Diagnostic Performance of Diffusion Weighted Imaging of Malignant and Benign Pulmonary Nodules and Masses: Comparison with Positron Emission Tomography

Background: Diffusion-weighted imaging (DWI) makes it possible to detect malignant tumors based onthe diffusion of water molecules. However, it is uncertain whether DWI has advantages over FDG-PET fordistinguishing malignant from benign pulmonary nodules and masses. Materials and
Methods: One hundredforty-three lung cancers, 17 metastatic lung tumors, and 29 benign pulmonary nodules and masses were assessedin this study. DWI and FDG-PET were performed.
Results: The apparent diffusion coefficient (ADC) value(1.27±0.35 ×10-3 mm2/sec) of malignant pulmonary nodules and masses was significantly lower than that (1.66±0.58×10-3 mm2/sec) of benign pulmonary nodules and masses. The maximum standardized uptake value (SUVmax:7.47±6.10) of malignant pulmonary nodules and masses were also significantly higher than that (3.89±4.04) ofbenign nodules and masses. By using optimal cutoff values for ADC (1.44×10-3 mm2/sec) and for SUVmax (3.43),which were determined with receiver operating characteristics curves (ROC curves), the sensitivity (80.0%) ofDWI was significantly higher than that (70.0%) of FDG-PET. The specificity (65.5%) of DWI was equal to that(65.5%) of FDG-PET. The accuracy (77.8%) of DWI was not significantly higher than that (69.3%) of FDGPETfor pulmonary nodules and masses. As the percentage of bronchioloalveolar carcinoma (BAC) componentin adenocarcinoma increased, the sensitivity of FDG-PET decreased. DWI could not help in the diagnosis ofmucinous adenocarcinomas as malignant, and FDG-PET could help in the correct diagnosis of 5 out of 6 mucinousadenocarcinomas as malignant.
Conclusions: DWI has higher potential than PET in assessing pulmonary nodulesand masses. Both diagnostic approaches have their specific strengths and weaknesses which are determined bythe underlying pathology of pulmonary nodules and masses.