The purpose of this study is to determine whether new magnetic resonance imaging (MRI) techniques can detect muscle changes over time in amyotrophic lateral sclerosis (ALS). Researchers will compare the data obtained from muscle MRIs with other measurements like the ALS-Functional Rating Scale-Revised, pulmonary function tests, strength assessments (hand-held dynamometry and ATLIS-Accurate Test of Limb Isometric Strength), respiratory function tests, and vital signs (including height and weight). This is a longitudinal study in which participants are tested at approximately 3-month intervals until the study ends (up to 1 year).