ABSTRACT
Objective:To assess the value of the parotid fat fraction (FF) and T 2 relaxation time (T 2 value) in the evaluation of early parotid involvment in patients with primary Sj?gren′s syndrome (pSS) using multi-echo Dixon technique and T 2 mapping imaging. Methods:From December 2018 to December 2019, 26 early pSS patients (pSS group) and 20 healthy controls (control group), matched to age and gender, were enrolled at the First Affiliated Hospital of Zhengzhou University in this prospectively study. All subjects underwent conventional MRI, DWI, multi-echo Dixon and T 2 mapping sequences before treatment. The ADC, FF and T 2 value of bilateral parotid parenchyma in pSS group and control group were measured respectively. Paired sample t test was used to compare the differences of ADC, FF and T 2 values between left and right parotid glands for pSS group and control group, while independent sample t test was used to compare the differences of ADC, FF and T 2 values between pSS group and control group. The ROC curves were drawn to evaluate diagnostic performance of ADC, FF and T 2 values to distinguish early pSS, and the difference of diagnostic efficacy of each parameter was compared by Delong test. Binary logistic regression analysis and ROC curve were used to evaluate the diagnostic performance of the combination of the 3 parameters in early pSS. Results:There were no significant differences of ADC, FF and T 2 values between left and right parotid glands for pSS group and control group (all P>0.05). The parotid ADC values were significantly lower in pSS group than control group ( t=4.641, P=0.006), while the FF and T 2 values of pSS group were significantly higher than those of control group ( t=-2.910, -6.411, both P<0.001). The areas under the ROC curve of ADC, FF and T 2 values to distinguish early pSS were 0.666, 0.750 and 0.862, respectively. The area under ROC curve of the combination of ADC, FF and T 2 values was 0.930, with a sensitivity of 73.1% and a specificity of 97.5%. T 2 values showed a better diagnostic efficacy than ADC values ( Z=2.626, P=0.009) and FF values ( Z=2.112, P=0.035) when distinguishing pSS group from control group. The area under ROC curve of the combination of ADC, FF and T 2 values showed a better diagnostic efficacy than each parameter alone ( Z=4.869, P<0.001, Z=3.628, P<0.001, Z=2.162, P=0.031). Conclusions:Multi-echo Dixon technique and T 2 mapping can quantitatively evaluate the parotid gland fat deposition and inflammatory response in the early stage of pSS. T 2 value has great potential in evaluating early parotid gland injury of pSS, and the combination of ADC, FF and T 2 values can further improve the diagnostic efficiency.
ABSTRACT
Objective The purpose of this study was to evaluate whether whole-tumor histogram-based analysis of readout-segmented echo-planar diffusion-weighted imaging (RESOLVE-DWI) ADC map can help in the discrimination of parotid gland tumors(pleomorphic adenoma, Warthin tumor, malignant parotid gland tumor). Methods The MR images(pre / post-contrast enhanced MRI, RESOLVE-DWI, ADC map) of 47 patients with a biopsy-or surgery-proven pleomorphic adenomas, 25 patients with Warthin tumors and 36 patients with malignant parotid gland tumors were retrospectively analyzed. Histogram-based analysis was performed with the software MaZda. ROIs were drawn on every section of the ADC map containing the tumor, then 12 Parameters(Area, MinNorm, MaxNorm, Mean,Variance, Skewness, Kurtosis, Perc.1％, Perc.10％, Perc.50％, Perc.90％, Perc.99％) derived from histogram were calculated. Statistical analysis among the three groups (One-way ANOVA or Kruskal-Wallis test) were performed to find out the statistical significance of each histogram parameter. Then LSD test or Mann-Whitney U test was used for pairwise comparison between groups. And the differential efficiency of each parameter was determined using ROC analysis. Results Overall, 9 parameters (MinNorm, MaxNorm, Mean, Variance, Skewness, Perc. 10％, Perc. 50％, Perc. 90％, Perc. 99％) among three groups were shown to be statistically significant (P<0.05). Between the pleomorphic adenomas and Warthin tumors, these 9 parameters were of statistical significance. Perc.50％revealed the highest diagnostic efficiency, followed by Mean and Perc.10％. Between the pleomorphic adenomas and malignant parotid gland tumors, also all these 9 parameters were of statistical significance. Mean was revealed to have the highest diagnostic efficiency, followed by Perc. 10％ and Perc. 90％. However, between the Warthin tumors and malignant parotid gland tumors, only 5 parameters (MinNorm, Mean, Skewness, Perc. 10％, Perc. 50％) were statistically significant. MinNorm was revealed to have the highest diagnostic efficiency, followed by Perc. 50％ and Perc. 10％. Generally, Mean, Perc. 10％ and Perc. 50％ were more effective in the differential diagnosis of these three types common parotid neoplasms. Conclusion Whole-tumor histogram analysis of ADC maps are effective in differentiating common parotid neoplasms.