Bronislaw Abramiuc, Abstract Co-Author: Nothing to Disclose

Niels R. van der Werf, Abstract Co-Author: Nothing to Disclose

Martin J. Willemink MD, Abstract Co-Author: Nothing to Disclose

Tineke Petra Willems MD, PhD, Abstract Co-Author: Nothing to Disclose

Tim Leiner MD, PhD, Abstract Co-Author: Speakers Bureau, Koninklijke Philips NV Research Grant, Bayer AG Research Grant, Bracco Group

Marcel Greuter PhD, Presenter: Nothing to Disclose

To investigate the effect of iterative reconstruction (IR) and low radiation dose for quantification of small coronary calcifications in clinical calcium scoring protocols on high-end computed tomography scanners from four major vendors.

An anthropomorphic thorax phantom with a cardiac cylinder containing 100 small calcifications (size 0.5-2 mm and density 92-548 mg HA/cm3) was scanned 5 times with clinical calcium scoring protocols at the vendor recommended clinical dose and at 25, 50 and 75% radiation dose reduction on Philips Brilliance iCT, Siemens Definition Flash, GE Discovery CT750 HD, and Toshiba Aquilion ONE. Each scan series included 3 increasing IR steps. The Agatston score (AS) and mass score (MS) were derived using vendor-specific software. Coronary calcium scores (CCS) at full dose were taken as reference, and statistical comparison with CCS at lower dose was performed using the Wilcoxon matched pairs test.

At full dose the CCS resulted in median (25th-75th percentiles) AS of 10 (8-37), 34 (29-37), 113 (43-141), 87 (84-97) for Philips, Siemens, GE and Toshiba, respectively, and MS of 4 (2-10), 8 (8-9), 18 (9-22), 20 (19-21) mg, respectively. At reduced radiation dose the median AS and MS generally increased. Increasing the IR level decreased the median CCS for GE (68 – 105 AS, 13 – 18 mg) and Toshiba (47 – 70 AS, 12 – 18 mg), but no significant difference was registered for Philips (10 – 11 AS, 4 – 6 MS). However, for Siemens the CCS increased (38 – 52 AS, 10 – 13 mg) with the first IR level, followed by a decrease (32- 45 AS, 9 – 11 mg) with higher IR levels. Compared to full dose CCS, the modified protocols (low dose + IR) resulted in similar CCS only for Philips (0.89 > P > 0.14), Siemens (0.68 > P > 0.08) and GE (0.89 > P > 0.07). For Toshiba, similarity was only achieved for filtered back projection reconstructed scans at 75% and 50% dose reduction (0.68 > P > 0.22).

Calcium scores increase at lower dose and decrease with IR. Calcium score in low-dose-IR protocols results in comparable scores with vendor recommended dose protocols for Philips, Siemens and GE.

The number of asymptomatic individuals at intermediate cardiovascular risk that will undergo coronary calcium scoring examination is growing. A reduced radiation dose at constant calcium score can be achieved with iterative reconstruction in combination with lower dose.

Abramiuc, B, van der Werf, N, Willemink, M, Willems, T, Leiner, T, Greuter, M, Does Iterative Reconstruction Allow for Radiation Dose Reduction in CT Coronary Calcium Scoring? A Multivendor in vitro Study on High-end CT Scanners.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006602.html