Multi-parametric MRI In The Diagnosis Of Lympho-associated Benign And Malignant Lesions Of The Parotid Gland

Objects:Establishing diagnosis on the basis of routine MR imagings between MALT lymphoma and tumor-like lymphoepthelial lesion in parotid gland is usually difficult.Multi-parametric MRI including ¹H-MRS,DWI-MR,DCE-MR can be useful in differential diagnosis of two lesions.Materials and methods:Twenty-five patients with tumor-like lyphoepithelial lesion and 20patients with MALT lyphoma in the parotid gland confirmed by pathology were examined preoperatively using routine MR series,¹H-MRS,DWI-MR,DCE-MR with a 1.5T MR unit.The localiazation for single-voxel ¹H-MRS was used by a point-spectroscopy（PRESS）at echo time of 144ms,and Cho was considered as a criterion to assess the MALT lymphoma.The mean ADC from both b values（500s/mm² and 1000s/mm²）were calculated from DWI-MR.TTP,TTS,SI_start,SI_max,SI_ending and ISI,RWO were seperately calculated from DCE-MR,and the types of TICs were analysed.Results:There was no significant difference between tumor-like lymphoepithelial lesion and MALT lymphoma in the parotid gland in the routine MR imagings（P>0.05）.There were significant differences in Cho peak,mean ADC（b=1000s/mm²）,TTP,ISI between two lesions,and lower mean ADC compared to malignant tumors’can reveal the pathological features of them.The sensitivity,specificity,accuracy of TTP from DCE-MR were all more than 90%.TICs were categorized into three types accordings to the threshold of TTP and ISI:（1）tumor-like lymphoepithelial lesion:plateau type（typeⅡ）and late increasing type（typeⅢ）;（2）MALT lymphoma:early increasing type（typeⅠ）.Accuracy of differential dagnosis between these lesions was increased by conbimation of ¹H-MRS,DWI-MR,DCE-MR.MALT lymphoma can be distingished from non-MALT lymphomas in the parotid gland by the feature of solid-cystic changes of neoplasm in CT and MR imagings.Conclusions:Multi-parameters MR（¹H-MRS、DWI-MR、DCE-MR）contributed greatly to differential diagnosis between tumor-like lymphoepithelial lesion and MALT lymphoma in the parotid gland.