis because of the prespecified criteria of excessive noise in the contrast-enhanced CT or total coronary artery occlusion.


RESULTS
The Pearson correlation of the contrast scan-derived calcium score with the measured CACS was r2 = 0.99. With standard CACS risk bands, agreement of the contrast-enhanced calcium score estimate with the measured CAC by quadratic weighted κ was 0.96. The 95% limits of agreement (Agatston units) were given by ±(3.2 + 0.14 × CACS + 4.44 mean square root of CACS). Inter-observer and intra-observer reliability with the intraclass correlation was 0.99.


CONCLUSIONS
The calcium score can be accurately measured from contrast-enhanced cardiac CT scans with the use of a Hounsfield unit threshold of 320.
Cardiology Department, St Vincent's Hospital, Darlinghurst Sydney 2010, Australia.
James M
JM
Otton
Jacob T
JT
Lønborg
David
D
Boshell
Michael
M
Feneley
Andrew
A
Hayen
Neville
N
Sammel
Ken
K
Sesel
Lourens
L
Bester
Jane
J
McCrohon
D000465:Algorithms; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D061205:Vascular Calcification / Q000000981:diagnostic imaging*
D003287:Contrast Media