Johnson DY, Farjat AE, Vernuccio F, et al. - Researchers performed this study on 100 patients who had four CT scans within 12 months with identical acquisition and contrast injection parameters, to quantify temporal variability in vascular and parenchymal enhancement within the same patient, as well as to investigate technique-associated factors contributing to this variability. They found that clinically important variability in enhancement of the abdominal aorta, portal vein, and liver parenchyma may be displayed by nearly one-third of patients despite the use of identical scanning and injection parameters. The only controllable factor related to variability in enhancement of the abdominal aorta was delay time. They noted that no other controllable factor was related to variability in the portal vein or liver parenchyma.