This project is focused on the development and validation of noninvasive biomarkers to characterize disease progression in Duchenne Muscular Dystrophy (DMD), Collagen VI related myopathies (Ullrich and Bethlem) and the Dysferiinopathies (LGMD2B/MM). Despite the poor prognosis of muscular dystrophy, therapeufic interventions have been lacking and outcome measures for clinical trials have been limited to measures of muscle funcfion and quality of life, serum biomarkers of muscle breakdown, and invasive muscle biopsies. Additional quantitative outcome measures that are noninvasive and sensitive to changes in muscle structure and composition are needed to facilitate the rapid translation of promising new interventions from preclinical studies to clinical trials. Therefore, Project 3 will focus on magnetic resonance imaging (MRI) and spectroscopy (MRS) strategies to monitor pathophysiological features of dystrophy. In Aim 1 a longitudinal MR natural history study will be implemented to evaluate the progressive involvement of the lower extremity muscles in three disfinct muscular dystrophy populations. In addifion, this aim will assess the relationship between alterafions in MR parameters and loss of muscle strength and funcfion. Aim 2 is an exploratory aim that focuses on the development of novel MR strategies to quantify fibrosis in dystrophic skeletal muscle. State-of-the art sequences, such as ultra short echo and spectroscopic imaging, will be opfimized and tested in murine models of muscular dystrophy in Aim 2a. Aim 2b will rely on the development of a newly designed coil and opfimized pulse sequences to quantitafively map muscle fibrosis and intramuscular fat in subjects with muscular dystrophy using a clinical 3T system. Finally, a combinafion of cardiac MR techniques will be implemented to evaluate cardiac funcfion and progressive myocardial involvement in boys with DMD. We anticipate that the MR techniques opfimized and validated in this study will be appropriate for clinical trials in a wide range of muscular dystrophies.