Aim: The aim of the present study was to evaluate the effects of radiation dose reduction and iterative reconstruction protocols on coronary artery calcium (Agatston) scores using a pulsating cardiac phantom.
Materials and Methods: We used a pulsating cardiac phantom containing three calcified cubes of different sizes (3-mm diameter: small, 4-mm diameter: medium, and 5-mm diameter: large) and four calcified hydroxyapatite cubes of varying density in order to model coronary artery calcification: 5% (44HU), 15% (233HU), 25% (586HU), and 35% (792HU). Images were acquired with a 320-slice MDCT (Aquilion ONE ViSION Edition, Toshiba, Nasu, Japan), using ECG gated volume scans with tube potential:120kV, 275 ms rotation time, 60, 70, 100, 150 and 240mA tube current. The Agatston scores at all dose variations in all five reconstruction methods (filtered back projection [FBP] and adaptive iterative dose reconstruction [AIDR3D]: Weak, Mild, Standard, and Strong) for all three phantom sizes were compared to the reference dose protocol reconstructed with FBP.
Results: When the FBP and AIDR 3D: Weak protocol were used, Agatston scores significantly increased in all phantom sizes as doses of radiation decreased (p<0.001). When the AIDR3D: Mild, Standard, and Strong protocols were used, no significant differences in Agatston scores were observed for any phantom size among different radiation dose protocols. For all radiation dose protocols, Agatston scores significantly decreased as IR levels increased (p<0.003, respectively). When AIDR 3D: Mild was used, no significant differences in Agatston scores were observed between IR and FBP protocols for any phantom size.
Conclusions: The AIDR3D: Mild protocol allowed for significant reductions in radiation dose relative to standard FBP protocols, without influencing Agatston scores. Therefore, evaluation of CAC score using a combination of low-dose radiation and IR may present a reliable alternative to conventional CAC scoring.