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

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

Bronislaw Abramiuc, 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

The dose in coronary calcium scoring (CCS) can be reduced with respect to filtered back projection (FBP) using iterative reconstruction (IR) in computed tomography (CT). However, the influence of dose on depiction of coronary calcium in moving coronary arteries in IR CT is still unknown. Therefore, the purpose of the current study was to evaluate the influence of dose on CCS in IR CT for high-end CT scanners of the four major vendors with moving calcifications.

Two calcifications of equal volume (198.4 mm3) but different mass (157.1, and 38.5 mg) were used in an anthropomorphic thorax phantom at a velocity of 20 mm/s. An extension ring was placed around the thorax phantom to resemble a medium sized patient. Vendor recommended clinical protocols were used. Subsequently dose was reduced by 80%. The phantom was scanned five times with a small translation on Brilliance iCT (Philips), Aquilion One (Toshiba), Discovery CT 750 HD (GE) and Somatom Definition Flash (Siemens). CCS was quantified as Agatston scores with vendor software.

For the 157.1 mg calcification full dose FBP resulted in CCS of 500±45, 442±14, 529±55 and 717±31 for Philips, Siemens, GE and Toshiba respectively. At 80% reduced dose CCS was 625±96, 552±21 and 665±36 and 710±30. Using IR CCS decreased with 7-15% to 527±54, 476±19, 614±29 and 639±27. For the 38.5 mg calcification full dose FBP resulted in CCS of 102±12, 99±15, 100±7 and 112±10. At 80% reduced dose CCS was 265±41, 157±11, 148±9 and 187±15. Using IR CCS decreased with 34-58% to 110±48, 90±5, 97±8 and 85±7.

Dynamic coronary calcium scores are overestimated up to 157% at 80% reduced dose, which can be compensated for up to 58% using iterative reconstruction, depending on calcification density and CT system.

Dose reduction in CT results in overestimated calcium scores and thereof overestimated patient’s risk estimates which can be compensated for by using iterative reconstruction.

van der Werf, N, Willemink, M, Abramiuc, B, Willems, T, Leiner, T, Greuter, M, Influence of Dose Reduction on Calcium Scores in Iterative Reconstructed CT: A Multivendor Dynamic Phantom Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006508.html