Role of diffusion-weighted magnetic resonance imaging in the differentiation of parotid gland tumors

Cross-sectional imaging and cytologic investigations in the preoperative diagnosis of parotid gland tumors – an updated literature review

“…The inter-cellular conditions, the different tissue type microstructures, and blood microcirculation in the capillary network may influence qualitatively the movement of water molecules. The quantitative evaluation of the water diffusion is possible with the help of the ADC maps generated by the axial DWI images [15,16,[24][25][26][27][28]. In order to obtain a numeric ADC value from a region of interest (ROI), the difference of the DWI aspect must be evaluated according to a mono-exponential model, taking into account a minimum of two optimal b-values, which vary on the investigated tissue [26].…”

“…Thus, the diffusion of water molecules in a particular tissue type is numerically characterized by the ADC value obtained from a particular ROI [26]. Normal tissue characteristics (extracellular space size, cellular and fiber density, and viscosity) and also tumor tissue features (cell differentiation, density, presence of necrotic or cystic areas, and nucleus/cytoplasm ratio) can be assessed with ADC [25]. Increased cellularity causes a restriction of water molecule diffusion, which leads to lower ADC values (malignant tumors).…”

“…Increased cellularity causes a restriction of water molecule diffusion, which leads to lower ADC values (malignant tumors). The low density of cellular components and increased interstitial space will generate high diffusion with high ADC values (benign lesions) [25][26][27]. Parotid glands tumors can present different ADC values, which can help in establishing a preoperative imaging differential diagnosis.…”

“…In most studies, differentiation of PMA from WT, as well as PMA from malignant tumors was successful based on ADC values [15,17,20,25,26,32,34]. Other authors did not obtain significant results regarding the differentiation of WTs from malignant tumors due to the overlap of their ADCs values [25,29,30,32,34]. However, differentiation of WTs from malignant ones, based on ADC maps, was possible in some studies [32,[35][36][37].…”

Multifocal Warthin’s Tumor: An Uncommon Presentation of Bilateral Cervical Lymphadenopathy

“…On magnetic resonance imaging (MRI), T1 shows low to intermediate signal, variable intensity on T2, and lack of enhancement with contrast [ 16 ]. Using MR diffusion weighted imaging (DWI), WT has a lower apparent diffusion coefficient (ADC) than pleomorphic adenoma and a comparable ADC to malignant salivary tumors [ 17 ]. A low ADC indicates decreased diffusion of water molecules in tissue, suggesting more cellular tissue.…”