Coronary artery calcium scoring is used to quantify the amount of calcium in the coronary arteries based on non-contrast-enhanced CT. Developments in CT provide a number of adjustable CT parameters like tube voltage, tube current and iterative reconstruction (IR). Calcium scoring was originally developed on electron beam tomography (EBT). Quantification of coronary calcification was developed by Agatston (Agatston calcium score), and a zero calcium score on EBT was indicative for over five year event-free survival.[1-3] EBT was based on tube voltage of maximum 130 kV....

An anthropomorphic thoracic phantom with a cylindrical insert containing 100 small calcium spots was used. (Figure 1) The HU density of the cylindrical phantom is comparable to unenhanced myocardium. The 100 calcium spots are divided into four planes of 25 spots. Spots varied in density (range 92-548 HA/cm3) and diameter (range 0.5-2 mm). Physical reference volumes and masses were known. The phantom was scanned on a third generation dual source CT scanner (Somatom Force, Siemens, Forchheim) at tube voltages of 70, 100 and 120 kV....

Tube voltage and IR grade influenced detectability of the calcium spots and calculated calcium scores. (Figure 2) Using filtered back projection, 25 spots were detected at a tube voltage of 70 kV. At tube voltages of 100 and 120 kV the detectability of the calcium spots decreased to 17 detected spots at 100 kV and 15 detected spots at 120 kV. Increased IR strength also decreased the number of detected spots. This effect was seen at all kV levels and was strongest for 70 kV....

Using a third generation dual-source CT scanner, detectability, Agatston score, volume and mass of calcifications in a stationary phantom decreased at increasing kV and at higher levels of IR. No single combination of kV and IR performed best for all three reference standards.

ADDIN RW.BIB[1] Arad Y, Spadaro LA, Goodman K, Newstein D, Guerci AD, Prediction of coronary events with electron beam computed tomography. J Am Coll Cardiol 2000;36(4):1253-60. [2] O'Malley PG, Taylor AJ, Jackson JL, Doherty TM, Detrano RC, Prognostic value of coronary electron-beam computed tomography for coronary heart disease events in asymptomatic populations. Am J Cardiol 2000;85(8):945-8. [3] Pletcher MJ, Tice JA, Pignone M, Browner WS, Using the coronary artery calcium score to predict coronary heart disease events: a systematic review and meta-analysis. Arch Intern Med...