Diffusion Weighted Imaging Can Distinguish Benign from Malignant Mediastinal Tumors and Mass Lesions: Comparison with Positron Emission Tomography

Background: Diffusion-weighted magnetic resonance imaging (DWI) makes it possible to detect malignanttumors based on the diffusion of water molecules. It is uncertain whether DWI is more useful than positronemission tomography-computed tomography (PET-CT) for distinguishing benign from malignant mediastinaltumors and mass lesions. Materials and
Methods: Sixteen malignant mediastinal tumors (thymomas 7, thymiccancers 3, malignant lymphomas 3, malignant germ cell tumors 2, and thymic carcinoid 1) and 12 benignmediastinal tumors or mass lesions were assessed in this study. DWI and PET-CT were performed before biopsyor surgery.
Results: The apparent diffusion coefficient (ADC) value (1.51±0.46 ×10-3mm2/sec) of malignantmediastinal tumors was significantly lower than that (2.96±0.86 ×10-3mm2/sec) of benign mediastinal tumors andmass lesions (P<0.0001). Maximum standardized uptake value (SUVmax) (11.30±11.22) of malignant mediastinaltumors was significantly higher than that (2.53±3.92) of benign mediastinal tumors and mass lesions (P=0.0159).Using the optimal cutoff value (OCV) 2.21×10-3mm2/sec for ADC and 2.93 for SUVmax, the sensitivity (100%) byDWI was not significantly higher than that (93.8%) by PET-CT for malignant mediastinal tumors. The specificity(83.3%) by DWI was not significantly higher than that (66.7%) for benign mediastinal tumors and mass lesions.The accuracy (92.9%) by DWI was not significantly higher than that (82.1%) by PET-CT for mediastinal tumorsand mass lesions.
Conclusions: There was no significant difference between diagnostic capability of DWI andthat of PET-CT for distinguishing mediastinal tumors and mass lesions. DWI is useful in distinguishing benignfrom malignant mediastinal tumors and mass lesions.