Phantom-calibrated versus automatic coronary artery mass quantification with multidetector-row computed tomography: in vitro and in vivo study.
BACKGROUND
Coronary artery calcium scoring is used as a method for cardiovascular risk stratification and monitoring of coronary heart disease. Automatic software-based calcium mass calculation has been proposed to improve the performance of the procedure.


OBJECTIVE
To compare two algorithms of calcium mass measurement, automatic and phantom calibrated, with respect to correlation, measurement error, and accuracy in vitro and in vivo.


METHODS
A cardiac phantom with calcium cylinder inserts was scanned with sequential non-overlapping collimation 4 x 2.5 mm, at 120 kV and 165 mAs. Fifty adults (37 men; mean age 46.2 years) were examined with the same settings using prospective electrocardiographic triggering to detect and quantify coronary artery calcifications. Calculations were performed with two methods: software-based automatic calcium mass measurement (ACM) and phantom-calibrated calcium mass measurement (CCM).


RESULTS
The total phantom calcium masses measured with ACM and CCM were 175.0+/-13.8 mg and 163.0+/-4.4 mg, respectively (P<0.0001), and ACM produced a higher mean error (4.5 vs. 3.2; P<0.05). Results of ACM and CCM were strongly correlated to each other (R=0.73-0.96; P<0.0001). Mean image noise in the patient study was 8.72+/-1.68 HU. Results of patient calcium scoring with ACM and CCM were significantly different (median 70.3 mg and 59.7 mg, respectively; P<0.0001), with a mean systematic error of 17.5% (limit of agreement between 14.6% and 20.4%). The use of ACM resulted in an altered quartile classification for 14% of patients, as compared to CCM; all of these patients were classified into a higher category.


CONCLUSIONS
Our data indicate that multidetector-row computed tomography coronary calcium mass determination based on dedicated phantom calibration shows lower measurement error than an automatic software-based calculation method. The tested automatic software does not yet seem to be a reliable option for calcium mass measurement.
Serafin
Z
Z
Department of Radiology and Diagnostic Imaging, Nicolaus Copernicus University, Collegium Medicum, Bydgoszcz, Poland. serafin@cm.umk.pl
Lasek
W
W
Laskowska
K
K
D002118:Calcium / Q000032:analysis*; D003331:Coronary Vessels / Q000033:anatomy & histology* / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
D002118:Calcium