Application Of Apparent Diffusion Coefficient In Parotid Neoplasms

Objective: To evaluate the value of apparent diffusion coefficient(ADC)in differential diagnosis of parotid neoplasms.Materials and Methods: DWI and ADC value of seventy-four patients(40 men,34 women,age range: 10-85 years old with mean age 51±15)with total seventy-four parotid neoplasms confirmed by surgery and pathologic examination were included into the study.DWI of all cases were acquired by single-shot EPI sequence at 3.0TMR.The ADCvalue were measured for moderate(500 s/mm2)and high(1000 s/mm2)b values on the entire lesions(ADCmean),small ROI in the most significantly restricted diffusion regions(ADCmin)and small ROI in the most significantly unrestricted diffusion regions(ADCmax).The mean ADC value of subtypes of the parotid tumor measured in different b values and different types of ROIs underwent nonparametric test for statistical analysis.Different types of ROC curves were drawn by indicators in which have statistical significance,and compared each other for statistical difference.Results:(1)There were 74 cases of parotid tumors including 54 cases of benign tumors,20 cases of malignant tumors.ADC mean value of Lymphoma was the smallest,while the ADC value of myoepithelioma was the largest.In different b value groups,ADCmax,ADCmean,ADCmin values decreased in turn,and there was a significant statistical difference between the three(p <0.01).The ADC value of the moderate b value group was higher than that of the high b value group,and there was significant difference between them(p <0.01).(2)The ADC values of benign tumors were higher than those of malignant tumors under different types of ROI and b values.The difference between them was statistically significant(P < 0.05).The area under the ROC curve(AUC)of ADCmin is the largest.(3)The ADC values of pleomorphic adenomas were the highest among the four tumor types(malignant tumor,pleomorphic adenomas,warthin tumor and other benign tumors)with different b values,followed by the other benign tumor,malignant tumors and then Warthin tumors(P<0.05).There was significant difference in ADC mean value between Warthin and pleomorphic adenoma,malignancy and pleomorphic adenoma.(4)In the benign epithelial tumors of the parotid gland,the ADC value of the pleomorphic adenoma was the highest,followed by the basal cell adenomas,and then Warthin tumors.(5)There was a significant difference of ADCmean values between pleomorphic adenomas(1.67 ± 0.30 × 10-3 mm2 / s)and non-pleomorphic adenomas(1.06 ± 0.33 × 10-3 mm2 / s)at high b values(P < 0.05).(6)Among malignant tumors,ADC mean value of lymphoma was the smallest,while the ADC value of mucoepidermoid carcinoma was the largest.(7)There was no significant difference in ROC curves between benign and malignant tumors,Warthin tumors and pleomorphic adenomas,malignant tumors and pleomorphic adenomas,basal cell adenomas and pleomorphic adenomas,pleomorphic adenomas and non-pleomorphic adenomas(P >0.05),except the ROC curves of benign and malignant tumor at high and moderate b values(P = 0.036).Conclusions:(1)Different b values and different ROI types affect the ADC value of the tumor.(2)ADC value of parotid benign and malignant tumors was of a certain value concerning differential diagnosis.So ADC values have a potential for the differential diagnosis of benign and malignant subtypes.The high b value is better than the moderate b value.(3)ADCmin,ADCmean,ADCmax were statistically different between some kind of tumours.Although the value of the three types of ROI on the diagnosis of various types of tumors was no significant difference.The AUC of ADCmean and ADCmin were larger than that of ADCmax.