Participants who are clinically scheduled to undergo F-18 FDG PET/CT myeloma evaluation will also undergo F-18 FDG PET/MRI, and C-11 acetate PET CT/MRI. On Day 1 of study, participants will undergo F-18 FDG PET/CT-MRI. F-18 FDG radiopharmaceutical is infused intravenously, followed by a 60 minute waiting uptake phase. After 60 minutes, participant will undergo PET/CT imaging for 30 minutes. At 90 minutes, participant will undergo PET/MRI imaging for 30 minutes. On Day 2 of study, participants will undergo C-11 PET/CT-MRI. C-11 radiopharmaceutical is infused intravenously, followed by a 10 minute uptake phase. After 10 minutes, participant will undergo PET/CT imaging for 30 minutes, followed by a 60 minute pause with the participant at rest. At the end of 60 minute pause, the participant is given the second C-11 acetate infusion, followed by a 10 minute waiting uptake phase. After 10 minutes, participant will undergo PET/MRI imaging for 30 minutes. On Day 3, study team member makes a phone call to participant for follow up.