Variability of myocardial CT measurements in vivo

Variability of myocardial CT measurements, as indicated by standard deviations of mean CT numbers from four myocardial regions, was compared in 12-second scans, 3-second scans, and gated end-diastolic and end-systolic images, all from the same 12 seconds of scan data, both without and with radiographic contrast enhancement in experimental animals. There were statistically significant differences (P less than 0.05) in standard deviations of myocardial CT measurements when comparing 3-second and 12-second scans without contrast (10.4 vs. 7.7 CT#s), and 12-second scans without and with contrast (7.7 vs. 11.2 CT#s). Standard deviations of mean myocardial CT measurements were significantly greater (P less than 0.01) in gated images (end-diastolic) when compared with 12-second scans, both without contrast (22.2 vs. 7.7 CT#s) and with contrast (20.2 vs. 11.2 CT#s). In this study variability of myocardial CT measurements increased as scan time decreased, with radiographic contrast enhancement and with gating cardiac images.