Imaging quality of PROPELLER diffusion‐weighted MR imaging and its diagnostic performance in distinguishing pleomorphic adenomas from Warthin tumors of the parotid gland

The aim of this study was to evaluate the imaging quality and diagnostic performance of fast spin echo diffusion‐weighted imaging with periodically rotated overlapping parallel lines with enhanced reconstruction (FSE‐PROP‐DWI) in distinguishing parotid pleomorphic adenoma (PMA) from Warthin tumor (WT). This retrospective study enrolled 44 parotid gland tumors from 34 patients, including 15 PMAs and 29 WTs with waived written informed consent. All participants underwent 1.5 T diffusion‐weighted imaging including FSE‐PROP‐DWI and single‐shot echo‐planar diffusion‐weighted imaging (SS‐EP‐DWI). After imaging resizing and registration among T2WI, FSE‐PROP‐DWI and SS‐EP‐DWI, imaging distortion was quantitatively analyzed by using the Dice coefficient. Signal‐to‐noise ratio and contrast‐to‐noise ratio were qualitatively evaluated. The mean apparent diffusion coefficient (ADC) of parotid gland tumors was calculated. Wilcoxon signed‐rank test was used for paired comparison between FSE‐PROP‐DWI versus SS‐EP‐DWI. Mann–Whitney U test was used for independent group comparison between PMAs versus WTs. Diagnostic performance was evaluated by receiver operating characteristics curve analysis. P < 0.05 was considered statistically significant. The Dice coefficient was statistically significantly higher on FSE‐PROP‐DWI than SS‐EP‐DWI for both tumors (P < 0.005). Mean ADC was statistically significantly higher in PMAs than WTs on both FSE‐PROP‐DWI and SS‐EP‐DWI (P < 0.005). FSE‐PROP‐DWI and SS‐EP‐DWI successfully distinguished PMAs from WTs with an AUC of 0.880 and 0.945, respectively (P < 0.05). Sensitivity, specificity, positive predictive value, negative predictive value and accuracy in diagnosing PMAs were 100%, 69.0%, 62.5%, 100% and 79.5% for FSE‐PROP‐DWI, and 100%, 82.8%, 75%, 100% and 88.6% for SS‐EP‐DWI, respectively. FSE‐PROP‐DWI is useful to distinguish parotid PMAs from WTs with less distortion of tumors but lower AUC than SS‐EP‐DWI. FSE‐PROP‐DWI allows distinguishing PMAs from WTs with an AUC of 0.880 using ADC. It achieves less geographic distortion than SS‐EP‐DWI. Nevertheless, it shows lower AUC in distinguishing PMAs from WTs than SS‐EP‐DWI.