Objectives: To evaluate the diagnostic value of diffusion-weighted MRI for differentiating metastatic from non-metastatic retropharyngeal lymph nodes (RLNs) in patients with nasopharyngeal carcinoma (NPC). Methods: Untreated patients with NPC (n 5 145) were scanned with both morphological MRI and diffusion-weighted imaging (DWI). RLNs (n 5 335) were classified as metastatic on the basis of response to therapy as assessed on follow-up MRI. Morphological (short-and long-axial diameters) and functional [mean apparent diffusion coefficient (ADC) and minimum ADC values] parameters of the RLNs were derived from DWI and compared between metastatic and non-metastatic groups. A receiver operating characteristic curve and the area under the curve were used to evaluate the effectiveness of individual criteria and to generate threshold values to diagnose RLN metastases. Results: Statistically significant differences between metastatic and non-metastatic RLNs were found for all four parameters derived from DWI (p , 0.001). At threshold values, accuracies of the ADC-based criteria (0.938 and 0.965 for mean and minimum ADC values, respectively) were greater than that of size-based criteria (0.838 and 0.809 for short-and longaxial diameters). The minimum ADC value at the threshold of 0.89 3 10 23 mm 2 s 21 was the most effective of all parameters in differentiating metastatic from non-metastatic RLNs with the sensitivity of 95.7%, specificity of 95.1% and accuracy of 96.5%. Conclusions: DWI is feasible for differentiating metastatic RLNs from non-metastatic nodes in patients with NPC with high accuracy, and the minimum ADC derived from DWI could serve as a standard clinical marker for disease status. Dentomaxillofacial Radiology (2015Radiology ( ) 44, 20140126. doi: 10.1259 Cite this article as: Li H, Liu X-W, Geng Z-J, Wang D-L, Xie C-M. Diffusion-weighted imaging to differentiate metastatic from non-metastatic retropharyngeal lymph nodes in nasopharyngeal carcinoma. Dentomaxillofac Radiol 2015; 44: 20140126.

HEAD AND NECK IMAGINGORIGINAL ARTICLE PURPOSE We aimed to investigate the magnetic resonance imaging (MRI) appearance of inflammatory myofibroblastic tumors (IMTs) in the maxillofacial region in order to improve diagnostic quality and resection efficacy. MATERIALS AND METHODSTen cases of pathologically identified IMTs were analyzed by MRI. The MRI features were examined, including tumor location, tumor shape, tumor margins, and involvement of the surrounding tissues. RESULTSOf ten masses investigated in this study, eight masses were irregular neoplasms with unclear margins and two masses, in the parotid gland, were regular neoplasms with clear margins. Precontrast T1-weighted images of all ten masses exhibited isointense signals compared to the adjacent tissue, while contrast-enhanced T1-weighted images showed strong enhancement. Six masses were hypointense and four masses were slightly hyperintense in T2-weighted images. Involvement of the adjacent structures was observed in eight of ten cases. Meanwhile, two patients experienced intracranial involvement. CONCLUSIONIMTs are rare tumors in the maxillofacial region, displaying a number of distinct MRI characteristics. Most importantly, they display low T2 signal intensity and strong enhancement, and they frequently invade surrounding structures. Thus, MRI can improve the accuracy of IMT diagnoses and provide critical information for surgical planning. Inflammatory myofibroblastic tumors (IMTs) are rare neoplasms composed of myofibroblasts accompanied by prominent small lymphocytes and plasma cells (1). They have previously been categorized in the inflammatory pseudotumor group, but they are now defined as a separate entity based on electron microscope and immunohistochemical findings. Recent studies have shown that cytogenetic clonal abnormalities and anaplastic lymphoma kinase expression are the best definitive markers for diagnosing IMTs (2, 3). IMTs most commonly involve the lung, although they have been described in almost all sites in the body, in both sexes, and at all ages (4). IMTs in the maxillofacial region are exceptionally rare, and the clinical presentation depends on the location of the tumor. Patients can present with fever, pain, swelling, otorrhea, and cranial nerve palsy (5). IMTs clinically mimic malignant lesions, and the clinical significance lies in the difficulty encountered in excluding malignancy, preoperatively. There have been only a few studies that reported substantial numbers of IMTs in the maxillofacial region. Recently, Yuan et al. (6) reported imaging findings for eight IMT cases in the maxillary sinus; however, only three of the patients underwent MRI analysis, and the researchers could not summarize the MRI characteristics. Therefore, we have retrospectively analyzed the MRI findings of ten cases with maxillofacial IMT and summarized the imaging features in order to improve the diagnosis of this tumor. Material and methods PatientsA total of ten patients with pathologically confirmed IMTs in the maxillofacial region were reviewe...