Quantification of Fat Infiltration in Oculopharyngeal Muscular Dystrophy: Comparison of Three MR Imaging Methods

Purpose: To analyze and compare three quantitative MRI methods to determine the degree of muscle involvement in oculopharyngeal muscular dystrophy (OPMD). Materials and Methods: Muscle fat content (MFC) was determined based on water-fat quantification using a 2-point Dixon (2PD) method and on a histogram analysis of the free induction decay (FID) signal of a gradient-spoiled steady-state free precession (SSFP) sequence. In addition, transverse relaxation times (T(2)) of muscle tissue were calculated using a monoexponential decay model. Results: We observed an increased mean MFC in OPMD patients as compared to healthy controls with the adductor magnus and soleus muscles being the most involved muscles in the thigh and calf, respectively. Furthermore, strong correlations (0.78 < R(2) < 0.94) between different quantitative MR methods were observed. Fewer outliers, however, were obtained by the 2PD method and T(2) measurements, suggesting these methods being superior to the SSFP-FID method. Conclusion: Quantitative MR techniques, such as fast multiecho Dixon methods and T(2) imaging, can reliably differentiate between healthy and dystrophic muscles in OPMD, even if muscles are only marginally affected. Quantitative methods thus represent a promising tool that may be able to monitor more objectively the individual disease progression and treatment response in future clinical trials in muscular dystrophies.