1. A method of enhancing a magnetic resonance imaging (MRI) image of a body or body region such as an organ or organ region in a subject, comprising: parenterally administering a composition consisting essentially of sodium ascorbate, meglumine ascorbate, or a mixture thereof to said subject in an MRI image-enhancing amount, wherein said sodium ascorbate, meglumine ascorbate, or mixture thereof is administered in an amount of from 0.02 grams per kilogram subject body weight, up 40 grams per kilogram subject body weight; and then generating, by MRI of the subject, an image of said body or body region, whereby said composition enhances the MRI image.