Effects of region of interest sizes on apparent diffusion coefficient measurements of pleomorphic adenoma, Warthin tumor, and normal parotid parenchyma

Magnetic resonance imaging (MRI) has become increasingly important in the diagnosis and evaluation of various diseases in clinical practice because of the advantages of multiple soft-tissue contrasts and absence of ionizing radiation. For parotid gland tumors, MRI is valuable for identifying tumor location and extension, and the relationship between the tumor and the facial nerve (1-14). As a functional method of MRI, diffusion-weighted imaging (DWI) with derived apparent diffusion coefficient (ADC) can provide useful information in the differentiation of various entities of parotid tumors (15). Yerli et al. reported that MRI combined with DWI seemed to have similar diagnostic potential as fine-needle biopsy in the differentiation of benign and malignant parotid masses (4)