| Backgrounds and Objective: Parotid gland tumor is a common head and neck cancer, pleomorphic adenoma, gland lymphoma, mucous epidermoid carcinoma are the most common tumors. The qualitative diagnosis of the is very important to the choice of surgical procedure. Fine needle aspiration cytology(FNAC) is the most reliable method for qualitative diagnosis of parotid gland tumors currently. FNAC is an invasive examination,and the lesion is small or in parotid gland deep lobe, FNAC can’t get correct diagnosis. Therefor preoperative diagnosis of parotid tumors preferred noninvasive imaging examination, included Ultrasound, CT, MRI and radionuclide imaging. Ultrasound examination is easy to operate, low cost and no radiation, as the preferred method. CT have high scanning speed and high density resolution, parotid gland tissue rich in fat, have a advantage to the detection and localization of parotid gland tumors, but the specificity of diagnosis of benign and malignant tumors is not very high. MRI have high resolution of soft tissue, multiplanar imaging and no radiation, is better for showing tumor boundary and invasion to the surrounding tissue. But is insensitive to the detection of calcificatio, and with long scan time, more artifacts, clinical application scope is limited. The specificity of Radionuclide imaging for diagnosis of parotid tumors is not high, only as a means of auxiliary examination. Spectrum CT is a emerging imaging technology in recent years, with 80 and 140 k Vp fast switch as the core technology, at the same time obtained two groups of different energy data. With the function of single energy imaging and material separation, it can quantitatively analyse the content of basic material(water, iodine, calcium, etc). Analysis Spectrum CT parameters between benign and malignant parotid gland tumors to investigate the value of gemstone spectral imaging(GSI) in diagnosis of benign andmalignant parotid tumors.Patients and Methods: Totally 62 patients with parotid tumors confirmed by surgery and pathology were enrolled in the study. All the patients underwent spectral imaging CT scan.26 men and 36 women, aged 12~85 years, the median age is 47.0 years old. Use GSI Viewer software for the image processing and analysis at GE AW4.5 workstations. ROI was set to get the iodine concentration, slope of spectral curve and Effective-Z on the 70 ke V image. Besides, conventional morphology characteristics such as location,shape,margin, cystic change sign were reviewed and recorded. According to the pathologic results, tumors were divided into benign group and malignant group, benign group were divided into pleomorphic adenoma group and Warthin’s tumors group again. Iodine concentration, slope of spectral curve, Effective-Z were compared between benign group and malignant group, pleomorphic adenoma group and malignant tumor group, Warthin’s tumors group and malignant group, pleomorphic adenoma group and Warthin’s tumors group by a two-sided Wilcoxon rank sum test. P value < 0.05 was considered statistically significant. The optimal threshold to predict malignancy was obtained by receiver operating characteristic curve(ROC), at the same time the corresponding sensitivity and specificity were obtained. Use univariate regression analysis to analyzed iodine concentration, location, shape, margin and cystic change, selcted the valuable indicators of differential diagnosis of benign and malignant tumor(P < 0.25).The valuable indicators included in the multivariate logistic regression analysis. Multivariate ROC analysis was performed to evaluate the efficacy of combining the iodine concentration and conventional morphology characteristics.Results: In non-contrast CT imaging, the median and quartile range of iodine concentration, slope of spectral curve, Effective-Z were-1.41×100 μg/ml(-2.25,0.16)、-0.10(-0.31,0.12)、7.25(7.17,7.40)in benign group,-1.13×100 μg/ml(-1.46,1.44)、1.01(-0.19,2.04)、7.17(7.13,7.48)in malignant group. Therewere no significant difference between the two groups(P>0.05). In the arterial phase,the median and quartile range of iodine concentration,slope of spectral curve,Effective-Z were 9.65×100 μg/ml(4.29,18.37)、0.69(0.31,1.59)、7.89(7.71,9.15) in benign group, 18.04×100 μg/ml(12.5,20.98)、1.56(1.29,2.65)、9.22(9.11,9.28)in malignant group.(Z value were-3.273、-2.43、-3.01,respectively;P <0.05). In venous phase,the median and quartile range of iodine concentration, slope of spectral curve, Effective-Z were 12.26×100 μg/ml(10.03,22.19)、1.23(0.65,2.08)、8.14(7.91,8.31)in benign group, 11.08×100 μg/ml(9.89,17.55)、1.22(1.07,2.25)、7.96(7.89,8.14)in malignant group. There were no significant difference between the two groups(P>0.05).In the arterial phase, taking Iodine concentration>18.90×100 μg/ml as the optimal threshold to predict malignancy, the sensitivity and specificity were 81.70% and 79.50%, respectively. For the multivariate analysis, thearea under the ROC was 0.8 8 in arterial phase, the sensitivity and specificity were 84.1% and 84.5%,respectively.Conclusion: Spectral CT multi-parameter imaging have a potential value in differential diagnosis of benign and malignant parotid tumors. However, there are some overlaps in the iodine concentration of benign and malignant tumors in the arterial phase. A comprehensive analysis combining spectrum parameter and conventional morphology characteristics has higher efficiency in differential diagnosis. |
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