Background: Magnetic resonance imaging (MRI) is a tool for getting pictures of the tissues and organs inside the body. MRI can help diagnose many injuries and diseases. But not all patients are equally likely to receive MRIs. Factors such as race or ethnicity, distance to imaging centers, mobility, and a lower income can limit some people s access to MRIs. A new ultra-low field (ULF) type of MRI, which can be used on a vehicle, may help take imaging scans to more people. But researchers need to know that UFL-MRI works just as well as standard MRIs.

Objective: To learn whether UFL-MRI is as good as standard MRI at detecting neurological disorders.

Eligibility: People aged 3 years or older who have or show symptoms of neurological disease (such as stroke, cancer, or epilepsy). Healthy adults are also needed.

Design: Participants will have 1 or 2 study visits. Adult participants will have a physical exam. They will receive two MRI exams: * Standard MRI. They will lie still on a narrow bed that will move into a large tube. They will wear earplugs to muffle the sounds. * ULF-MRI. They will lie on a stretcher, and only their head will be inside a smaller tube. The noises will be quieter. They will wear earplugs to muffle the sounds. Some adults may receive a contrast agent given through a small tube attached to a needle in the arm. The contrast agent helps the researchers see differences in the body more clearly. This may be done during 1 or both MRIs. Children will have only 1 ULF-MRI. Some participants may be invited to have additional visits for up to 6 months.