Comparison of 10, 20, and 40 level electron beam computed tomography studies for coronary calcium.

There are increasing data to support the use of the electron beam computed tomography (EBCT) scanner for early detection of coronary artery disease (CAD). A negative scan essentially rules out significant disease. How many EBCT 3 mm contiguous slices are needed to cover the coronary circulation? To answer this question, 104 consecutive patients referred for EBCT scan for evaluation of coronary artery calcium (CAC) were asked to participate. The sensitivity and negative predictive value (NPV) of calcium scores for the first 10 slices and first 20 slices, the second 20 slices, and the total scan were recorded. Scores greater than one were regarded as positive. The number of levels required to cover the entire heart was also recorded. Fifty-nine patients (56.7%) had a positive calcium score for the total scan. Of these, 53 were positive for the first 10 slices (sensitivity = 89.8%, NPV 88.2%), and 57 were positive for the first 20 slices (sensitivity = 96.6%, NPV 95.7%). The median number of levels required to cover the entire heart was 34, and 97.2% of cases were covered in 40 or fewer levels. The use of 20 slices for purposes of detecting CAC is a reasonable choice for the C-100 scanners, because this would be accomplished in a breath hold. When the first slice starts at the base of the right pulmonary artery, all patients with CAC were identified. The C-150 scanner with the ability to scan on each heartbeat would increase sensitivity and NPV by acquiring 30 to 40 slices in a single breath hold.