Magnetic resonance imaging in response assessment of mediastinal tuberculous lymphadenopathy: Going beyond size

Role of Diffusion-Weighted Magnetic Resonance Imaging for Characterization of Mediastinal Lymphadenopathy

BACKGROUND

To assess the diagnostic performance of diffusion-weighted (DW) magnetic resonance imaging (MRI) in the characterization of mediastinal lymph nodes and compare them with morphological parameters.

METHODS

A total of 43 untreated patients with mediastinal lymphadenopathy underwent DW and T2 weighted MRI followed by pathological examination in the period from January 2015 to June 2016. The presence of diffusion restriction, apparent diffusion coefficient (ADC) value, short axis dimensions (SAD), and T2 heterogeneous signal intensity of the lymph nodes were evaluated using receiver operating characteristic curve (ROC) and forward step-wise multivariate logistic regression analysis.

RESULTS

The ADC of malignant lymphadenopathy was significantly lower (0.873 ± 0.109 × 10^-3 mm²/s) than that of benign lymphadenopathy (1.663 ± 0.311 × 10^-3 mm²/s) (p = 0.001). When an ADC of 1.0955 × 10^-3 mm²/s was used as a threshold value for differentiating malignant from benign nodes, the best results were obtained with a sensitivity of 94%, a specificity of 96%, and an area under the curve (AUC) of 0.996. A model combining the other three MRI criteria showed less sensitivity (88.9%) and specificity (92%) compared to the ADC-only model.

CONCLUSION

The ADC was the strongest independent predictor of malignancy. The addition of other parameters failed to show any increase in sensitivity and specificity.

Pediatric mediastinal masses

Mediastinal masses are categorized based on the International Thymic Malignancy Interest Group (ITMIG) classification into prevascular, visceral and paravertebral compartments. The schema is based on cross-sectional imaging, mainly CT, and helps with generating a differential diagnosis based on location of the mass. Up to half of all pediatric mediastinal tumors are malignant. In this review we describe mediastinal masses that are relevant to the pediatric population, as well as the role of MR imaging of mediastinal masses and its advantages.