Hyperpolarized Pyruvate (13C) Magnetic Resonance Imaging In Patients With Fatty Liver Disease

Inclusion Criteria: Part 1 (Imaging Optimization): 1. Able and willing to sign informed consent. 2. Age \>= 18 years old at the time of study entry. Part 2 (Pilot Study): * Group 1 (Fatty Liver Patients without NASH): 1. NAFL as determined by either clinical suspicion of fatty liver disease based on: 1. steatosis by imaging or histology, 2. no significant alcohol consumption, 3. absence of coexisting liver disease OR NAFL determined by liver biopsy 3 months prior to the scan, with the presence of fat on histology but absent ballooning or fibrosis. (nonalcoholic steatohepatitis activity score (NAS) \<= 3). 2. Able and willing to sign informed consent. 3. Age ≥ 18 years old at the time of study entry. 4. Alcohol consumption \< 2 drinks/day for men and \<1 drink/day for women 5. Hepatitis B surface antigen (HBsAg), Hepatitis C Virus (HCV) antibody, human immunodeficiency virus (HIV) antibody negative. 6. Serum alanine aminotransferase (ALT) \< 400 microliter (uL) * Group 2 (NASH Patients): 1. NASH as determined by liver biopsy 3 months prior to the scan. a) NASH defined as NAS score greater than or equal to 4 with confirmation of NASH by an anatomic pathologist. 2. Able and willing to sign informed consent. 3. Age \>= 18 years old at the time of study entry. 4. Alcohol consumption \< 2 drinks/day for men and \<1 drink/day for women 5. HBsAg, HCV antibody, HIV antibody negative. * Group 3 (Healthy volunteer): 1. No known history of diabetes or liver disease. 2. Able and willing to sign informed consent. 3. Age \>= 18 years old at the time of study entry. 4. Body mass index \< 25. 5. Liver panel normal (aspartate aminotransferase (AST), ALT, alkaline phosphatase, bilirubin). 6. HBsAg, HCV antibody, HIV antibody negative. 7. Hemoglobin A1c \< 5.7%. 8. Estimated glomerular filtration rate (eGFR) \>= 60 mL/min/1.73m\^2 Exclusion Criteria: Part 1 (Imaging Optimization): For Cohorts 1/B only: 1. Poorly controlled hypertension, with blood pressure at study entry \> 160 mmHg systolic or \> 100 mmHg diastolic. 2. Congestive heart failure with New York Heart Association (NYHA) status ≥ 2. 3. Pregnant or nursing. 4. Participants unwilling or unable to undergo magnetic resonance (MR) imaging, including participants with contra-indications to MRI, such as cardiac pacemakers or non-compatible intracranial vascular clips. 5. Participant size too large to fit in MR scanner. Part 2 (Pilot Study): All groups 1. Poorly controlled hypertension, with blood pressure at study entry \> 160 mmHg systolic or \> 100 mmHg diastolic. 2. Current treatment with oral medication for diabetes. 3. Pregnant or nursing. 4. Participants unwilling or unable to undergo MR imaging, including patients with contra-indications to MRI, such as cardiac pacemakers or non-compatible intracranial vascular clips. 5. Participant size too large to fit in MR scanner. 6. Congestive heart failure with New York Heart Association (NYHA) status \>= 2.