EBCT has been the primary technology used for major coronary calcium studies.  However, because of its high costs (equipment, siting, and maintenance) and lack of acceptable image quality for most routine CT imaging, the number of EBCT sites has been limited.  This has, in turn, limited the acceptance of coronary calcium scoring as a diagnostic procedure.  Now, however, the world leaders in traditional helical CT technology (GE, Siemens, Philips, Marconi, Toshiba) have validated a hybrid technology (GHCT) which allows the standard hospital CT system to also perform cardiac scoring.  While there are several studies that offer validation of this technology, the following article offers the widest perspective.

1. Evaluation of Subsecond Gated Helical CT for Quantification of Coronary Artery Calcium and Comparison with Electron Beam CT

Background: Since its introduction early in the 1990s, helical CT has become the pre-dominant technology for obtaining CT images for medical applications. Recent improve-ments in the temporal resolution of helical CT (subsecond) and the addition of retrospective cardiac gating are combined in this report evaluating cardiac-gated helical CT for quantifying coronary artery calcium. We compare total calcium scores determined on subsecond gated helical CT with the current reference for coronary calcium evaluation, electron beam CT.
Methods: We compared total calcium scores obtained using a general purpose, unmodified helical CT scanner with scores obtained using electron beam CT in 36 individuals who were 68 ± 11 years old (age range, 41-85 years).
Results: Correlation coefficients ranged from 0.97 to 0.98 (Pearson’s product moment) and from 0.95 to 0.96 (Spearman’s rank order), depending on the coronary calcium scoring method used. Agreement in the classification of participants as “healthy” or “diseased” at threshold total calcium scores of 10, 100, 160, 200, 400, and 680 was, respectively, 94%, 97%, 89%, 92%, 94%, and 100% using the conventional electron beam CT scoring method and an equivalent method with helical CT.
Conclusions: A general purpose, current generation helical CT scanner equipped for retrospective cardiac gating can accurately quantify coronary calcium, and the results are highly correlated to scores obtained with electron beam CT. As an alternative method for measuring coronary calcium, gated subsecond cardiac helical CT offers greater availability and lower cost, thereby making population-based screening for coronary artery calcium more feasible.