The Value Of MR Multi-parameter Imaging In Differential Diagnosis Of Benign And Malignant Parotid Pleomorphic Adenoma

Objective:To explore the value of MR multi-parameter imaging in the differential diagnosis of benign and malignant parotid polymorphic adenomas.To provide an intuitive imaging basis for the choice of clinical treatment for pleomorphic adenoma of the parotid gland.Methods:81 cases of pleomorphic adenoma of parotid gland,including 49 cases of benign adenoma and 32 cases of malignant adenoma,were analyzed retrospectively.MRI plain scan and contrast-enhanced examination of parotid gland were performed in all patients before operation.The morphological features,ADC and TIC of MRI in benign and malignant pleomorphic adenomas were compared with the corresponding statistical methods.Results:1.General data:Age:The average age of benign group and malignant group were 44.9±15.8 years old and 51.0±11.3 years old.T test showed that there was significant difference between the two groups（P<0.05）.2.Clinical manifestation:The benign group was mostly a mass with no pain,mobility and toughness,and there was no history of sudden enlargement and facial nerve symptoms.The malignant group usually had pain,poor mobility and hard mass,accompanied by sudden history of enlargement,and about half of them had facial nerve symptoms.χ² test showed that the differences between the two groups were statistically significant（P<0.01）.3.The morphological changes of MRI:Location,size,morphology and signal:Benign group was mostly located in shallow lobe,the average maximum diameter was 2.8±1.6cm,most of them were morphological rule,signal uniformity and no cyst change;In malignant group,most of them were involved deep lobe,the average maximum diameter was 3.9±2.0cm,most of them were irregular shape,uneven signal intensity and cystic degeneration.Edge,capsule and local lymph node change:Most of benign group were boundary clear,complete envelope and no enlarged lymph node;and most of malignant group were boundary unclear,the capsule incomplete,accompanied by enlarged lymph nodes.The differences between the two groups was statistically significant byχ² or t test（P<0.01）.4.TIC and semi-quantitative analysis of DCE-MRI:TIC:The TIC of benign group was mostly A-type curve,and The TIC of malignant group was mostly B-type and C-type curve.There was significant difference between the two groups byχ² test（P<0.01）.If A-type curve was regarded as benign tumor and B-type and C-type curves regarded as malignant tumor,the sensitivity was 58.3%,the specificity was 87.9%.Semi-quantitative analysis:The differences of Tpeak,MSI,EER and ESI between the two groups were statistically significant by Mann-Whitney U or t test（P<0 01）.5.ADC value:The average value of ADC in benign group and malignant group were 1.61±0.27×10^-3mm²/s and 1.32±0.13×10^-3mm²/s.The difference between the two groups was statistically significant（P<0.01）;When the value threshold was1.44×10^-3mm²/s,the sensitivity was 87.5%and the specificity was 73.5%.6.TIC combined ADC value:In the B-type and C-type curves,when the ADC value threshold was 1.46×10^-3mm²/s,the sensitivity was 89.3%and the specificity was 88.4%.Conclusion:MR multi-parameter imaging has important value in differentiating benign from malignant pleomorphic adenoma of parotid gland.TIC combined with ADC value can improve the diagnostic efficiency of parotid pleomorphic adenoma,and clinical data also helpful to distinguish benign and malignant pleomorphic adenoma of parotid gland.