Coronary calcium scores are systematically underestimated at a large chest size: A multivendor phantom study

• For all major vendors, the detected amount of coronary calcium depends on chest size.
• Coronary calcium scores can be underestimated up to 50% at a larger chest size.
• Scores are even underestimated with routinely used weight-adjusted scan protocols.
• CT systems from different vendors result in different Agatston scores.
• Future risk of cardiovascular events may be underestimated with a larger chest size.

ObjectiveTo evaluate the effect of chest size on coronary calcium score (CCS) as assessed with new-generation CT systems from 4 major vendors.MethodsAn anthropomorphic, small-sized (300 × 200 mm) chest phantom containing 100 small calcifications (diameters, 0.5–2.0 mm) was evaluated with and without an extension ring on state-of-the-art CT systems from 4 vendors. The extension ring was used to mimic a patient with a large chest size (400 × 300 mm). Image acquisition was repeated 5 times with small translations and/or rotations. Routine clinical acquisition and reconstruction protocols for small and large patients were used. CCS was quantified as Agatston and mass scores with vendor software.ResultsThe small-sized phantom resulted in median (interquartiles) Agatston scores of 10 (9–35), 136 (123–146), 34 (30–37), and 87 (85–89) for Philips, GE, Siemens, and Toshiba, respectively. Mass scores were 4 mg (3–9 mg), 23 mg (21–27 mg), 8 mg (8–9 mg), and 20 mg (20–20 mg), respectively. Adding the extension ring resulted in reduced Agatston scores for all vendors (17%–48%) and mass scores for 2 vendors (11%–49%). Median Agatston scores decreased to 9 (5–10), 79 (60–80), 27 (24–32), and 45 (29–53) units, and median mass scores remained similar for Philips at 4 mg (4–6 mg) and Siemens at 8 mg (7–8 mg) and decreased for the other vendors to 13 mg (11–14 mg) and 10 mg (8–13 mg), respectively.ConclusionThis multivendor phantom study showed that CCS can be underestimated up to 50% (49%–66%) for Agatston scores and 49% (36%–59%) for mass scores at a larger chest size, which may be relevant for women and large patients. However, CCS underestimation by chest size differs considerably by vendor.