Magnetic resonance imaging of part-solid nodules a pilot study

Purpose: The aim of the study was to assess whether magnetic resonance imaging (MRI) characteristics can distinguish benign from malignant part-solid pulmonary nodules and predict the aggressiveness of the latter. We also sought to compare MRI-derived parameters with morphologic and physiological values derived from conventional examinations such as computed tomography and positron emission tomography/computed tomography. Materials and Methods: This was an institutional review board- approved pilot study of 28 participants (23 women, mean age 73.5±13.8 y) with 32 biopsy-proven lesions. 3-T unenhanced pulmonary MRI examinations were performed with regions of interest drawn around lesions for T1, T2, T2∗, and diffusionweighted sequences. Apparent diffusion coefficient (ADC) and T2∗values were calculated. Two weeks later the regions of interest were redrawn. MRI parameters were compared with lesion pathology, maximal standard uptake value (SUVmax), and Hounsfield units (HU). MRI lesion visibility was correlated with solid component size and the percentage of solid component. Intraobserver and interobserver agreements were determined. Results: Only ADC values correlated with malignancy (P<0.05). ADC≥1.28 μm²/ms predicted malignancy with 83.3% sensitivity (area under the curve 0.79). ADC and T2∗correlated with adenocarcinoma subtypes (P<0.05). No MRI parameters predicted tumor differentiation (P>0.11). SUVmax did not correlate with any MRI parameters (P>0.56). Visibility on T1-weighted images correlated with the percentage of solid components (P<0.03). T1 and T2 values showed significant correlation with HU measurements of the entire nodule (P<0.001 and P<0.024, respectively) and HU measurements of solid components (P=0.031 and 0.008, respectively). Conclusions: 3T MRI with quantitative ADC values demonstrated potential for discriminating benign part-solid pulmonary nodules from malignant lesions. ADC and T2∗values correlated with adenocarcinoma subtypes. No MRI parameters correlated with SUVmax. T1 and T2 values showed significant correlation with HU measurements of the entire nodule and of the solid components.