Statistical analysis
All statistical analyses were carried out using SPSS for Windows 15.0
(SPSS Inc., Chicago, IL, USA). Continuous variables with normal
distribution were expressed as mean ± standard deviation (SD), and
categorical variables were expressed as number and percentage.
Sensitivity and specificity values, accuracy, positive and negative
predictive values were analyzed by the contingency table and calculated
for CDUS CTA as the gold standard method. Bland-Altman plot was
generated to evaluate agreement between two measurements of sac diameter
(CDUS and CTA) by constructing limits of agreement. These limits are
calculated by using the mean and standard deviation of the differences
between two measurements. At least 95% of paired measurements were
expected to lie within ± 2 SD of the mean difference. Linear regression
analysis was conducted to assess proportional bias. Type-I error of 0.05
was set as statistically significant.