Chemical-shift and diffusion-weighted magnetic resonance imaging of thymus in myasthenia gravis: usefulness of quantitative assessment.

Aim ofthis work is to prospectively investigate the usefulness of chemical-shift (CS) and diffusion-weighted (DW) magnetic resonance imaging (MRI) in patients with myasthenia gravis (MG) for distinguishing thymic lymphoid hyperplasia (TLH), normal thymus (NT) and thymoma (THY) by using the signal intensity index (SII) and the apparent diffusion coefficient (ADC). CS-MRI and DW-MRI are both useful tools for evaluating patients with MG. We found that the SII is more accurate than the ADC to differentiate TLH and NT from THY. Furthermore, the ADC is a non invasive parameter that could be used for distinguishing TLH from NT, which is useful in selecting patients for surgery since, for non-thymomatous MG, acceptable rates of complete stable remission after thymectomy are found in TLH but not in NT.