Statistical analysis
The statistical analysis was conducted using SPSS 17.0 (IBM Corp, Armonk, NY, USA). All data were presented as mean, maximal/minimal value (max./min.), standardized deviation (SD) and 95% confidence interval (95% CI). The normality distribution of the data was evaluated using the Shapiro-Wilk test. The intra-group correlation coefficient (ICC) was used to evaluate the consistency of the same examiners measured at an interval of 24 h. The data conforming to normal distribution were expressed in the form of “x ± s”, and the differences were analyzed by independent sample t-test. The data that did not conform to normal distribution were analyzed using Mann-Whitney 