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

Background Assessment of response to antitubercular treatment (ATT) in mediastinal tuberculous lymph nodes (LNs) is challenging. Gold standard techniques such as biopsy and culture involve invasive procedures. Radiographic persistence of mediastinal LNs even after completion of ATT poses a treatment dilemma. In this study, we evaluated the changes in signal intensity (SI) and apparent diffusion coefficient (ADC) values of mediastinal LNs on magnetic resonance imaging (MRI), for response assessment to ATT. Materials and Methods After institute ethics approval, a retrospective analysis of MRI images of 22 patients with 55 mediastinal tuberculous LNs was done. Clinically responsive patients of mediastinal tuberculous LNs who underwent chest MRI prior to ATT, or within 1 month of starting ATT, and second MRI performed at least after 2 months of start of the treatment were included. LN size, T1 and T2 signal characteristics (homogenously/heterogeneously and hyperintense or hypointense), T2 and T1 SI ratio, ADC values, and contrast enhancement characteristics were compared. Paired t-test and McNemar test were performed at a significance level of α =0.05. Results Size of LN reduced, but 45 LNs measured >8 mm in second MRI. There was statistically significant decrease in the T2 and T1 SI ratios in second MRI, P = 0.026 and 0.008, respectively. No statistically significant difference was found in ADC values, P = 0.31. Conclusions Decrease in T2 and T1 SI ratios of mediastinal tuberculous LNs can be used as a noninvasive imaging parameter to suggest response to ATT. However, ADC value is not a useful indicator of treatment response.