To Evaluate The Role Of Multimodal Magnetic Resonance Imaging In The Diagnosis Of Benign And Malignant Parotid Tumors

Objective:Parotid gland tumor is a common salivary gland tumor in the oral and maxillofacial region.Its pathological types are complex,and surgical treatment is the first choice.Accurate identification of the nature of parotid gland tumors before operation is of great reference significance for the formulation of surgical plans.Magnetic resonance imaging（MRI）is a commonly used imaging method,which has the advantages of high soft tissue resolution,no ionizing radiation,multi-sequence,multi-planar imaging and so on.Studies have found that conventional magnetic resonance imaging is more to provide morphological information of tumors,but it has certain limitations in the diagnosis of benign and malignant tumors.In recent years,with the development of3.0T MRI scanner and parallel imaging technology,the speed,coverage,and signal-to-noise ratio of magnetic resonance imaging have been improved.Multimodal magnetic resonance imaging combined with other weighted scanning modes on the basis of conventional MR Plain scan has attracted more and more researchers’attention.The aim of this study is to retrospectively analyze the imaging characteristics of 3.0T conventional MRI combined with diffusion-weighted imaging（DWI）and susceptibility-weighted imaging（SWI）multimodal magnetic resonance imaging in benign and malignant parotid tumors,which will help to improve the accuracy of preoperative diagnosis of benign and malignant parotid tumors.The diagnostic value of multimodal magnetic resonance imaging was further explored.Materials and Methods:A total of 91 patients with parotid gland tumors confirmed by surgery and pathology in the First Affiliated Hospital of Dalian Medical University from January 2016 to December 2022 were retrospectively analyzed.All patients underwent 3.0T magnetic resonance imaging（MRI）before operation.The scan sequence included T1 weighted imaging（T1WI）,T2 weighted imaging（T2WI）,diffusion-weighted imaging（DWI）,susceptibility weighted imaging（SWI）scan.The general data and imaging characteristics of tumor were recorded in our hospital’s medical records system,and the average value of the apparent diffusion coefficient(ADC_mean)of quantitative parameters calculated from DWI images and the classification of the semi-quantitative parameter intratumoral sensitivity signal（ITSS）generated from SWI images were measured.Tumors were divided into benign group and malignant group according to histopathological diagnosis.Count data were compared usingχ2 test or Fisher exact test.Shapiro-Wilk method was used to test the normality of measurement data.Two independent sample t test was used to compare the differences in normal distribution,and Mann-Whitney U test was used to compare the differences in non-normal distribution.Taking pathological diagnosis of malignancy as a positive event,the diagnostic efficacy was evaluated by ROC curve,and the diagnostic efficacy was analyzed by ADC_mean,ITSS,and ADC_mean+ITSS combined diagnosis.Results:1.General data analysis:among 91 patients with parotid gland tumors,76 cases were benign tumors and 15 cases were malignant tumors.Among benign tumors,pleomorphic adenoma had the highest incidence,followed by adenolymphoma and so on.The incidence of mucoepidermoid carcinoma was the highest among malignant tumors,followed by acinar cell carcinoma,adenoid cystic carcinoma and secretory carcinoma and so on.The mean age of the benign group was 55.24±14.76 years,and the mean age of the malignant group was 58.00±11.98 years.2.Morphological findings on conventional MRI:on T1WI and T2WI,benign parotid tumors usually have the imaging characteristics of complete capsule and clear imaging boundary.Most malignant parotid tumors have the imaging characteristics of incomplete capsule and unclear imaging boundary.There were statistically significant differences between benign and malignant parotid tumors in terms of capsule and imaging boundary.3.ADC_meananalysis of DWI:The median ADC_meanof benign group was 1.22×10-3mm2/s,and that of malignant group was 0.88×10-3 mm2/s,and the benign group was significantly higher than the malignant group.By Mann-Whitney U test,P values<0.05,statistically significant;When the cut-off value of ADCmean was 1.02,the sensitivity was 73.33%,and the specificity was 73.33%.4.ITSS analysis of SWI:The proportion of ITSS grade 0 in the benign group was51.32%,and the proportion of ITSS grade 2 in the malignant group was 60%.The difference was statistically significant.In the ROC curve,when the optimal cut-off value of ITSS was 1,the sensitivity was 80.00%and the specificity was 93.42%.5.Multimodal MRI analysis of ADC_meancombined with ITSS:When the optimal cut-off value was 0.15,the sensitivity was 93.33%and the specificity was 93.33%.The results showed that the predictive diagnostic value of the combination of ITSS grade and ADC_meanvalue was higher than that of ITSS grade and ADC_meanvalue alone.6.Conventional MRI diagnostic analysis:Conventional MRI had a good consistency with pathological diagnosis in the diagnosis of benign and malignant parotid gland tumors.ROC curve analysis showed that the area under the curve AUC was 0.674,the sensitivity was 40%,and the specificity was 94.74%.Conclusions:Conventional MRI,DWI and SWI have their own advantages and disadvantages in the diagnosis of benign and malignant parotid tumors.Based on the analysis of conventional MRI imaging and multimodal imaging characteristics of DWI and SWI,the ROC curve analysis results of ITSS combined with ADC_meanindex showed that the sensitivity was 93.33%and the specificity was 93.33%.Therefore,multimodal MRI is superior to single MRI parameter in the differential diagnosis of benign and malignant parotid gland tumors,and has high clinical application value.